Biological Determinants and Homosexuality
By Bruce L. Gerig

An interviewer once asked the social theorist Michel Foucault what he thought about “innate [biological] predispositions,” and he replied: “No comment. . . .  I don’t believe in talking about things that go beyond my expertise.”1    Yet sometimes it is very important, even critical, in the study of a broad topic to read beyond one’s specialty, to deepen and clarify one’s understanding.    As early as 1983 Jo Durden-Smith and Diane deSimone published a book titled Sex and the Brain in which they wrote: “In humans, monkeys, rats, guinea pigs, birds—practically everywhere we look in nature—the quantities of sex hormones available to the fetus during critical periods of early development stamp onto the developing brain a variety of masculine and feminine sexual and social behaviors—usually, but not always, in accordance with the genetic sex.”2    And during the past half century, a flood of scientific research and peer-reviewed articles has appeared, in disciplines as diverse as biology, neurology, endocrinology, genetics, psychology, ethnology and anthropology, exploring sexual orientation.3    This research has recently been summarized in three books: Stanford University biologist Joan Roughgarden’s Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People (2004), British psychologist Glenn Wilson and psychobiologist Qazi Rahman’s Born Gay: The Psychobiology of Sex Orientation (2005), and American neuroscientist Simon LeVay’s Gay, Straight, and the Reason Why: The Science of Sexual Orientation (2011)—the last title offering a bibliography of over 600 scholarly sources.

Rahman and Wilson, in an earlier article (2003), noted that any study of homosexual orientation wades into the nurture/nature debate; yet while social constructionists argue that sexuality is fluid and can only be understood in socio-political contexts, biological scientists feel that postmodern philosophy is a poor intellectual framework in which to understand the biology that underlies human sexual development.4    This does not mean that psychological and sociological factors have no influence (LeVay; Brill and Pepper);5 yet what roles do biological factors play in determining sexual attraction and gender identity?    Not that biological research is easy.    Nicholas Kristof (2003) calls for caution because of possible researcher bias, frequent use of small samples, and difficulties in finding good random samples, including both gays and straights.6    Yet, a more fundamental difficulty here lies in the fact that invasive (modification) research on human fetuses and living brains cannot be done, for obvious ethical reasons; and so most evidence for fetal sexual development and brain/body interaction in humans must be gathered indirectly.    Still, vital information has been gleaned in recent years from six areas: animal research which suggests models for human study, human sexual anomalies that appear in nature, gender differences in adults and in gender atypical children, twin and family studies, search for correlative evidence, and examination of psychological causation studies and theories—all of which will be discussed below.  

Animal research and models.    During the past half century some of the most significant findings in biological science relating to homosexual orientation have come from animal laboratories.    William C. Young (1959) at the University of Kansas reported that injecting female guinea-pig fetuses with testosterone prevented them as adults from performing lordosis (i.e., raising their rumps to invite sexual mounting by males), the most typical female sexual behavior.7    With rats, Young further discovered that when he castrated male babies (who are born at a much earlier stage of development than guinea pigs and humans), they later failed to act sexually like male rodents, even when given testosterone injections.    Therefore Young and his colleagues concluded that a lack of testosterone early in life feminizes the male pup’s developing brain.8    Robert Goy (1981, 1986, 1988) and colleagues at the University of Wisconsin in Madison found that when female macaque monkeys were injected with testosterone in the womb, later as juveniles they began to engage in male-like fighting and sex play and as adults they commonly exhibited male-typical sexual behavior.    Moreover, these researchers found several critical times when sexual hormones played a decisive role in brain genderization.9    In the 1980s more research was carried on, with hamsters, ferrets, pigs and zebra finches, which also showed that when female fetuses were injected with androgens (male sex hormones), they matured to prefer female sex partners; and conversely when male fetuses were injected with testosterone blockers, they matured to prefer male sex partners.10 

As LeVay notes, animal experiments are fundamental to the study of human biology, although this is not to say that animals are the same as humans, since every species is unique.11     Yet similarities often do exist, which can shed light on probable human physiological processes.    Not only do males and females, in animals and humans, have differing genital structures and secondary sex characteristics (i.e., not directly related to reproduction), but also there are differences in male and female brains which have been observed—especially in the hypothalamus, a small region at the base of the brain which regulates sexual and other basic functions.12    For example, Roger Gorski (1978) and his group at UCLA discovered a region called SDN-POA (sexual dimorphic nucleus of the preoptic area) which was eight times larger in male rats than in female rats.    Dimorphic simply means differing in structure between males and females.13    Later, this same team (1989) found a comparable region in humans called INAH3 (third interstitial nucleus of the anterior hypothalamus), which appears two-to-three times larger in men than in women.14    Then LeVay (1991) reported from a small autopsy study that gay men had a significantly smaller INAH3 region than straight men, more like straight women.15    A Netherlands brain study (2008) found that male-to-female transsexuals also had a smaller INAH3 than non-transsexual men.16 

Now biologist Bruce Bagemihl (1999) has documented that same-sex courtship and sex are not unnatural among vertebrate animals, presenting evidence to show that homosexual behavior and partnerships have been observed by scientists in nearly three hundred species, ranging from birds to primates.17    Yet, as LeVay notes, in most cases this is not an exclusive preference, since most of these animals also engage in heterosexual acts.    Also, some homosexual choices may be “second-best.”    For example, Konrad Lorenz (2006) and his Austrian colleagues noted that male-male pairing among greylag geese (Anser anser) took place during years when female numbers were reduced by predators; however, when males and females appeared in more equal proportions, the males tended to mate with females—except for older males whom the females rejected.18    Still, an exclusive, durable sexual preference for same-gender partners has been found in domesticated sheep (Ovis aries), where about 10 percent of the rams refuse to mate with ewes, but instead seek to mate only with other rams.19   Furthermore, Charles Roselli’s group at Oregon Health and Science University found differences in the hypothalamus of homosexual rams and heterosexual rams, the former having a SDN-POA about half the size of the latter.    Yet, apart from their choice of same-sex partners, these homosexual rams otherwise displayed typical male sexual behavior.    The researchers therefore theorized that these homosexual rams had experienced somewhat lower levels of testosterone at certain times as fetuses in the womb, which had feminized their brain to a certain degree20—which then resulted in an intermediate, partial sexual inversion.  

Human anomalies in nature.    Congenital adrenal hyperplasia (CAH) is a genetic condition affecting certain genetic females (with XX chromosomes) which disrupts the synthesis of androgen-inhibiting cortisone in the adrenal glands, so that instead the male hormone androstenedione is produced, which is then converted into testosterone and dihydrotestosterone.    While these genetic females have ovaries, excessive androgens (male sex hormones) in the fetus masculinize the genitalia so that they turn out to be ambiguous.    Some are born with an enlarged clitoris (with or without a vaginal opening), while others have a micropenis or a full penis with (empty) scrotum.    If diagnosed early, corrective surgery and hormone treatment can allow a CAH infant to be raised as a normal girl.21    Yet numerous studies done on CAH girls have reported elevated rates of homosexual (lesbian) desire.    John Money (1984) and colleagues noted in a group of 30 CAH women that 48 percent reported lesbian attraction and 22 percent had engaged in lesbian behavior.22    German researchers interviewed 34 CAH women, compared to 14 non-affected sisters, and found in the group of CAH women over 21 years of age that 44 percent expressed lesbian interest, much higher than in the control group.23    A Canadian study of CAH women, aged 18 or older, also found significantly higher rates of lesbian fantasy and less sexual experience with men than in a control group of non-affected sisters or female cousins, although little actual lesbian activity was reported in this CAH group.24    LeVay notes that now nineteen studies investigating CAH women all have found a number to be “very significant shifted” toward lesbian interest.25    A recent study of 39 women in the Kinsey studies who had the severe form (called “salt-wasting” CAH) showed that 5 turned out to be exclusively lesbian, 16 displayed from mild to strong bisexual feelings, and 18 turned out to be exclusively heterosexual.26    The fact that all of these CAH women did not turn out to be lesbian shows that other biological factors come into play here, even if unidentified.    Still, the CAH women with even the milder form of CAH showed a modest but significant homosexual shift, compared to women in general.27  

