Chapter 3. Theories of causes of sexual orientation and the homosexual heterosexuals

SO YOU SAY YOU’RE STRAIGHT: The one in five hidden homosexual heterosexuals  by the late Dr Neil McConaghy book proposal placed here on StraightGuise.com with permission by the author’s daughter, Dr. Finola McConaghy.


Contact Dr. Finola McConaghy at the address and phone below:


Dr Finola McConaghy BVSc, DipVetClinStud, PhD

Technical Services Manager

Nature Vet

Street: 11 Moores Rd.

Postal: PO Box 147

Glenorie NSW 2157 Australia

Phone: +61 2 9652 7000

Fax: +61 2 9652 7001

Mob: 0427 427 477
All rights reserved.

Chapter 3.   Theories of causes of sexual orientation and the homosexual heterosexuals

It was pointed out in the Introduction that discussion of sexual orientation is largely limited to women and men’s feelings of sexual attraction to or choice of sexual partners of one or the other sex.  Few theories of the causes of sexual orientation give attention to causes of the desire and ability to love or to form attachments or bonding relationships with members of one or other sex, or of the wish to parent children.  Current theories of the causes of sexual orientation have the additional limitation that almost all do not take into account evidence discussed in the previous chapters.   This is firstly, that the majority of the approximately 20% of men and women who anonymously report having experienced some same-sex attraction do not acknowledge this in non-anonymous interviews, and secondly, that most of those who do acknowledge it both anonymously and non-anonymously identify as heterosexual.  Hence most theories of causation of homosexuality treat it as a categorical state and rely on the statements of the men and women investigated that they are homosexual, bisexual, or heterosexual.  The theories are therefore based on studies of the less than 3% of the population who identify as homosexual or bisexual.  Causes of the homosexual feelings of the homosexual heterosexual majority with these feelings remain unexplored.

Greenberg pointed out such theories have a long history, with some focussing on environmental and others on biological causes. In an account attributed to Aristotle in the fourth century B.C., men who enjoyed being subjected to sexual intercourse, that is, those who took what is now commonly termed the passive role, were considered effeminate due to being anatomically constituted contrary to nature.   Their seminal fluid was believed to be secreted in the rectum, rather than in the genital system.  Further it was claimed that the seminal fluid caused the region where it was secreted to produce sexual excitement in response to friction.   In these men the secretion was small in quantity and did not force its way out, but quickly cooled down, resulting in their being insatiable like women. The homosexual behavior of the presumably larger number of men who took the active role, many of whom would be equivalent to contemporary homosexual heterosexual men, was not considered to require explanation in classical Greek and Roman society, as it was considered part of normal sexuality.   The second century scientist Ptolemy, best known for attempting to reconcile the observed movements of the planets with the theory that like the sun they all moved round the earth, related sexual preferences to the influence of planetary configurations. The fifteenth century Platonic scholar Marsilio Ficino observed that some men naturally loved men and this was especially true of those at whose birth Venus was in a masculine sign. An Italian surgeon of the time, William of Bologna, attributed lesbianism to a growth from the mouth of the womb appearing outside the vagina as a pseudo-penis.  Greenberg dismissed this theory with the comment that it was obviously not derived from clinical observation.   In fact as a surgeon William may have observed some women with lesbian tendencies who showed enlarged clitorises.   As discussed subsequently this association can occur due to congenital adrenal hyperplasia.  In a 1749 English pamphlet homosexuality was attributed to defective upbringing.  Boys were then being raised at home rather than, as previously, being apprenticed or sent to boarding schools.  The pamphlet argued that they were pampered by their mothers and kept from the rough and tumble play of boys so that they grew up effete, without the manly traits that would enable them to dominate and thus satisfy women.  Being unable to please women they chose rather to be involved in unnatural vices with one another.   This explanation has much in common with a psychoanalytic theory, discussed in the next section.


Psychosocial theories fail to account for homosexual heterosexuality 

In the discussion in his 1948 book of the possible factors determining homosexual behavior, Kinsey emphasized the importance of acknowledging that existence of a gradient of homosexuality with a significant number of people he rated as Kinsey 1 and 2 who were predominantly but not exclusively heterosexual and Kinsey 4 and 5 who were predominantly but not exclusively homosexual.  Ignoring this, in arguing that homosexuality results from negative psychosocial experiences, psychosocial theories treat homosexuality as a categorical condition. which results from negative psychosocial experiences.   In the absence of such experiences heterosexuality results naturally.   The theories can therefore provide no explanation for the development of homosexual feelings in the majority of men and women with these feelings, the homosexual heterosexuals.   Instead they  ignore their existence.

Psychoanalytic theories: parental relationships

The earliest and still influential psychosocial explanations for categorical homosexuality were based on psychoanalysts’ interpretations of the case histories of men and women who reported homosexual feelings or behaviors in the course of treatment and were therefore labeled as homosexuals.  The analysts’ interpretations were of course subject to possible bias both by the patients and the therapists.  Freud, the initiator of psychoanalysis, attributed homosexuality to a deviation in the development of what he termed the Oedipus complex. This complex is the central concept of psychoanalytic theory.  Freud postulated that when aged about three to five boys love their mother, and wish to replace their father as her sexual partner, but fear that in response their jealous father, as a talionic (eye-for-an-eye) punishment, will castrate them.   Oedipus was the hero in Greek mythology who killed his father and married his mother, not aware that he was related to either.   When he learned what he had done, he put out his eyes, interpreted by Freud as symbolic self-castration.   Freud believed that the nature of a boy’s relationships with his mother and father determined the way he dealt with his Oedipal feelings and hence his future emotional health.    Freud accounted for the development of women by a variation of this theory.  When a girl was aged three to five she realized she did not have a penis.   Suffering penis envy, she concluded she had been castrated by her mother as a potential rival for the love of her father.   Her resulting negative feeling to her mother was termed the Electra complex.   In Greek mythology, Electra encouraged her brother to kill their mother because she had killed their father.  Freud believed that constitutional factors, that is factors present at birth, as well as parental relationships could influence the development of the Oedipus or Electra complex and so contribute to the causation of homosexuality.

In 1962 the psychoanalyst Bieber advanced a concept which still influences the thinking of the general public.  He concluded that only experiential and not constitutional factors were responsible for homosexuality.  Bieber was the first analyst to provide research data to support his theory.  He examined the case histories of 106 men labeled homosexual and 100 men labeled non-homosexual, all of whom had sought treatment with 77 therapists. He was aware which label was given the men, a possible source of bias.  Bieber found the homosexual men tended to report to the analysts that their mothers established close-binding often explicitly seductive relationships with them, producing sexual over-stimulation and intense guilt and anxiety about heterosexual behavior, so promoting compulsive homosexual activity.  He found the fathers of the homosexual men were often detached, hostile and rejecting, so that they did not act as male models to protect their sons from demasculinization.  Bieber also found that in comparison to heterosexual men treated, significantly more of the homosexual men in childhood were fearful of physical injury, avoided fights, played predominantly with girls and avoided participation in competitive sport, that is they showed opposite sex-linked behaviors.  This association was established by the research discussed in Chapter 2, where it is pointed out that homosexual heterosexual men and women also show more opposite sex-linked behaviors.    As Bieber classified the men studied as homosexual or non-homosexual this association would have been over-looked.   Like the 1749 English theorist, Bieber attributed these behaviors of the homosexual men to maternal over-protection.   In contrast Bene pointed out in 1965 that a number of investigations of male homosexuals found the presence of poor relationships with their father to be more common than undue attachments to their mothers, and provided further data to support this finding.  She subsequently reported evidence that homosexual women experienced parental relationships similar to those of homosexual men. She concluded that the role of the father was more important than that of the mother in causing homosexuality in men and women.

The association of homosexuality with poor parental, and particularly paternal, relationships could be due not to the relationships producing homosexual feelings but to parents responding negatively to the childhood sissy and tomboyish behaviors of men and women with homosexual feelings, including the homosexual heterosexuals.  Silove and I reported evidence supporting this conclusion.   Men who anonymously reported a number of opposite sex-linked in their childhood and currently were more likely to have current negative parental and particularly paternal relationships and to have had negative paternal relationships in childhood.  However some opposite sex-linked behaviors shown by the men were associated with their experiencing maternal overprotection in childhood and adolescence, consistent with the findings of Bieber.  Opposite sex-linked behaviors anonymously reported by women were more consistently associated with negative relationships with both parents.   In relation to the consistent findings of negative relationships of men categorically classified as homosexual with their fathers, Harry found that homosexual as opposed to heterosexual male undergraduates reported experiencing more parental physical abuse in adolescence, the extent correlating with features of childhood femininity. The questions used did not allow him to determine whether the abuse was parental or maternal.  However the finding that abuse was more strongly related to negative relationships with fathers than mothers suggested paternal abuse was the major form.

Learning theories: conditioning

In the 1960’s learning theories begin to compete with psychoanalytic theories to provide psychosocial explanations for human behavior, including homosexuality.   One was based on conditioning, a form of learning discovered by the Russian physiologist, Pavlov, around 1900.  He found that dogs when regularly given food following a signal, such as the ringing of a bell, would after a time commence to salivate to the sound just as they did to the food.  Pavlov considered a connection was set up in the dog’s brain that linked the areas of the brain that represented the food and the sound.   He termed the learned response to the sound a conditional reflex, and the following of the sound with the food, reinforcement.  If after the conditional reflex to food was established, the sound was regularly repeated, but not reinforced by being followed by food, it gradually ceased to produce salivation.  The conditional reflex was said to be extinguished. In 1965 McGuire, Carlisle, and Young  suggested homosexuality was produced by conditioning.  An initial sexual experience with a member of the same sex supplied the basis for subsequent fantasies accompanying masturbation.  The resulting regular temporal association of fantasized members of the same sex with sexual arousal led by conditioning to their producing sexual arousal in the subject, both in fantasy and reality.   At the same time, any possible arousal by members of the opposite sex was extinguished through lack of reinforcement.   A similar theory had been advanced by Aristotle in Historia Animalium, when he argued that the sexual activity of adolescent boys with men should be controlled because the memory of pleasure experienced brings forth the desire to renew the connection which accompanied this pleasure.

The conditioning theory provided the basis for the introduction of aversive therapy in the 1960’s, to attempt to convert homosexual to heterosexual feelings.  Studies investigating the use of this therapy are reviewed in Chapter 5.  In 1978 I reported evidence that conditioning did not modify the physiological basis of sexual orientation.  Some men who sought treatment because of problems controlling homosexual feelings were married and had experienced regular and satisfying heterosexual intercourse with their wives.   It could be expected that conditioning would have led to their sexual arousal to women being increased by the arousal being regularly associated with the presence of their wives.  This did not occur.  Their penile volume responses to moving films of nude women and men demonstrated the same level of sexual arousal to men and women as did the penile responses of men who sought treatment for problems with homosexual feelings who had no experience of heterosexual intercourse.  As discussed in Chapter 5, this method of assessment of penile volume responses provides an accurate measure of men’s degree of heterosexual and homosexual feelings.

Unlike the psychoanalytic theory of Bieber the conditioning theory provided no explanation for the association of homosexuality in adulthood with opposite sex-linked behaviors in childhood, discussed in Chapter 2.  However like that theory, it can account for the development of exclusive homosexuality, but not for the presence of homosexual feelings in the much larger number of homosexual heterosexual men and women with these feelings, but predominant heterosexual feelings.  This was particularly true of the theory advanced by some psychoanalysts as well as learning theorists that fear and consequent avoidance of heterosexuality were major determinants of homosexuality. Ellis in reviewing theories of the causation of homosexuality in 1996 reported that a 1990 survey of psychiatrists and other physicians in England, found that over half considered homosexuality largely due to fear of heterosexual activity and/or unsuccessful heterosexual experiences.  He also cited a finding opposing the fear of homosexuality theory for lesbian women.  They recalled no more traumatic experiences with men than did women who identified as heterosexual.

Stoller and Herdt in 1985 criticized the conditioning theory of the etiology of homosexuality using anthropological evidence concerning the Sambia, an isolated New Guinea tribe.

As a phase in their initiation, prepubertal boys fellated postpubertal males.  The boys were told that they needed to ingest semen to become masculine adults. The postpubertal males enjoyed being fellated and only experienced heterosexual activity when they married in their late teens or early 20’s.  Stoller and Herdt stated that only a few mature men ever again had sexual activity with boys and most loved their lust for women, a lust Stoller and Herdt considered the conditioning theory predicted should not be there. They gave an account of one man they termed an aberrant case who in adulthood was indifferent to hunting, no fighter, and preferred gardening, an activity of women and older men.  Prepubertally, he had wished to be born a girl and though he feared and resisted initiation, he rapidly commenced to enjoy performing fellatio.  Following puberty he enjoyed being fellated.  He failed to consummate his marriage and continued sexual activity with boys, harboring taboo wishes to fellate them.  Herdt and Stoller attributed his aberrant development to his unusual childhood.  His mother was rejected by his father and he was told his father was dead.  His mother became bitter to all men, and withdrew from community life, including contact with men.  Stoller and Herdt considered the unavailability of the father as a man worthy of identification prevented adequate resolution of the Oedipus complex, so that the subject remained excessively identified with his mother. Again this analysis of the sexual behavior of the Sambian adults accepted the categorical classification that men were either heterosexual or homosexual, and did not consider the possibility that anonymous reporting may have revealed the presence of homosexual heterosexuals among Sambian men.   Certainly the fact that most of their overt homosexual behavior took place before adulthood makes it compatible with the homosexual behavior in the representative sample of United States men studied by Laumann et al. discussed in Chapter 1.  Many of these men would be classified as homosexual heterosexuals.

Social learning theories

Baldwin and Baldwin in 1989 re-analysed Sambia men’s development from a social learning perspective, pointing out the need to include social and cognitive factors in addition to direct conditioning experiences. They considered that the heterosexual development of most Sambia boys could be due to their thinking about attaining the high status of manhood while fellating postpubertal males, so interfering with the conditioning of homosexual arousal. Also as the boys were initially coerced into fellatio, their negative reactions could cause them to fantasy doing something else, again interfering with conditioning. Baldwin and Baldwin pointed out that the man termed an aberrant case was socially isolated and in addition experienced aversive socialization, with “humiliation, banishment and bastardization dominating his childhood”. They suggested his reported enjoyment of fellating postpubertal boys could be due to the experience being his first truly rewarding social interaction. This positive response could therefore cause him to experience sexual arousal to the boys, which by conditioning would produce his later homosexual feelings.

Both Herdt and Stoller’s and Baldwin and Baldwin’s accounts are typical of psychoanalytic and social learning explanations of human development.  Apart from the commitment to the categorical classification of subjects as homosexual or heterosexual, both plausibly accounted for the histories of the men who were studied, but made no attempt to deal with relevant additional data.  Neither of the accounts referred to the evidence demonstrating that homosexual feelings and/or behaviors are associated with opposite sex-linked behaviors in early childhood, not only in men and women who identify as homosexual, but also in those who anonymously report non-predominant homosexual feelings.   Evidence of these associations had been reported by the time they were writing.  Dislike of fighting and interest in women’s activities were shown by the so-called aberrant man in his adulthood.  Herdt and Stoller did not report whether these and other sex-linked behaviors were shown by him in his childhood prior to his commencing fellating older men.  Such behaviors if present would have suggested he was already predisposed to experience homosexual feelings. Both approaches also demonstrated no awareness that a theory is not scientifically acceptable because it plausibly accounts for certain data. It is necessary that it also provides reasons to reject other equally plausible theories, and ideally should be capable of predicting future events.  Freud himself said of psychoanalysis that it cannot predict an event, although after the event psychoanalysis can explain it with certainty.

