Sexual Orientation and the Brain

Androgen Insensitivity Syndrome or AIS is a condition where an individual has male internal organs with a vagina. AIS may be seen in a chromosomally normal male who had reduced sensitivity to masculinizing hormones during gestations. (Seligman, Martin E P., PhD. What You Can Change...and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Androgen Insensitivity Syndrome (AIS) – A congenital condition in which the androgen receptor is nonfunctional, causing affected XY fetuses to develop with the outward appearance of females. (LeVay, Simon. Gay, Straight, and the Reason Why: The Science of Sexual Orientation. p 297. NY: Oxford University Press, 1 edition, 2010.)

For most people, heterosexual impulses predominate, although all are bisexual to some degree. (Viorst, Judith. Necessary Losses. p 107-109. NY: Simon & Schuster, 1986.)

There are exclusive homosexuals and optional (bisexual) homosexuals. Compares exclusive homosexuality in males with Androgen-Insensitivity Syndrome (AIS) and MF transsexuality. (Seligman, Martin E P., PhD. What You Can Change...and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

AGS is a condition where an individual has female internal organs plus a form of penis and scrotum. AGS may be seen in a chromosomally normal female who was exposed to a bath of masculinizing hormones during gestation. (Seligman, Martin E P., PhD. What You Can Change...and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Androphylia is a term to describe the disposition to be attracted to men; bisexuality to describe the disposition to be attracted to both sexes; and gynephilia to describe the disposition to be attracted to women. Of note: the presence of homosexuality is higher among males; the presence of bisexuality is higher among females. (LeVay, Simon and Janice Baldwin. Human Sexuality. p 166-180. MA: Sinauer Associates, Inc., Third Edition, 2009.)

The anterior commissure (one of the three main bridges between the hemispheres) is 10%-12% larger in the female brain and in the brains of homosexual males. (Blum, Deborah. Sex on the Brain. p 45-47. NY: Penguin Books, 1997.)

Brain imaging: Gay males and women responded to two odors (thought to be involved in sexual arousal) in the same way. Heterosexual males responded differently. (Dowd, Maureen. Are Men Necessary? p 152-156. NY: G. P. Putnam’s Sons, 2005.)

The female brain is less arousable than the male brain and responds differently to visual/auditory arousal stimuli. Study: levels were higher in males than females after viewing an erotic film. Influenced by testosterone, norephinephrine tends to rise with hyperactivity, euphoria, self-assertion, and aggressiveness. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 243-254. NY: Arbor House Publishing, 1983.)

Under Western law, doctors glance at the genitals of a newborn and pronounce it either male or female. Transsexual men and women then are stuck with the label of the sex they were assigned at birth whether or not it matches their brain function. (Feinberg, Leslie. Transgender Warriors--Making History from Joan of Arc to Dennis Rodman. p x-xii. NY: Beacon Press, 1997.)

A female may be attracted to females if her brain’s mating center was masculinized with male hormones during gestation. The female will remain feminine in behavior if the behavior center was converted by male hormones, more masculine or butch if the behavior center was not converted. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 183-186. NY: Broadway Books, 1998.)

Male attraction to the female is programmed during sexual differentiation of the brain. There is now little doubt that same-sex preference may be rooted in a process that occurgs during the 16th to the 26th weeks of pregnancy. (Joy, Donald M., PhD. Bonding. p 95. TX: Word Books, 1985.)

The more older brothers a boy has, the more likely he is to be gay, thought to stem from prenatal influences such as androgen levels in the womb. (All in the Family. Scientific American Mind,” October/November 2007. www.sciammind.com)

The term bisexual describes the disposition to be attracted to both sexes. The presence of bisexuality is higher among females. (LeVay, Simon and Janice Baldwin. Human Sexuality. p 166-180. MA: Sinauer Associates, Inc., Third Edition, 2009.)

A bisexual individual has the potential to be sexually/romantically attracted to more than one sex, but not necessarily at the same time or to the same degree. (Baumgardner, Jennifer. Look Both Ways—Bisexual Politics. p 41-60. NY: Farrar, Straus and Giroux. 2008.)

Bisexual men are often married and engage in casual sex with other males for variety. Bisexual women seek long-term relationships with members of either gender and are more likely to alternate partners. (Wilson, Glenn. The Great Sex Divide. p 86-87. England: Peter Owen Publishers, 1989.)

Brain imaging: Gay males and women responded to two odors (thought to be involved in sexual arousal) in the same way. Heterosexual males responded differently. (Dowd, Maureen. Are Men Necessary? p 152-156. NY: G. P. Putnam’s Sons, 2005.)

The preoptic anterior nucleus seems to regulate masculine brain functions (e.g., mounting in response to female signals). In humans this area of the hypothalamus is about twice as large in males as in females. (Wilson, Glenn. The Great Sex Divide. p 35-36. England: Peter Owen Publishers, 1989.)

Homosexual males tend to have fewer neurons in the 3rd interstitial nuclei of the anterior hypothalamus (INAH-3) as compared to the straight male brain (but more than in the female brain). (Blum, Deborah. Sex on the Brain. p 42-48. NY: Penguin Books, 1997.)

The hypothalamus is the sex center. Less than an ounce in weight and about the size of a cherry, it is larger in the male brain than in the female brain or in the brains of homosexuals or transsexuals. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 190-200. NY: Broadway Books, 1998.

The anterior commissure (one of the three main bridges between the hemispheres) is 10%-12% larger in the female brain and in the brains of homosexual males. (Blum, Deborah. Sex on the Brain. p 45-47. NY: Penguin Books, 1997.)

The third interstitial nucleus of the anterior hypothalamus is of similar size in the brains of females and homosexual males; twice as large in heterosexual males. (Howard, Pierce J., PhD. The Owner’s Manual for the Brain. p 223-226. GA: Bard Press, 1994, 2000.)

The brain areas of males and females related to sex differ. Genes create the basic template, primarily during gestation, that is acted upon by hormones. (Carter, Rita, Ed. Mapping the Mind. p 73. CA: University of California Press, 1998.)

