TeenHealthFX - Answers - Homosexuality: Choice Versus Biological Components

Sexuality: Gay, Straight & Bisexual / Question
Published: March 26, 2009

Dear TeenHealthFX,

You wrote, "In addition, a lot of research shows that one's sexual orientation is determined by genetics and biology," to someone who had some thoughts about homosexuality. Please send me a list of all the research that proves that homosexuality is genetic. I have never seen any research that PROVES homosexuality is innate and genetic. And so, please let me know your research. My email address is xxxxxxxxxxxxx. If you can't send me any information (which I believe you can not) please don't tell inquiring young people that homosexuality is genetic.

Signed: Homosexuality: Choice Versus Biological Components

Dear Homosexuality: Choice Versus Biological Components,

There is still a great deal of research currently being done, and that needs to be done, in order to pinpoint the exact contributing factors that lead to a person’s sexual orientation. However, there are many studies that do point to genetic or biological causes as being important contributing factors. The main point that TeenHealthFX would like to make is that homosexuality is not viewed in medical and scientific communities as a choice people make or as something that just happens to them (such as with the idea that people can “turn” gay). FX would also like to point out that homosexuality is not looked at in medical and mental health communities as a mental illness. And the purpose of pointing out these facts is to promote a sense of tolerance and acceptance, and to help our society work towards equality for all people of all sexual orientations.

To see various statements on homosexuality related to this issue, please see the list below:

American Psychological Association: Statement on Homosexuality:

The American Psychological Association released a Statement on Homosexuality in 1994-JUL. The first two paragraphs read: “The research on homosexuality is very clear. Homosexuality is neither mental illness nor moral depravity. It is simply the way a minority of our population expresses human love and sexuality. Study after study documents the mental health of gay men and lesbians. Studies of judgment, stability, reliability, and social and vocational adaptiveness all show that gay men and lesbians function every bit as well as heterosexuals.

Nor is homosexuality a matter of individual choice. Research suggests that the homosexual orientation is in place very early in the life cycle, possibly even before birth. It is found in about 10 percent of the population, a figure which is surprisingly constant across cultures, irrespective of the different moral values and standards of a particular culture. Contrary to what some imply, the incidence of homosexuality in a population does not appear to change with moral codes or social mores. Research findings suggest that efforts to repair homosexual are nothing more than social prejudice garbed in psychological accouterments.”

APA Brochure: Answers to Your Questions About Sexual Orientation and Homosexuality:

“…many scientists share the view that sexual orientation is shaped for most people at an early age through complex interactions of biological, psychological and social factors.”

“…psychologists do not consider sexual orientation for most people to be a conscious choice that can be voluntarily changed.”

“…homosexuality is not an illness, mental disorder, or emotional problem.”

Academy of Pediatrics and Council on Child and Adolescent Health

Both organizations have stated that homosexuality is not a choice and cannot be changed.

Reverend Rob Schenck

The accumulating amount of biological evidence is having an effect on many. The Rev. Rob Schenck, a prominent Washington, D.C., evangelical leader, told a large gathering of young evangelicals that he believes homosexuality is not a choice but rather a predisposition, something "deeply rooted" in people. Schenck stated that this conversion came about after he'd spoken extensively with genetic researchers and psychologists. He argues that evangelicals should continue to oppose homosexual behavior, but that "many evangelicals are living in a sort of state of denial about the advance of this conversation."

Born Gay: The Psychology of Sex Orientation

After spending years sifting through all the available data, British researchers Glenn Wilson and Qazi Rahman come to an even bolder conclusion in their forthcoming book Born Gay: The Psychobiology of Sex Orientation, in which they write: "Sexual orientation is something we are born with and not `acquired' from our social environment."

Nature Versus Nurture

For much of the 20^th century, the dominant thinking connected homosexuality to upbringing. Freud looked at homosexuality as being caused by overprotective mothers and distant fathers. However, various research studies over the years have pointed to genetics and biological components as being contributing factors to sexual orientation as opposed to issues around upbringing. And there has been a lack of scientific evidence over the years to prove upbringing as a main or sole contributing factor. Listed below are some of the many studies that have been done in this area, shown in a chronological progression:

In 1991, a neuroscientist in San Diego named Simon LeVay told the world he had found a key difference between the brains of homosexual and heterosexual men he studied. LeVay showed that a tiny clump of neurons of the anterior hypothalamus - which is believed to control sexual behavior - was, on average, more than twice the size in heterosexual men as in homosexual men. LeVay's findings did not speak directly to the nature-vs.-nurture debate - the clumps could, theoretically, have changed size because of homosexual behavior. But that seemed unlikely, and the study ended up jump-starting the effort to prove a biological basis for homosexuality.

Later in 1991, Boston University psychiatrist Richard Pillard and Northwestern University psychologist J. Michael Bailey announced the results of their study of male twins. They found that, in identical twins, if one twin was gay, the other had about a 50 percent chance of also being gay. For fraternal twins, the rate was about 20 percent. Because identical twins share their entire genetic makeup while fraternal twins share about half, genes were believed to explain the difference.