Androgen-insensitivity syndrome (AIS) is a hereditary condition found in some genetic males (XY) passed on through X chromosomes, which produces receptor cells that respond poorly or not at all to male sex hormones (androgens) in the fetus, so that the body is moved in a feminine direction.28    In the “complete” state of this condition (CAIS) individuals develop female genitalia, but they have no pubic hair and are infertile.    They have internal, undescended testes (which are often removed surgically).    A U.S. study of 14 CAIS “women” found that all but one reported sexual attraction, fantasy, and behavior toward men (Wisniewski et al., 2000).29    A Cambridge University study of 22 CAIS “women,” compared to 22 controls matched for age, race, and sex of rearing, found that the CAIS “women” were as likely to have heterosexual interests as genetic females (XX) and to be married or living with a man (Hines et al., 2003).30    Wilson and Rahman note that these “CAIS data are powerful evidence supporting the prenatal androgen theory because they show that a lack of androgen action leads to sexual attraction toward men” in these CAIS genetic males.31    Sometimes the condition does not come to light until puberty, as with Mrs. Went, an English housewife, who having the external appearance of a female, did not discover that she had CAIS until she visited a gynecologist at age 23 to see why she was not menstruating or growing pubic hair.32 

In other cases XY males have displayed a genetic anomaly in which the body is unable to process the male sex hormone dihydrotestosterone, with gender-bending effects.    There seemed to be nothing wrong with the life of “Amaranta Ternera,” who lived in the Dominican Republic, but there was something unusual with her genes, extending down through seven generations—for thirty-eight of her descendants were born appearing as girls, but when they reached puberty they became boys.    For example, four of the ten children born to Gerineldo and Pilar Babilonia went through this remarkable transformation: they were born with an apparent vagina and were raised as girls, but then at puberty their girlish voice began to deepen and their “clitoris” grew into a penis, and two testicles in a scrotum descended from the lips of their “vagina.”    So the children’s names and clothes were changed, and thereafter they were raised as boys.    Today they are muscled, sexually potent men.    Interestingly, after this sexual change, these children had no difficulty adjusting to their new gender, sexual orientation, and male role—for genetically they were male.    What they inherited from Amaranta was not an insensitivity to testosterone, but rather an inability to process it into another male hormone, dihydrotestosterone, which is responsible in the male fetus for shaping the male genitalia.    These children were implanted with a masculinized brain before birth, although it lapsed in a feminine phase until puberty; then, however, male hormones surged forth to change the children’s sexual organs and their sense of identity into male (Durden-Smith and deSimone).33  

Sometimes other accidents of nature shed light on the formation of sexual orientation.    For example, it has been observed that when damage occurs to the BSTc (central subdivision of the bed nucleus of the stria terminalis, in the hypothalamus), altered sexual behavior can occur, including hypersexuality, change in sexual orientation, and fetishism.34    Also, heterosexual men afflicted by Klüver-Bucy syndrome—caused by damage to the temporal lobe (front part) of the brain, including the amygdala (which processes emotions, sexuality and social functions, and is a major source of input to the medial preoptic area of the hypothalamus35)—can experience homosexual feelings.36    Both of these cases show that changes in brain circuitry related to sexual function (in the hypothalamus) can produce feelings of homosexual attraction in previously heterosexual men, although usually in a reduced form.37 

Gender differences in general and in gender atypical children.    It is clear that boys and girls in general display fairly consistent gender differences.    Boys usually prefer rough-and-tumble games and playing with cars, guns, and balls, while girls prefer playing with dolls and dishes.    Boys are better with throwing accuracy, and girls better with fine hand movements.    Girls are more people-oriented, boys are more thing-oriented.    Now while parental encouragement, role modeling, peer pressure, and other social forces may exert a certain effect here, a great deal of evidence now suggests that biological factors play a critical role.38    Not only can such gender (and gender-variant) behaviors be observed in animals (including apes, monkeys and rodents) but these gendered traits appear very early in human life.    For example, it has been observed that newborn girls prefer to look at faces, while newborn boys prefer to look at mechanical mobiles (Connellan et al., 2001); and differences in toy preferences are observable at 3–8 months (Alexander et al., 2009).39    Stephanie Brill (Children’s Hospital, Oakland, CA) and Rachel Pepper (Yale University) note that transgender children may also have a sense of who they are between the ages of 2–4.    For example, Alejandro, from the time he could barely talk, tried to tell his parents that he was not a boy but a girl; and soon he was trying on his older sister’s dresses and his mom’s makeup.40   Therefore, gender-identity difference, as well as homosexual orientation, appear to derive from variations in sex hormone exposure, other biological variables, and brain sexual differentiation during fetal development (LeVay).41 

Richard Friedman and Jennifer Downey (2002) note how researchers have found that most CAH girls (with increased male hormone activity in the fetal stage) tend to show less interest in doll-play and feminine self-adornment than expected with girls; and when they grow up, they tend to place more emphasis on career than on marriage.    As children they display a greater preference for boy playmates and rough-and-tumble activities, which continues into adolescence (Berenbaum, 1999).42    In fact, Friedman and Downey write, “The influence of prenatal androgen on childhood gender role behavior is robust, has been demonstrated in many independent studies, and occurs when there is virtually no androgen [found later] in the blood.”    These effects cannot be explained in psychoanalytic terms, they add.43    Still, the fact that most CAH women experience menstrual cycles shows that the degree to which the brain was androgenized prenatally was not enough to alter the normal feminization pattern in the hypothalamus that regulates the menstrual cycle.    As noted earlier, most (genetically male) CAH girls will grow up to become heterosexual women, although the frequency of lesbian fantasy in this group is “undeniably increased.”44 

Now one of the strongest findings related to sexual orientation research is that children who will eventually become gay or lesbian (“pre-gay children”) show greater childhood gender nonconformity (CGN), or atypicality, than children who will grow up to be heterosexual adults (Wilson and Rahman).45   Of course the idea that gay men must be feminine and lesbians masculine in appearance and behavior overlooks considerable diversity in life, as also with heterosexuals.    Some gay males appear indistinguishable from the average heterosexual male, or even push their masculinity.    In fact, LeVay notes that gay people may arrive at their sexual orientation through quite different pathways.46   Some male athletes who later come out as gay describe how they always loved sports, defying expectations at this point.    Yet, Richard Isay, a psychiatrist who is also gay, has noted that “Each of the several hundred gay men I have seen in consultation or treatment over the past 30 years has described having had one or more gender-discordant traits during childhood.    Most frequently they report a lack of interest in ‘rough-and-tumble’ or aggressive sports; many speak of having preferred to play with girls rather than boys. . . .  Almost all recall that as children they felt a close bond with their mothers, with whom they shared many interests.”47    Of course, strongly non-conforming children are likely to experience more anxiety and depression than other children, and so later seek out psychiatric help; yet still there seems to be some truth to the stereotyping here (LeVay).48 