The female brain is less arousable than the male brain and responds differently to visual/auditory arousal stimuli. Study: levels were higher in males than females after viewing an erotic film. Influenced by testosterone, norephinephrine tends to rise with hyperactivity, euphoria, self-assertion, and aggressiveness. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 243-254. NY: Arbor House Publishing, 1983.)

The preoptic anterior nucleus seems to regulate masculine brain functions (e.g., mounting in response to female signals). In humans this area of the hypothalamus is about twice as large in males as in females. (Wilson, Glenn. The Great Sex Divide. p 35-36. England: Peter Owen Publishers, 1989.)

Homosexual males tend to have fewer neurons in the 3rd interstitial nuclei of the anterior hypothalamus (INAH-3) as compared to the straight male brain (but more than in the female brain). (Blum, Deborah. Sex on the Brain. p 42-48. NY: Penguin Books, 1997.)

The third interstitial nucleus of the anterior hypothalamus is of similar size in the brains of females and homosexual males; twice as large in heterosexual males. (Howard, Pierce J., PhD. The Owner’s Manual for the Brain. p 223-226. GA: Bard Press, 1994, 2000.)

The hypothalamus is the sex center. Less than an ounce in weight and about the size of a cherry, it is larger in the male brain than in the female brain or in the brains of homosexuals or transsexuals. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 190-200. NY: Broadway Books, 1998.

Homosexual males: the anterior commissure is larger (than in heterosexual males) and is about the size of that in the brains of heterosexual females. (Baron-Cohen, Simon, Dr. The Essential Difference: The Truth About the Male and Female Brain. p 111. NY: Basic Books, 2003.)

Research has discovered more about how male versus female brain differentiation occurs. They altered female rat brains by giving estradiol, a testosterone derivative that triggers a mechanism by which certain genes in the brain are "unsilenced," allowing them to initiate the process of masculinization. This process involves a group of enzymes known as DNA methyltransferases or Dnmts that modify DNA to repress gene expression. Physically, these were female rats, but in their reproductive behavior, they were males. (Bridget M Nugent and Margaret M McCarthy, et al. “Brain feminization requires active repression of masculinization via DNA methylation.” Nature Neuroscience, 2015; DOI: 10.1038/nn.3988)

Despite almost a century of psychoanalytic and psychological speculation, there is no substantive evidence to support the suggestion that the nature of parenting or early childhood experiences play any role in the formation of a person's fundamental heterosexual or homosexual orientation. It would appear that sexual orientation is biological in nature, determined by a complex interplay of genetic factors and the early uterine environment. Sexual orientation is therefore not a choice. ―The Royal College of Psychiatrists, 2007.

 Heterosexuals and homosexuals can choose (at some level) the type of behaviours they will exhibit. But exhibiting some heterosexual behaviours will not remove a gay person’s sense of same-gender attraction or make it go away. The reverse is also true. Much as a left-hander who is forced to behave as a right-hander, it is not the person’s first choice and will usually be less comfortable. Human beings all get to make choices about how to conduct their lives, but not about their feelings of sexual attraction. (Marcus, Eric. Is it a Choice? p 9-12. NY: HarperCollins, 2005.)

Provides a table and description of things that can be changed and those that can’t (e.g., Sexual identity is unchangeable, Sexual Orientation is probably unchangeable). (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 244-260. NY: Fawcett Books, 1993.)

“Nobody in science now believes that sexual orientation is caused by events in adolescence ... Homosexuality is an early, probably prenatal, and irreversible preference.”  ―Author and Geneticist Matt Ridley. Summary of 14 studies that show brain and body differences between heterosexual and homosexual individuals (e.g., inner ear, finger lengths, finger ridges, startle reflex, maternal side, etc.). Ontario Consultants on Religious Tolerance. Religious Tolerance.org    http://www.religioustolerance.org/hom_caus4.htm

 

In two million marriages in the US, at least one spouse is gay, lesbian, or bisexual. When a husband or wife comes out of the closet, it is a profound crisis that cuts across race, socioeconomic class, religion, and age. (Buxton, Amity Pierce, PhD.The Other Side of the Closet—the Coming-Out Crisis for Straight Spouses and Families. p xiii-xv. NY: John Wiley and Sons, 1991, 1994.)

Based on his survey of 18,000 people, Researcher Robert Epstein believes that the terms "gay" and "straight" can be highly misleading.  "Sexual orientation actually lies on a smooth continuum, and the way people state their orientation is often a poor predictor of their true sexual behaviors and fantasies.” Studies have shown that the same continuum of scores exists in the United States and in the average of scores from a dozen other countries. Fewer than 10% of subjects scored as “pure” heterosexual or homosexual. Characterizing sexual orientation properly requires two numbers. One number reflects the person’s mean sexual orientation (e.g., the placement of the person on that continuum). The other number reflects the sexual orientation range (e.g., the amount of “choice” the person has in expressing his/her orientation, which also forms a continuum). According to Epstein, a quiz is available at the following URL: http://MySexualOrientation.com (Scientific American Mind: Feb/Mar 2006 issue for “Do Gays Have a Choice?” and Oct/Nov 2007 issue, www.sciammind.com)

Sexual orientation is controlled by the hypothalamus. It is half the size in the gay brain as compared to the heterosexual brain. Between 5%-10% of boys have a smaller nucleus and a stronger biological tendency toward homosexuality. (Gurian, Michael. The Wonder of Boys. p 232-233. NY: Jeremy P. Tarcher/Putnam, 1996.)

Several studies have shown that homosexual men have an increased prevalence of non-right-handedness and atypical patterns of hemispheric functional asymmetry. Non-right-handedness in men has been associated with increased size of the corpus callosum (CC), particularly of the isthmus, which is the posterior region of the callosal body connecting parietotemporal cortical regions. (Witelson, Sandra F., et al. Corpus Callosum Anatomy in Right-Handed Homosexual and Heterosexual Men. Archives of Sexual Behavior. Volume 37, Number 6(2008), 857-863, DOI: 10.1007/s10508-007-9276-y)

See Transvestite (below) for additional information.