Theories that attribute homosexuality exclusively to social factors and totally exclude biological factors have some difficulty dealing with the extensive data demonstrating that the opposite sex-linked behaviors associated with adult homosexuality appear at a very early age.   In 1966 Zuger found  the marked effeminate behaviors he studied began in many of the subjects almost as soon as their motor and speech development allowed their manifestation. This early development cannot be explained in terms of inadequate resolution of the Oedipal situation as this situation does not develop until after three years of age.  To account for it social learning theories need to postulate that the children showed opposite sex-linked behaviors by modeling their behavior on that of the significant role models to whom they were exposed in their first two to three years.  These models would generally be their parents.  However Maccoby, a leading authority of childhood development, reported in 1980 that she found no relationship between the degree to which children and their parents showed same and opposite sex-linked behaviors.  Clinicians’ impressions concerning the families of effeminate boys have varied widely.  Green and Money considered a lack of forceful paternal dominance, greater maternal concern, and the relatively fragile build of many of the boys, were important factors producing their effeminacy.  Stoller believed that the pre-school effeminate boy’s parents found his femininity most endearing and encouraged it.  Zuger considered the closeness of effeminate boys with their mothers was secondary to their femininity, rather than responsible for it.  Bakwin and Bakwin found the families of effeminate boys were not unusual and concluded from this and the early age at which the behaviors appeared that they were biologically determined.   The many studies of children reared by openly lesbian and gay couples support the conclusion that sexual orientation is not influenced by parental role modes.  Patterson in a 1996 review pointed out the studies found the children showed no greater levels of sex-atypical behaviors and interests than did children reared by heterosexual parents.

Self-labeling theory, referred to in Chapter 2, remains a popular social learning explanation of homosexuality.  While it makes no attempt to account for the presence of homosexual feelings in homosexual heterosexuals or for early development of opposite sex-linked behaviors in children who later identify as homosexual, it does provide an explanation why children who show such behaviors are likely to later identify in this way.   This theory points out that boys and girls who show these behaviors are labeled as sissies or tomboys, terms which imply they are potentially homosexual.  This leads to them labeling themselves in this way and therefore becoming sexually attracted to members of the same sex.   A related theory is that boys and girls who for unexplained reasons show minimal same sex-linked behaviors feel inadequate when faced with social demands to be masculine or feminine, respectively, and so seek refuge by adopting opposite sex-roles.

Social constructionist theories

Social constructionist theories like the earlier social learning theories attribute the development of personality factors entirely to social factors but depart from those theories by rejecting the scientific method to establish their conclusions.  Celia Kitzinger approvingly pointed out in her 1995 discussion of the application of these theories to the development of sexual identity, that the theories take little interest in findings established by empirical research, but rather challenge the methodology of such research.  Adopting a post modernist approach, scientific findings are rejected as not taking into account the historical and social context in which they were made.  The role of male power in the social construction of meanings, rhetoric, and narrative in establishing science, is considered to invalidate its findings as science is one of the means by which the patriarchy maintains the oppression of women.   Kitzinger pointed out that writers who considered the possibility that biological factors contributed to sexual identification, are labeled essentialists, often as a term of abuse.  Those who attempted to avoid the label by pointing out that they accepted that social factors also contributed were closet essentialists who should be outed.  She stated that any theorists who claimed there is or could be scientific evidence offering accurate facts about homosexuality against which the theories or beliefs of social constructionists could be judged are essentialists, despite their self-designation as social constructionists.

In applying social constructionist theory to homosexuality Kitzinger retained the categorical classification that men and women are either heterosexual or homosexual.  She considered that in understanding homosexuality the concept advanced by Foucault in 1978 in his History of Sexuality remains central for many who adopt the social constructionist view.  This concept is that when doctors commenced to consider homosexuality to be an illness, to use Foucault’s widely quoted statement “The nineteenth-century homosexual became a personage, a past, a case history, and a childhood, in addition to being a type of life, a life form, and a morphology, … with a possibly mysterious physiology… The sodomite had been a temporary aberration; the homosexual was now a species.”   Foucault thus argued that prior to the nineteenth century homosexual behaviors, commonly labeled sodomy, were regarded as isolated acts.  There was no concept of a “homosexual” as a person who had a disposition to carry out homosexual acts or who experienced homosexual feelings.  Kitzinger also pointed out that  social constructionist research on sexuality was often believed to have been initiated by a 1968 paper by Mary McIntosh which proposed that the homosexual should be sen as playing a social role rather than having a condition.   McIntosh considered the homosexual role did not exist in many societies, and only emerged in England towards the end of the seventeenth century. Kitzinger did not deal with the apparent conflict between this view and that of Foucault that prior to the nineteenth century the concept of a homosexual role did not exist.   It may be she considered holding two opposing views by social constructionists was compatible with their post modern perspective.

Homosexuality: a disposition or a temporary aberration

Whether homosexual behavior and feelings result from a disposition or are a temporary aberration has major implications for theories of its causation.   Such theories are not required if they do not express a disposition.  Instead what then needs to be explained is why men and women adopt aberrant behaviors that have at times been regarded as sinful and punished by torture and death.   However there is extensive evidence dating back to ancient Greece and Rome to oppose Foucault’s belief that the homosexual role did not express a disposition but was a social construct of the nineteenth century.  The concept of someone who was innately and exclusively homosexual was implicit in the account Plato, writing in the fifth century B.C., attributed to Aristophanes in his Symposium, discussed in more detail in Chapter 4.  Aristophanes described women who directed their affections towards women and gave little attention to men, and men who loved men throughout their boyhood, and took pleasure in physical contact with them. In adulthood, these men became lovers of boys, and it required the compulsion of convention to overcome their natural disinclination to marriage and procreation; they were quite content to live with one another unwed.   Boswell stated in his 1990 book that this account contained the only classical Greek reference to lesbianism as a concept.  Male homosexuality was of much greater concern in all their discussions of sexuality.  Only males were thought to have the moral character and intelligence necessary for friendship and possibly for real love.  As pointed out earlier Aristotle in the fourth century B.C. had suggested an anatomical reason why men who enjoy being subjected to sexual intercourse were effeminate by nature.  Dover in his book on homosexuality in ancient Greece commented that Greek recognition that some people are more homosexual that others need not surprise us.  He quoted a reference in legal writings to the extraordinary enthusiasm of an Athenian man for homosexual relations, and Xenophon’s use of the word tropos, translated as way, character, disposition, or inclination, in describing the behavior of another man known for his strong attraction to youths.

Boswell pointed out that in classical Rome awareness of the existence of adult males who preferred to be penetrated were common enough they were given a special name and he believed their behavior was not disparaged if they were not male citizens.  He also found writings of the time  pointing out that some men and women showed a consistent preference for members of one or the other sex.  A character in a novel claimed that it is possible to discern the sexual preference of a friend by noting the gender of his servants.   The Roman emperor Hadrian was considered to have been sexually interested exclusively in males, and a young woman’s marriage in second or third-century Rome was said not to necessarily indicate anything about the direction her sexual preferences for men or women.  Boswell concluded that though the earlier constructs of homosexuality may have differed from contemporary ones, this did not mean there was no awareness of specifically homosexual or heterosexual orientations in earlier societies.  There was sufficient evidence that they were common and familiar concepts, but received little attention as they had minimal social or ethical impact.  Eva Cantarella in her book on bisexuality in the ancient world pointed out that Martial in one of his satires attacked a women as having no interest in men and being only interested in genital sex with women.  She also cited a reference in a Roman book on diseases to women who are more interested in sex with women than with men.  They were termed tribades and considered like molles, that is, male passive homosexuals, to have a mental disease.  Apart from molles Cantarella considered the Roman terms, cinaedi, pathici, and effeminati were used to describe passive male homosexuals and that for the ancient world an effeminate person meant a passive male adult.

Paul’s epistle to the Romans (1: 26,27) has been interpreted as treating homosexuality as a disposition rather than as a aberrant behavior:   “God gave them up unto vile passions: for their women changed the natural use into that which is against nature: and likewise also the men, leaving the natural use of the woman, burned in their lust one toward another, men with men working unseemliness…”  However the few references to homosexuality in the Bible suggest male homosexuality, both active and passive, was considered a sin rather than a disposition.  Leviticus 20, 13 stated that “If a man lie with mankind, as with womankind, both of them have committed an abomination; they shall surely be put to death; their blood is upon them.”   The change from treating involvement in homosexual activity as a disposition to a sinful choice may have been related to the change in attitude to active homosexual behavior which occurred in later Rome under the influence of Christianity, discussed in more detail in Chapter 4.  Like passive behavior it became regarded negatively and requiring punishment.  In Athens and early Rome while passive homosexual behavior by adult citizens was considered contemptible, it was accepted that many, perhaps most men would naturally take any available opportunities to have sex with passive males.

Christian Roman laws punishing men for homosexual behavior, active or passive, were retained in Christian Europe after the fall of Rome. However Boswell considered that at least at some periods in Christian Europe homosexual men were aware that other men had a similar disposition to the extent they could be regarded as a community.  A claim made in Renaissance Florence that sodomites defended themselves with scriptural references, was considered by him to indicate a considerable degree of cohesion and defensiveness on the part of such a community.  In his 1980 book he described what he termed a gay subculture which developed in Europe from 1050-1150 with its own slang which became diffused among the general population.  The word Ganymede was used as a term for gay people in general.   Ganymede was the beautiful boy abducted to Olympus by Zeus to be his cup-bearer and one of his sexual partners.  Boccaccio writing in the middle of the fourteenth century in the Decameron referred to a man who was as fond of women as a dog was of the stick and that in the “use against nature” (that is, sodomy) he had not his match among the most abandoned.  In another of his stories, a wife complained that when she married she had supposed her husband had the desires which men had and should have, but women were not to his mind.   She and her husband resolved the difficulty by sharing the services of a youth.   Nickie Roberts in her 1003  book “Whores in History” cited a 1230 reference to prostitutes abusing clerics who rejected their approaches as sodomites, indicating they believed that sodomy was associated with a disposition to lack sexual interest in women.

Hergemoeller in his book on the persecution of homosexuals in the Middle Ages reported that the Paris bishop Guillaume d’Auvergne in 1230 wrote that “it is the custom that sodomites stick out their sexual organs at one another and this is a sign that they recognise one another.” Hergemoeller commented that it showed that the bishop regarded sodomites not as isolated figures, but as a group which had an internal code of signals.  Based on the records of legal prosecutions of sodomites in Venice and several German cities in the fifteenth and sixteenth centuries, he concluded that in these cities there were areas where men sought sexual contact with other men.  These areas included particular inns and shops, the wall and fortification installations, and public conveniences.   He added that studies in Paris, London, and Amsterdam showed that in the following centuries these conveniences expanded into a network of what were termed tea houses.   Similar methods of seeking partners for casual sex by subcultures of homosexual men would seem to have been used for centuries, paralleling the contemporary behavior of homosexual men termed cruising beats.     Hergemoeller also found records of men who during the Renaissance were executed, commonly by burning, having been found to have dressed as women for several years and adopted female names.  Some had concealing their genitalia to act as prostitutes with men.

Greenberg also reported evidence of urban social networks of homosexual men which had persisted from medieval times or emerged during the Renaissance.  The University of Bologna in 1375 was stated to be infested with sodomites, who were denounced.  Many escaped when warned by a sodomite priest.  In Venice a coterie of homosexual sodomites came to light in 1406, and in 1488 the authorities sealed off the porch of a church to stop the sodomites from using it as a gathering place. The observation of the fifteenth century Platonic scholar Marsilio Ficino that some men naturally loved men was quoted earlier in this chapter.  Greenberg interpreted the account by the French humanist, Montaigne of observing a marriage of male couples in a church in Rome in 1580 as evidence that sodomy as a disposition was coming to be accepted by some elements within the church.  Boswell also made this interpretation when he reported that following the marriage many of those involved were executed by burning.  He considered the fact that many were involved suggested the existence of a community.

Greenberg found documentation of male homosexual networks in the larger French cities of the fifteenth and early sixteenth century.  Comedies celebrating male homosexuality, produced by subcultures, were performed as street theatre during the annual Carnival season.  These networks continued into the seventeenth century. In his 1990 book Boswell cited a description by Louis XIV’s sister-in-law of the sexual preference of men at the seventeenth century French court which he considered similar to those encountered to-day.  Some preferred women, some liked both men and women, some preferred men, some preferred children, and some had little interest in sex.  Greenberg reported that throughout the eighteenth century cafes in Paris catering to men with homosexual tastes flourished without police interference.  Towards its latter part lesbianism was said to have become almost fashionable especially among actresses and women of the French court.  They patronized certain cafes, some of which were also frequented by men from the homosexual subculture, and they also met at private social gatherings from which men were excluded.  Greenberg commented that their incomes and independent social lives enabled these women to create an urban lesbian culture, probably for the first time in history.  Despite the severe repression of sodomy by the Inquisition in Portugal and Spain, male homosexual social networks developed in both countries.  Greenberg cited an observation that “in seventeenth century Lisbon, there were inns openly patronized by sodomites, balls where transvestites danced… and men who served as go-betweens for male sexual encounters.”   As noted earlier in Paris, in Spain a subculture emerged in the cities where men used an elaborate system of signals to recognize one another. van der Meer in his article on sodomy and the third sex reported evidence from records and related writings, mainly in relation to the legal persecution of sodomites in the Netherlands, that the concept of same-sex activity as part of a role, rather than casual acts developed there in the period from the late seventeenth to the second half of the nineteenth centuries.

Greenberg considered a subculture organized around homosexual choice was not at first established in England, due to the failure of homosexual men to develop a specific identity.   He attributed this to the homosexual behavior of the members of the court of James I, including the king himself, as well as of the rakish characters of plays written following the restoration of Charles II, so that homosexuality was not then exclusive.  He continued that homosexual networks formed in the eighteenth century, even in smaller towns.  Bath had its own topography of sodomy, safe-fields, pick-up streets and he believed this was also the case in Dublin, York, Bristol, Exeter, and Norwich.   They were rudimentary compared to London where there were parks and walks where men seeking homosexual contacts could meet.  As discussed in Chapter 2, clubs and taverns known as molly-houses where homosexual men could socialize served as more sheltered areas.

In Fielding’s 1742 novel “The History of the Adventures of Joseph Andrews”, the failure of the virtuous Joseph to respond to the advances of Lady Booby, is said to be imputed by her to his youth, his folly, his awe, his religion, to everything but what would instantly have produced contempt, want of passion for her sex; or that which would have aroused her hatred, want of liking for her.  As pointed out in Chapter 2, in Smollett’s 1748 novel, “The Adventures of Roderick Random”, the attendants of the effeminate captain accused of maintaining a relationship not fit to be named are considered to “be of their patron’s disposition”.   Later in the novel Roderick is informed that Earl Strutwell who had promised him help in advancing his career was notorious for a passion for his own sex.   Greenberg cited an 1824 report on the state of the French prisons by the physician Louis-Rene Villerme which distinguished the “circumstantial” homosexuality of inmate “pederasts” who played the “male” role, from that of their “female” partners called gironds or petits jesus, whose involvement was instinctive or preferential.

This evidence that over centuries and in various cultures there was a concept of the homosexual as, to quote Foucault, a personage and a life form means the concept cannot have been socially constructed by the medicalization of homosexuality in the nineteenth century.  If  the homosexual role is the expression of a disposition, then theories of causation of sexual orientation need to account for this disposition, and of course for the presence of the homosexual feelings in the women and men who adopt this role, but also in the much greater number of homosexual

heterosexuals.  The failure of social constructionists to acknowledge this evidence of a homosexual disposition, incompatible with the view of Foucault, a view regarded as central to their theory of the cause of homosexuality, is consistent with their rejection of scientific evidence.  As Kitzinger pointed out this rejection had always been a feature of radical or strong social constructionism and became particularly prominent in its postmodern form.

