Thursday, June 4, 2009

Science On Sexual And Gender Diversity - by Tim Palmer and Rev. Debra W. Haffner

An excerpt from:

Time To Seek – A Study Guide On Sexual And Gender Diversity

by Timothy Palmer and Rev. Debra W. Haffner  -  From 

Religious Institute on Sexual Morality, Justice, and Healing 

Science On Sexual And Gender Diversity 

There have been a number of scientific studies exploring the origins, or etiology, of sexual orientation during the past 20 years, particularly the origins of homosexuality. There has been little research on the causes of heterosexuality. The balance of scientific research suggests that an individual’s adult sexual orientation is caused by a complex array of genetics, prenatal hormones, socio-cultural influences, psychosocial factors, or some combination of these. The research demonstrates that adult sexual orientation and gender identity, in all their complexities, are neither a choice nor a preference. All people, regardless of orientation or identity, have the responsibility to make ethical, moral choices about their sexual behaviors and relationships.

What has science revealed about the origins of sexual orientation?

Several studies have revealed that typical or atypical exposure in the uterus to androgens, the male sex hormone, may influence adult sexual orientation in both women and men and in both gay and straight persons.7 Lesbians, on average “are exposed to more prenatal androgens than heterosexual women,”8 and homosexual men may have a different androgen exposure, either through timing or concentration, than straight men. Several researchers have studied the effect of a mother’s stress on prenatal hormones during early pregnancy, and the results have been mixed. In some studies, women with gay sons reported greater maternal stress during the early months of pregnancy.9 

Research studies have found higher rates of homosexuality in families, among biological brothers, and among identical twins, indicating “clear evidence for a genetic component to both male and female sexual orientation.”10 Geneticists have found at least four genetic regions that may contribute to male sexual orientation. A wellknown study in the early 1990s reported the discovery of a genetic region—the Xq28 region on the X chromosome, inherited from the mother’s side—that appeared to be present in about three-quarters of gay men (as well as some straight men). No such gene was found in lesbian women.11 A 2005 study that used more sophisticated genetic mapping techniques identified three additional genetic regions that may contribute to sexual orientation in men. (Women were not part of this study.)12 Other research has found a “fraternal birth order effect” among gay men: the incidence of homosexuality increases 33% with each older brother a man has. (A birth order effect does not appear to exist for lesbian women.) This correlation exists only among biological brothers, not among sisters, adopted brothers or step-brothers. This correlation is present even if the brothers are not raised in the same household.13 

A variety of studies has found small but significant anatomical differences between heterosexual and homosexual populations that suggest a genetic component to sexual orientation. These studies reveal: 

• differences in the size, structure, and function of specific parts of the brain between men and women and among people of differing sexual orientations;14

• differences in the neural circuitry of gay and straight men;15

• finger lengths in lesbians that are more like heterosexual men than heterosexual women;16

• an earlier average age of puberty for gay men compared with straight men;17 and

• the rate of eye blinking (human startle response) among lesbians is more like straight men than straight women.18 

One researcher concluded that “sexual orientation may be laid down in neural circuitry during early fetal development.”19 However, he has also cautioned that “whether neural differences underlie sexual orientation per se or are the consequence of homosexual or heterosexual behavior is yet to be determined.”20 

No study has identified a single factor that explains sexual orientation in all people. In the words of the American Psychiatric Association, “there are probably many reasons for a person’s sexual orientation, and the reasons may be different for different people.”21 

Is there a gay—or straight—gene?

As science learns more about genetics, many scientists believe that additional evidence will emerge that sexual orientation is predominantly genetic in nature. In a comprehensive 2002 review article in the Annual Review of Sex Research, the authors reported that “although precise genetic mechanisms have yet to be definitely specified, these are likely to be identified in the future.”22  However, no study has identified a single “gay gene” or “straight gene” that determines sexual orientation, and researchers believe that “given the complexity of sexual orientation, numerous genes are likely to be involved.”23 

What doesn’t cause an individual’s sexual orientation? 

Despite long-held misconceptions, there is no peer-reviewed research to indicate that parenting style, a parent’s sexual orientation, or incidents of sexual abuse cause an individual’s adult sexual orientation. According to the American Psychiatric Association, “No psychosocial or family dynamic cause for homosexuality has been identified, including histories of childhood sexual abuse.”24 Childhood sexual behaviors do “not appear to relate to eventual adult sexual orientation” nor do parental-child interactions.25 

Is homosexuality a mental illness or disorder? 

For more than 30 years, the major health and mental health professional organizations in the United States have agreed that homosexuality is an expected variation of sexual orientation. The American Academy of Pediatrics, the American Counseling Association, the American Psychiatric Association, the American Psychological Association, the National Association of School Psychologists and the National Association of Social Workers, together representing half a million health and mental health professionals, have all taken the position that homosexuality is not a mental disorder.  