Sexual orientation may be defined as the direction of a person’s sexual attraction. A person may be disposed to experience sexual attraction to individuals of the opposite sex (heterosexual or straight), to individuals of both sexes (bisexual or bi), or to individuals of the same sex (homosexual or gay or lesbian). Androphylia is a term to describe the disposition to be attracted to men; bisexuality to describe the disposition to be attracted to both sexes; and gynephilia to describe the disposition to be attracted to women. Of note: the presence of homosexuality is higher among males; the presence of bisexuality is higher among females. (LeVay, Simon and Janice Baldwin. Human Sexuality. p 166-180. MA: Sinauer Associates, Inc., Third Edition, 2009.)

Homosexual males: the anterior commissure is larger (than in heterosexual males) and is about the size of that in the brains of heterosexual females. (Baron-Cohen, Simon, Dr. The Essential Difference: The Truth About the Male and Female Brain.p 111. NY: Basic Books, 2003.)

Contributors to the development of homosexuality may include: Direct alteration of hormones during fetal development, use of drugs that impact androgens (e.g., Depo-Provera, diazepam, marijuana), maternal severe emotional stress (stress hormones may cross the placenta and interfere with testosterone production in the baby), immune reaction against chemicals necessary for sexual differentiation. (Wilson, Glenn. The Great Sex Divide. p 78-80. England: Peter Owen Publishers, 1989.)

Most straight males are very uncomfortable with the idea of homosexuality, no matter how liberated they maybe in their thinking. Females seem to be far less threatened by homosexual contact. (Goldberg, Herb, PhD. The Hazards of Being Male. p 24. NY: Nash Publishing, 1976.)

Contributors to the development of homosexuality may include: Direct alteration of hormones during fetal development, use of drugs that impact androgens (e.g., Depo-Provera, diazepam, marijuana), maternal severe emotional stress (stress hormones may cross the placenta and interfere with testosterone production in the baby), immune reaction against chemicals necessary for sexual differentiation. (Wilson, Glenn. The Great Sex Divide. p 78-80. England: Peter Owen Publishers, 1989.)

Avoiding and suppressing does not dissipate the heart's natural yearnings. It just stock-piles emotional energy. In addition, shutting down some emotions and feeings may shut off most other emotions, as well. (Rix, Jallen, EdD. Ex-Gay; No Way. Survivial and recovery from Religious Abuse. p 13-14; 190-196. Scotland: Findhorn Press, 2010).

The brain has a number of emotion systems. When one is active, the others tend to be inhibited. Once aroused, sexual desire can override many other systems—people risk all types of adverse consequences for an adulterous fling. Doing the right thing doesn’t always flow naturally from knowing the right thing to do. (LeDoux, Joseph. Synaptic Self, How Our Brains Become Who We Are. p 321-323. NY: Penguin Books, 2002.)

There is an endocrine basis for homosexual preference if fetal development is interrupted and mother’s androgens are interfered with at the time of sexual differentiation in the brain. (Joy, Donald, PhD. The Innate Differences Between Males & Females (Audio Cassette). CO: Focus on the Family, 1967.)

Study: Homosexuality tends to run in families. 3x greater chance of a male being gay if he has brothers, uncles, cousins, or parents (more on the mother’s side and fewer on the father’s side) who are also gay. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 179-186. NY: Broadway Books, 1998.)

Study of 944 men, Psychologist Anthony Bogaert of Brock University in Ontario Canada: Risk of being gay increases with number of older brothers. Some mothers may develop antibodies to male fetuses and, in subsequent pregnancies, the antibodies may impact portions of the fetal brain that determine sexual orientation. (Klein, Joe. Born Gay, the Brother Factor. p 55. TIME, July 10, 2006.)

Several studies also have shown that homosexuality tends to run in families. The probability that the brother of a gay man is gay is about four times higher than normal. Similarly, the odds that the sister of a lesbian is also a lesbian is significantly higher than normal. However, male homosexuality and lesbianism tend to run in different families: sisters with gay brothers are not more likely than normal to be lesbian. A 1993 study that traced the pedigree of pairs of gay brothers found that homosexuality tends to run on the maternal side of the family tree: the brothers had a higher than average number of maternal nephews and uncles who are gay. (Source)

Studies: the real percentage of gay twins who were separated at birth and who have identical genetic makeup is 60-70%, or 2 out of 3. (Why Men Don’t Listen and Women Can’t Read Maps. p 179-186. NY: Broadway Books, 1998.)

The author explains how that, when there is no sexual activity or romance involved, the brains of individuals may connect in close friendships regardless of gender or sexual orientation of the individuals involved. When this happens there is often an openness and depth of sharing of information that is not typically observed in romantic and/or sexual relationships. (De La Cruz, Melissa, and Tom Dolby, editors. NY: Plume, 2007, 2008.)

The term “gay,” used to describe people who are conscious of an erotic preference for individuals of their own gender, probably antedates the term “homosexual” by several centuries. (Boswell, John. Christianity, Social Tolerance, and Homosexuality. p 41-50. IL: University of Chicago Press, 1980.)

(My husband) had no choice about being a homosexual. If he had, he would have chosen his marriage, family, and unique ministry. By Lyla White. (White, Mel. Stranger at the Gate: To be Gay and Christian in America. p 5-7. NY: Plume, 1995.)

Homosexuality: A brief Study by Himel Shagor In recent time and age, many passionately debated topics have come under the scrutiny of socio-biologists, trying to determine their causation and origins; one such topic is homosexuality.1 Society has two views2 of homosexuality, for this paper they are: The conservative view: • Homosexuality is an aberration, the orientation is a disorder, and the behaviour is pathological. The progressive view: • Homosexuality is a normal variant in the human condition and that homosexual behaviour is natural. [Accessed Mar 2015.  https://www.mukto-mona.com/Articles/himel_shagor/Homosexuality_Study.pdf]

 

All over the world on all continents and in all cultures, brain differences exist between female brains and male brains. (Gurian, Michael, PhD, with Barbara Annis. Leadership and the Sexes. p xxCA: Jossey-Bass, 2008.)

Refer to Gender Differences for additional information.