In 1993 Dean Hamer discovered what was referred to as the "gay gene." However, Hamer, a Harvard-trained researcher at the National Cancer Institute, hadn't quite put it that boldly or imprecisely. He found that gay brothers shared a specific region of the X chromosome, called Xq28, at a higher rate than gay men shared with their straight brothers. Following this study, the clear focus of sexual-orientation research shifted to biological causes without much science produced to support the old theories tying homosexuality to upbringing. Researchers who suspect that homosexuality is inborn - whether because of genetics or events happening in the womb - have looked everywhere for clues: Prenatal hormones, birth order, finger length, fingerprints, stress, sweat, eye blinks, spatial relations, hearing, and handedness.

Swedish researchers reported finding important differences in how the brains of straight men and gay men responded to two compounds suspected of being pheromones - those scent-related chemicals that are key to sexual arousal in animals. The first compound came from women's urine, the second from male sweat. Brain scans showed that when straight men smelled the female urine compound, their hypothalamus lit up. That didn't happen with gay men. Instead, their hypothalamus lit up when they smelled the male-sweat compound, which was the same way straight women had responded. This research once again connecting the hypothalamus to sexual orientation comes on the heels of work with sheep. About 8 percent of domestic rams are exclusively interested in sex with other rams. Researchers found that a clump of neurons similar to the one LeVay identified in human brains was also smaller in gay rams than straight ones.

Scientists in Vienna announced that they had isolated a master genetic switch for sexual orientation in the fruit fly. Once they flicked the switch, the genetically altered female flies rebuffed overtures from males and instead attempted to mate with other females, adopting the elaborate courting dance and mating songs that males use.

A large-scale, five-year genetic study of gay brothers is underway in North America. The study received $2.5 million from the National Institutes of Health. Relying on a robust sample of 1,000 gay-brother pairs and the latest advancements in genetic screening, this study promises to bring some clarity to the murky area of what role genes may play in homosexuality.

William Reiner, a psychiatrist and urologist with the University of Oklahoma, has evaluated more than a hundred cases of children born with disorders of “sexual differentiation.” For decades, the standard medical response to boys born with severely inadequate penises (or none at all) was to castrate the boy and have his parents raise him as a girl. But Reiner has found that nurture - even when it involves surgery soon after birth - cannot trump nature. Of the boys with inadequate penises who were raised as girls, he says, "I haven't found one who is sexually attracted to males." The majority of them have transitioned back to being males and report being attracted to females. During fetal development, sexual identity is set before the sexual organs are formed, Reiner says. Perhaps it's the same for sexual orientation. In his research, of all the babies with X and Y chromosomes who were raised as girls, the only ones he has found who report having female identities and being attracted to males are those who did not have "receptors" to let the male sex hormones do their “masculinizing” in the womb. What does this all mean? "Exposure to male hormones in utero dramatically raises the chances of being sexually attracted to females," Reiner says. "We can infer that the absence of male hormone exposure may have something to do with attraction to males." Michael Bailey says Reiner's findings represent a major breakthrough, showing that "whatever causes sexual orientation is strongly influenced by prenatal biology." Bailey and Reiner say the answer is probably not as simple as just exposure to sex hormones. After all, the exposure levels in some of the people Reiner studies are abnormal enough to produce huge differences in sexual organs. Yet, sexual organs in straight and gay people are, on average, the same. More likely, hormones are interacting with other factors.

Canadian researchers have consistently documented a "big-brother effect," finding that the chances of a boy being gay increase with each additional older brother he has. (Birth order does not appear to play a role with lesbians.) So, a male with three older brothers is three times more likely to be gay than one with no older brothers, though there's still a better than 90 percent chance he will be straight. They argue that this results from a complex interaction involving hormones, antigens, and the mother's immune system.

New York University researcher Lynn S. Hall, who has studied traits determined in the womb, speculates that prenatal stress is an important biological component in sexual orientation. This prenatal stress would probably occur during the first trimester, when the brain is really developing, particularly the structures like the hypothalamus that influence sexual behavior. This stress might have been based on his position in the womb or the blood flow to him or any of a number of other factors not in his mother's control. Yet more evidence that identical twins have womb experiences far from identical can be found in their often differing birth weights. Taken together, the research suggests that early on in the womb, as the fetus's brain develops in either the male or female direction, something fundamental to sexual orientation is happening. Nobody's sure what's causing it. But here's where genes may be involved, perhaps by regulating hormone exposure or by dictating the size of that key clump of neurons in the hypothalamus. Before researchers can sort that out, they'll need to return to the question of whether, in fact, there is a "gay gene."

Homosexuality runs in families - studies show that 8 to 12 percent of brothers of gay men are also gay, compared with the 2 to 4 percent of the general population.

No matter how imperfect these studies are, when you put them all together and examine them closely, the message is clear: While post-birth development may well play a supporting role, the roots of homosexuality, at least in men, appear to be in place by the time a child is born.

Signed: TeenHealthFX