Sexual scripts

Kitzinger said John Gagnon and William Simon were other sociologists frequently cited as originators of social constructionism.  They believed that sex was not an instinctive force or biological drive, controlled by inner psychic forces or hormonal fluctuations, but rather a social construct. In their 1973 book “Sexual Conduct” they argued that sexual behaviors were determined solely by subjects putting into practice the sexual behaviors they had read about or heard described in their social experiences. Gagnon and Sinon  termed these descriptions scripts.  They considered that oral (mouth) -genital contact was perhaps the most tension producing technique in sexual experimentation of men and women when they were writing, in view of the accepted attitudes to the penis and vagina in terms of their odor, taste, and cleanliness.  In fact, anilingus, mouth-anus contact would seem more tension-producing in these terms.  The failure of Gagnon and Simon to refer to it suggests they considered it of minimal importance as a sexual practice, and believed few women and men would had encountered a script for anilingus in the current socially available descriptions of sexual behaviors.  Yet in Hunt’s 1974 investigation of the sexual behavior of U.S. women and men, a quarter of married men and women under 35 were performed anilingus, presumably without a script.

No recognition of oral-anal acts was present in the 1994 report by Johnson and colleagues of the sexual behaviors of their representative sample of the population of Great Britain.  In asking about oral sex they defined it as a man’s or woman’s mouth on the partner’s genital area, which they assumed would be taken by the subjects to mean cunnilingus or fellatio.    Anal sex was defined as a man’s penis entering a partner’s anus (rectum or back passage).  In the 1994 report of the sexual behavior of United States men and women, Laumann and colleagues also did not include oral-anal contacts in their investigation of oral and anal sex.  In their interviews of subjects, the initial question asking about oral sex stated oral sex meant stimulating the genitalia with the mouth, that is licking or kissing the partner’s genitalia or when your partner does this to you.   Subsequent questions concerning oral sex did not provide this definition.   Laumann and colleagues considered the subjects’ answers applied only to fellatio and cunnilingus.  Hence they assumed the subjects would retain the initial definition in their memories rather than they had a script for oral sex than would include oral-anal activities.

In the current literature anilingus is mainly investigated in relation to the risk of transmission of AIDs, usually in homosexual populations.  In the gay culture familiarity with it as a sexual behavior is indicated by its being termed “rimming”.   Laumann and colleagues asked the subjects about fantasies of anal stimulation by their or their partner’s fingers.   About 20% of white men and women reported the fantasy of a partner stimulating their anus with their fingers was very or somewhat appealing.  A somewhat higher percentage of men and lower percentage of women found the fantasy of their stimulating the partner’s anus with their fingers appealing.  In their discussion of the findings Laumann and colleagues treated the report that fantasies of these two sexual activities were appealing reflecting their actual practice.   Nevertheless they concluded that in general, anal eroticism has not been incorporated into the sexual script of most Americans.   The data concerning anal sexual activities therefore does not provide strong evidence for the theory that sexual behaviors are totally motivated by the limited scripts provided by society.  It is possible that while some behaviors are initiated after being learned about in scripts, others are initiated in exploratory sexual activities. Hunt believed the most dramatic changes in sexual activity that had occurred in the years prior to his 1974 study were in what he termed the formerly all-but-unmentionable oral-genital acts, which were still classified as punishable crimes against nature in most of the states in the U.S.  Whereas in the 1948 study of Kinsey and colleagues 15% of high school men included oral-penile and oral-vaginal contacts in their marital sexual activities, in Hunt’s study 55% did.  Equivalent changes in college men were from 40% to 60%, in high school women from 48% to 55%, and in college women from 55% to 72%.  Exposure to reports that these oral-genital sexual acts were being performed could have provided social scripts which played a role in this increase.   However while the nature of sexual acts could change over time under the influence of social scripts, biologically determined sexual arousal could provide the motivation to carry out the acts.  In relation specifically to homosexuality, a number of men and women, particularly in rural areas in the past, reported that when they commenced to experience feelings of attraction to members of the same sex they had been unaware that such feelings existed.  They consequently believed they were the only person in the world with them.  That is, they became aware of these feelings without a social script.  The inability of social script theory to account for the existence of homosexual heterosexuals would seem even more evident.  As their existence is ignored by almost all writers on sexuality, and they can only be identified when given the opportunity to report their awareness of feelings anonymously, there is clearly as yet no social script for this awareness.

Kitzinger considered that the debate in the 1980’s between the social constructionist and what she termed the essentialist position, that biological factors could be involved in determining sexual orientation was the hottest philosophical controversy to hit psychology for years.   She believed that the reason the debate no longer attracted the same passion was not that  one position had gained precedence, but that the debate became wearisome, and was seen as impeding developments within each theoretical position.  Academics working within one position, now made little more than token reference to the work of those within the other position.   A more plausible reason for the lack of interest in debating the social constructionist theory by “essentialist” researchers who considered biological factors could contribute, resulted from the lack agreed upon rules for debate.  Evidence obtained using the scientific method is seen as central by “essentialist”  but of no significance by social constructionists.


Biological theories account for homosexual heterosexuality

If biological factors have a role in determining sexual orientation it would be producing homosexual and heterosexual feelings.   As some biological factors could vary in strength their influence could account for the dimensional distribution of these feelings discussed in Chapter 1, with the majority of men and women with these feelings being aware of predominant heterosexual feelings, that is being homosexual heterosexuals.   However while the factors given significance in psychosocial theories account only for the presence of exclusive heterosexual or homosexual feelings, whether and how women and men with homosexual feelings produced by biological factors express them in behaviors and whether they identify as heterosexual, bisexual, or homosexual would be strongly influenced by social factors.  Social theorists have given little attention to this possible role of social factors in determining sexual identity, as this would require acceptance that biological factors are also involved.

That biological factors play a significant role in determining men’s sexual feelings is indicated by the resistance of a physiological measure of these feelings to change.   Such change would be expected if social factors significantly influenced this measure.  Changes in a heterosexual direction of feelings and behaviors have been reported to follow psychological treatments aimed at converting sexual orientation from homosexual to heterosexual in men and women who sought this conversion.  A number of articles in the October 2003 issue of the Archives of Sexual Behavior debated the significance of these changes and the ethical acceptability of the treatments employed.  I pointed out that the changes in the heterosexual direction of the reported sexual feelings and behaviors of the men treated were not accompanied by changes in the ratio of their penile volume responses to pictures of men and women.   The failure of these responses to change with treatment, dealt with in more detail in Chapter 5, suggest their physiological basis is not determined by learning but by biological processes which may be unable to be modified.   Research aimed at identifying these processes have concentrated on genetic and hormonal factors, both of which can act with varying degrees of influence.  At the same time most of the workers carrying out this research have continued to accept the categorical classification that men and women are either heterosexual or homosexual, with some accepting a third category, those who identify as bisexual, often including them with those who identify as homosexual.   In their studies the men and women are studied non-anonymously, and are asked to classify themselves into these categories.  Hence only a fraction of the approximately one in five of the population with some homosexual feelings are investigated as having these feelings, since as pointed out in  Chapter 1, only 1.4% of women and 2.8% of men stated they consider themselves homosexual or bisexual, lesbian or gay in the representative population sample studied by Laumann and colleagues.

Genetic Factors

Early in the study of sexual orientation such well-known nineteenth century writers as Krafft-Ebing, Havelock Ellis, and Hirschfeld suggested that genetic, that is inherited factors, could be influential in its determination.  They considered the fact that homosexuality seemed to be more common in some rather than other families was consistent with this belief.  Pillard in 1996 reviewed studies by himself and colleagues which supported the earlier less systematic reports of this finding.  In the studies he cited, men who identified as being bisexual, or predominantly or exclusively homosexual, had significantly more brothers, but not sisters, who identified similarly, compared to men who identified as heterosexual.  Women who identified as lesbian showed a trend to have more sisters who identified as lesbian and brothers who identified as gay than did non-lesbian women.  This and subsequent additional findings that women compared to men who identify as homosexual were more likely to have sisters as well as brothers who identify as homosexual has been considered evidence that different genetic factors cause homosexuality in women than men.

Pillard pointed out that if genetic factors contributed to the development of homosexuality it must be more frequent than expected in members of the same family.   However if this was found to be the case, it would not be proof that it was due to a genetic factor, as it could result from other factors, such as different methods of rearing within families.   He did not mention the possible relevance of a report in another chapter of the book containing his review.  This was that up to 40% of men and women who identified as gay or lesbian in a newspaper survey stated they had not revealed this identity to their family and up to 59% had not revealed it to coworkers.  If in families with more than one member aware of homosexual feelings, one openly identified as homosexual, it is likely the other members aware of the feelings would be more willing to identify as homosexual  than would members of families in which they were the only ones who was aware of these feelings.  This would result in homosexuality appearing to be more common than expected in families in which two or members identified as homosexual than in families in which only one member identified as homosexual.  Differences in willingness to identify as homosexual also needs to be taken into account in relation to the evidence discussed next, which is considered more specific in demonstrating a genetic contribution to causation of homosexuality, namely, twin and adoption studies.

Twin and adoption studies.  In twin studies, the incidence of homosexuality in identical twins (who have the same genes) is compared with the incidence in same-sex non-identical twins who like non-twin siblings have only half the same genes.   If a condition is determined totally by genetic inheritance, it should be present in all identical twins, but a half or less of same-sex non-identical twins.   If the inheritance is what is termed dominant, it will be present in half the non-identical twins.   If it is recessive, it will be present in a smaller percentage, as other genes reduce its likelihood of being expressed, termed its penetrance.   A 1952 study by Kallmann reported of 37 men who identified as homosexual and had identical twins that all the twins also identified as homosexual.   Of 26 men who identified as homosexual and had non-identical male twins, only three of the twins identified as homosexual.  If this finding had been verified by being found to be present in further studies of groups of male homosexual twins, it would have established that identification as homosexual in men was determined entirely genetically.  However subsequent studies of twins one of whom identified as homosexual found that the likelihood of the other twin identifying as homosexual was around 50% for identical and about 15% for non-identical male twins.  The few investigations of lesbian twins found similar relationships.  The findings of these twin studies therefore indicated that though genetic factors did not have a total influence in causing men and women to identify as homosexual, they had a strong influence.  The percentage who so identified, was much higher that the less than 3% of men and women who identified as homosexual or bisexual in the representative sample of the  total population studied by Laumann et al.

A 1991 study by Bailey and Pillard produced more complex findings.   They advertised in gay publications for men who identified as gay or bisexual and had a male twin or an adopted brother.   The men who volunteered were asked what was the sexual orientation of their twins, adopted brothers and any other brothers. They were also asked if the twins or adopted brothers could be sent questionnaires that included questions about their sexual identity.   Fifty-two percent of the identical, 22% of the non-identical twins, 9% of their non-twin brothers, and 11% of the adopted brothers identified as homosexual.   The finding with the identical twins was consistent with that of previous studies. However genetic factors should influence non-identical twin brothers to the same extent as they influence non-twin brothers as both have the same percentage of identical genes.   The fact that about twice as many non-identical twins identified as homosexual as did non-twin brothers indicated that additional factors to genetic ones were responsible for their identification as homosexual.  The authors considered the unexpected finding could be due to there being different causes for homosexuality in twins and non-twins, or to sampling error.  Sampling error is an error due to chance or other factors resulting in a non-typical group of subjects being selected for research.

The finding with the adopted brothers further complicated the theory of genetic causation.  Adopted brothers of course have no genetic factors in common with their non-biological siblings. Genetic influences causing men to identify as homosexual should therefore not differ in adoptive brothers and men in the general population.  The authors suggested that the finding that 11% of adopted brothers identified as homosexual rather than 3% or less, as expected from the finding of Laumann and colleagues, could have been due to the selection procedure.  Men who identified as homosexual whose male twins or adopted brothers were also homosexual, may have been more likely to volunteer for studies of sexual orientation than men who identified as homosexual whose male twins or adoptive brothers were heterosexual.  If this was the case, the selection procedure would have been likely to result not only in a non-representative increase in the number of adoptive brothers identifying as homosexual.  More identical twins both of whom were homosexual may  have been over-represented compared to identical twins only one of whom was homosexual.  This would have led to overestimation of the strength of the genetic factor, as assessed by comparing the 52% of identical twin pairs who identified as homosexual with the 3% of men in the population who identify as homosexual.

A further factor could have contributed to the unexpectedly higher number of adoptive brothers who identifed as homosexual.   Those with some homosexual feelings may have been more likely to identify as homosexual if they were members of families in which another member identified as homosexual rather than adoptive brothers who were members of families in which no other member did.  Both sampling error and the family environment in relation to the acceptance of homosexuality could therefore influence the determination of the apparent strength of the genetic factor, as estimated in family studies of volunteers.  These factors could also have biased the findings of a subsequent study by Bailey and colleagues which investigated gay or bisexual women who had a twin or adopted sister.   Forty-eight percent of the identical and 16% of the non-identical female twins, and 6% of adopted sisters identified as homosexual or bisexual.

Genetic factors in homosexual heterosexuals.   Unlike most studies investigating genetic influences on sexual orientation, ideally they should be carried out on subjects representative of the total population, and be anonymous to allow the approximately 20% of homosexual heterosexual men and women to report their awareness of  degrees of homosexual feelings, which they do not reveal in non-anonymous investigations.   These subjects have been ignored in most research investigating possible genetic causes of sexual orientation as it investigated men and women volunteers who identify non-anonymously as heterosexual, bisexual, or homosexual.  However a few studies including one by Buhrich and colleagues have used anonymous questionnaires including the Sex-linked Behaviors Questionnaire to investigate the heterosexual/homosexual ratio of feelings of male twins.   They found identical twins had more similar ratios than non-identical twins, indicating genetic factors contributed to the sexual feelings of homosexual heterosexuals.   Other studies have shown a significant genetic contribution to the development of anonymously reported opposite sex-linked behaviors in men, which as discussed in Chapter 2, are associated with degree of homosexual feelings, and are more commonly present in homosexual heterosexuals compared with heterosexuals who report no homosexual feelings.

Interaction of genetic and environmental factors.   In addition to genetic factors contributing to sexual orientation, environmental factors, biological or social, must be involved to account for the finding that only about half the identical twins of men and women who identify as homosexual also identify as homosexual although they have the same genes.   The possibility needs to be considered that genetic factors operate to cause both identical twins to have the same ratio of homosexual to heterosexual feelings, but in some twins social factors influence one but not the other to identify as homosexual. This can be ruled out as a total explanation.  Blaszczynski and I investigated the penile volume responses to moving pictures of nude men and women of a pair of identical male twins only one of whom identified as homosexual.  The twins’ reports that one experienced predominant homosexual and the other predominant heterosexual feelings were confirmed by their penile volume responses.  In reporting the finding in 1980 we reviewed the studies of other male twins of whom one identified a heterosexual and one as homosexual. In all cases the twin who identified as homosexual showed increased opposite sex-linked behaviors, in particular reduced rough and tumble play in childhood, compared to the twin who identified as heterosexual.  The hypothesis is discussed subsequently that the levels of sex hormones to which men and women are exposed prenatally (before birth), influence both their sexual feelings and sex-linked behaviors, such as rough and tumble play.  If it is correct the finding of greater opposite sex-linked behaviors in each homosexual compared to his heterosexual identical twin suggests that in prenatal development the homosexual twin was exposed to a reduced level of male hormones compared to the heterosexual twin.  Identical twins share the same placenta.  In 15 to 30% this results in a transfusion syndrome which impairs their blood circulation.  As a consequence identical twins have about twice the number of congenital malformations and three times the fetal death rate of non-identical twins or single born children.  Predominant homosexual feelings in one identical twin could therefore be due the transfusion syndrome or other factors differentially stressing that twin and so altering his or her but not the co-twin’s levels of sex hormone at a critical period in their prenatal development.  