Genes have power to switch on and become dominant (penetrant). Huntington’s, 100% penetrant; Type 1 Diabetes, 30% penetrant; Gay gene, 50-70% penetrant (e.g., 10% of males carry gay gene). (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 177-186. NY: Broadway Books, 1998.)

The brain areas of males and females related to sex differ. Genes create the basic template, primarily during gestation, that is acted upon by hormones. (Carter, Rita, Ed. Mapping the Mind. p 73. CA: University of California Press, 1998.)

Evidence suggests that genes influence sexual orientation and other aspects of gender. Structural and functional differences exist between the brains of gay and straight individuals. (LeVay, Simon. Gay, Straight, and the Reason Why: The Science of Sexual Orientation. p 43. NY: Oxford University Press, 1 edition, 2010.)

Studies at U of Illinois: Sexual orientation is a complex trait (e.g., there is no one “gay” gene). Genes play an important role in determining whether a man is gay or heterosexual but other factors are also important. "Our best guess is that multiple genes, potentially interacting with environmental influences, explain differences in sexual orientation." (Lead researcher Dr Brian Mustanski.)

Studies of male twins have suggested that about 50 per cent of the variability of sexual orientation is due to genes. This would leave about 50 per cent due to various environmental factors. There is a growing sense that genes play a role in male sexual orientation. The evidence for a genetic contribution to female homosexuality is less well developed, but the case is hardly closed. (Juan, Stephen, PhD, U of Sydney. Whatever Happened to the Gay Gene?)

Study of 944 men, Psychologist Anthony Bogaert of Brock University in Ontario Canada: Risk of being gay increases with number of older brothers. Some mothers may develop antibodies to male fetuses and, in subsequent pregnancies, the antibodies may impact portions of the fetal brain that determine sexual orientation. (Klein, Joe. Born Gay, the Brother Factor. p 55. TIME, July 10, 2006.)

Studies of male twins have suggested that about 50 per cent of the variability of sexual orientation is due to genes. This would leave about 50 per cent due to various environmental factors. There is a growing sense that genes play a role in male sexual orientation. The evidence for a genetic contribution to female homosexuality is less well developed, but the case is hardly closed. (Juan, Stephen, PhD, U of Sydney. Whatever Happened to the Gay Gene?)

An approximate location of genes that may have an impact on sexual orientation in males is X928 region of the X chromosome. The pattern for females has not been established. The likelihood of this gene becoming penetrant is largely dependent on testosterone levels 6-8 weeks after conception. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 178-186. NY: Broadway Books, 1998.)

Study: Homosexuality tends to run in families. 3x greater chance of a male being gay if he has brothers, uncles, cousins, or parents (more on the mother’s side and fewer on the father’s side) who are also gay. The real percentage of gay twins who were separated at birth and who have identical genetic makeup is 60-70%, or 2 out of 3. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 179-186. NY: Broadway Books, 1998.)

Study: Females had 6 times the chance of birthing a gay son if the mothers experienced severe stress during early pregnancy. Stress, sickness, and some medications tend to suppress testosterone levels. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 181-186. NY: Broadway Books, 1998.)

Contributors to the development of homosexuality may include: Direct alteration of hormones during fetal development, use of drugs that impact androgens (e.g., Depo-Provera, diazepam, marijuana), maternal severe emotional stress (stress hormones may cross the placenta and interfere with testosterone production in the baby), immune reaction against chemicals necessary for sexual differentiation. (Wilson, Glenn. The Great Sex Divide. p 78-80. England: Peter Owen Publishers, 1989.)

According to Dr. Donald Joy, the Old Testament Biblical death penalty for homosexual acts, reviewed in light of New Testament writings, really involves no procreation. The penalty involves being the end of the person’s biological line. (Joy, Donald, PhD. The Innate Differences Between Males & Females (Audio Cassette). CO: Focus on the Family, 1967.)

“Nobody in science now believes that sexual orientation is caused by events in adolescence ... Homosexuality is an early, probably prenatal, and irreversible preference.”  ―Author and Geneticist Matt Ridley. Summary of 14 studies that show brain and body differences between heterosexual and homosexual individuals (e.g., inner ear, finger lengths, finger ridges, startle reflex, maternal side, etc.). Ontario Consultants on Religious Tolerance. Religious Tolerance.org    http://www.religioustolerance.org/hom_caus4.htm

Most homosexual orientation develops during gestation. Patterns tend to be firmly in place by age 5. Discusses lack of success of change therapies (e.g., push bisexuals to confine behaviors to opposite sex only, or enforce celibacy, or push the individuals to attempt suicide). (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 171-186. NY: Broadway Books, 1998.)

The brain areas of males and females related to sex differ. Genes create the basic template, primarily during gestation, that is acted upon by hormones. (Carter, Rita, Ed. Mapping the Mind. p 73. CA: University of California Press, 1998.)

The brain is hard wired during gestation. Differences are most noticeable after puberty when the brain becomes fully activated as a result of being bathed in hormones. (Howard, Pierce J., PhD. The Owner’s Manual for the Brain. p 215-221. GA: Bard Press, 1994, 2000.)

Study: Females had 6 times the chance of birthing a gay son if the mothers experienced severe stress during early pregnancy. Stress, sickness, and some medications tend to suppress testosterone levels. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 181-186. NY: Broadway Books, 1998.)

Sexual preferences are partly determined by hormones before birth. Typically there are higher numbers of male homosexuals over lesbians (e.g., more opportunities for something to “go wrong” in the process of converting the standard female embryo into a sexually competent male). (Wilson, Glenn. The Great Sex Divide. p 80-81. England: Peter Owen Publishers, 1989.)

Androgen Insensitivity Syndrome or AIS is a condition where an individual has male internal organs with a vagina. AIS may be seen in a chromosomally normal male who had reduced sensitivity to masculinizing hormones during gestations. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Study: testosterone injected into pregnant guinea pigs during 30th-65th day of gestation resulted in the birth of masculinized female young. As adults they showed more masculine components in sexual behavior patterns. The effects of androgens administered during pregnancy were permanent. (Foss, B.M., ed. Brain and Behavior 1, Mood, States and Mind. p 394-395. Britain:Penguin Books, 1969.)