Can an individual’s sexual orientation be changed through therapy? 

Homosexuality and bisexuality do not need to be “cured” or treated, although many individuals successfully seek counseling to accept their sexual orientation and for help in coming out.  The American Psychiatric Association affirms that “those who have integrated their sexual orientation into a positive sense of self function at a healthier psychological level than those who have not.”26  Individuals who seek “reparative therapy” to become heterosexual often do so because of personal distress, possibly caused by family or societal pressures, or by religious teachings that condemn bisexuality and homosexuality. A position statement adopted by the American Psychiatric Association in 2000 stated, “In the last four decades, ‘reparative’ therapists have not produced any rigorous scientific research to substantiate their claims of cure.”27 One small study in 2003, involving 200 subjects recruited from the “ex-gay” movement, found that highly motivated people can alter their sexual behavior or self-identity, but reversing their underlying attraction to persons of the same sex is rare.28 Because of both the potential for harm and the professional consensus that homosexuality is not a disorder, professional organizations such as the American Academy of Pediatrics, American Medical Association, American Psychiatric Association, American Psychological Association and the National Association of School Psychologists have spoken out against such therapies. 

What causes an individual’s gender identity? 

Gender identity, like sexual orientation, is not fully understood. The diversity of gender identities among human beings argues against simple explanations or a discrete cause. It is likely that a combination of biological factors, such as genetic and hormonal differences, early life experiences and other social influences all contribute in some way to the development of an individual’s gender identity. 

There is some evidence to suggest biological influences for gender identity. For example, transsexualism may be a “neuro-developmental condition of the brain.”29 In one small study, a part of the brain called the “bed nucleus of the stria terminalis” was found to be the same size and neuron count in transsexual women (natally born males) as in women in the general population, rather than as men in the general population.30 It is  hypothesized that hormones influence this brain development during the “fetal period, then around the time of birth, and also post-natally.” Hormones may be affected by “genetic influences, medication, environmental influences, stress or trauma to the mother during pregnancy.”31 

A consensus statement by 25 researchers from the United States and Europe concluded that “there is no evidence that nurturing and socialization in contradiction to the phenotype [physical attributes] can cause transsexualism, nor that nurture which is entirely consistent with the phenotype can prevent it.”32 In other words, parenting style and environmental factors neither cause a person to be transgender nor prevent it. 

When does gender identity emerge? 

Gendered behaviors emerge in early childhood and demonstrate the biological and genetic diversity of people. Starting as early as age three, children may exhibit gender variance – a strong, persistent preference for behaviors typically associated with the other sex, not their own. (SeeDefinitions, page 7.) Many gender-variant children voluntarily hide or discontinue these behaviors by the time they start school.33 This change usually is brought about by criticism, fear or a desire to conform. Rejection, bullying and criticism can create adjustment difficulties for gender-variant children. 

Do gender-variant children grow up to be gay? 

Gender variance does not cause homosexual orientation, but it can be an indicator of it in males. Nearly 70 percent of gender-variant boys later identify as adult gay men34 but some will be heterosexual. Most gender-variant girls, however, grow up to be heterosexual or bisexual women.35


For More Information

Answers to Your Questions About Sexual Orientation and Homosexuality. American Psychological Association (Washington, D 2007).

Answers to Your Questions About Transgender Individuals and Gender Identity. American Psychological Association (Washington, DC, 2006).

Gay, Lesbian & Bisexual Issues. American Psychiatric Association.


Gender Identity Research & Education Society.

Hamer, Dean and Peter Copeland. The Science of Desire: The Search for the Gay Gene and the Biology of Behavior. New York: Simon and Schuster, 1994. 

If You Are Concerned About Your Child’s Gender Behaviors: A Parent Guide. Children’s National Medical Center, Washington, DC.

Just the Facts about Sexual Orientation & Youth: A Primer for Principals, Educators & SchoolPersonnel (Washington, DC, 1999).

LeVay, Simon. The Sexual Brain. Cambridge, MA: The MIT Press, 1993.


Questions for Group Discussion / Individual Reflection 

1. What difference does it make to our policies and programs if we believe that sexual orientation—whether bisexual, heterosexual or homosexual—has a biological component? 

2. For those of us who are heterosexual, when did we discover our sexual orientation? Could we change our sexual orientation through therapy? Could our sexual orientation change if we met “the right person” of the same sex? People of other sexual orientations are often asked these kinds of questions; why are they not usually asked of straight people? 

3. Studies have found that religious people who believe that homosexuality (or heterosexuality) is not a choice but something people are born with are more likely to oppose discrimination and affirm the rights of LGBT people. Why do you think that’s true? Does it affect how you think about these issues?

Reprinted with permission from - Religious Institute on Sexual Morality, Justice, and Healing

Read full text Time To Seek – A Study Guide On Sexual And Gender Diversity on 

Religious Institute on Sexual Morality, Justice, and Healing

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