To study childhood gender nonconformity, researchers have conducted retrospective studies, which interview large numbers of gay and straight adults about their childhood.    UCLA psychologists interviewed gay men, lesbians, straight men and straight women (198 in each group), recruited from the general population; and they found that those adults who remembered playing baseball between the ages of 5–8 included 57% of the straight men, 49% of the lesbians, 28% of the straight women, and 19% of the gay men (Grellert et al., 1982).49    A more recent study looked at how consistently pre-gay boys differ from pre-straight boys in Turkey, Brazil, and Thailand; and researchers here found that pre-gay boys were less likely to be interested in sports and more likely to associate with girls and girls’ activities than pre-straight boys (Cardoso, 2009).50   More ideal (but harder to do) are prospective studies, which begin with children as children and then follow them into adulthood.    The best-known study of this kind was done by UCLA psychiatrist Richard Green (1987) between the late 1960s and early 1980s, which included 66 feminine boys and 56 other boys, matched for other variables.    Most of the feminine boys would have preferred to have been girls, some even appearing transsexual, while the control group was generally selected (i.e., not necessarily for being “masculine”).    Green interviewed the children and their parents during the boys’ childhood and adolescence periods.    At the end, he found in the “other” group (the 35 whom he was able to follow to the end) all turned out heterosexual.    However, among the 44 markedly effeminate boys (whom he was able to follow to the end), 33 became homosexual or bisexual, and 11 heterosexual.    Although some of the feminine boys did turn out to be heterosexual, still in 75 percent of these boys a marked femininity in childhood was a predictor of homosexual or bisexual interest in adulthood.51 

Twin and family studies.    It would be unlikely if the approximately 30,000 genes on the 46 human chromosomes in a fertilized egg (XX pairs in the female and XY pairs in the male) did not have some impact on many of an individual's personal traits (including physical appearance and gender, as well as innate predispositions and talents), even in subtle and indirect ways (such as predisposing a boy to prefer fashion or the arts instead of rough-and-tumble sports).52    That a person’s genetic code can also influence a person’s sexual orientation is seen in twin and family studies, although not as an “all-domineering influence” (LeVay).53   Of special interest are monozygotic (identical) twins, who come from a single fertilized egg and so share essentially all of the same genes, and dizygotic (fraternal) twins, who come from two different eggs in the same mother, fertilized by two different sperm, and so share about one-half of their genes.54    In twin studies published in the early 1990s, Michael Bailey (Northwestern University), Richard Pillard (Boston University) and other investigators found that homosexuality was shared among 50 percent of identical-twin brothers, with a lower but still significant rate among fraternal-twin brothers.55    Fred Whitam (1993) and his group at Arizona State University found even higher rates of 65 percent and 29 percent, respectively.56    Using a larger twin registry, an Australian study found a 30 percent rate for pairs of male twins and a 50–60 percent rate for pairs of female twins (Kirk et al., 2000).57    Some researchers have suggested that identical twins generally share around 80 percent of the same characteristics, ranging from from height and health to IQ and political views—although upbringing also plays a role.    Therefore, of special interest are identical twins who have been raised apart.    Psychologist Thomas Bouchard and colleagues at the University of Minnesota tracked sixty such pairs (raised apart), and found that still their behaviors, personalities and social attitudes, displayed in answers to lengthy batteries of tests, were often remarkably alike.    The first such pair Bouchard met were James Arthur Springer and James Edward Lewis, who were only reunited at age 39 after having been given up by their mother and separately adopted as one-month-olds.    Living in Ohio, both liked mechanical drawing and carpentry, their favorite subject in school was math and their least liked subject was spelling, and they even married and divorced a woman named Linda and then married another woman named Betty.58   Both had carpentry workshops installed in their homes, loved car-racing and hated baseball, drank the same brand of beer (Miller light) and smoked the same brand of cigarettes (Salem), and had suffered from migraine headaches from their teenage years.    Each bit his fingernails, wrote love notes to his wife which were left around the house, and had a ten-pound weight gain at the same age as the other twin—to name a few similarities.59    Yet another set of twins, Oskar Stohr and Jack Yufe, separated six months after their birth in Trinidad, seemed to show more the influence of nurture, since Oskar was raised as a Catholic and then joined the Hitler youth, while Jack stayed in the Caribbean, was raised as a Jew, and then lived for a time in Israel.    Yet, when the twins were reunited in their fifth decade, they displayed similar speech and thought patterns, similar ways of walking, a taste for spicy food, and common peculiarities like flushing the toilet before using it.60    Now no one claims that there is a gene for marrying women with the same first name or flushing the toilet before using it; instead researchers view such similarities as “coincidences” and “statistical anomalies.”    Still, such studies strengthen the case for the power of nature and genetic influence.    As Bouchard notes, “There probably are genetic influences on almost all facets of human behavior.”    However, he holds that identical twins raised apart are still probably only about 50 percent similar, because other (social) factors play a role here as well.61 

But what about cases of identical twins where one of them is gay or lesbian and they are raised apart?    Although such pairs are hard to find, Bouchard located six such cases, including two pairs of brothers and four pairs of sisters.    One gay twin didn’t know that he had a gay brother until they met by chance in a gay bar.    The other male pair included one twin who identified himself as gay, although he had had relationships with women earlier in his life, while his twin brother identified himself as straight, although he had had a homosexual relationship earlier in his life.    However, among the women, in each pair one woman was lesbian or bisexual while the other twin was heterosexual (Ekert et al., 1986).62    Although the sample here is small, considering the larger twin studies LeVay suggests that male homosexuality in some cases may be inherited.63  

Yet Ray Blanchard (1996) and colleagues in Toronto found in a review of fourteen studies, including 7,000 male participants, done in several countries and spanning several decades, that in all of these studies gay men tended to be born later in birth sequence than heterosexual men.    They also found that gay men have significantly more older brothers (on an average 1.31, compared with 0.96 for straight men), although the number of younger brothers or older or younger sisters showed no effect.64    This observation, called the “fraternal birth order effect” or “big brother effect,” is backed up by the Kinsey data;65 and this effect seems even stronger with very effeminate gay men.66    Blanchard estimated that the odds of being gay increase around 33 percent with each older brother.67    Therefore, the more sons a woman has, the greater the likelihood that one or more of them will be gay.    Wilson and Rahman call this “one of the most reliable correlates of male sexual orientation.”    Still, no such correlation was observed with lesbians.68    Blanchard’s group estimated that one in seven gay men may owe their sexual orientation to this big brother effect.69    Also, no proof was found in these studies that incestuous sexual play led to homosexual orientation nor that the big brother effect stems from living with older brothers or from family dynamics.70    Although the precise biological mechanism is still uncertain, Blanchard proposed that a mother’s immune system keeps track of how many male fetuses she has carried, stimulating production of antibodies in the carrying of later male fetuses to protect her balance of sex hormones.71    With homosexual orientation, genetics cannot account for everything, nor can birth order, nor can varied exposure to prenatal male sex hormones; indeed many biological factors may come into play (Wilson and Rahman).72    As Stanford University biologist Joan Roughgarden explained, human sexuality and gender expression are a “rainbow” of diversity.73   Each individual has his or her unique “gene committee” which fashions what becomes “that individual’s embodiment of gender and sexuality,” and normal people (including those whom some would call ‘abnormal’) appear “as genetically diverse as snowflakes.”74    Homosexuality does seem to run in families, although a maternal link has not yet been verified; and a single “gay” gene seems unlikely.75    Roughgarden also believes that since gender identity seems set by the first year of life, sexual orientation may also begin to solidify then.76    However, why ten percent of males appear to be gay and five percent of women appear to be lesbian (based on Kinsey’s statistics), no one knows.77 

Search for correlative evidence.    Because of the difficulty in tracing direct genetic and hormonal influences, scientists have sought to investigate brain gender differentiation by conducting indirect research on what are called "correlates," which may be found in neuroanatomical brain features, neuropsychological features, and overall body features.78   More specifically, if a link can be shown to exist between homosexual orientation and certain general dimorphic variations (differences in physical and psychological features between males and females) which are biologically determined, then homosexual orientation probably also shares a biological basis.79    With regards to brain features, we have already noted significant differences discovered in the hypothalamus between gay men and straight men and between male-to-female transsexuals and straight men, probably due to lower testosterone levels experienced during critical phases of fetal brain development.       