The term “life-style choice” is sometimes used by individuals who do not want to acknowledge the biological (e.g., genetic and chromosomal) basis of homosexuality. (Gurian, Michael. The Wonder of Boys. p 231-233. NY: Jeremy P. Tarcher/Putnam, 1996.)

Sexual preference is set in the human brain about 6-8 weeks after conception. Theoretically, at least, this could be controlled with hormones during fetal development. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 180-186. NY: Broadway Books, 1998.)

Because it is based on the impact of male hormone on the brain during fetal development, homosexuality is mostly genetic rather than a choice. The genetic combination of red hair and freckles occurs at the same rate as homosexuality. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 171-186. NY: Broadway Books, 1998.)

“Nobody in science now believes that sexual orientation is caused by events in adolescence ... Homosexuality is an early, probably prenatal, and irreversible preference.”  ―Author and Geneticist Matt Ridley. Summary of 14 studies that show brain and body differences between heterosexual and homosexual individuals (e.g., inner ear, finger lengths, finger ridges, startle reflex, maternal side, etc.). Ontario Consultants on Religious Tolerance. Religious Tolerance.org    http://www.religioustolerance.org/hom_caus4.htm

 

Gynephilia is a term to describe the disposition to be attracted to women. Of note: the presence of homosexuality is higher among males; the presence of bisexuality is higher among females. (LeVay, Simon and Janice Baldwin. Human Sexuality. p 166-180. MA: Sinauer Associates, Inc., Third Edition, 2009.)

A 2003-2004 GLSEN National School Climate survey (GLSEN stands for Gay, Lesbian, and Straight Education Network) found that four out of five LGBT high school students routinely experience verbal, physical, or sexual harassment while at school. (Jennings, Kevin, GLSEN Ex-director. One Teacher in Ten. p xiv. CA: Alyson Publications, 1983, 2005.)

Refer to Cerebral Hemispheres (Brain Function) for additional information.

In some true hermaphrodites the testis and the ovary grow separately but bilaterally, in others they grow together within the same organ, forming an ovo-testis. Not infrequently, at least one of the gonads functions quite well, producing either sperm cells or eggs, as well as functional levels of the sex hormones, androgens or estrogens. Although in theory it might be possible for a true hermaphrodite to become both father and mother to a child, in practice the appropriate ducts and tubes are not configured so that egg and sperm can meet. Pseudohermaphrodites, on the other hand, possess two gonads of the same kind along with the usual male (XY) or female (XX) chromosomal makeup. But their external genitalia and secondary sex characteristics do not match their chromosomes. Thus merms have testes and XY chromosomes, yet they also have a vagina and a clitoris, and at puberty they often develop breasts. They do not menstruate, however. Ferms have ovaries, two X chromosomes and sometimes a uterus, but they also have at least partly masculine external genitalia. Without medical intervention they can develop beards, deep voices and adult-size penises. (Fausto-Sterling, Anne, professor. The Five Sexes: Why Male and Female Are Not Enough. The Sciences March/April 1993, p. 20-24.)

Hermaphrodites are defined as true bisexuals: one active ovary and one active testis. Theoretically they could impregnate themselves, but are usually raised as either girls or as boys. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 90-186. NY: Arbor House Publishing, 1983.)

According to Professor Anne Fausto-Sterling, a biologist and gender theorist, if people ought to be classified in sexes at least five sexes rather than two, are needed. For some time medical investigators have recognized the concept of the intersexual body. But the standard medical literature uses the term intersex as a catch-all for three major subgroups with some mixture of male and female characteristics: the so-called true hermaphrodites (herms), who possess one testis and one ovary (the sperm- and egg-producing vessels, or gonads); the male pseudohermaphrodites (merms), who have testes and some aspects of the female genitalia but no ovaries; and the female pseudohermaphrodites (ferms), who have ovaries and some aspects of the male genitalia but lack testes. (Fausto-Sterling, Anne, professor. The Five Sexes: Why Male and Female Are Not Enough. The Sciences March/April 1993, p. 20-24.)

Most straight males are very uncomfortable with the idea of homosexuality, no matter how liberated they maybe in their thinking. Females seem to be far less threatened by homosexual contact. (Goldberg, Herb, PhD. The Hazards of Being Male. p 24. NY: Nash Publishing, 1976.)

Homophobia often involves multiple prejudices so it more accurately would be labeled homophobias. Such prejudices are not limited to heterosexuals. They can be found among homosexuals and repressed homosexuals, between gay men and lesbians. Homophobias could be described as sexism and as an uncomprehension or dislike of another type of sexuality. (Fone, Byrne. Homophobia--a History. p 6-9. NY: Picodor, 2000.)

Mirror neurons play a key role in sexual response and may play a role in homophobia. When people see sexually aroused genitals of thepreferred sex (e.g., opposite for heterosexuals, same for homosexuals), the brain's mirror neurons and reward centers fire. So when a heterosexual male sees two other men in sexual acts, he can't help but experience it in his mind's body, even if it is at a subconscious level. For the straight male, this is unappetizing and may make a live-and-let-live attitude more difficult to adopt. (Blakeslee, Sandra, and Matthew Blakeslee. The Body Has a Mind of Its Own. p 178-179. NY:Random House, 2008.)

The term “gay,” used to describe people who are conscious of an erotic preference for individuals of their own gender, probably antedates the term “homosexual” by several centuries. (Boswell, John. Christianity, Social Tolerance, and Homosexuality. p 41-50. IL: University of Chicago Press, 1980.)

There is an endocrine basis for homosexual preference if fetal development is interrupted and mother’s androgens are interfered with at the time of sexual differentiation in the brain. (Joy, Donald, PhD. The Innate Differences Between Males & Females (Audio Cassette). CO: Focus on the Family, 1967.)

Contributors to the development of homosexuality may include: Direct alteration of hormones during fetal development, use of drugs that impact androgens (e.g., Depo-Provera, diazepam, marijuana), maternal severe emotional stress (stress hormones may cross the placenta and interfere with testosterone production in the baby), immune reaction against chemicals necessary for sexual differentiation. (Wilson, Glenn. The Great Sex Divide. p 78-80. England: Peter Owen Publishers, 1989.)