The “gay gene”.   The most powerful evidence of a genetic contribution to sexual orientation would be finding genes which influenced it.   The media in the early 1990’s widely reported such a finding, the discovery of what was termed the gay gene by Hamer and colleagues.  These authors investigated families in which at least two brothers identified as homosexual.  A number had maternal relatives who also identified as homosexual, suggesting that in them homosexuality was transmitted through the mother rather than the father.   Women have two X chromosomes  (strings of genes), whereas men have one X and one Y chromosome.   Genetic transmission that occurs through mothers only must be through their X chromosomes.   The authors therefore sought for the responsible gene in the X chromosomes of the brothers and found a similar linkage of genes at a particular location on the chromosomes of  33 of 40 pairs of brothers, an association very unlikely to be due to chance.   The finding is yet to be replicated, that is found by other researchers.   As discussed in Chapter 1, Hamer’s study found that almost all relatives of the gay men studied were easily categorized as either gay or straight with few if any in between, and that most men who reported any attraction to men reported predominant or exclusive attraction to them.   This finding at variance with the substantial evidence that the majority of men who anonymously report homosexual feelings also report predominant heterosexual feelings suggests that the non-anonymous self-reports of many of the relatives could not be considered truthful.

Independent evidence that genes on the X chromosome can in part determine homosexual interest was provided by a study of 16 men with the chromosomal abnormality XXY, that is, with  two instead of one X chromosomes.   The 16 were identified among 4139 men investigated by Schiavi and colleagues. Compared with matched normal chromosomal XY men, the XXY subjects reported significantly less pleasure in gymnastics and less interest in boys’ games and were judged as significantly less masculine by an interviewer blind to their chromosomal condition. Significantly more reported having engaged in homosexual activities.  The authors commented that no significant familial or early environmental differences were identified between the XXY and XY men.

Homosexuality and evolution.  That homosexuality could be in part genetically determined has been questioned on the basis that the genes responsible would be eliminated by natural selection, as homosexual behavior would be detrimental to the survival of the species.   Miller in a recent article in the Archives of Sexual Behavior made the ill-informed statement that homosexuals, lacking attraction to females, produce relatively few descendants.   He concluded that whatever a population’s initial homosexuality rate was, that rate would soon diminish to virtually zero.  Bell and Weinberg in their 1978 study found men who identified as homosexual had one-third and women who identified as homosexual had one-half the number of children than did the heterosexual comparison group.  It is not known how many children the much larger number of unidentified homosexual heterosexuals have.  If there is a genetic contribution to the presence of homosexual feelings, men and women with some homosexual feelings whether predominant or not, would carry genes which would influence the degrees of homosexual feelings in their children.  There is no reason to believe the number of women and men with a homosexual component who have children is insufficient to maintain the current prevalence of homosexual feelings in the population.

Theorists with an evolutionary perspective have argued that as homosexual behavior has not been eliminated over time it must contribute to the survival of the species.  This contribution could be through the association of homosexual feelings with sex-linked behaviors.  Hutt in 1972 argued that these behaviors had developed due to evolutionary pressures.  She reviewed evidence that most men as compared to women showed greater sense of direction, agility, strength, aggression, and ability to enjoy the company of male groups and to function in a hierarchical team in co-operative activity.  She considered that in the long period in which men’s major role was to hunt over wide-ranging territories men with these qualities would be more effective hunters and so increase the likelihood of survival of the tribes to which they belonged.   Hence by natural selection the percentage of men with these qualities would increase.   The major role of women was to care for children and gather food closer to where they lived.   Women would therefore be selected who showed greater skills in nurturing children and the sick and injured and in interacting socially, as they needed to cooperate with the other women with whom they lived closely.  Hutt reviewed evidence than women had greater esthetic, social and religious interests and men, greater political and theoretical interests.  Her generalizations included that boys were object-oriented and had better differentiated concepts with respect to impersonal matters, termed instrumental abilities; girls, being person-oriented, differentiated more subtly along social and emotional dimensions, termed emotional-expressive abilities.

Evolution and the homosexual heterosexuals.    I suggested in 1993 that rather than all men and women having totally same-sex behaviors, the presence of some men and women with opposite sex-linked behaviors in a tribe could give it additional flexibility and creativity. This flexibility would seem particularly desirable in the complex human societies that have evolved from the earlier tribes and have resulted in an enormous increase in human population.  These societies require men and women to adopt a wide variety of roles both occupationally and socially and to interact with varying degrees of intimacy. Women and men with greater opposite sex-linked behaviors may be more suited to some of these roles than those with less such behaviors.  A 1971 study by Mussen provided data consistent with this speculation.  Males aged 17 to 18 years with more masculine interests and instrumental rather than emotional-expressive characteristics, showed better social adjustment and a relaxed happier attitude than did those with the opposite characteristics.  When they were in their early thirties the males who had more feminine characteristics showed greater leadership ability, social initiative and sense of personal worth.   Different sex-linked behaviors would appear to be more valuable in different circumstances.

If the genes which produce sex-linked behaviors also produce sexual feelings this would account for the association of the degree of same to opposite sex-linked behaviors with the degree of heterosexual to homosexual feelings, discussed in Chapter 2.  If the association does result from the action of the same genes the percentage of men and women selected by evolutionary pressure because they had a degree of opposite sex-linked behaviors would also have had a degree of homosexual feelings.  If this theory is correct, the dimensional distribution of sexual feelings in women and men with the majority with homosexual feelings having predominant heterosexual feelings is a by-product of the evolutionary selection of men and women who have different degrees of the same and opposite sex-linked behaviors.

Homosexuality in primates.   This theory with its suggestion that the differing social roles of women and men led to the evolutionary selection of some with varying degrees of homosexual feelings needs to be extended to take into account the homosexual behavior of their primate ancestors.   This has been neglected in attempts to explain the causes of homosexuality in humans.   Bagemihl in his 1999 detailed examination of animal homosexuality cited Vasey, a major  researcher of primate behavior, as tracing its occurrence in primates to the Oligocene period of animal development, 24-37 million years ago.   Vasey’s estimate was based on the distribution and characteristics of homosexual behaviors in contemporary primates.  In a theory related to that attributing the development of human homosexuality to evolutionary pressures, Bagemihl argued that non-sexual behaviors linked with genetically determined sexual activities by cultural learning could have increased the survival of primate species.  Though culture is typically associated with humans, cultural traditions that can be extremely complex have been observed in non-human species.  These are behaviors that are shown by some but not all groups of the species and are transmitted by learning to the young of the group.  Those observed included behaviors as diverse as foraging and hunting techniques, forms of social organization, and communication patterns, as well as sexual activities.   Certain mounting behavior of female Japanese macaques were found to be more popular in some troops over time, only to wane and be replaced by others.   Also some masturbation techniques among female primates appeared to be learned by observation.

Bagemihl considered nonreproductive aspects of animal sexuality, including homosexuality, may have contributed to a number of cultural milestones considered to characterize humans, such as the development of communication and of tools.   He pointed out that bobonos or pigmy chimpanzees, believed by some to be the primates most similar to humans, have one of the most diverse sexual repertoires of any species, with a wide variety of behaviors and positions used in sexual interactions, both heterosexual and homosexual.  As a result some bobonos developed an elaborate system of gestural communication used specifically during sex, which Bagmihl considered could have major implications for understanding primate communication systems and the development of human language.  About a dozen hand and arm gestures, each with a specific meaning, are used by the bobonos to initiate sexual activity and negotiate body positions with a partner of the opposite or same sex.  Examples include requests for the partner to move into a facing position for copulation, to spread their legs or to move their genitals around to facilitate a sexual interaction.  Bagemihl  suggested that the bobonos’ communication during sex may have evolved from crude attempts to move the partner, to become more ritualized touching and directive gestures.  This sequence resembled the progression from purely representative gestures to highly codified manual signals identified in the development of human sign languages.  It was the beginning stage of abstraction, the creation of symbols, the hallmark of human language.  A number of theorists have suggested that the first human communication system may have been a system of hand signals.

Unlike studies in which primates were taught human sign language, demonstrating that they had strong but unexpressed linguistic capacities, the bobonos devised the system of hand and arm signals spontaneously.   The social context that prompted the development was the highly variable and plastic nature of their sexuality.  Bagemihl concluded that primate evolution has been characterized by an increasing separation of sexuality from its reproductive function, including the development of numerous types of homosexual and nonprocreative heterosexual activities, most prominent in humans and bonobos.  Scientists have identified an increase in complexity of communication systems used during sexual interactions among apes, proceeding from gorillas, to common chimpanzees, bobonos, and humans.  As sexual interactions became more variable, sexual communication systems became more sophisticated.

In contrast to the earlier belief that tool use was a characteristic of humans, Bagemihl commented that over 20 different types of tool use have been identified in primates and other species.  Possibly the best-known was the use of sticks to capture and eat termites or ants.   Less well known was the use of objects for sexual stimulation.  A number of primates in both the wild and in captivity used them as masturbatory aids, at times deliberately forming them by cutting leaves or twigs.   Bagemihl pointed out that similar types of activities occur in humans, with evidence of the use of dildos made of a variety of materials for masturbation and for inducing sexual pleasure in a partner, found  in ancient Egypt and Greece, and in the traditions of many  indigenous peoples.  He added that few if any anthropologists have considered that sexual stimulation may have been a component of tool use among early humans, or even played a part in its development.  If nonreproductive sexual practices contributed to the development of communication and use of tools by humans, the increased potential to survive associated with these activities would account for the evolution of a genetic basis for an extensive repertoire of sexual behaviors, including homosexual behaviors.

Though the evidence is strong that genetic factors contribute significantly to men and women’s identification as homosexual and to the ratio of their heterosexual to homosexual feelings and the related degree of their sex-linked behaviors, it is not clear how they do so.  An independent area of research suggests it may be by altering the hormonal environment to which the person is exposed in prenatal development.

Sex Hormone Influences

When the possibility that biological factors could influence sexual preference was considered sex hormones were obvious candidates to investigate.  As with research investigating genetic factors  most of the investigations were on the minority of men and women with homosexual feelings who identify as homosexual or bisexual, compared with those who identify as heterosexual.  An initial theory postulated that homosexuality in men and women was due to their having higher levels of opposite sex hormones than did heterosexual men and women.   Acting on this theory, in the 1930’s and 40’s unsuccessful attempts were made to convert homosexual men to heterosexuality by giving them male sex hormones.   Subsequently when accurate assessments of sex hormone levels in the blood were developed, a study by Masters and colleagues attracted widespread attention which found a strong relationship between men’s testosterone levels and Kinsey scores, such that the men with lower levels showed higher degrees of homosexuality.   However a number of subsequent studies failed to find this relationship.  Almost all of the men who identified as homosexual were found to have normal levels of testosterone.    Though some studies found a percentage of homosexual women had increased levels of male hormones compared to those of heterosexual women, the women studied often included transsexual women.  Transsexual women frequently obtain such hormones from non-medical and at times illegal sources to increase their masculine appearance.  It is likely that if any included in the groups studied did so, they would not have reported it. They could account for the percentage of lesbians who had increased levels of these hormones.

When no relationship between reported sexual orientation in men and most women and their current levels of sexual hormones was found, it was considered that the levels of these hormones to which they were exposed prenatally could be of significance in determining their later sexual behaviors.  It had already been established that prenatal sex hormone levels determined whether the fetus developed physically as female or male.  This development in mammals is initiated by differences in the genes on the X and Y sex chromosomes.  A gene, Sry, on the Y or male chromosome acting with other genes induces the development of the male gonad, the testis.  Without it a female gonad, the ovary develops.  Subsequent sex differentiation of the fetus is produced by the hormones produced by the testis or ovary.   The testis produces high levels of testosterone which either directly or after conversion to the hormone estradiol results in male development of the external and internal genital anatomy.   Without the testis, testosterone levels are low and a female development of external and internal genital anatomy results.   These physical developments occur in a series of stages termed critical periods.  Fluctuations in sex hormone levels in any of the critical periods in fetal development can result in anatomical defects specific to that period.   It was considered that changes in critical periods of development of the brain structures which determined sexual behaviors could also be influenced by fluctuations in hormonal levels to which the fetus was exposed.  Such brain changes could determine the ratio of same to opposite sexual and sex-linked feelings and behaviors.

Prenatal or immediately postnatal hormone influences on animal sexuality.  It is of course not acceptable to subject humans to experimental studies modifying their sex hormone levels.  Studies were initiated in a number of mammalian species to determine if modifications of their sex hormone levels resulted in changes in sex-linked or sexual behaviors.  Female mammals were exposed to increased levels of testosterone both by administering the hormone to their mothers when pregnant with them, and to the mammals themselves soon after birth.  Male mammals were exposed to reduced levels of testosterone by castration shortly after birth or by administration of anti-androgens to their mothers when pregnant with them.  Anti-androgens are hormones that reduce testosterone activity.  The mammals whose intrauterine or immediate postnatal sex hormonal environment was altered in this way were compared to mammals whose hormone levels were not altered.  In adulthood those with altered hormone levels showed increased opposite sex-linked behaviors and some features of opposite sex behaviors, compared with mammals whose hormone levels were not altered.

Male rats whose testosterone levels were reduced in these ways before or soon after birth, as adults initiated little or no copulatory behavior with females, referred to as demasculinization.  When as adults they and male rats not so treated were given the female hormones estrogen and progesterone in doses sufficient to cause female rats to become sexually active, the treated rats showed increased lordosis (an arched back female sexual response) when tested with stud males, referred to as feminization.  Female rats exposed to increased testosterone levels while in the uterus or shortly after birth, as adults showed reduced copulation with males and increased mounting of females compared to females whose hormone levels had not been altered. However the rats like other mammals treated in this way commonly also showed alterations of genital morphology towards those of the opposite sex, such as reduced penile size in the males, or increased clitoral size in the females.  It was argued that these alterations rather than brain changes could be responsible for the behavioral changes.

Ward in 2002 reviewed her research investigating the effect of stressing pregnant rats by temporarily restraining them in plastic tubes and exposing them to light.  It resulted in their male offspring when adult showing demasculinization and feminization of sexual activity similar to that produced in rats whose levels of testosterone were reduced during fetal development or soon after birth.  Unlike the latter rats, those whose mothers were stressed showed no changes in genital structure.  Ward cited studies that found similar changes in sexual behavior in the adult male off-spring of females stressed during pregnancy by social crowding, or malnutrition.  In response to stress animals produce hormones which temporarily block testosterone production.  Ward argued that the stressed pregnant rats produced these hormones, so impairing their male fetuses’ production of testosterone.   The testosterone level of male rat fetuses normally shows a marked surge on days 18 and 19 of the pregnancy.  Ward exposed a group of pregnant rats to stress on these two days of the pregnancy.  Half the group were injected with testosterone at the same time.  In adulthood the rats whose stressed mothers had not been given testosterone showed increased opposite sex behaviors.  The sexual behaviors of those whose stressed mothers had been given testosterone were similar to that of male rats whose mothers had not been stressed.  Ward argued that the increased opposite sex behaviors of rats whose mothers had been stressed on days 18 and 19 of pregnancy but not given testosterone must have been due to the stress blocking the surge of testosterone which would have otherwise have occurred.    The lack of this surge was compensated for by the administration of testosterone at this time to the other stressed mothers.

As in Ward’s previous studies the opposite sex behavioral changes in adulthood produced by stress without testosterone administration at 18 and 19 days of fetal development were not accompanied by opposite sex changes in genital anatomy, indicating the behavioral changes were not due to genital changes.  They must therefore have been due to prenatal alterations in the function of brain structures responsible for sexual behaviors.  In previous studies when the hormone levels to which rat fetuses were exposed were modified earlier than days 18 and 19 of the pregnancy, opposite sex alterations of genital anatomy resulted as well as opposite sex behaviors in adulthood.   Ward concluded the genital anatomy of the fetuses were established by days 18 and 19 of fetal development and so could not be modified by alterations in testosterone levels.  The brain structures determining sexual behaviors were not established by this time.   However there was a critical period for this establishment after which the sexual behaviors could not be changed by modification of sex hormone levels.  Mammals whose testosterone levels were experimentally reduced some time after birth did not show alterations in their sexual behavior similar to those shown by mammals whose testosterone levels were modified prior to or soon after birth.