Relating to neuropsychological features (cognitive or mental abilities), men typically score better on mental rotation (like turning an object around in their imagination), in perceiving and judging spatial relations, in targeting and intercepting moving objects (like throwing and catching a ball), and in finding their way in unfamiliar environments (by reading maps and relating themselves to compass points).    In contrast, women typically score better in verbal fluency (such as recalling many related words quickly), in remembering the location of objects, in social and communicative skills (such as reading people’s faces), and in showing empathy (understanding people’s emotions).    Although some researchers have claimed that these aptitudes are learned, this division between the genders has been observed universally; and there is direct evidence relating this to elevated levels of testosterone in the fetuses of CAH women, who later display enhanced skills with male-typical cognitive abilities, like targeted throwing.80    In terms of personality, men typically are more assertive, competitive, aggressive, independent, and interested in getting things done, while women typically are more expressive, social, empathetic, altruistic, and open to feelings.81   Now relating to gay men and lesbians, there appears to be a considerable crossover here to the opposite gender.    One study of heterosexual and homosexual men and women (60 in each group) showed large differences between straight and gay men, the former doing better on tasks like mental rotation and judgment of line orientation, while the gay men did better on tasks like verbal fluency and object location memory, like women.    Such results have been corroborated by numerous studies.    These cognitive differences have nothing to do with IQ, and are found (as we have seen) in children as well.    Yet the data for lesbians is less consistent and marked.82    Evidence from many sources, including brain-damage cases, shows that men process language almost entirely using the left hemisphere of the brain, while women use both halves of the brain; and this may explain why men are typically better at spatial tasks, because more of their left brain is available for this.    However, gay men, like women, appear more bilaterally organized (using both sides of the brain) in language processing—although no difference was seen here between lesbians and straight women.83 

Relating to overall body features (physical characteristics), Rahman and his team found reliable differences between straight men and straight women in pre-pulse inhibitions (PPIs), observed in eye-blinking when a person is startled by a loud sound (like a scratching noise), especially if preceded by a weaker sound.    In humans and animals, females have shown a lower PPI response than men.    A British study found that lesbians tended to respond like straight men, and gay men like straight women, only not statistically-significant in the latter case (Rahman et al., 2003).84    Relating to penis size, data from the Kinsey archives on 935 gay males and 4,187 heterosexual males showed that gay men self-reported an average erection length of 6.32 inches while heterosexual men reported a lower average of 5.99 inches. (Bogaert and Herschberger, 1999).85   This finding backs up an earlier study where the researchers did the measuring themselves (Nedoma and Freund, 1961), ruling out possible self-reporting exaggeration.86    Male rhesus monkeys exposed to higher levels of androgens in the womb tend to develop larger penis sizes (Herman et al., 2000).87    Since this seems to run counter to the theory that gay men generally experience lower androgen levels during critical points of fetal development, Bogaert and Herschberger suggest that gay men might also have experienced a spike in testosterone levels at another point in fetal development critical for genital development.88    Relating to left-handedness, a meta-analysis of twenty studies showed that gay people overall have a greater chance of being left- or both-handed, over straights; and this seems to be more so in lesbians (91 percent) than in gay men (34 percent).    It is thought that this is due to a certain masculinization in lesbians and a certain hyper-masculinization in gay males at some point (Lalumčre et al., 2000).89    Relating to finger-length on the right hand, the index finger (second finger) compared to the ring finger (fourth finger) appears to be dimorphic.    This 2D:4D ratio is obtained by dividing the length of the index finger by the length of the ring finger.    While early studies suggested that gay men and lesbians appeared more like the opposite gender in this regards, results from follow-up studies have been inconsistent.90    Yet one study suggested that butch lesbians may have 2D:4D ratios more like men, while femme lesbians do not (Brown et al., 2002).91    At least, CAH women (exposed to higher amounts of testosterone as fetuses) have more male typical 2D:4D ratios in the right hand than other women (Brown et al., 2002).92   With regards to other suggested correlates, later studies have failed to confirm that gay men have less fingerprint ridges than straight men, i.e., that they appear more like women in this regards.93    Later studies also have failed to confirm that on the average gay men display less weight and height than straight men, and vice versa for women.94    Nor have later studies confirmed that gay people reach puberty earlier than straights,95 nor that the hair on the top of gay men’s heads tends to whirl in a counterclockwise fashion, opposed to the clockwise whirl found more commonly on straight men.96    Overall, related to correlative research, it must be said that in many cases the ongoing results here have been uneven and even contradictory; and in the end they shed little light on the larger picture of how sexual orientation and gender orientation develop in the fetus.

Psychological causation studies and theories.    In a number of cases attempts have been made with infant boys lacking a normal penis to raise them as girls—almost always with disastrous results.    The most famous case involved two identical twins named Bruce and Brian Reimer, who were born on August 22, 1965 to a couple living in Winnipeg, Manitoba, Canada.    Seven months later, when the boys’ foreskins appeared to be closing up, their parents, Ron and Janet, took them to the hospital to be circumcised; however, the attending physician who used an electrocautery needle instead of a scalpel ended up burning off Bruce’s entire penis.    (Brian’s condition eventually corrected itself over time.)97    The Reimers, concerned about Bruce’s future happiness without a penis, took him to see John Money, a famous psychologist at Johns Hopkins University Medical Center in Baltimore, after hearing the charismatic doctor speak in February 1967 on TV about his work with transsexuals and intersex babies, expressing his view that through surgery and hormone treatment a child could be raised happily as either male or female.98    Money would later view the Reimer twins case as the ultimate experiment that would prove that nurture, not nature, determines gender identity and sexual orientation.99    So in July 1967 at Johns Hopkins Hospital Bruce had both testicles removed and a rudimentary external vagina formed; he was renamed “Brenda” and was henceforth to be raised as a girl.100   Probably his parents did not know that this was the first sex reassignment surgery that had ever been done on a developmentally normal child.101    Later Money published reports, through the 1970s, that his work was an unqualified success: learning and environment were indeed turning Brian into a happy little boy and Brenda into a happy little girl.102    Yet Brian later recalled that “there was nothing feminine about Brenda . . . She walked like a guy . . . She talked about guy things . . . We both wanted to play with guys, build forts and have snowball fights and play army.”    Brenda refused to play with the dolls given to her.103    When Money was told about this, he replied that Brenda was simply going through a ‘tomboy’ phase.    Indeed, when she entered the first grade, she was always fighting with the kids and playing in the dirt.104 

Money had requested that the Reimers bring both Brenda and Brian to Baltimore once a year to see him, even though the children found these visits bewildering and unsettling.    In his office Money showed them nude photos of children and adults (to reinforce each child’s gender identity); and at age 6 he had Brenda get down on all fours, while Brian thrust his crotch against her from the rear.105    When Brenda was age 7 Money began to urge her to have additional vaginal surgery, which she was determined not to have; instead she dreamed of someday having a mustache and driving a sports car.106    In the sixth grade (at age 14), one of the many psychiatrists in Winnipeg who saw Brenda urged her parents to tell her the truth about what had happened; and when Ron, her father, told Brenda that a doctor had ‘made a mistake down there,’ she asked, “Did you beat him up?”107    Actually Brenda felt greatly “relieved,” because, as she would later explain, “Suddenly it all made sense why I felt the way I did. . . .  I wasn’t crazy.”108    Brenda at first refused to take the estrogen pills prescribed for her—she didn’t want breasts—although she finally did because Money warned her that otherwise she would grow disproportionately long limbs.109    On her last visit to see Money on May 2, 1978, Brenda panicked when Money introduced her to a transsexual—obviously a man dressed like a woman—and she ran out of his office.    Later she told her mother that if she was ever forced to see Money again, she would kill herself.110 

