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Are People "Born Gay?"
A look at the most cited biological research studies

"Born gay." The idea that homosexuality is genetic, or at least biologically predetermined and unchangeable, has received a great amount of media coverage presenting it as "new scientific fact." What is often not known is that this "born gay" idea is not new, not proven, and frequently contradicted by what the researchers actually said. At least as far back as 1899, German researcher Magnus Hirschfeld regarded homosexuality as congenital - meaning, "born that way" - and he asked for legal equality based on this thinking.

Now, a century later, the idea that homosexual persons are born that way has again received a great amount of media attention. As new research studies were published, the popular press presented these as evidence that people are "born gay" and that sexual orientation is therefore unchangable. What has been quietly happening, though, is that the "science" behind this idea is falling apart. Here we briefly examine the three most cited studies, from Simon LeVay, Michael Bailey & Richard Pillard, and Dean Hamer.

Simon LeVay and the INAH-3

"Time and again I have been described as someone who 'proved that homosexuality is genetic' ... I did not."

Simon LeVay in The Sexual Brain, p. 122.

Simon LeVay, a neuroscientist, studied the brains from 41 corpses, including 6 women, 19 homosexual men, and 16 men presumed to be heterosexual. A small area of the brain, the INAH-3, was similar in size in women and homosexual men, but larger in heterosexual men. He suggested that this might be evidence for an actual structural difference in the brains of gay men. There are, however, numerous problems with this study:

LeVay data from p.1036

The points on the graph represent the size of INAH-3 in the brains from corpses of 6 women (F), 16 men (M; presumably heterosexual) and 19 homosexual men (HM)

  • In comparing the size of the INAH-3, he presumed that the 16 "heterosexual" men were, in fact, heterosexual. Only two of them had denied homosexual activities; for the rest, sexual histories were not available. Thus, he was actually comparing homosexual men with men of unknown sexual orientation! This, obviously, is a major flaw in scientific method.
  • The volume of the INAH-3 may not be a relevant measure:
    • Scientists disagree on the most accurate way to measure the INAH-3. LeVay measured the volume; other scientists claim it is more accurate to measure the actual number of neurons. Clarifying the potential problem, some have suggested that using a volume method to project impact on sexual orientation may be like trying to determine intelligence by a person's hat size.
    • When different laboratories have measured the four areas of the INAH (including INAH-3), their results conflicted. For example, Swaab and Fliers (1985) found that the INAH-1 was larger in men, while LeVay (1991) found no difference between men and women. Allen et al (1989) found the INAH-2 to be larger in men than in some women, while LeVay (1991) again found no difference. See Byne (1994), page 52.

The above problems aside, even the data from LeVay's study did not prove that anyone was born gay. This is the case for at least two reasons:

  • Both groups of men covered essentially the same range of sizes. One could be gay (HM) with a small INAH-3 or with a large one. One could also be in the "heterosexual" category (M) with either a small or large INAH-3. Clearly, these men were not held to a sexual orientation by their INAH-3 biology! As the data shows, the INAH-3 size of three of the homosexual men puts them clearly in the "heterosexual" category (with one having the second largest INAH-3!). If all you know about any of LeVay's subjects is INAH-3 size, you could not accurately predict whether they are heterosexual or homosexual, male or female.
  • A study that showed a clear difference in INAH-3 sizes, would still leave another question unanswered: are men gay because of a smaller INAH-3, or was their INAH-3 smaller because of their homosexual actions, thoughts, and/or feelings? It is known that the brain does change in response to changes in behaviour and environment. For example, Newsweek reported that "in people reading Braille after becoming blind, the area of the brain controlling the reading finger grew larger." As well, in male songbirds, "the brain area associated with mating is not only larger than in the female, but varies according to the season" (Newsweek, Feb. 24, 1992, p. 50).

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Bailey & Pillard: Twins and Other Brothers

Bailey and Pillard studied pairs of brothers -- identical twins, non-identical twins, other biological brothers, and adoptive brothers -- where at least one was gay. At first glance, their findings looked like a pattern for homosexuality being genetically influenced. Identical twins were both homosexual 52% of the time; non-identical twins, 22%; other biological brothers, 9.2%; and adoptive brothers, 10.5%. A closer look reveals significant problems with a "born gay" conclusion to this study:

  • "In order for such a study to be meaningful, you'd have to look at twins raised apart," says Anne Fausto Sterling, a biologist. The brothers in this study were raised together in their families.
  • All the results were different from what one would expect if homosexuality was directly genetic:
    • Because identical twin brothers share 100% of their genes overall, we would expect that if one was homosexual, the other would also be homosexual, 100% of the time. Instead, this study found that they were both homosexual only 52% of the time.
    • Although completely unrelated genetically, adoptive brothers were more likely to both be gay than the biological brothers, who share half their genes! This piece of data prompted the journal Science to respond: "this . . . suggests that there is no genetic component, but rather an environmental component shared in families" (Vol. 262 Dec.24, 1993).
    • If homosexuality were genetic, one would expect each number in the column "Results from the B & P study" to be identical to the corresponding number in the "Expectation if genetic" column. Each one is significantly different!
Both are Homosexual:
  Shared genes 
if genetic
Results from 
B&P study
Identical twin brothers 100 % 100 % 52 %
Non-ident. twin brothers  50 %  50 % 22 %
Other biological brothers  50 %  50 %  9 %
Adoptive brothers    0 %  1-4 % 11 %
  • Finally, Bailey & Pillard did not use a random sample. The men in the study were recruited through advertisements in gay newspapers and magazines.