The adult female offspring of rats stressed during pregnancy did not show alterations in sexual behavior after birth, indicating the behavior was not sensitive to the reduction in prenatal testosterone level which would have been expected to result from the stress.  In contrast, adult female rats whose mothers had been given testosterone or other masculinizing hormones during the pregnancy or who themselves had been given testosterone within one hour of birth showed a decrease in receptivity to copulation with males and increased mounting behaviors compared to adult female rats not exposed to these procedure.    Presumably unlike increasing their testosterone levels, further lowering of the already low testosterone levels of female rats in their fetal development has no effect on their sexual behavior.

Adkins-Regan in 1988 reviewed evidence relevant to a claim that the opposite sexual behaviors produced in mammals by experimental modification of sex hormone levels were not equivalent to the sexual behaviors of homosexual women and men.  The reason for the claim was that while the modifications had produced changes in the frequency of male and female behaviors, they had been reported to produce a preference for partners of the same rather than the opposite sex.   In making the claim, it was assumed that homosexual men and women exclusively preferred partners of the same sex and the existence of homosexual heterosexuals was ignored.  Studies were initiated to investigate whether changes in prenatal hormonal levels of mammals modified partner preference in addition to the sexual behaviors previously investigated.   Male rats whose testosterone levels were blocked by anti-androgens immediately after birth were allowed as adults to choose as sexual partners either a female rat in heat or a male rat, both of which were tethered in position.  Some hormonally modified rats vacillated, running backwards and forwards between the two every few seconds; others preferred the male rat.  In another study male rats were castrated 24-36 hours after birth.  Some were then given testosterone 2 and 4 days after birth.  When as adults all the rats were given testosterone those in both groups preferred females, but when given estrogen, those who had received testosterone after birth preferred females, while those who had not preferred males.   It was concluded that absence of testosterone around birth feminized the rats but the feminization was expressed only if the rats were given estrogen in adulthood.  In a further study some female rats were given testosterone 5 days after birth, and others not.  As adults the females in both groups had their ovaries (the source of female hormones) removed.   Without these hormones, four weeks later the rats in both groups showed no preference for male or female rats.  When all were then given estrogen or testosterone replacement, those given testosterone 5 days after birth preferred females, those not given it preferred males.   Adkins-Regan reviewed similar studies which demonstrated that in other species of mammals and birds, sex hormone levels around the time of birth were important determinants of their sexual preference for males or females when adult.

Roselli and colleagues in 2002 reported evidence that preference for sexual partners of the same sex in animals could be influenced by sex hormones changes which occurred naturally as well as due to experimental modification.   They pointed out that about 10% of rams exhibit a sexual partner preference for males as compared to females and therefore could be classified as male-oriented or homosexual.  Rams that showed no sexual interest in females though repeatedly exposed to them, and courted and mounted males when provided with a choice between females in heat and males, were compared with rams that exhibited high libido toward estrous females.  The male-oriented rams showed significantly lower blood levels of testosterone and estradiol than did the female-oriented rams.  Roselli and colleagues concluded the lower testosterone level was due to decreased capacity for making testosterone as the male-oriented rams showed reduced levels of hormones necessary for synthesis of testosterone in their testes.  Perkins had reported in 1997 that the testosterone levels in the blood of rams she termed heterosexual as they showed no homosexual behaviors, increased when they were exposed to ewes.   The testosterone levels of the rams she termed homosexual who showed no heterosexual behaviors, increased when they were exposed to rams.

Experimental modifications of sexual hormones in primates, mammals closer in evolutionary development to humans, have focussed less on the effects on sexual behaviors, presumably due to the time necessary for the primates to show these behaviors in adolescence and adulthood.  Instead effects on sex-linked behaviors, in particular rough and tumble play, which can be examined in the childhood of the primates, have been investigated.   Rough and tumble play is the most definitive sex-linked behaviors in the primate group of mammals, being shown much more frequently by male as compared to female juveniles.  Whiting and Edwards concluded from its presence in diverse human cultures throughout the world that it seemed the best candidate for a sex-linked behavior that was biologically determined. Harlow demonstrated that in male rhesus monkeys this sex-linked behavior occurred in the absence of social influences from older primates, further evidence it was biologically determined.  Male monkeys deprived when infants of the company of other monkeys except for brief periods when they could mix with similarly deprived peers, showed male levels of this play.  In studies by other researchers, female offspring of pregnant rhesus monkeys injected with male hormone during the appropriate critical period showed as juveniles levels of rough and tumble play approaching those of males.  As discussed in Chapter 2, degree of rough and tumble play in childhood is related to  later ratio of heterosexual/homosexual feelings in humans.  Lack of participation in rough games and contact sport in men consistently, and presence of increased tomboyish behavior in women less consistently, correlated with increased homosexual feelings or behaviors.

Goy and colleagues investigated the effect of exposure to increased levels of testosterone at different periods in the prenatal development of female rhesus macaques.   Those exposed early in the pregancy subsequently showed  masculinization of their genitalia and increased rates of mounting their mothers and peers (that is, male-typical behaviors) compared to normal females, but did not differ from normal females in their rates of rough play.  Those exposed late in their prenatal development did not show masculinization of their genitalia, but showed increased rates of rough play and of mounting their peers, but not of mounting their mothers.  Goy and his colleagues concluded that the individual behavior traits that are components of the juvenile sexual role are independently regulated by the organizing actions of male hormones and have separate critical periods.

Some academics have questioned the relevance to human behavior of the findings in non-human mammals of relationships between changes in hormonal levels in fetal development and later opposite sex-linked and sexual behaviors and sexual preference.  Understandably scholars who adopt social constructionist theories question this more than do scholars who consider biological factors are likely to contribute to establishing sexual preferences.   Certainly the research has demonstrated that brain structures determining sexual behaviors and preference in adulthood are established at critical periods in fetal development in the mammalian species investigated.   These findings support the significance of the findings of similar relationships in human subjects between changes in sex hormone levels changes in fetal development and later sexual preference.

Prenatal hormonal influences on human sexuality: adrenal hyperplasia.   The most dramatic finding supporting the prenatal hormone theory in relation to the sexual orientation of men and women was reported in German by Kaplan in 1990.  He assessed the sex hormone levels of male and female fetuses in the third month of their development from samples of the amniotic fluid, the fluid that surrounds the fetus in the uterus.  When they were aged 18, 70% of the men with the lowest testosterone levels identified as homosexual.  A similar but weaker trend for the women with the highest testosterone level to identify as lesbian at aged 18 was also found.    Due to the lack of scientific rigor in the report of the study its findings have attracted little attention, and no attempt appears to have been made to repeat it. The hypothesis that biological and in particular hormonal factors during intrauterine development influence sex-linked behaviors in humans has received greater support than the hypothesis linking these factors with sexual orientation.  In part this could result from assessment of sexual orientation needing to rely on the men and women’s self report.   Their reluctance to accurately make such reports at least non-anonymously was discussed in Chapter 1.  Sex-linked behaviors of children can be assessed by observation and as adults, women and men appear more willing to non-anonymously report opposite sex-linked behaviors in childhood and currently than homosexual feelings or behaviors.

Melissa Hines and colleagues found a significant relationship between the degree of male sex-linked behaviors of normal female children when aged three and a half and the testosterone levels of their mothers when they were pregnant with the children.  There was no equivalent relationship in boys, which the researchers attributed to the testosterone levels of male fetuses being already high, so that small differences in the mothers’ levels would not make a marked difference.  A similar relationship in regard to current opposite sex-linked behaviors was reported by Udry in  women aged 27 to 30 whose mothers had blood taken in the second trimester of the pregnancy.   The women whose mothers’ blood showed  higher levels of effective testosterone reported greater opposite sex-linked behaviors, including reduced interest in housework, attaching greater importance to a career as compared to marriage, and showing less interest in enhancing their feminine appearance. Their sexual orientation was not investigated, but fewer had  married.  Udry found the apparent prenatal hormonal effect interacted with the social effect of being encouraged by their mothers to act in a feminine manner from age 5 to 15.  This encouragement increased the female sex-linked behaviors of women whose mothers had lower levels of testosterone, but not women whose mothers had higher levels of testosterone.  Udry concluded women needed natural tendencies to be feminine for encouragement to enhance their femininity to be effective.   Without these tendencies encouragement would have no effect.

Findings of studies attempting to link maternal stress to sexual orientation in humans have proved controversial.   Conflicting findings were reported as to whether more men who identified as homosexual were born in Germany during World War II, when their mothers were subjected to the stress of heavy bombing, compared to periods before or subsequently.   Conflicting results were also reported from studies investigating whether more mothers of men and women who identified as homosexual reported being subjected to stress during pregnancy than did mothers of men and women who did not so identify.   One study found that women but not men whose mothers reported being stressed compared to those whose mothers did not report this experienced  higher levels of homosexual fantasies.   Another study found that mothers who rated themselves as prone to stress compared to those who rated themselves as not prone to stress were more likely to have sons with higher levels of female sex-linked behaviors in childhood.

Studies similar to those modifying the intrauterine hormonal environment of animals, of course cannot be conducted on human subjects.   However relevant evidence is obtained from what have been termed natural experiments, when human subjects have conditions which cause them to have abnormal levels of sex hormones before birth.   Another source of evidence is from the use of hormones to treat pregnant women.  As discussed in Chapter 1 initial studies of both types produced negative findings.   In one, the girls had congenital adrenal hyperplasia, resulting in their being exposed prenatally to excess male hormones produced by their own overactive adrenal glands.  In the other, the boys’ mothers had been given high doses of female hormones during pregnancy.  This was done with the aim of reducing the likelihood of abortion in women who were considered at increased risk of spontaneous abortion.  About half the girls were prepubertal, and a half adolescent.   The boys were aged 16.  All the 62 girls and boys who had been prenatally exposed to increased levels of opposite sex hormones reported no homosexual feelings, as did all but one of the 48 comparison normal girls and boys of equivalent ages who were not exposed to increased hormone levels.  From the data discussed in Chapter 1, it would be expected that about 20% of normal adolescent girls and boys would have been aware of some homosexual feelings.  That only one (2%) of the 48 comparison subjects reported such feelings should have alerted the authors and readers of the studies to question the accuracy of the subjects’ non-anonymous reports of the presence of homosexual feelings.  Instead the finding that none of the subjects exposed prenatally to increased levels of opposite sex hormones reported homosexual feelings or behaviors was accepted by the scientific community as supporting the then current belief that only social and not biological factors determined sexual orientation.  When the girls with adrenal hyperplasia were subsequently interviewed in adulthood, they reported an increased incidence of homosexual feelings compared with comparison women.   They had felt unable to talk about their sexual feelings and behaviors when they were adolescent.  Though the girls with adrenal hyperplasia reported no homosexual feelings in adolescence they did report they had shown as children significantly more tomboyish behavior than did comparison girls without adrenal hyperplasia.  As discussed in Chapter 2, tomboyism, unlike “sissy” behaviours in boys, is not subject to strong social disapproval and presumably the girls felt able to report it in non-anonymous interviews.    Also unlike sexual fantasies it can be partially confirmed by interviews with peers, teachers and parents.   It was concluded at the time that tomboyish behavior in girls could be in part under hormonal control.

Dittmann in a 1997 review of the sexual behaviour of women with congenital adrenal hyperplasia found that subsequent studies confirmed the findings discussed.  Compared to healthy controls, commonly their sisters, women with congenital adrenal hyperplasia showed increased opposite sex-linked behaviors in childhood and adolescence.  In adulthood they reported less heterosexual and increased homosexual feelings and behaviors.  The findings were less clear-cut in studies in which most subjects were aged less than 16, did not use intensive interviews, or which were carried out in areas with a presumably conservative or religious sociocultural background.  These studies elicited the information by non-anonymous interview so that as expected the percentage of the comparison women, particularly adolescents, who reported any homosexual feelings and/or behaviors was considerably less than the 20% that might be expected if the information was elicited by anonymous questionnaire.  In Dittmann’s own study no control sisters reported having had or wished to have a same-sex relationship, compared to 44% of the adult women with congenital adrenal hyperplasia.   This figure of 44% was markedly higher than that of  20% of adult women who anonymously reported homosexual feelings or behaviors in Sell and colleagues’ study of representative samples of the population of the United States.   Dittmann also found a significant reduction in heterosexual feelings and behaviors in women with adrenal hyperplasia compared to their unaffected sisters.   There would seem no reason why the unaffected woman would exaggerate their heterosexual interest or the women with adrenal hyperplasia would minimize it.  Some women with congenital adrenal hyperplasia decide to live as men in adulthood.

Opponents of the hypothesis that changes in hormonal levels affect sexual and sex-linked behaviors in humans argued that the increase in rough and tumble and other male sex-linked play shown by  women with adrenal hyperplasia was due not to the associated prenatal increase in male hormone levels, but to the psychological effect of having the illness.  This argument is weakened by the findings of Hines and Udry mentioned earlier that prenatal exposure to higher testosterone levels produces increased opposite sex-linked behaviors in childhood and adulthood in healthy women.   Hyperplasia of the adrenal glands produces increased levels of testosterone prenatally in men also.   Consistent with the theory that high prenatal levels of male compared to female hormones would produce higher ratios of heterosexual to homosexual feelings, men with this hyperplasia reported they were exclusively heterosexual.   This finding cannot be considered conclusive, in view of the percentage of men with some homosexual feelings who only report these in anonymous studies, as discussed in Chapter 1.

Ehrhardt and colleagues in a 1985 study concluded increased homosexual feelings were experienced by women  whose mothers when pregnant with them had been given diethylstilbestrol.   This hormone has a masculinizing effect on brain development.   When aged 17-30, 24% of the women reported lifelong bisexual or homosexual responsiveness (Kinsey scale 2 to 6) in the preceding 12 months.  None of the equivalently aged comparison 30 women whose mothers had not been given the hormone reported any lifelong homosexual responsiveness.  The non-anonymously reported absence of homosexual feelings in these comparison normal women like the absence in the comparison normal subjects in the previous studies discussed should have been been considered questionable by the researchers.  It is possible that women who knew they had been exposed prenatally to masculinizing hormones and hence had a medical reason to account for homosexual feelings may have been more prepared to non-anonymously report having these feelings than were the women not so exposed.  As the 24% of exposed women who reported these feelings was in the range of the 20% or so of women in the population samples investigated  who reported this awareness anonymously. The failure of Ehrhardt and colleagues like other workers carrying out genetic research to recognize the existence of this 20%, most of whom are homosexual heterosexuals, means that their conclusion is questionable that that administration of diethylstilbestrol to mothers increases the likelihood of their female children experiencing homosexual feelings in adolescence and adulthood.   Further research which allows all the women to report their feelings anonymously may clarify this issue.

Ehrhardt found that unlike women with adrenal hyperplasia, women exposed to diethylstilbestrol did not show increased tomboyishness in childhood.   If the increased number of women who reported homosexual feelings following prenatal exposure to the hormone compared with those not exposed was a valid finding, the failure of the women to report increased tomboyism was consistent with the findings discussed in Chapter 2.  These were that women as compared to men showed a weaker association between opposite sex-linked childhood behaviors and degree of homosexual feelings in adulthood.  The difference between men and women could result from the critical periods in intrauterine brain development for the establishment of sex-linked behaviors and of the ratio of homosexual/heterosexual feelings overlapping more completely in men than women.   Adrenal hyperplasia in women would produce exposure to increased male sex hormones throughout both critical periods.  It would be expected, as the findings discussed earlier indicated, that these women would show both increased homosexual feelings and tomboyism.   The women in Ehrhardt’s study whose mothers received diethylstilbestrol at varying periods during the pregnancy, would be exposed to the hormone over different periods of their intrauterine development.  In some this would have affected the critical period for only one of the two sets of behaviors, that is, sex-linked behaviors or sexual feelings.  These women would not show an association between tomboyism and increased homosexual feelings. The possibility that the critical periods for the two sets of behaviors differed in human females was consistent with findings of Goy and colleagues in female rhesus macaques of separate critical periods in prenatal brain development for different juvenile sexual role behaviors.