The brain areas of males and females related to sex differ. Genes create the basic template, primarily during gestation, that is acted upon by hormones. (Carter, Rita, Ed. Mapping the Mind. p 73. CA: University of California Press, 1998.)

“Nobody in science now believes that sexual orientation is caused by events in adolescence ... Homosexuality is an early, probably prenatal, and irreversible preference.”  ―Author and Geneticist Matt Ridley. Summary of 14 studies that show brain and body differences between heterosexual and homosexual individuals (e.g., inner ear, finger lengths, finger ridges, startle reflex, maternal side, etc.). Ontario Consultants on Religious Tolerance. Religious Tolerance.org    http://www.religioustolerance.org/hom_caus4.htm

Sex hormones create masculinization over time, so males can be more or less masculine. Females can be masculinized but not defeminized. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 104-117. NY: Arbor House Publishing, 1983.)

Variations in androgens (male sex hormones) and estrogens (female sex hormones) can affect both body asymmetry and the degree/direction of gender differentiation in the brain. (Howard, Pierce J., PhD. The Owner’s Manual for the Brain. p 215-221. GA: Bard Press, 1994, 2000.)

Sex hormones create masculinization over time, so males can be more or less masculine. Females can be masculinized but not defeminized. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 104-117. NY: Arbor House Publishing, 1983.)

For some lesbians, their hormone balance was probably more like that of males during fetal development (e.g., some lesbian women have unusually high testosterone levels). (Wilson, Glenn. The Great Sex Divide. p 75-76. England: Peter Owen Publishers, 1989.)

Lesbians tend to exhibit attributes associated with exposure to higher testosterone levels while in the womb. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 165-168. NY: Broadway Books, 1998.)

Defines five layers related to human sexuality: Sexual identity, orientation, preference, role, and performance. Believes that the deeper the layer (e.g., core sexual identity) the more difficult it would be to achieve change. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Provides a table and description of things that can be changed and those that can’t (e.g., Sexual identity is unchangeable, Sexual Orientation is probably unchangeable). (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 244-260. NY: Fawcett Books, 1993.)

Refer to Sexuality and the Brain for additional information.

Sexual orientation is controlled by the hypothalamus. It is half the size in the gay brain as compared to the heterosexual brain. Between 5%-10% of boys have a smaller nucleus and a stronger biological tendency toward homosexuality. (Gurian, Michael. The Wonder of Boys. p 232-233. NY: Jeremy P. Tarcher/Putnam, 1996.)

The preoptic anterior nucleus seems to regulate masculine brain functions (e.g., mounting in response to female signals). In humans this area of the hypothalamus is about twice as large in males as in females. (Wilson, Glenn. The Great Sex Divide. p 35-36. England: Peter Owen Publishers, 1989.)

Homosexual males tend to have fewer neurons in the 3rd interstitial nuclei of the anterior hypothalamus (INAH-3) as compared to the straight male brain (but more than in the female brain). (Blum, Deborah. Sex on the Brain. p 42-48. NY: Penguin Books, 1997.)

The third interstitial nucleus of the anterior hypothalamus is of similar size in the brains of females and homosexual males; twice as large in heterosexual males. (Howard, Pierce J., PhD. The Owner’s Manual for the Brain. p 223-226. GA: Bard Press, 1994, 2000.)

The hypothalamus is the sex center. Less than an ounce in weight and about the size of a cherry, it is larger in the male brain than in the female brain or in the brains of homosexuals or transsexuals. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 190-200. NY: Broadway Books, 1998.

Sexual identity is in place at time of birth and relates to hormonal processes that template the brain near the end of the first trimester of pregnancy. Other factors (e.g., child rearing, societal conditioning) likely do little except reinforce or disturb one’s core sexual identity. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Sexual orientation (heterosexual or homosexual) is a close cousin to sexual identity in both depth of layer and inflexibility. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

For most people, heterosexual impulses predominate, although all are bisexual to some degree. (Viorst, Judith. Necessary Losses. p 107-109. NY: Simon & Schuster, 1986.)

Some things can be changed and some can’t (e.g., Sexual identity is unchangeable, Sexual Orientation is likely unchangeable as well). (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 244-260. NY: Fawcett Books, 1993.)

For most people, heterosexual impulses predominate, although all are bisexual to some degree. (Viorst, Judith. Necessary Losses. p 107-109. NY: Simon & Schuster, 1986.)

There are exclusive homosexuals and optional (bisexual) homosexuals. Compares exclusive homosexuality in males with Androgen-Insensitivity Syndrome (AIS) and MF transsexuality. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Contributors to the development of homosexuality may include: Direct alteration of hormones during fetal development, use of drugs that impact androgens (e.g., Depo-Provera, diazepam, marijuana), maternal severe emotional stress (stress hormones may cross the placenta and interfere with testosterone production in the baby), immune reaction against chemicals necessary for sexual differentiation. (Wilson, Glenn. The Great Sex Divide. p 78-80. England: Peter Owen Publishers, 1989.)

During prenatal development there is a restricted time frame during which the brain takes on male or female characteristics. Scientists had thought that once this window closed, it could not be reopened but researchers have found otherwise. DNA methyltransferases or Dnmt enzymes control expression of genes that play a role in inflammation and immunity, and also in the sexual differentiation of the brain. Microglia, inflammatory immune cells, also appear to play a role in masculinization, in part through their production of prostaglandins, a neurochemical normally associated with illness. The immune system is integral to the development of the brain but this study is the first to show that it is also important for establishment of sex differences in the brain. (Margaret McCarthy, PhD, and Bridget Nugent, PhD, et al. “Brain feminization requires active repression of masculinization via DNA methylation.” Nature Neuroscience, 2015; DOI: 10.1038/nn.3988)

Three intersexes, herm, merm and ferm, deserve to be considered additional sexes each in its own right. Indeed, I would argue further that sex is a vast, infinitely malleable continuum that defies the constraints of even five categories. (Fausto-Sterling, Anne, professor. The Five Sexes: Why Male and Female Are Not Enough. The Sciences March/April 1993, p. 20-24.)