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Dean Hamer and the Xq28 Genetic Markers

Hamer studied 40 pairs of homosexual brothers, and reported that 33 pairs shared a set of five genetic markers. Reporting the story, Time magazine's cover read "BORN GAY Science Finds a Genetic Link" (July 26, 1993). Hamer, however, was more cautious. He felt that it played "some role" in a minority of 5 to 30% of gay men (The Science of Desire by Dean Hamer and Peter Copeland. New York: Simon & Schuster, 1994. Pages 145-146). This is a rather distant reality from finding the "gay gene" and it left two critical questions: just how much influence was "some role" thought to be, and what about the other 70 to 95%?

  • Based on a simple genetic theory, one would expect 50%, or 20 pairs, to have the same markers. Why did 7 pairs of gay brothers not share a set of genetic markers?
  • Hamer did not check to see if the heterosexual brothers of the homosexual men also had such a genetic marker. Thus, there was no control group in this study. Here too, this obviously is a major flaw in scientific method.
  • Since that time, Science has reported that George Ebers, a researcher at the University of Western Ontario, has attempted to duplicate the study but found "no evidence, not even a trend," for the "genetic link." In the scientific world, that is a big problem. More recently, another study by Rice et al. has also stated that its results "do not support an X-linked gene underlying male homosexuality."

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Now even the gay and pro-gay press are acknowledging the problems. In her 1996 book, Gender Shock, writer and lesbian woman Phyllis Burke, quoting Dr. Paul Billings, an internist and human geneticist, calls the born gay idea "a new fish story." A gay publication, "The Guide," writes Hamer's story under the title "Gene Scam?"

As well, Parents, Family and Friends of Lesbians and Gays (PFLAG), one of the larger pro-gay organizations, explains that there is no conclusive evidence that people are born gay in its booklet "Why Ask Why? Addressing the Research on Homosexuality and Biology."

Born gay? Ironically, what the studies actually suggest is that persons who experience same-sex attraction are not prisoners of their biology. That's good news for same-gender-attracted people who would rather pursue other options.

The media seized upon a study suggesting the existence of a 'gay gene.' Now that it is unravelling, mum's the word.

The Guide, October 1995

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References to Main Articles:

  • LeVay, S. (1991). A difference in hypothalamic structure between heterosexual and homosexual men. Science, 253, August, 1034-1037. Data in chart from p. 1036.
  • Bailey, J.M & Pillard, R.C. (1991). A genetic study of male sexual orientation. Archives of General Psychiatry, 48, December, 1089-1096.
  • Hamer, D. et al. (1993). A linkage between DNA markers on the X chromosome and male sexual orientation. Science, 261 16 July, 321-27.
  • [Square brackets list which of the three above articles are reviewed:]
  • Byne, William & Parsons, Bruce (1993). Human sexual orientation: the biologic theories reappraised. Archives of General Psychiatry, 50, March 1993, 228-237. [LeVay, Bailey & Pillard]
  • Byne, William (1994). The biological evidence challenged. Scientific American, May 1994, 50-55. [all three]
  • Cole, Sherwood O. (1995). The biological basis of homosexuality: a Christian assessment. Journal of Psychology and Theology, 23(2), 89-100. [all three]
  • Dallas, Joe (1992). Born gay? Christianity Today, June 22, 20-23. [LeVay, Bailey & Pillard]
  • LeVay, Simon & Hamer, Dean H. (1994). Evidence for a biological influence in male homosexuality. Scientific American, May 1994, 44-49. [LeVay, Hamer]
  • Looy, Heather (1995). Born gay? a critical review of biological research on homosexuality. Journal of Psychology and Christianity, 14(3), 197-214. [all three]
  • Marshall, Eliot (1995). NIH's "Gay Gene" study questioned. Science, 268, Jun 30 1995, 1841. [Discusses G.C. Eber's attempt at replicating Hamer's work].
  • Muir, J.G. (1996). Sexual orientation - born or bred? Journal of Psychology and Christianity, 15(4), 313-321. [all three]
  • PFLAG (1995). Why Ask Why? Addressing the Research on Homosexuality and Biology. Privately published booklet. [all three]
  • Rice, G. et al. (1999). Male Homosexuality: Absence of Linkage to Microsatellite Markers at Xq28. Science, 284(5414), 665-667. [Hamer]
Adapted from: Are People "Born Gay?"