When BBC-TV reporters showed up in Winnipeg one day in 1979 to make a documentary on gender identity, psychiatrist Keith Sigmundson confessed that he doubted Brenda “will ever make an adjustment as a woman.”111   The film The First Question aired in Britain on May 19, 1980, although out of fear of Money, Sigmundson had forced an agreement that the program would not be sold or shown in Canada nor in the U.S.112    Meanwhile, in September 1979 Brenda’s parents enrolled her in a vocational school, at age 14, for the ninth grade, where the boys told her, “You’re a fucking gorilla”—because of how she walked and because of her deep voice, which somehow had changed at puberty like her brother’s.113    Brenda told one understanding psychiatrist, Mary McKenty, that she wanted to become a boy now and had chosen “David” as her new name, after the giant-slayer in the Bible.    McKenty, not afraid of Money, supported this; and suddenly the new “David” appeared much happier.    He made his debut as a boy to his extended family in August 1980, a week after his 15th birthday, at a wedding reception.114    He began taking testosterone injections, endured a painful, double mastectomy (to remove his breasts), and then shortly after his 16th birthday had a rudimentary penis constructed from muscles and skin from one of his thighs—although over the next year he was hospitalized 18 times for blockages and infections.    Afraid of meeting Brenda’s old acquaintances, it was two years before David would leave the house, to visit fast-food places and bars.115    Later he learned of a new type of penis constructed through microsurgery, that would provide sensation, which he had done shortly after his 22nd birthday, which took three surgeons 13 hours to perform.116    Although he despaired of ever finding a wife, he fell mutually in love with a slightly-overweight but pretty, nurturing women named Jane, who liked and accepted David just as he was; and so they were married on September 22, 1990.117 

After the BBC-TV documentary David was contacted by another psychologist, Milton Diamond of the University of Hawaii–Manoa, who studied intersexes and who disagreed with Money’s theories and believed that his protocols had done a lot of harm to children.    Diamond had earlier done his graduate work under biologist William Young at the University of Kansas, where in the late 1950s his team made the discovery that when testosterone was given to female guinea-pig fetuses this propelled them later to perform male sexual activity (mounting), and vice versa with males.118    David was surprised to learn that his case was famous in medical literature and that it was still being used as a precedent to perform sex reassignment surgeries on children.    So he agreed to let Diamond and Sigmundson write an update on his case, although he would be referred in it as “Joan” and “John.”119    Written over the winter of 1994, it was finally published in the March 1997 issue of Archives of Pediatrics and Adolescent Medicine; and here the authors noted that “no support” exists for the idea that “individuals are psychosexually neutral at birth or that healthy psychosexual development is dependent on the appearance of the genitals” in a child.120    Furthermore, psychiatrist William Reiner wrote in an editorial which accompanied the article that what is “critical to psychosexual development” is “the prenatal hormonally differentiated brain,” not genital anatomy or social-environmental influences.    Reiner also reported on six XY males he was studying who had been castrated at birth due to severe genital abnormalities and were then raised as females; and he noted that all of these “girls” displayed striking masculine characteristics, with two of them declaring themselves to be male before the age of 12, and another three describing themselves as the “most masculine girl I know.”121    Diamond and Sigmundson noted other cases where genetic males reassigned as females switched back to live successfully as males.122   Then in June 1997 David was introduced to journalist John Colapinto and agreed to let him write a feature article on him for Rolling Stone (because David was a rock’n’roll fan), which appeared December, 1997.123    David later collaborated with Colapinto to produce a full-length biography titled As Nature Made Him: The Boy Who Was Raised as a Girl (2001, updated 2006)—a story which should be read by all those truly interested in understanding sexual orientation and gender identity, as well as to observe how academic theory can sometimes go far astray and cause great harm.  

Yet in the end, David came to an unfortunate end.    First, he was never the same after his twin brother, Brian, took his own life, with an overdose of antidepressants.    Then David lost his full-time job as night watchman at a slaughter-house, which he loved, which left him brooding at home.    Then finally, Jane asked for a temporary separation, trying to get her own life together.    All of this, along with the rage, frustration, and humiliation that David had felt his whole life, led him to take a rifle and shoot himself in his car in a parking lot, at age 38, on May 5, 2004.124    Although this story deals with a heterosexual, the way in which homosexual orientation and  cross-dressing or transsexual orientation cases are firmly and nearly irreversibly rooted in prenatal experiences are no different.

A century ago the Austrian psychotherapist Sigmund Freud wrote that a normal infant passed through different libidinous (erotic) stages and that those who later became homosexual had failed to leave the oedipal phase where the infant is erotically fixated on his mother; and so later in life they seek out male rather than female sexual partners.125    Modern psychologist Daryl Bem (1996) of Cornell University acknowledges that biological factors (such as prenatal hormones) influence a child’s personality, especially relating to gendered traits, and non-gender-conforming boys tend to view themselves as different from boys in general; yet he also advocates that because of this, they later tend to look upon other males as sexually-desirable objects.126    However, no real scientific evidence supports either Freud’s mother-fixation theory or Bem’s “exotic becomes erotic” theory, or the latter’s belief that seeking to change the atypical behavior of such children will prevent a later homosexual orientation.127    Then UCLA psychiatrist Richard Green (1987) believes that femininity often triggers rejection by a child’s father (probably true) and so by improving the son’s relationship with his father and male peers the likelihood of that child growing up to be gay can be decreased.    But this attempted “socialization” overlooks the biological fact that “genes and hormones continue to exert a sustained and even growing influence over a person’s life span” (LeVay).128    The deeply-ingrained gender and sexual orientation of atypical, pre-gay children is reflected in how they often suffer as children and as adults; so if they could easily change, why would not many of them?    But they do not—because of how gender and sexual preferences have been irrevocably implanted on their brains.129 

Behavior psychologists have held that the minds of newborns are pretty much blank slates, and that sexual orientation stems from a child’s earliest sexual and pleasurable acts, e.g., a person’s being gay may have resulted from early homosexual contact with an older sibling or a male adult.    However, cross-culture studies contradict this.    For example, among the Sambians in New Guinea all boys are required to engage in sexual contacts with older males for several years before they have any access to females; yet most if not all of these boys become heterosexual men (Herdt, 1981).130   Also, homosexual behavior is common among British boys who attend single-sex boarding schools; and yet male adults from such schools turn out no more gay than other men in Britain (Wellings et al., 1994).131   In fact, most young people seem to develop an awareness of their sexual orientation while they are still virgins.    Ellen DeGeneres, who was molested by her stepfather, told Allure magazine, “But I was a lesbian way before that.    My earliest memories are of being a lesbian” (Associated Press, May 18, 2005).132    Also, if one out of three girls in the U.S. are molested before she reaches the age of eighteen (by one broad definition, in Dominguez), then why don’t more of these girls turn out to be lesbian?133