A finding that sons but not the daughters of mothers who had taken methadone during their pregnancy showed a number of increased opposite sex-linked behaviors, compared to children whose mothers had not taken drugs, was related to hormonal influences.  Findings based on observation of sex-linked behaviors of course do not require non-anonymous reporting to be accepted as valid.  It was suggested that, as had been found in animals, methadone reduced the production of testosterone during uterine development.   The reason daughters were not affected could be due to reduction in the already low levels of testosterone to which they were exposed prenatally had no effect on their later sexual behavior.   As pointed out earlier reduction of testosterone levels to which female rat fetuses were exposed by stressing their pregnant mothers had no effect on their later sexual behaviors.

Hormonal factors versus rearing in determining sexual identity and orientation

                                                Androgen insensitivity

Another condition in which human fetuses are exposed to modification in the effective level of testosterone is that of androgen insensitivity, an inherited tendency for specific organs, including the brain and genitals to be insensitive to testosterone.   Genetic, that is XY, males in whom this insensitivity is complete, have external female genitals at birth, are reared as girls, and become sexually attracted to males.   There are no legal objections to their marriages to men unlike those of XY transsexual men who have been converted sexually to women.  Androgen insensitivity is usually recognized only at puberty when menstruation does not occur.   Genetic males in whom this insensitivity is partial are born with external genitals with varying degrees of male and female appearance.    Males and females with such ambiguous external genitalia are termed hermaphrodites.  The sex in which they are reared is commonly determined by the appearance of their genitals.  Those in whom it is more male are reared as boys and those in which it is more female, are reared as girls.  Usually those reared as boys identify as males and following puberty are attracted to women.   Perhaps slightly less commonly, those reared as girls identify as female and following puberty are sexually attracted to men.

Researchers of human sexuality remain divided as to whether sexual identity and orientation are determined entirely by the sex in which males and females are reared, or whether biological factors, particularly prenatal levels of sex hormones, play a significant role.  Those who emphasize the role of rearing support this by the fact that men with androgen insensitivity are successfully reared as girls.  Those who consider prenatal sex hormones play a role argue that like their genitals, the brain structures of men with the condition are feminized prenatally due to lack of effective testosterone, with both being feminized to an equivalent degree.  The sex chosen in which the children with adrenal insufficiency are reared is determined by the degree to which their genitals appeared more male or more female.   This degree will match the degree to which their brain structures are masculinized or feminized and hence whether their sexual identity is more male or female. The fact that they usually accepted the sex identity in which they were reared is not determined by the rearing process but to the identity chosen matching that determined by the brain changes.

5-alpha-reductase deficiency  

The role of biological factors versus sex of rearing also remains unresolved in relation to  genetic males with an inherited deficiency of the enzyme 5-alpha-reductase.   Prenatally they develop testes which produce testosterone in their uterine development but the enzyme deficiency prevents the conversion of testosterone to the hormone dihydrotestosterone, which is necessary for masculinizing male fetuses’ external genitals.  Males with the deficiency therefore develop a form of hermaphrodism with their external genitals sufficiently feminine in appearance at birth that they are raised as girls.  With the approach of puberty, due to the associated marked increase in production of testosterone, their voices deepen, and they develop a muscular physique, with substantial growth of the penis, which previously resembled a clitoris in size. They do not develop breasts and in most the testes then descend into the scrotum, if they had not already done so. They commence to have erections so they are capable of penetrative sexual intercourse.    Testosterone does not need to be converted to dihydrotestosterone to masculinize the prenatal development of the brain.  The prenatal hormone theory concerning development of sexual identity and orientation therefore predicts that majority of males with the enzyme deficiency would have masculinized brains and so develop a male sexual identity and predominant heterosexual feelings whether or not they were raised as girls.

In 1979 Imperato-McGinley and colleagues reported an investigation of males with the condition from 23 inter-related families in three rural villages in the Dominican Republic.  The authors considered 18 had been unambiguously raised as girls.  Seventeen began to realize they were different from other girls in the village when between seven and 12 years of age they did not develop breasts, their bodies began to change in a masculine direction, and masses (the descending testes) were noticed in their groin or scrotum.  They showed concern over their true sex identity, and 16 of the 17 commenced to dress as men and adopted a male identity during or following puberty, when they became convinced they were men and experienced sexual interest in women.  The time of first sexual intercourse with females was 15 to 18 years for the subjects raised as girls, 15 to 17 years for those raised as boys, and 14 to 16 years for 20 normal male control villagers.  One of the 17 continued to dress as a woman but was said to have male mannerisms and a heterosexual orientation, engaging in sexual activity with women of the village.  The authors did not comment on whether he showed fetishistic arousal to women’s clothes, which would have indicated a disposition to cross-dress along with heterosexual orientation, that is, a transvestite adjustment, as discussed in Chapter 2.

The eighteenth man raised as a girl also did not adopt a male identity.  At age 16 she lived with a village man who left her after a year.  She then left the village and lived alone working as a domestic and had no further sexual activity with men.  She wore false breasts, yet her build and mannerisms were masculine.  She denied any attraction to women and desired sex-conversion of her genitalia so she could be a normal woman.  These findings are compatible with this man showing predominant homosexual feelings. If the same factors were operating in these men to produce homosexual feelings as operate in the normal population, it would be expected that one of 18 males could be predominantly homosexual.   Imperato-McGinley and colleagues commented that there were no laws against homosexuality but there was strong social pressure against it. A predominantly homosexual male reared as a girl could prefer to go on living as a girl rather than change to be identified as a male homosexual.  It would be of interest to know if this subject compared to the remainder had shown more “sissyish” as opposed to rough and tumble play in childhood, as do most men who identify as homosexual rather than heterosexual.   This data was not reported.

Theorists who believed sex of rearing accounts for sexual identity and sexual orientation explained the adoption of a male sexual identity of the men with 5-alpha-reductase deficiency who were raised as girls as due to their being raised ambiguously, that is, as neither female or male.  The abnormal appearance of their external genitalia at birth was considered to result in their mothers and possibly others being uncertain concerning their sex.  Herdt and Davidson in 1988 reported five males in New Guinea with 5-alpha-reductase deficiency who were reared as girls.  All changed to a male role after puberty.  The authors considered the change occurred only under the greatest external public pressure, but gave little evidence of the nature of this pressure.  Three had died, one of whom was said to have showing odd behavior as a child before the condition was discovered, climbing trees and carrying male artifacts, such as a bow and arrows.   That is he showed male sex-linked behavior.  One of the two still alive suffered ridicule when the condition was discovered following puberty and he shifted to a distant town to escape the stigma, but continued to dress and identify as a man there.  It would be expected that if the subject’s sex identity as a woman was strong, he would have lived as a woman when freed from the stigma.

Hence the findings of Herdt and Davidson and of Imperato-McGinley and colleagues were interpreted either as demonstrating the effect of sex hormones during uterine development, or of sex of rearing on later sexual identity and orientation, depending on the bias of the interpreter.  This also applied to the findings reported in 1983 by Rosler and Kohn of a number of males with hermaphrodism due to 17 beta-hydroxysteroid dehydrogenase deficiency.  This produced a sexual development similar to that produced by 5-alpha-reductase deficiency.  All the males were reared as girls but spontaneously adopted a male sex role and identity following puberty.  The authors stated that careful inspection of the external genitalia at birth would be required to detect the difference from female genitalia and all were reared unequivocally as girls.


Adherence to the belief that sexual identity and orientation is determined by sex of rearing uninfluenced by biological factors resulted in a tragic outcome for a boy commonly referred to in the literature as Joan-John.   John’s penis was severely burnt by the electrocautery knife during circumcision.   Recognition that surgical construction of a penis would be difficult and conviction that that without a normal penis he would not be capable of having heterosexual intercourse led to his treating clinicians to persuade his parents he should be raised as a girl, Joan.  His testes were removed, surgery commenced for later construction of a vagina, and he was given female hormones.   For several years it was regularly reported in the scientific literature that Joan was adjusting well to living as a girl.  The reports received widespread attention both in textbooks and in the media.   An article in Time magazine of January 8, 1973, reported Joan’s case as casting doubt on the role of biological factors in establishing major psychological sex differences.   However reports of Joan’s progress ceased to appear.  In 1982 Diamond was asked to consult on Joan’s progress for a British Broadcasting Commission (BBC) television program on sexuality.  It was found that Joan when 13 years old was first seen by psychiatrists different from her previous ones.  She was considered to be beset with problems, and unlikely to ever adjust to being a woman.   The therapist who had made the earlier reports withdrew his support for the BBC program.  Diamond commented that it was regrettable that researchers in the United States were dependent on a BBC investigative journalist team for information concerning a case originally and so prominently reported in the American literature.

Diamond was subsequently able to obtain detailed information about Joan-John’s progress.  In 1994 he was living as a man, and married.  Joan-John’s mother reported than in childhood Joan most often rejected the girl’s toys, clothes, and activities that were repeatedly offered her.   She would play with her brother’s toys, dress in boy’s clothes, did not shun rough and tumble sports or avoid fights, and was regarded as a tomboy.  She was discriminated against by female and male peers because of her apparent masculinity and teased with names like “caveman” and “gorilla”.  Around age 10 the then Joan realized she wasn’t feminine.  When 12 she was commenced on the female hormone, estrogen, but disliked the feelings and the breast development it caused, and rebelled against taking it.  At age 14 Joan decided to live as a male, John, requested male hormones, breast removal, and surgical construction of a penis.  He was told what had happened to him when he was an infant, which led to him experiencing relief.  He remains angry he wasn’t told the truth from the beginning.  In his male role he was accepted by both male and female peers and it was considered his subsequent adjustment was similar to that of other boys with abnormal genital development.  At age 25 he married a woman some years his senior, and adopted her children.  His reconstructed penis lacked sensation, reducing his sexual pleasure, and he resented that he was rendered unable to biologically father children.

Kipnis and Diamond criticized the recommendation in pediatric textbooks of the 1990’s that female genital conversion should be carried out on infant boys whose penises cannot be stretched to two centimeters, and surgical reduction should be carried out on the clitorises of girls if they are  longer than about one centimeter.   They estimated that 100 to 200 pediatric surgical sex reassignments were performed in the United States annually on newborns found to have ambiguous external genitalia.   They found that other boys reared as girls following loss of their penis in infancy also assumed male roles, while boys with very small penises who did not undergo conversion surgery had a good outcome.   A literature review produced no articles on the hazards, psychosocial or otherwise, of having a large clitoris.  John’s traumatic experience was one stimulus for the appeal of the Intersex Society of North America that the accepted procedure of immediate surgical “correction” of the sexually anomalous external genitalia of children born with intersex conditions should be ceased.    They argued that assignment to a male or female gender should be delayed or not done at all and that intersex should be accepted as an alternative gender.   Rejection of the evidence that biological factors, in particular prenatal differences in levels of sex hormones, influence sexual identity and orientation would seem premature and may result in inappropriate therapeutic decisions.

My older brother made me a homosexual: immune reaction or personality effect?

“My mother made me a homosexual” was not an uncommon graffito some years ago,  commonly followed by the response “If I gave her the wool would she make me one too?”   As pointed out earlier, the psychoanalytic theory emphasizing the role of mother in psychologically producing homosexuality in her male children has received no empirical support.   However Blanchard put forward a theory that mothers could cause their sons to be homosexual by a biological process.  He found in an extensive review of published studies that having older brothers and sisters, that is being later in birth order, was a reliable and consistent correlate of homosexual orientation in men.  Blanchard and Bogaert investigated whether the effect was due to the men having an excess of older brothers only or older siblings of both sexes.  They pointed out that if the relationship with homosexual orientation in men was due to their having more older brothers, the men would also have more older sisters.   Using a statistical technique they showed that the effect was due to the presence of older brothers, not sisters, so they termed it a fraternal birth order effect.  In a subsequent study Blanchard and colleagues calculated that one gay man in seven owed his sexual orientation to the fraternal birth order effect.  They advanced a biological explanation for the effect.  This was that the fetus was treated as a foreign body within the mother.  It could therefore produce an immune reaction on her part that would influence the fetus’s brain development and hence his or her later sexual behavior.   As they found the birth order effect in men but not women who identified as homosexual, they concluded the maternal immune reaction was provoked only by male fetuses, and increased in strength with the each pregnancy with a male fetus.  The relevant fetal antigen, that is the chemical that provoked the immune reaction, could be male-specific, Y-linked H-Y antigen.  As female fetuses do not produce H-Y antigen they would not provoke the immune reaction.

The men and women who were investigated in the studies reviewed by Blanchard were volunteers who identified as heterosexual, homosexual or bisexual.   In the representative sample of men and women whose sexual behavior was reported by Laumann and colleagues, whereas 1.6 % of the women and 2.7% of the men identified as homosexual or bisexual, 5% of the women and 7% of the men reported awareness of some homosexual feelings, and 2% of women and 4% of men reported having had same sex partners in the past five years. Bogaert investigated the birth order in these women and men. Consistent with the earlier studies degree of being born later in birth order significantly predicted the degree of the men’s but not the women’s homosexual feelings and behaviors.  Laumann et al. employed face-to-face interviews in addition to anonymous questionnaires in their study.  As discussed in Chapter 1, the percentage of men and women who report awareness of homosexual feeling or having carried out homosexual behaviors is considerably higher when completely anonymous questionnaires are employed, approximately 20% as compared with less than 8% in the study by Laumann and colleagues.  Most of the 20% are those termed homosexual heterosexuals.

Fraternal birth order in homosexual heterosexuals.   I and colleagues investigated the fraternal birth order in seven groups of subjects:  319 male twins, 49, 54 and 61 female medical students and 66, 116, and 50 male medical students.   They anonymously completed the Sex-linked Behaviors Questionnaire. Sixteen percent of the men and 37% of the women reported current awareness of some homosexual feelings.  In all seven groups the men and women who reported this awareness had significantly more older brothers and sisters than those who were not aware of any homosexual feelings.  The findings require confirmation by other researchers.   It they are confirmed, as the birth order effect was present in women as well as men, it could not be explained as due to a maternal immune reaction that affected only male fetuses. The men and women in the seven groups who were aware of predominant but not exclusive heterosexual feelings had as many older siblings as those with predominant homosexual feelings.  This was contrary to what was expected if the birth order effect acted biologically.   If it did, it would be expected the effect would be weaker in subjects whose homosexual feelings were less predominant, and they would have fewer older siblings than those with predominant homosexual feelings.  A non-biological explanation for the effect could be that older siblings are less likely than younger siblings to accept they have some homosexual feelings.  Sulloway reviewed evidence indicating relative to their younger brothers, eldest brothers were more conforming, conventional, defensive, and less likely to take risks.   A finding by Rust and colleagues also suggested that the birth order effect may act by a social rather than a biological process.  They found that at age three, boys with older brothers and girls with older sisters showed higher levels of same-sex behaviors than singletons and those with opposite sex siblings.   If having older brothers caused some males to develop homosexual feelings due to a biological process, men with older brothers  would be expected when children to show increased opposite-sex behaviors compared to men with  older sisters.  The evidence discussed earlier indicated biological factors producing homosexuality also produced opposite-sex behaviors.

