|By Dr. Nadia El-Awady
IslamOnline’s Health & Science Editor
Much research has been done over the years to discover the scientific origins of homosexuality. Mostly it has been to disprove the fact that homosexuality is a matter of choice. None of the research done up to this date, however, is conclusive. Only varying theories exist according to the results of such research.
Research available on the topic of homosexuality can be divided into three categories:
- Anatomical differences
- Genetic investigations
- Biological causes
- Anatomical differences
Simon LeVay, a self-proclaimed homosexual, presented research in 1991 that was much publicized by the media. His report found neuroanatomic differences between homosexual and heterosexual men. Much of the field’s current visibility is due to the wide publicity surrounding this study of INAH3, the third interstitial nucleus of the anterior hypothalamus, which is normally three times larger in men than in women. LeVay examined hypothalamic tissue from 19 homosexual men, all of whom died of AIDS; 16 heterosexual men, six of whom had died of AIDS; and six women of unknown sexual orientation. He found that INAH3 was two to three times larger in heterosexual men than in homosexual men.
This study was the first ever to imply that there were neuroanatomic differences between homo and heterosexual men; thus, naturally, it was the subject of much controversy relating to both its scientific and its social implications. Many homosexual activists argued that the study bolstered their contentions that some people are born gay and that becoming gay was not a matter of choice. They thus arrived at the conclusion that homosexuals should be granted protection against discrimination. Many scientists, however, assailed LeVay’s methodology and the conclusions of his work. These counter-arguments did not receive the same amount of media attention.
Another neuroanatomical difference between homo and heterosexual men was reported in 1992 by University of California at Los Angelos investigators Laura S. Allen, a research scientist, and Roger Gorski, a professor of neurobiology (L.S. Allen, R. Gorski, Proceedings of the National Academy of Sciences, 89:7199-202).
The anterior commissure, a relatively small bundle of axons connecting the two brain hemispheres, which is larger in women than in men, was found to be also larger in gay men than it is in heterosexual men. In a related study, Dick F. Swaab and coworkers at the Netherlands Institute for Brain Research reported that a hypothalamic structure, known as the central subdivision of the bed nucleus of the stria terminalis, is larger in men than in women, and also larger in men than in male-to-female trans-sexuals. (J.N. Zhou et al., Nature, 378:68-70, 1995).
This anatomical work came under heavy criticism by William Byne, director of the Neuroanatomy Laboratory of Neuropsychiatric Disease at New York’s Mount Sinai Medical Center. “A general problem with this work is that there have been dozens and dozens of reports of sex differences in the human brain since the middle of the last century. But not a single one of these has been corroborated, except for the one that men tend to have slightly larger brains than women. The reason for that is that it’s tremendously difficult to do morphometric studies in the human brain. I would be surprised if there weren’t sex differences in the human brain, since there are sex differences in just about every organ system in humans. But to date, we can’t say with any confidence where the sex differences are.”
Byne also thinks that even if the sex differences are real, LeVay’s findings could have been confounded by the fact that all his original gay subjects died of AIDS. LeVay maintains that he controlled this by examining the brains of heterosexual men who died of AIDS, as well as one gay man who died of other causes. Dr. William Byne argued that, “[LeVay’s] inclusion of a few brains from heterosexual men with AIDS did not adequately address the fact that at the time of death virtually all men with AIDS have decreased testosterone levels as the result of the disease itself or the side effects of particular treatments. Thus it is possible that the effects on the size of the INAH3 (hypothalamus) that he attributed to sexual orientation were actually caused by the hormonal abnormalities associated with AIDS.” (E. Byne, “The Biological Evidence Challenged,” Introduction