In summary, animal studies have demonstrated that when female fetuses are given testosterone injections, the animals later tend to exhibit a sexual attraction for their own sex and male sexual behavior.    Also, when male fetuses experience lowered levels of testosterone, they move in the opposite direction sexually.    That this androgen (male hormone) theory of sexual development relates to humans is shown in CAH females, who for genetic reasons experience elevated testosterone levels in the womb; and many later experience lesbian attractions.    That not all become lesbian, however, shows that multiple biological factors come into play here.    Conversely, CAIS “women,” genetic males whose androgen receptor-cells respond poorly or not at all to androgens, develop feminine genitalia and generally live out their lives as women.    Although bisexuality is far more common among animals than exclusive, lasting homosexuality, about 10 percent of common rams (Ovis aries) show sexual attraction for only other rams, although otherwise they exhibit normal male sexual behavior.    Equally interesting is the fact that a certain spot (called oSDN) in the hypothalamus, a small region at the brain’s base which is concerned with sexual and other basic functions, was found to be smaller (and more female-like) in homosexual rams than in heterosexual rams.    In human brains a corresponding area (INAH3) was also found to be smaller in gay men than in straight men.    Moreover, numerous gender differences generally appear between boys and girls, and “atypical” or “ non-conforming” children often grow up to be gay or lesbian.    CAH girls also typically display an atypical  preference for boy playmates, rough-and-tumble activities, and later male occupations.    Therefore, it becomes clear that through complex and varying factors the brain of a human fetus is implanted with a certain (typical or atypical) gender identity and sexual orientation very early in life—which express themselves in a “rainbow” of diversity (Roughgarden).    Studies of identical twins raised apart but then reunited show that their genetic closeness leads to many similar characteristics, not resulting from social learning; and this may relate to gay men as well.    Cases like that of Bruce/Brenda/David Reimer, who because of a damaged penis was raised as a girl but never felt like a girl and later rebelled against this, show that it is very difficult to change one’s pre-natal gender identity and sexual orientation.    The fact that gay and transgender children suffer so much to try to fulfill their deep-seated gender and sexual desires show that these desires are very deeply and early implanted on the brain, and they are not easily altered.   


FOOTNOTES:    1. Foucault, pp. 11-12.    2. Durden-Smith and deSimone, p. 92.   3. Ibid., p. xiii; Wilson and Rahman, p. 9.    4. Rahman and Wilson 2003a, p. 1338.    5. LeVay 2011, pp. 76–77; Brill and Pepper, pp. 9, 11–12.    6. Kristof, A19.    7. Phoenix et al., pp. 369–382; LeVay 1996, p. 115.    8. Grady et al., pp. 176–182; LeVay 1996, p. 116.    9. Goy et al., pp. 552–571; LeVay 1996, p. 117.    10. Ibid., p. 120.    11. LeVay 2011, p. 45.    12. Ibid., p. 46.    13. Gorski et al., pp. 333–346; LeVay 2011, pp. 46–47.    14. Allen et al., 1989, pp. 497–506; LeVay 2011, p. 47.    15. LeVay 1991, pp. 1034–1037; LeVay 2011, p. 198.    16. Garcia-Falgueras and Swabb, pp. 3132–3146; LeVay 2011, pp. 199–200, 214.    17. Bagemihl, passim.    18. Kotrschal et al., pp. 45–76; LeVay 2011, pp. 66–67.   19. Perkins and Fitzgerald, pp. 1787–1794; LeVay 2011, pp. 69–70.    20. Roselli et al., pp. 478–483; LaVay 2011, pp. 214–215.    21. Strong and DeVault, p. 185; Wilson and Rahman, p. 74.    22. Money et al., 1984, pp. 405–414; Wilson and Rahman, p. 75.   23. Dittman et al., pp. 153–170; Wilson and Rahman, p. 75.    24. Zucker et al., pp. 300–318; Wilson and Rahman, p. 75.    25. LeVay 2011, p. 134.    26. Meyer-Bahlburg et al., pp. 85–99; LeVay 2011, pp. 135–136 and cf. Figure 6.1.    27. LeVay 2011, p. 136.    28. Strong and DeVault, p. 185.    29. Wisniewski et al., pp. 2664–2669; Wilson and Rahman, p. 76.    30. Hines et al., pp. 93–101; Wilson and Rahman, p. 76.    31. Wilson and Rahman, p. 76.   32. Durden-Smith and deSimone, p. 93.    33. Ibid., pp. 96–98.    34. Roughgarden, p. 227.    35. LeVay 2011, p. 297.    36. Ibid., pp. 218–219.    37. Ibid., p. 219.    38. Ibid., pp. 75–77.   39. Connellan et al., pp. 113–118; Alexander et al., pp. 427–433; LeVay 2011, p. 78.    40. Brill and Pepper, pp. 4, xiii.    41. LeVay 2011, p. 276.    42. Berenbaum, pp. 102–110; Friedman and Downey, pp. 73–74.    43. Friedman and Downey, p. 74.    44. Ibid.,  p. 69.    45. Wilson and Rahman, pp. 127–128.    46. LeVay 2011, pp. 74-75.    47. Isay, pp. 187–194; LeVay 2011, pp. 83–84.    48. LeVay 2011, pp. 84, 292–293.    49. Grellert et al., pp. 451–478; LeVay 2011, pp. 84–85 and cf. figure 4.1.    50. Cardoso, pp. 726–735; LeVay 2011, p. 86.    51. Green, passim; LeVay 2011, pp. 89–90.    52. Rahman and Wilson 2003a, p. 1342.    53. LeVay 2011, p. xv.    54. Ibid., p. 161.    55. Ibid., pp. 161–163.    56. Whitam, pp. 207–226; LeVay 2011, pp. 161–163.    57. Kirk et al., pp. 345–356; LeVay 2011, p. 164.    58. Allen 1998, online, part 2, p. 1.   59. Bouchard et al., pp. 223–228; Friedman and Downey, p. 43.    60. Allen 1998, online, part 2, pp.  1–2.   61. Ibid., part 2, p. 3.    62. Ekert at al., pp. 421–425.    63. LeVay 2011, pp. 166–167.    64. Blanchard and Bogaert 1996b, pp. 27–31; Wilson and Rahman, p. 97.    65. Blanchard and Bogaert 1996a, pp. 551–579; Wilson and Rahman, p. 97.    66. Blanchard and Sheridan, pp. 40–47; Wilson and Rahman, p. 97.   67. Blanchard and Bogaert, 1996b, pp. 27–31; Wilson and Rahman, p. 97.    68. Wilson and Rahman, p. 97.    69. Cantor et al., pp. 63–71; Wilson and Rahman, p. 99.    70. Wilson and Rahman, pp. 101–102.    71. Ibid., pp. 103–104.   72. Ibid., pp. 103–105.    73. Roughgarden, p. 4.    74. Ibid., pp. 202, 215.    75. Ibid., p. 253.    76. Ibid., p. 257.    77. Ibid., p. 259.    78. Rahman and Wilson 2003a, pp. 1350–1357.   79. Cf. Olson, p. 115.   80. Wilson and Rahman, pp. 116–118.    81. LeVay 2011, p. 99.    82. Wilson and Rahman, pp. 118–119.    83. Ibid., p. 122.    84. Rahman et al., 2003b, pp. 1096–1102; Wilson and Rahman, p. 115; LeVay 2011, pp. 147–148.    85. Bogaert and Herschberger, pp. 213–221; Wilson and Rahman, p. 85.    86. Nedoma and Freund, pp. 100–103; Wilson and Rahman, p. 85.    87. Herman et al., pp. 52 –66; Wilson and Rahman, p. 85.    88. Bogaert and Herschberger, pp. 213–231; LeVay 2011, p. 229.    89. Lalumčre et al., pp. 575 –592; Wilson and Rahman, p. 124.    90. Wilson and Rahman, pp. 77–79.    91. Brown et al., 2002a, pp. 123–127; LeVay 2011, p. 140.    92. Brown et al., 2002b, pp. 380–386; LeVay 2011, p. 139.   93. Wilson and Rahman, p. 82.    94. Ibid., pp. 87.    95. LeVay 2011, p. 223.   96. Ibid., pp. 235–236.    97. Colapinto 2006, pp. 9, 12–17.    98. Ibid., pp. 18, 22, 39.   99. Colapinto 2004, online p. 1.    100. Colapinto 2006, p. 53–56.    101. Colapinto 2004, online p. 1.    102. Money and Tucker, pp. 95–98; Colapinto 2006, online p. 1.    103. Colapinto 2006, pp. 57–58.    104. Ibid., pp. 59, 63.    105. Ibid., pp. 79–80, 86–87.   106. Ibid., pp. 91–93.    107. Ibid., pp. 123–124.    108. Ibid., p. 180.    109. Ibid., pp. 129–131.    110. Ibid., pp. 136–141.   111. Ibid., pp. 168–170.    112. Ibid., pp. 175, 169.    113. Ibid., pp. 163–165, 148.   114. Ibid., pp. 150, 182–183.    115. Ibid., pp. 183–185.    116. Ibid., p. 190.    117. Ibid., pp. 191­–192, 195.    118. Ibid., pp. 40–42; Phoenix et al., pp. 368–382; LeVay 2011, p. 55.    119. Colapinto 2006, pp. 207–209.    120. Diamond and Sigmundson, p. 303.    121. Reiner 1997, pp. 224–225; cf. Reiner 1996, passim; Reiner and Gearhart, passim; Colapinto 2006, pp. 209–210, 211–213.    122. Diamond and Sigmundson, p. 303.    123. Colapinto 2006, pp. 216, 248.    124. Colapinto 2006, “A Tragic Update,” Appendix, pp. 10–13; Colapinto 2004, online pp. 1–3.    125. Freud, passim; LeVay 2011, pp. 28–29.    126. Bem, pp. 320–335.    127. LeVay 2011, pp. 93–95.    128. Green, passim; LeVay 2011, pp. 95.    129. LeVay 2011, pp. 292–293; Wilson and Rahman, pp. 40–41.   130. Herdt, passim; LeVay 2011, pp. 33–35.    131. Wellings et al., pp. 204–209; LeVay 2011, p. 35.    132. Quoted in LeVay 2011, p. 36.    133. Dominguez et al., pp. 202–207; LeVay 2011, p. 37.   