Brain structural differences and sexual orientation

Evidence previously discussed indicated that changes in sexual behavior of adult animals and humans resulting from prenatal alterations in levels of sex hormones were due to the hormones producing permanent differences in their brain structure at critical periods in its development. To support this theory some researchers investigated the structure of areas of the brain which they believed could influence sexual behaviors.  One such area was the medial preoptic anterior (MPOA) region of the hypothalamus, situated at the base of the brain and connected to the pituitary gland. The pituitary gland produces hormones which regulate the release of sex hormones from the ovary, testis, and adrenal glands. Lesions in the MPOA in vertebrate animals (those with a backbone) have been found to disrupt masculine sexual behaviors and influence whether males or females are preferred as sexual partners.   It has been suggested the MPOA is the most critical brain structure for the control of masculine sexual behaviors in all vertebrate animals.  In rats it contains cell groups that are markedly larger in males than females.  In male rats prenatally subjected to the effect of maternal stress the cell groups are similar in size to those in normal female rats.  Roselli and colleagues found significantly less activity of the chemical, aromatase, in this area of the hypothalamus in rams sexually attracted to males compared to those attracted to females.    Aromatase activity is necessary for the conversion of testosterone in the brain to an active form.  Roselli and colleagues suggested this brain area was exposed to less masculinizing hormones during a critical period in fetal development of rams attracted to males.  Perkins found an area of the brain termed the amygdala was organized more like that of ewes in the rams she classified as homosexual compared to those she classified as heterosexual rams.   She suggested this could explain why the homosexual rams were sexually attracted to males. The amygdala is structurally connected to the hypothalamic area.  Perkins pointed out that the amygdala in rats is generally believed to be involved in the perception of a potential mate.  The findings of Roselli and colleagues and Perkins are of particular interest as the rams, unlike the rats and mice studied, showed same-sex preference in their normal development rather than as a result of experimentally induced hormonal changes.

When differences were sought in the brain structures of men and women the hypothalamus was an obvious area to study.  Byne and colleagues in their review found these  investigations had produced mainly conflicting findings.  This is understandable given the nature of the investigations.   Just as different individuals vary in a number of ways, such as height, weight, and skin color, the structures of areas of their brains will also differ in a number of ways, the significance of which are yet unknown.  When differences are sought in selected areas of the brains of two groups of subjects, such as men and women, or self-identified heterosexuals and homosexuals, a number of the differences found will be due to chance.  In a second study other chance differences will be found.   As determining the structure of human brains requires detailed scrutiny most studies can investigate only a few subjects.  This increases the likelihood that differences found between brain areas of the subjects in the two groups will be due to chance.  Only when the differences found in a series of studies are identical can they be considered to be related to the difference between the two groups.

A finding that attracted public attention as a possible difference in brain structure of men classified as heterosexual or homosexual was reported by LeVay in 1991.    He confirmed an earlier finding that an area termed the third interstitial nucleus of the anterior hypothalamus (INAH3) was larger in heterosexual men than women.  LeVay found in addition that the INAH3 was smaller in homosexual than heterosexual men, and comparable in size to that of heterosexual women.   LeVay’s attribution of the size difference in the homosexual men to their sexual orientation was criticized on the basis that the majority had died from HIV infection, and brain changes from the infection may have produced the difference.   However Byne and colleagues subsequently reported they found no influence of HIV status on INAH3 size. As expected they found that INAH3 was significantly larger in heterosexual men than women.  In addition they found its size to be intermediate in homosexual men between the size in the heterosexual men and women, but the difference was not statistically significant.   Hence Byne and colleagues report provided some support for LeVay’s evidence that INAH3 is related to men’s sexual orientation.   The men and women in these studies were those who had identified as heterosexual or homosexual, or classified as such on the basis of their known behavior. Clearly there is a need for further studies, which preferably should investigate the size of INAH3 in relation to the subjects’ reported degree of homosexual as compared to heterosexual feelings.  It would seem extremely difficult to carry out such a research study using anonymous reports of sexual feelings.  However Laumann and colleagues’ investigation of a representative population sample showed that a significant number of men and women reported homosexual feelings who did not express them in behaviors and classified themselves as heterosexual rather than bisexual or homosexual.  As this group is likely to be classified as heterosexual in studies of brain structure, their inclusion would reduce any differences found in the size of IHAH3 in the subjects classified as homosexual compared to heterosexual, if the size is related to the degree of heterosexual compared to homosexual feelings.

Finger length differences

In most women the length of the index compared to the fourth finger is about the same size.  It is smaller in most men from the age of two, with the difference more marked for the right hand. As most physical differences in men and women are attributed to differences in androgen levels to which they were exposed prenatally, it was suggested this was also the case for the differences in finger length.  The suggestion was supported by a 2002 report by Brown and colleagues that women and men with congenital adrenal hyperplasia and hence exposed prenatally to increased androgen levels showed a right handed finger-length ratio more typical of males compared to women and men without that condition.  Men with a more male finger length ratio have been found to be more athletic than those with a less male pattern.  As men who identify as homosexual have been consistently found to be less involved in sports it could be expected they would show a less male finger length ratio.

Studies investigating whether the finger length ratios of men and women who identify as homosexual differ from those who identify as heterosexual were recently reviewed by McIntyre.   Their findings were conflicting.  He pointed out that Brown and colleagues found that women at a Gay Pride Mardi Gras who classified themselves as butch (masculine in role) compared to those who classified themselves as femme (feminine in role) were more likely to show a right hand finger length pattern typical of men.  Brown and colleagues also reported a finding of other workers that finger length ratios in homosexual men were likely to more characteristic of women the more their Kinsey scores indicated a homosexual orientation.   These findings raised the possibility that differences in finger length ratio could be found within groups of men and women with homosexual feeling depending on the degree of these feelings.  Brown and colleagues suggested that finger length differences might be found if homosexual men were classified according to whether or not they reported opposite sex-linked behaviors in childhood.  They considered that the men who showed these behaviors had been exposed to lower prenatal levels of testosterone, and hence should have a more female finger length ratio than did men who did not show the behaviors and whose homosexuality was due to other causes.   However McIntyre in his study found a relationship in the opposite direction.  Homosexual men who reported more marked opposite sex-linked behaviors in childhood had a more male finger length ratio than did those who reported less marked opposite sex-linked behaviors.  If finger length ratio is related to degree of homosexual feelings, the significant number of homosexual heterosexuals with some homosexual feelings who identify as heterosexual in most studies could reduce any differences between the groups of men and women in these studies who identify as heterosexual or homosexual.  Investigations of finger length ratios in subjects allowed to report their ratio of heterosexual to homosexual feelings anonymously are required to investigate this possibility.

In their 2000 study Williams and colleagues found a significant relationship between men having more older brothers and a more masculine right hand finger length pattern.  This is the reverse of what would be expected when as discussed earlier, the more older brothers a man has, the more likely he will identify as homosexual.  Williams and colleagues suggested that men with more older brothers, including those who become homosexual, were exposed prenatally to higher levels of male hormone than men with fewer older brothers.  This suggestion, contrary to the usual theory that homosexual men compared to heterosexual men have been exposed to lower rather than higher prenatal levels of male hormone, has recently been advanced by other workers to account for other findings discussed in the next section.  Lippa pointed out in a 2003 review that ethnic differences are more important in determining finger length ratios than are sex differences or differences in sexual orientation, yet are frequently not taken into account in studies investigating differences in men and women or subjects who identify as homosexual or heterosexual.  Failure to establish that the groups compared do not differ in ethnic composition may account for some of the conflicting findings reported.   Clearly further research which takes into account the existence of the homosexual heterosexuals, as well as other relevant factors, is required to resolve these issues.

Other physical differences: Hormonal influences or developmental instability

Studies have sought evidence regarding the theory that prenatal exposure to altered sex hormone levels influences sexual orientation by assessing subjects’ right or left handedness. Most studies found a higher percentage of men and women who identified as homosexual were left handed than were men and women who identified as heterosexual, with the difference usually being stronger in women.  A weak trend was also found for more men to be left-handed than women.   The latter finding led to the suggestion that left-handedness resulted from the higher levels of male hormones in men than women in their prenatal development.  Consistent with this suggestion more women who had congenital adrenal hyperplasia or whose mothers were given diethylstilbestrol when pregnant with them were found to be left-handed than comparison women without these conditions.  As discussed earlier, both conditions are associated with increases in male hormone levels prenatally and the former and possibly the latter condition is associated with increased homosexual feelings in adulthood. As left-handedness was attributed to prenatal exposure to higher levels of male hormones, the finding that more men who identify as homosexual than as heterosexual were left-handed led some researchers to conclude that homosexual men compared to heterosexual men had been exposed prenatally to higher prenatal male hormone levels and were hypermasculine.  This theory opposite to that usually advanced was as discussed above also advanced by Williams and colleagues to explain the relationship they found between men having more older brothers and a more masculine right hand finger length pattern.  Lippa in a 2003 article questioned this theory in relation to handedness.  He found no difference in rates of left handedness in women and men who identified as heterosexual and attributed the weak trend found in the general population for men to be more left-handed than women to the greater number of homosexual men than women in that population.  As both the homosexual men and women were more left-handed than heterosexuals, the greater number of homosexual men than women would result in the total male population being more left-handed than the total female population.   As left-handedness was not more common in heterosexual men than women, he considered the increased incidence of left-handedness in homosexual men and women was not due to increased prenatal androgens but to what has been termed developmental instability.  This instability is considered due to chance factors which limit the individual’s optimum development and are considered to affect males more than females.   Such chance factors include infectious agents and toxins, and genetic variations in susceptibility to stressors.

McFadden reported in 2002 that brain electrical responses to sounds in women who identified as homosexual were intermediate between those of heterosexual men and women.  Th responses in men who identified as homosexual were more in the masculine direction than those of heterosexual men.  McFadden initially considered this finding indicated that during prenatal development the hearing systems of homosexual compared to heterosexual men were exposed to increased levels of male hormone.   He discussed additional findings he considered consistent with this difference in prenatal hormone levels, including reports that the penises of homosexual men were larger in circumference and length than those of heterosexual men.  The men had carried out the measurements privately.  The possibility that homosexual men could be more likely than heterosexual men to exaggerate the size of their penises was considered implausible. In a subsequent report with a colleague, Loehlin, McFadden revised his opinion, considering the finding of the brain responses to sounds being in a hypermasculine direction in homosexual men could be due not to prenatal hormonal factors but to developmental instability.

Mustanski and colleagues reported in 2002 a failure to replicate earlier findings of a relationship between homosexual identity and differences in palmar skin ridge patterns, also considered to be influenced by prenatal hormonal levels.  They suggested the earlier findings could be due to different methods of measuring skin ridge patterns, increasing the likelihood of some methods showing the relationship by chance.

Cognitive differences 

Sanders and colleagues in a 2002 review pointed out that conflict persists concerning the existence and nature of differences in cognitive abilities of women and men despite the amount of research devoted to investigating this issue.   Studies found that while generally women have greater verbal abilities and men greater visual-spatial abilities, this is not found for all abilities classified in this way.  The contrary findings have been explained as due to the classification of abilities into verbal abilities and visual-spatial groups being too broad, so that when various abilities are placed in one or other category, some will be placed inappropriately.  Men and women perform equally well on tests of vocabulary, classified as a verbal ability.  Women are better than men at locating objects, classified as a spatial ability.  This increased ability in women has been explained as having been selected during evolution during the period when women were located food in the area near where they lived.   Men’s superiority in the visual-spatial ability of determining their location in wide-ranging territories was selected when they were hunters.   The differences found for most tests of verbal and spatial abilities between women and men have been attributed to the two sides of the brain, the cerebral hemispheres, functioning more independently, termed asymmetrically, in men than in women.  Most verbal abilities in women are localized in the right as well as the left hemisphere.  In men most verbal abilities are localized to the left side only, and are therefore inferior to those of women. The spatial abilities in which men are superior are represented in the right hemisphere, the function of which is enhanced in men compared to women.

The degree to which the brain develops symmetrically is attributed in part to the difference in prenatal levels of sex hormones in men and women.  Consistent with the hypothesis that sexual orientation is also associated with altered prenatal sex hormone levels, recent reviews by Diamond, Miller  and Hershberger and Segal found the majority of studies indicated that men who identified as homosexual showed the female pattern of greater functional brain symmetry and of verbal than spatial abilities, compared to heterosexual men.  Hershberger and Segal found the homosexual member of male monozygous (“identical”) triplets showed cognitive abilities more typical of women than men, compared to the two heterosexual triplets.  The possibility that the superior visual-spatial superiority of heterosexual men could reflect practice effects due to their greater interest in sport does not seem to have been considered.  Though lesbians have been more rarely studied than homosexual men, girls with congenital adrenal hyperplasia with its associated increased prenatal levels of male hormones, opposite sex-linked behaviors, and incidence of adult homosexuality, showed better spatial processing than girls without the condition.   Men’s superiority in most spatial abilities as compared to women has been considered to result in their being far more likely than women to be mathematical geniuses.  There seems to be no investigation as to whether homosexual men are less likely than heterosexual men to be mathematical geniuses.  Certainly one was.  Turing was famous for his role in the development of computers and breaking the German Enigma code in the Second World War.  He subsequently pleaded guilty to a charge of having consensual sex with a man and continued covert homosexual activity after completing compulsory estrogen treatment.

A factor which could contribute to the conflicting findings concerning sex differences in  cognitive function of women and men was pointed out by Sanders and Wenmoth in 1998. They found that abilities related to brain lateralization varied with fluctuations in hormonal levels in adulthood.  Spatial tasks were performed better and those involving verbal ability were performed worse by women during the time of their menses when estrogen levels were low.   The reverse pattern occurred during the mid-cycle when their estrogen levels were high. Female-to-male transsexuals showed a rapid shift from female to male patterns of cognitive ability following testosterone administration, with deterioration in verbal and improvement in spatial abilities. Male-to-female transsexuals treated with anti-androgens and estrogen showed the reverse change, improvement in verbal and deterioration in spatial abilities.   If these findings are successfully repeated they would demonstrate that cognitive abilities are related less to the structure than the function of the brain hemispheres. They would also demonstrate that this function is not permanently established during fetal development, but is modified in changes in hormone levels in adulthood.  In relation to differences in other cognitive factors, Diamond quoted evidence that children exposed prenatally to higher levels of androgenic progestins showed more independent, individualistic, self-sufficient personalities.  Those exposed to estrogens were more group oriented and group dependent.  The former differences were considered to be associated with maleness and the latter with femaleness.

Like other areas of research into causes of sexual orientation, most of the studies of cognitive differences related to homosexuality treat sexual orientation as categorical, investigating subjects identified as heterosexual, homosexual, or bisexual.  Future research will need to give more attention to the homosexual component present in the significant percentage of homosexual heterosexuals, who currently are only able to be investigated anonymously, and would either not have volunteered for these studies or been included as exclusively heterosexual.

Relation of homosexual feelings and behaviors

Dunne and colleagues in their study of 1824 male and 3077 female twins aged 17 to 50,  found that 15% of men and 8% of women anonymously reported having had sexual contact with a person of the same sex.   Almost half of these men and a quarter of the women stated they had never been sexually attracted to a same sex person.   About 6% of men and 11% of women had been sexually attracted to but never had sexual contact with a person of the same sex.  Sell and colleagues in their anonymous study of representative samples of the populations of the United States, United Kingdom and France similarly found that about 8% of men and 10% of women reported same sex attraction but not behavior since age 15.  They did not state whether any of the 10% of men and 8% of women who reported same sex behavior since age 15 had never experienced same sex sexual attraction.

Factors influencing why some men and women do not act behaviorally on homosexual feelings of which they are aware, have not been explored in any detail. In a 2003 study Spitzer recruited 143 men and 57 women who had sought and reported a positive response to what he termed reparative therapy to convert homosexual to heterosexual feelings.  Ninety three percent stated that religion was extremely or very important in their lives, suggesting as could be expected that it is a significant factor in causing people to attempt to suppress their awareness of homosexual feelings and not express them in behaviors.  Presumably others do not express these feelings in behaviors due to current social disapproval and possible negative consequences if they do so, discussed in Chapter 4.  As pointed out in that chapter many scholars believe that in ancient Greece and Rome, where taking an active homosexual role was not subject to disapproval, a large percentage of the male population carried out such activity.