A lesbian is defined as a female body with a masculinized brain. Rates approximate 1 lesbian for every 8-10 gay males. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 171-186. NY: Broadway Books, 1998.

For some lesbians, their hormone balance was probably more like that of males during fetal development (e.g., some lesbian women have unusually high testosterone levels). (Wilson, Glenn. The Great Sex Divide. p 75-76. England: Peter Owen Publishers, 1989.)

Lesbians tend to exhibit attributes associated with exposure to higher testosterone levels while in the womb. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 165-168. NY: Broadway Books, 1998.)

These initials or terms have been used collectively to encompass lesbian, gay, bisexual, and transgender individuals. They are not necessary agreeable to everyone the terms encompass, however. For example, some argue that transgender and transsexual issues are not the same as those of lesbian, gay, and bisexual individuals. (Source)

Traditionalists fail to understand that, for gay individuals, their condition is not just a yearning to commit a catalog of sexual acts. Theirs is that most human of all conditions, the yearning to love and be loved in return. (Canning, Richard, Editor. Fifty Gay and Lesbian Books Everybody Must Read. Essay by Aaron Hamburger. p 2-3. NY: Alyson Books, 2009.)

An inherited enzyme deficiency that causes genetic males to develop as females until puberty (e.g., specific district of the Dominican Republic). At puberty, androgen production suddenly increases and the individual turns into a typical male. (Wilson, Glenn. The Great Sex Divide. p 77-79. England: Peter Owen Publishers, 1989.)

Refer to Sexuality and the Brain for additional information.

There are three basic mating circuits: lust, romantic love, and attachment. Types of love (e.g., eros, mania, ludus, storge, agape, pregma) can be described as different blends of these three circuits. (Fisher, Helen, PhD. Why We Love. p 94-100. NY:Henry Holt and Company, 2004.)

Known as the master gland and directed by the hypothalamus, the pituitary controls the levels and cycling of sex hormones. (Brynie, Faith Hickman. 101 Questions Your Brain Has Asked About Itself But Couldn’t Answer, Until Now. p 19-20. CT: Millbrook Press, 1998.)

Sexual preference is set in the human brain about 6-8 weeks after conception. Theoretically, at least, this could be controlled with hormones during fetal development. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 180-186. NY: Broadway Books, 1998.)

According to Dr. Donald Joy, Ashbury Theological Seminary, the Old Testament death penalty for homosexual acts must be considered in light of New Testament writings. The death penalty involves being the end of the person’s biological line. (Joy, Donald, PhD. The Innate Differences Between Males & Females (Audio Cassette). CO: Focus on the Family, 1967.)

Internal sex organs: Both genetically male (XY) and genetically female (XX) fetuses start out with two sets of internal primordial structures, the Wolffian and the Mullerian.

  • In the presence of testicular hormones, the Wolffian ducts develop (e.g., prostate and vas) and the Mullerian ducts regress.
  • In the absence of testicular hormones the reverse happens. The Wolffian ducts regress and the Mullerian ducts develop (uterus and fallopian tubes).

External sex organs: Both male and female fetuses also start out with a single set of external primordial structures:

  •  Testosterone stimulates these structures to differentiate into penis and scrota, becoming recognizably male by about week 9-10 of gestation.
  •  In the absence of testosterone, these same structures become clitoris and labia, regardless of the levels of estrogen or progesterone. So, no hormonal influence from the female gonads (ovaries) appears to be needed for differentiation of female external genitalia. 

(Hines, Melissa, PhD. Brain Gender. p 21-43. NY:Oxford University Press, 2004.)

Sex is defined as biological differences in genitals and reproductive functions; gender is defined as referring to classifications of masculine and feminine that may vary with the culture, the time, and the place. (Eakins, Barbara Westbrook, and R. Gene Eakins. Sex Differences in Human Communication. p 5. Boston: Houghton Mifflin Co,1978.)

According to Anne Fausto-Sterling, a biologist and gender theorist, if people ought to be classified in sexes at least five sexes rather than two, are needed. For some time medical investigators have recognized the concept of the intersexual body. But the standard medical literature uses the term intersex as a catch-all for three major subgroups with some mixture of male and female characteristics: the so-called true hermaphrodites (herms), who possess one testis and one ovary (the sperm- and egg-producing vessels, or gonads); the male pseudohermaphrodites (merms), who have testes and some aspects of the female genitalia but no ovaries; and the female pseudohermaphrodites (ferms), who have ovaries and some aspects of the male genitalia but lack testes. (Fausto-Sterling, Anne, professor. The Five Sexes: Why Male and Female Are Not Enough. The Sciences March/April 1993, p. 20-24.)

For most people, heterosexual impulses predominate, although all are bisexual to some degree. (Viorst, Judith. Necessary Losses. p 107-109. NY: Simon & Schuster, 1986.)

Study: Exposing a pregnant rat to stress can alter testosterone levels that lead to brain masculinization. Many more offspring exhibit homosexual behavior. (Quartz, Steven R., PhD, and Terrence J. Sejnowski, PhD. Liars, Lovers, and Heroes. p 164-165. NY: HarperCollins Publishers Inc., 2002.)

There is a connection between maternal stress (e.g., associated with insufficient amounts of androgen to the fetus) and sexual preference. Effects of stress to developing fetuses can be episodically epidemic (e.g., war, abandonment) especially if events contribute to stress between the 16-26th weeks of gestation. (Joy, Donald, PhD. The Innate Differences Between Males & Females (Audio Cassette). CO: Focus on the Family, 1967.)

Contributors to the development of homosexuality may include: Direct alteration of hormones during fetal development, use of drugs that impact androgens (e.g., Depo-Provera, diazepam, marijuana), maternal severe emotional stress (stress hormones may cross the placenta and interfere with testosterone production in the baby), immune reaction against chemicals necessary for sexual differentiation. (Wilson, Glenn. The Great Sex Divide. p 78-80. England: Peter Owen Publishers, 1989.)