Alexander, G. M., T. Wilcox, and R. Woods.   Sex Differences in Infants’ Visual Interest in Toys.   Archives of Sexual Behavior, 38 (2009), pp. 427–433.

Allen, Arthur.   “Nature & Nurture: When It Comes to Twins, Sometimes It’s Hard to Tell the Two Apart.   Why the Genes Aren’t Everything.”   Washington Post, January 11, 1998.   Online,, 3 parts.

Allen, L. S., M. Hines, J. E. Shryne, and R. A. Gorski.   “Two Sexually Dimorphic Cell Groups in the Human Brain.”   Journal of Neuroscience, 9 (1989), pp. 497–506.

Bagemihl, Bruce.   Biological Exuberance: Animal Homosexuality and Natural Diversity, 1999. 

Bem, Daryl J.   “Exotic Becomes Erotic: A Developmental Theory of Sexual Orientation.”   Psychological Review, 103 (1996), pp. 320–335.

Berenbaum, S. A.   “Effects of Early Androgens on Sex-typed Activities and Interests in Adolescents with Congenital Adrenal Hyperplasia.”   Hormonal Behavior, 35 (1999), pp. 102-110.

Billis, Alice Ogden, and Terry L. Hufford.   Science, Scripture and Homosexuality, 2002. 

Blanchard, R., and A. F. Bogaert.   “Biodemographic Comparisons of Homosexual and Heterosexual Men in the Kinsey Interview Data.”   Archives of Sexual Behavior, 25 (1996a), pp. 551–579.

________, and A. F. Bogaert.   “Homosexuality in Men and Number of Older Brothers.”   American Journal of Psychiatry, 153 (1996b), pp. 27–31.

________, and P. M. Sheridan.   “Sibling Size, Sibling Sex Ratio, Birth Order, and Parental Age in Homosexual and Non-homosexual Gender Dysphorics.”   Journal of Nervous and Mental Disease, 180 (1992), pp. 40–47.

Bogaert, A. F., and S. Herschberger.   “The Relation between Sexual Orientation and Penile Size.”   Archives of Sexual Behavior, 28 (1999), pp. 213–221.

Bouchard, T. J. Jr., D. T. Lykken, M. McGue, N. L. Segal, and A. Tellegen.   “Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart.”   Science, 250 (1990), pp. 223–228.

Brill, Stephanie, and Rachel Pepper.   The Transgender Child: A Handbook for Families and Professionals, 2008.

Brown, W. M., J. C. Finn, B. M. Cooke, and S. M. Breedlove.   “Differences in Finger Length Ratios between Self-identified “Butch” and “Femme” Lesbians.”   Archives of Sexual Behavior, 31 (2002a), pp. 123–127.

________, M. Hines, B. A. Fane, and S. M. Breedlove.   “Masculinized Finger Length Patterns in Human Males and Females with Congenital Adrenal Hyperplasia.”   Hormones and Behavior, 42 (2002b), pp. 380–386.

Cantor, J. M., R. Blanchard, A. D. Paterson, and A. F. Bogaert.   “How Many Gay Men Owe Their Sexual Orientation to Fraternal Birth Order?”   Archives of Sexual Behavior, 31 (2002), pp. 63–71. 

Cardoso, F. L.  “Recalled Sex-typed Behavior in Childhood and Sports Preferences in Adulthood of Heterosexual, Bisexual, and Homosexual Men from Brazil, Turkey, and Thailand.”   Archives of Sexual Behavior, 38 (2009), pp. 726–736.    

Colapinto, John.   As Nature Made Him: The Boy Who Was Raised as a Girl, (2000) 2006.

________.   “Gender Gap: What Were the Real Reasons behind David Reimer’s Suicide?”    Slate, June 3, 2004, online, accessed October 24, 2011.

Connellan, J., S. Baron-Cohen, S. Wheelwright, A. Batki, and J. Ahluwalia.   “Sex Differences in Human Neonatal Social Perception.”   Infant Behavior and Development, 23 (2001), pp. 113–118. 

Diamond, Milton, and H. K. Sigmundson.   “Sex Reassignment at Birth: Long-term Review and Clinical Implications.”   Archives of Pediatric and Adolescent Medicine, 151 (1997), pp. 298–304.

Dittman, R. W., M. E. Kappes, and M. H. Happes.   “Sexual Behavior in Adolescent and Adult Females with Congenital Adrenal Hyperplasia.”   Psychoneuroendocrinology, 17 (1992), pp. 153–170. 

Dominguez, R. C., C. F. Nelke, and B. D. Perry.   “Child Sexual Abuse.”   In D. Levinson, ed., Encyclopedia of Crime and Punishment, 2002, pp. 202–207.   

Durden-Smith, Jo, and Diane deSimone.   Sex and the Brain, 1983.

Ekert, E. D., T. J. Bouchard, J. Bohlen, and L. L. Heston.   “Homosexuality in Monozygotic Twins Reared Apart.”   British Journal of Psychiatry, 148 (1986), pp. 421–425. 

Foucault, Michel, with interviewer James O’Higgins.   “Sexual Choice, Sexual Act: An Interview with Michel Foucault.”   Samandundi 58–59, 1982–1983, pp. 10–24.

Freud, Sigmund.    Three Essays on the Theory of Sexuality, 1905, reprinted 1975. 