Reasons advanced as to why men and women engage in homosexual behavior without being aware of homosexual attraction have included that it is facultative, carried out in situations where no opposite sex partners are available, such as prisons, or when men were at sea for long periods.  Sell and colleagues in their anonymous study found as did Laumann and colleagues in their non-anonymous study that most men and women carried out homosexual behavior only in adolescence or early adulthood.  This suggests that curiosity combined with heightened sexual arousal and possibly greater opportunity are factors which could cause these young people to experiment with homosexual behavior.  However some women and men who report homosexual behavior without homosexual feelings may be suppressing awareness of such feelings.  This possibility was supported by the finding of Dunne and colleagues that the men and women who reported homosexual behavior without feelings showed greater opposite sex-linked behaviors in childhood than did the men and women who reported no homosexual behavior or feelings.  As discussed in Chapter 2, opposite sex-linked behaviors in childhood have been consistently found to be associated with homosexual feelings and behaviors in adulthood.

Humphries in his 1970 book “Tearoom trade” reported his observations of men who frequented public lavatories for homosexual activity.  He found that many were the recipients of fellatio carried out briefly without emotional interaction.  He followed up a number by identifying their home addresses from the number plates of their cars parked nearby and found that about half were married and identified socially as heterosexual. His research probably would not be currently ethically acceptable as it was conducted without informed consent.   Possibly many of the men he observed who made homosexual contacts in public lavatories as well as those who currently behave similarly and are termed “men who have sex with men”, carry out homosexual behaviors as a form of sexual gratification with minimal or no feelings of sexual preference for same sex persons.   This is not true of them all.  Men who carried out homosexual acts in public lavatories sought treatment for the behavior from the author as they found they were unable to cease it when they wished to do so.   In a 1978 study I reported that many of these men were married and identified publicly and usually to their wives as heterosexual but experienced predominant homosexual interest.  Their report was confirmed by their penile volume responses to moving films of nude men and women.

Dunne and colleagues’ subjects anonymously reported whether they considered themselves heterosexual (straight), bisexual, or homosexual (lesbian/gay).  About 6% of the men and 4% of the women considered themselves bisexual or homosexual.  These percentages were much less than the approximately 20% who reported some homosexual feelings or behavior, though about twice the percentage of the men and women who identified as homosexual or bisexual in the representative population sample in the non-anonymous study of Laumann and colleagues.  It would seem that adults who identify to themselves as bisexual or homosexual and who usually express homosexual feelings to a significant degree in their sexual behavior are mainly those who experience very predominant or exclusive homosexual feelings.  A percentage of these self-identified homosexuals identify as homosexual publicly to some or all of their acquaintances.  As the majority of subjects with homosexual feelings behave in their overt sexual activity and identity as exclusively heterosexual and as only a small percentage identify publicly as homosexual, the common perception will remain unchanged that sexual orientation is dichotomously distributed with almost all men and women being heterosexual and only a small percentage homosexual.  While this situation persists, the existence of homosexual heterosexuals will remain unacknowledged.


Sexual orientation as choice of sex of attachment or bonding partners: social and biological factors

While there is extensive evidence concerning the sex of preferred attachment or bonding partners in animals, discussed in the next chapter, there has been little interest in this choice in humans, despite the frequent non-scientific references to same-sex, particularly male, bonding.  Expression of intense attachments to same sex persons has been accepted at periods when sexual activity with same sex persons was proscribed, and could be punished with death. One of the most powerful such expressions is recorded in Samuel II of the Bible.   When informed of the death in battle of his friend Jonathan, David in his lament says “O Jonathan, slain upon thy high places.  I am distressed for thee, my brother Jonathan.  Very pleasant hast thou been unto me: Thy love to me was wonderful, passing the love of women.”  The intensity of Ruth’s attachment to her her mother-in-law Naomi was demonstrated in her statement in Judges:  “For whither thou goest, I will go; And where thou lodgest, I will lodge; Thy people shall be my people, and thy God my God; Where thou diest, will I die, and there will I be buried.”

Strong attachments between men appeared to be accepted as natural during the European Renaissance.   In the essay “Of friendship” published by the Frenchman, Montaigne, in 1580, he described “the unspotted friendship, which we (he and Steven de la Boetie) … have so sincerely, so entire and inviolably maintained betweene us…”  At their first meeting, they “found themselves so surprized, so knowne, so acquainted, and so combinedly bound together, that from thence forward, nothing was so neere unto us, as one unto the other.”  Montaigne compared their friendship with other relationships, considering it superior to affection toward woman, because the fire of women though more active, fervent, and sharp, was rash, wavering and diverse, subject to fits and stints.  Unlike lustful love, in true friendship, there was a constant and settled heat, all pleasure and smoothness, that had no pricking or stinging in it.  Marriage was ordinarily concluded to other ends, so that a thousand strange knots were to be unknit, and troubled the whole course of lively affection, whereas there was no commerce or business depending on friendship.  “The ordinary sufficiency of women cannot answer this conference and communication, the nurse of this sacred bond: nor seeme their minds strong enough to endure the pulling of a knot so hard, so fast, and durable.”  The love between males in classical Greece, “a licence which is justly abhorred by our customs”, was inferior as it required a disparity of age and so did not provide the perfect union and agreement of their friendship.

Intense emotional attachments between men were expressed in Elizabethan poetry.  Sir Philip Sidney wrote:

“My true love hath my heart, and I have his

By just exchange the one to the other given…

He loves my heart, for once it was his own,

I cherish his because in me it bides.”

Shakespeare’s famous sequence of sonnets give an account of the powerful emotional relationship of the male narrator with a young man, “the master-mistress of my passion”.    One makes the point that the youth having a penis (prick) prevents the passion from being expressed sexually:  “And for a woman wert thou first created; Till Nature, as she wrought thee, fell a-doting, And by addition me of thee defeated, By adding one thing to my purpose nothing.  But since she prick’d thee out for women’s pleasure, Mine by thy love, and thy love’s use their treasure”.   When the sonnets were reprinted half a century later in 1640, pronouns in some of them were altered from male to female, possibly due to the increase in Puritan values, soon to be powerfully expressed under the rule of Oliver Cromwell.

There seems to be no research investigating whether there could be a biological basis for choice of sex of bonding partners as separate from sexual partners in humans.  In her 2002 account of choice of sexual partners in the pair-bonding zebra finch Adkins-Regan pointed out that many humans choice of sexual partners was expressed in the context of close relationships or pair-bonds of variable duration.  Most studies of sexual partner preference in animals investigated species that in the wild did not form pair-bonds or other close relationships.  She considered that though they were excellent models for what she termed copulatory preferences, other animals needed to be studied to provide insights into the pair-bonding aspects of sexual relationships, and the most appropriate group were birds.   A substantial number of the larger long-lived species of birds tended to pair for life with partners typically of the opposite sex.   It was not uncommon for some to copulate with birds other than their partner, and the males might sing to other birds but 90% of their offspring were produced by copulations between paired individuals.  Only paired birds sat in direct physical contact with and preened each other, and spent significant time in a nest box together.  Adkins-Regan pointed out that as with human couples living together, most of the time paired birds spent with each other was devoted to activities other than copulating.  She did not point out other similarities.   About 10% of women and 25% of men in Laumann and colleagues’ representative study reported they had sex outside the relationship while married or living with a partner.  Diamond in his 1991 book “The Rise and Fall of the Third Chimpanzee” quoted evidence that between 5 and 30% of British and American children were adulterously conceived.

Adkins-Regan found that though the copulatory frequency of monogamous, pair-bonding zebra finches was low, the pairs could be identified as they only preened each other and spent time in the nest box together.  She reported that significantly more females injected with the female hormone estradiol benzoate for the first two weeks after hatching and housed in an all-female group cage during juvenile development, as adults tried to pair with other females, compared to those similarly housed which as comparisons received placebo (non-active) injections. In some cases the treated females successfully paired with female partners, as they were effective in keeping males away from the partners.   Adkins-Regan suggested hormones had an organizational effect on the brains of the finches, as they did in the nonpair-bonding rats and other mammals, as demonstrated in the research discussed earlier.   To influence pair bonding in female finches the organizational effect required reinforcement by all-female housing.  Adkins-Regan also investigated the effect of removing adult male finches from some breeding cages when nestlings were less than a week old.  Though males and females share nearly equally in incubation and feeding of their young, females will continue to care for them in the absence of the male.  Adult males were left in the cages in the comparison group.  The male and female birds reared in the cages from which adult males were removed did not show the usual preference for opposite sex partners, and were more likely to pair with a same-sex partner than the comparison birds reared with adult males.  Adkins-Regan commented that this was the only experimental manipulation to date that has altered the sexual preference of male zebra finches.   She considered related findings would be needed from studies of group-living pair-bonding mammals such as marmosets and titi monkeys, before it was safe to assume that similar processes might operate in human beings.  Zebra finches pair as soon as they become sexually mature and remain paired year round even when they are not breeding.  The association of their pair-bonding and choice of sexual partners suggests that both could be determined by the same social and biological factors.

In opposition to this conclusion, Fisher and colleagues considered that in mammals including humans there were at least three discrete, interrelated emotion-motivation systems for mating, reproduction, and parenting, the systems for lust, attraction, and attachment.  Lust, the sex drive, was a craving for sexual gratification and was associated primarily with the action of the sex hormones, estrogens and androgens.  It evolved to motivate individuals to seek sexual activity with any appropriate member of their species.  The attraction system focussed on a preferred mating partner.  In humans it was usually called romantic love, obsessive, passionate love, and infatuation.   There was some evidence it was associated with increased levels in the brain of the chemical transmitters, dopamine and norepinephrine, and reduced levels of serotonin.  Attachment behavior was characterized in birds and mammals by mutual territory defense and/or nest building, mutual feeding and grooming, and maintenance of proximity and shared parental chores. The attachment system evolved to motivate individuals to sustain partnerships long enough to complete parental duties.  In humans it was often called companionate love.  It was associated with activity of the neuropeptides, oxytocin and vasopressin in the brain.   Fisher and colleagues considered their hypothesis that romantic love was associated with a different area of brain activity than those associated with lust and attachment was supported by an independent study.  The brain activity of 17 women and men who reported being deeply in love was assessed by functional magnetic brain mapping.  Photographs of the loved one compared to those of friends produced brain activity limited to an area of the brain known to be associated with emotion.

Fisher and colleagues considered the degree of activity of the brain systems for the three types of feelings varied across species, in individuals within a species, across the life span of individuals, and in males as compared to females.   They considered that though the three systems usually acted together they could act independently.  They cited evidence that middle-aged men and women given testosterone to increase sexual desire, experienced increased sexual thoughts and sexual activity, but not increased romantic or attachment feelings to their sexual partner.   In my clinical experience men given anti-androgen hormones to reduce inappropriate sexual urges, report a decrease in frequency of sexual thoughts and desire, but no change in their romantic or attachment feelings.  Men and women can feel strongly attached to a partner, while being sexually and/or romantically attracted to another person.   However men and women who report romantic attraction to a person, appear always to experience sexual desire for them, though they may report their desire for togetherness is  stronger.

The evidence is that women in most cultures are more likely than men to be sexually attracted to or at least prepared to have sexual activity only with partners with whom they feel romantically attracted.   A research finding subsequently used in a popular song was reported by Clark and Hatfield in 1989.   Four men and five women aged about 22 years were instructed to individually approach members of the opposite sex on the campus of Florida State University and say “I have been noticing you around campus.  I find you to be very attractive”.  Then they asked according to a randomized procedure, one of three questions: “Would you go out with me tonight?”,  “Would you come over to my apartment tonight?”,  or “Would you go to bed with me tonight?”.  Fifty percent of both men and women approached agreed to the request to go out; no women, but 69% of men agreed to the other two requests.  The men were reported to be at ease with those requests, saying “Why do we have to wait till tonight?” or “I can’t tonight, but tomorrow would be fine”.  Men who refused gave apologies, such as “I’m married”, or “I’m going with someone”.  The women’s responses to the latter two requests were “You’ve got to be kidding” or “What is wrong with you? Leave me alone”.

Fisher and colleagues did not discuss whether the three systems of feelings might differ in relation to sexual orientation.   It would seem that lust as compared to romantic attraction plays a stronger role in motivating men who identify as homosexual as compared women who identify as lesbian, as it does with heterosexual men compared to women.  Attachment also seems to play a stronger role in female than male homosexual relationships.  In Bell and Weinberg’s study of men and women who identified as homosexual, the majority of men reported having 100 or more same sex partners, the majority of homosexual women, less than 10.   The majority of men said more than half their male partners were strangers, with whom they had sex only once, whom they did not see again socially, and for whom they had no affection.  The majority of homosexual women said none of their female partners were strangers, and they had affection for most of them.  Less than 16% of the women said that they had sex only once with, or did not see again socially, more than half their female partners.   Twenty-nine percent of the women as compared to 16% of the men said they had had six or more “affairs”, defined as relatively steady relationships with same sex partners.  Ninety percent of the women and 78% of the men were in love with the partner of the first affair.   Seventy-two percent of the women were currently involved in an affair as compared to 51% of the men, but its duration tended to be longer in men, being more than 5 years in 31% of men, compared to 15% of women.   Eighty percent of the women and 66% of the men involved in an affair were living with the partner.   Over half the homosexual women but less than half the homosexual men considered a permanent living relationship with a partner was very important or the most important thing in life.  Most men living with a same-sex partner kept their incomes separate and were having sex with other same-sex individuals.  The majority of women living with a same-sex partner combined their incomes and did not have sex with other same-sex individuals.

Homosexual men report having had markedly more sex partners than do heterosexual men.  In the representative study of Laumann and colleagues, men who identified as homosexual or bisexual had a mean of 43 partners since age 18, whereas those who identified as heterosexual had a mean of 16.   It has been pointed out that the greater number does not necessarily reflect a stronger  lust motivation in homosexual than heterosexual men.  It could be due to fact that it is easier to have casual sex activity when both partners are male, as both have higher lust motivation.  Heterosexual casual sex activity is limited by the woman’s lower lust motivation.   The widespread disapproval of homosexuality is likely to result in greater difficulty of maintaining homosexual than heterosexual partnerships for a long duration, so that homosexual compared to heterosexual men and women are more likely to seek new partners.   In the study of Laumann and colleagues, the mean number of partners since age 18 for women who had some same-sex partners was 20, whereas the number for women who had no same-sex partners was 5.  Only 30% of all the men in the study, of whom 97% identified as heterosexual, were in love with their first sexual partner, indicating the strength of lust motivation in heterosexual men.

Fisher and colleagues did not discuss whether there was a fourth brain system for desire for parenting, different from that for attachment, which accounted for the marked differences in people’s desire for children.  There has been little investigation of the strength of this desire in either heterosexual or homosexual adults.  The increased number of homosexual couples who have or are planning to have children as this has become socially more acceptable indicate that social factors influence at least the ability to act on this desire.   The increasing number of heterosexual couples who feel able to say they do not plan to have children also indicates the importance of social factors.  Hopefully future research will use anonymous questionnaires to identify and include in studies of sexual and parental relationships the approximately 20% of homosexual heterosexual women and men most of whom overtly adopt a heterosexual life-style.

In relation to the study of sexual orientation, it could be argued that different factors are responsible for the homosexual feelings of homosexual heterosexuals and of men and women with predominant homosexual feelings.   If so, this should be revealed by the investigation of men and women in relation to the ratio of their anonymously reported heterosexual to homosexual feelings in addition to their identification as heterosexual, homosexual, or bisexual.  However as pointed out in Chapter 2, it has been established that there is a relationship between opposite sex-linked behaviors and homosexual as compared to heterosexual feelings whether they are predominant or not. If the theory that opposite sex-linked behaviors are strongly influenced by prenatal hormonal exposure is valid, it would indicate that at least this hormonal factor is important in the development of homosexual feelings in both identified homosexuals and homosexual heterosexuals.  Information from anonymous studies should also help clarify the relationship between degree of heterosexual to homosexual feelings, feelings and expression of lust, love, attachment and desire for parenting, and adoption of a heterosexual as opposed to a gay or lesbian life-style.

Professional Web Site Powered by Bold Business Tools