These terms are used to describe individuals who are categorized (by their will or by social consensus) as neither male nor female. The term "third" is usually understood to mean "other.” Anthropologists, since at least the 1970s, have described gender categories in some cultures which they could not adequately explain using a two-gender framework. (Source)

The term transgender was coined in the 1970s by Virginia Prince in the USA, as a contrast with the term transsexual, to refer to someone who does not desire surgical intervention to change sex and/or who considers that they fall somewhere between the genders, not identifying strictly to one gender or the other, identifying themselves as neither fully male, nor female. (Source)

The term transgender, which often refers to those who change their gender, is increasingly being used to signify a gendered subjectivity that is neither male nor female. An example of this is found on a form for the Harvard Business School. It has three gender options: male, female, and transgender. (Source)

Many female transgender individuals and transmen tend to clearly perceive two groups. Many are in a relationship with women and so identify themselves as lesbians, until transition. (Boyd, Helen. Love, Sex, and Life as a Crossdresser. p xiii-xiv. CA:Seal Press. 2003.)

Transgenders tend to identify themselves as individuals who were assigned a sex, usually at birth and based on their genitals, but who believe this is a false or incomplete description of themselves. (Source)

Transgender is a general term applied to a variety of individuals, behaviors, and groups involving tendencies to vary from the usual gender roles. A transgender individual may have characteristics that are normally associated with a specific gender, identify elsewhere on the traditional gender continuum, or exist outside of it (e.g., identify as bigender, agender, genderqueer, or third gender). (Source)

A transsexual is an individual whose brain does not match their genitals. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. P148-173. NY: Fawcett Books, 1993.)

Transsexuals who inject estrogen to transition from male to female become less confrontational. They are more likely to use indirection aggression (e,.g., sarcasm, irony, gossip). Estrogen must be "the sap of the agreeble disposition." (Fisher, Helen, PhD. Why Him? Why Her? p 115-116. NY: Henry Holt and Company, 2009.)

The word transsexual, unlike the word transgender, has a more precise medical definition. Harry Benjamin, a German endocrinologist, widely known for his clinical work with transsexuals, created the Benjamin Scale that defines different levels of intensity related to transsexualism. Some transsexuals have undergone surgery; some believe that to be a transsexual one must at least have a desire to undergo surgery. (Benjamin, Harry. (1966). The Transsexual Phenomenon. p 23. NY: Julian Press, 1966.)

The hypothalamus in male transsexuals is the size of the hypothalamus in the female brain or smaller. Approximately 20% of transsexuals opt to undergo a sex-change operation. One in 3-5 attempts suicide. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 173-186. NY: Broadway Books, 1998.)

Transsexuals are individuals who identify as, or desire to live and be accepted as, a member of the sex opposite to that assigned at birth. The term transgender pertains to a person who does not identify with conventional categories of female or male, but combines elements of both or moves between the two. (Source)

Under Western law, doctors glance at the genitals of a newborn and pronounce it either male or female. Transsexual men and women then are stuck with the label of the sex they were assigned at birth whether or not it matches their brain function. (Feinberg, Leslie. Transgender Warriors--Making history from Joan of Arc to Dennis Rodman. p x-xii. NY: Beacon Press, 1997.)

The hypothalamus in male transsexuals is size of hypothalamus in the female brain or smaller. Approximately 20% undergo a sex-change operation. One in 3-5 attempts suicide. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 173-186. NY: Broadway Books, 1998.)

I know I’m not a man—about that much I’m very clear; and I’ve come to the conclusion that I’m probably not a woman, either. The trouble is, we live in a world that insists we be one or the other. (Bornstein, Kate. Gender Outlaw. p 7-9. NY: Vintage Books, 1995.)

A transvestite is an individual who wears clothing of the opposite sex in order to become sexually aroused. (Seligman, Martin E P., PhD. What You Can Change…and What You Can’t. p 148-173. NY: Fawcett Books, 1993.)

Crossdressers come from all walk of life, and all ages, and races. They may be heterosexual, bisexual, or homosexual. Many female transgender individuals and transmen, tend to clearly separate themselves into two groups. Many are in a relationship with women and so identify themselves as lesbians, until transition. (Boyd, Helen. Love, Sex, and Life as a Crossdresser. p xiii-xiv, 29-30. CA: Seal Press. 2003.)

Transvestites should not be confused with transgenders or transsexuals. Transvestites generally have less desire to permanently change their sex, but simply enjoy being able to cross-dress from time to time. (Source)

According to Michael A. Gilbert, professor at the Department of Philosophy, York University, Toronto, a cross-dresser is a person who has an apparent gender identification with one sex, and who has and certainly has been birth-designated as belonging to one sex, but who wears the clothing of the opposite sex because it is the clothing of the opposite sex. (Gilbert, Michael ‘Miqqi Alicia.’ The Transgendered Philosopher; in Special Issue on What is Transgender? from The International Journal of Transgenderism, Special Issue July 2000.)

The trauma of growing up gay in a world that is run primarily by straight men is deeply wounding in a unique and profound way. Straight men have other issues and struggles that are no less wounding, but they are quite different from those of a gay man. (Downs, Alan, PhD. The Velvet Rage. Overcoming the Pain of Growing up Gay in a Straight Man’s World. p 5-6. NY: Da Capo Press, 2005, 2006.)

Refer to Trauma and the Brain for more information.

Studies of male twins have suggested that about 50 per cent of the variability of sexual orientation is due to genes. This would leave about 50 per cent due to various environmental factors. There is a growing sense that genes play a role in male sexual orientation. The evidence for a genetic contribution to female homosexuality is less well developed, but the case is hardly closed. (Juan, Stephen, PhD, U of Sydney. Whatever Happened to the Gay Gene?)

Study: Homosexuality tends to run in families. 3x greater chance of a male being gay if he has brothers, uncles, cousins, or parents (more on the mother’s side and fewer on the father’s side) who are also gay. The real percentage of gay twins who were separated at birth and who have identical genetic makeup is 60-70%, or 2 out of 3. (Pease, Barbara and Allan. Why Men Don’t Listen and Women Can’t Read Maps. p 179-186. NY: Broadway Books, 1998.)

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