Friedman, Richard C., and Jennifer I. Downey.   Sexual Orientation and Psychoanalysis: Sexual Science and Clinical Practice, 2002.

Garcia-Falgueras, A., and D. F. Swabb.   “A Sex Difference in the Hypothalamic Uncinate Nucleus: Relationship to Gender Identity.”   Brain, 131 (2008), pp. 3132–3146.  

Gorski, R. A., J. H. Gordon, J. E. Shryne, and A. M. Southam.   “Evidence for a Morphological Sex Difference within the Medial Preoptic Area of the Rat Brain.”   Brain Research, 148 (1978), pp. 333–346.

Goy, R. W., F. B. Bercovitch, and M. C. McBrair.   “Behavioral Masculinization Is Independent of Genital Masculinization in Prenatally Androgenized Female Rhesus Macaques.”   Hormones and Behavior, 22 (1988), pp. 552–571.

Green, Richard.   The “Sissy-boy Syndrome” and the Development of Homosexuality, 1987.  

Grellert. E. A., M. D. Newcomb, and P. M. Bentler.   “Childhood Play Activities of Male and Female Homosexuals and Heterosexuals.”   Archives of Sexual Behavior, 11 (1982), pp. 451–478.

Herdt, G. H.   Guardians of the Flute: Idioms of Masculinity, 1981.

Herman, R. A., B. Jones, D. R. Mann, and K. Wallen.   “Timing of Prenatal Androgen Exposure: Anatomical and Endocrine Effects on Juvenile Male and Female Rhesus Monkeys.”   Hormones and Behavior, 38 (2000), pp. 52–66.

Hines, M., S. F. Ahmed, and L. A. Hughes.   “Psychological Outcomes and Gender Related Development in Complete Androgen Insensitivity Syndrome.”   Archives of Sexual Behavior, 32 (2003), pp. 93–101.

Isay, Richard A.   “Gender Development in Homosexual Boys: Some Developmental and Clinical Considerations.”   Psychiatry, 62  (1999), pp. 187–194.

Kirk, K. M., J. M. Bailey, M. P. Dunne, and N. G. Martin.   “Measurement Models for Sexual Orientation in a Community Twin Sample.”   Behavior Genetics, 30 (2000), pp. 345–356. 

Kotrshcal, K., J. Hemetsberger, and B. M. Weiss.   “Making the Best of a Bad Situation: Homosexuality in Male Greylag Geese.”   In Volker Sommer and Paul L. Vasey, eds., Homosexual Behavior in Animals: An Evolutionary Perspective, 2006, pp. 45–76.     

Kristof, Nicholas.   "Gay at Birth?"   New York Times, October 25, 2003, A19.

Lalumičre, M. L., R. Blanchard, and K. J. Zucker.   “Sexual Orientation and Handedness in Men and Women: A Meta-analysis.”   Psychological Bulletin, 126 (2000), pp. 575–592.

LeVay, Simon.   “A Difference in Hypothalamic Structure between Heterosexual and Homosexual Men.”   Science, 253 (1991), pp. 1034–1037.

________.   Gay, Straight, and the Reason Why: The Science of Sexual Orientation, 2011.

________.   Queer Science: The Use and Abuse of Research into Homosexuality, 1996.

Meyer-Bahlburg, H. F., C. Dolezal, S. W. Baker, and M. I. New.   “Sexual Orientation in Women with Classical or Non-classical Congenital Adrenal Hyperplasia as a Function of Degree of Prenatal Androgen Excess.”   Archives of Sexual Behavior, 37 (2008), pp. 85–99. 

Money, John, and Patricia Tucker.   Sexual Signatures: On Being a Man or Woman, 1975.

________, M. Schwartz, and V. G. Lewis.   “Adult Heterosexual Status and Fetal Hormonal Masculinization and Demasculinization: 46, XX Congenital Virilizing Adrenal Hyperplasia and 46, XY Androgen-Insensitive Syndrome Compared.”   Psychoneuroendocrinology, 9 (1984), pp. 405–414.

Nedoma, K., and K. Freund.    “Somatosexulni Nalezy u Homosexualnich Muzu [Somatosexual Findings in Homosexual Men].”   Ceskoslovenska Psychatrie, 57 (1961), pp. 100–103.

Olson, Daniel L.   "Talking about Sexual Orientation: Experience, Science, and the Mission of the Church."   In James M. Childs, Jr., Faithful Conversation: Christian Perspectives on Homosexuality, 2003, pp. 97–119.        

Perkins, A. and J. A. Fitzgerald.   “Luteinizing Hormone, Testosterone, and Behavioral Response of Male-Oriented Rams to Estrous Ewes and Rams.”   Journal of Animal Science, 70 (1992), pp. 1787–1794.

Phoenix, C. H., R. W. Goy, A. A. Gerall, and C. W. Young.   “Organizing Action of Prenatally Administered Testosterone Propionate on the Tissues Mediating Mating Behavior in the Female Guinea Pig.”   Endocrinology, 65 (1959), pp. 369–382.

Rahman, Qazi, and Glenn Wilson.   "Born Gay?  The Psychobiology of Human Sexual Orientation."   Personality and Individual Differences, 34 (2003a), pp. 1337–1382.

________.   V. Kumari, and G. D. Wilson.   “Sexual Orientation Related Differences in Pre-Pulse Inhibition of the Human Startle Response.”   Behavioral Neuroscience, 117 (2003b), pp. 1096-1102.

Reiner, William G.   “Case Study: Sex Reassignment in a Teenage Girl.”   Journal of the American Academy of Child and Adolescent Psychiatry, 35 (1996), pp.799–803.

________.   “To Be Male or Female—That is the Question” (Editorial).   Archives of Pediatric and Adolescent Medicine, 151 (1997), pp. 224–225. 

________, and J.P. Gearhart.  “Discordant Sexual Identity in Some Genetic Males with Cloacal Exstrophy Assigned to Female Sex at Birth.”   New England Journal of Medicine, 350 (2004), pp. 333-341.

Roselli, C. E., K. Larkin, J. A. Resko, J. N. Stellflug, and F. Stormshak.  “The Volume of a Sexually Dimorphic Nucleus in the Ovine Medial Preoptic Area / Anterior Hypothalamus Varies with Sexual Partner Preference.” Endocrinology, 145  (2004), pp. 478-483.

Roughgarden, Joan.   Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People, 2004.

Strong, Bryan, and Christine DeVault.   Human Sexuality, 1994.  

Wellings, K., J. Field, A. M. Johnson, and J. Wadsworth.   Sexual Behavior in Britain: The National Survey of Sexual Attitudes and Lifestyles, 1994. 

Whitam, Fred L.   “Culturally Invariant Properties of Male Homosexuality: Tentative Conclusions from Cross-Cultural Research.”   Archives of Sexual Behavior, 12 (1983), pp. 207–226. 

Wilson, Glenn, and Qazi Rahman.   Born Gay: The Psychobiology of Sex Orientation, 2005 (reprinted 2008).  

Wisniewski, A. B., C. J. Migeon, H. F. L. Meyer-Bahlburg, J. P. Gearhart, G. D. Berkovitz, T. R. Brown, and J. Money.   “Complete Androgen Insensitivity Syndrome: Long Term Medical, Surgical and Psychosexual Outcome.”   Journal of Clinical Endocrinology and Metabolism, 85 (2000), pp. 2664–2669.

Zucker, K. J., S. J. Bradley, G. Oliver, J. Blake, S. Fleming, and J. Hood.   “Psychosexual Development of Women with Congenital Adrenal Hyperplasia.”   Hormones and Behavior, 30 (1996), pp. 300–318.


Updating the earlier article BORN GAY? (2004).

© 2012 Bruce L. Gerig

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