For those of us who grew up gay or lesbian, and who often knew ‘something’ was different about us from an early age, a study by neuro-scientist Simon LeVay, one of the first researchers who posited that sexual orientation is connected to fetal brain development, was of little surprise even as it created waves of controversy in academia.

LeVay originally shook things up in 1991 when he published a paper in Science, the journal of the American Association for the Advancement of Science, in which he observed the nucleus of the hypothalamus of homosexual men was smaller, and more closely aligned to that of women, than it was in heterosexual men, and concluded this difference indicated at least a suggestion that sexual orientation was biological rather than a learned or acquired behaviour.  He did warn, however, that his findings were not to be taken as suggesting there was a genetic cause.

"It’s important to stress what I didn’t find. I did not prove that homosexuality is genetic, or find a genetic cause for being gay. I didn’t show that gay men are born that way; the most common mistake people make in interpreting my work. Nor did I locate a gay centre in the brain. The [section of the hypothalamus studied] is less likely to be the sole gay nucleus of the brain than [it would be] a part of a chain of nuclei engaged in men and women’s sexual behavior."

In other words, what LeVay’s original study found was the size difference in the hypothalami of homosexual vs heterosexual males and those of females was one of several factors involved in the possible biological basis of sexual orientation and the sexual behaviour associated with it.  What differences might lie within lesbian brains was not studied.  It would be interesting to see if, in fact, lesbian hypothalami were larger than heterosexual women and more aligned with that of heterosexual men.

The LeVay study should also not be interpreted, I would suggest, as saying that homosexual men are more ‘women-like’ than heterosexual men.  Of course, in some quarters, that is exactly what occurred.  Those that believe gay men are all effeminate or ‘want to be women’ (and that view is still out there, surprisingly enough) obviously never encountered a beefy, butch, cigar-smoking, shaved-head blue-collar/redneck Leather Daddy...  Cripes, all one needs to do is watch porn put out by Raging Stallion Studios or COLT for that little theory to get tossed out the window!!  But I digress....

More recently, LeVay released another study, Gay, Straight and the Reason Why: The Science of Sexual Orientation (Oxford University Press, 2011) in which he states that homosexuality has nothing to do with psychological issues, childhood sexual trauma, or ‘choice’ in the usual sense of the word.  He reinforces his view that sexual orientation is associated with prenatal brain structure differences.  Again, this will come as little or no surprise to anyone who has come out as gay, lesbian or bisexual.  It’s something the GLBTQ community has maintained for decades.

"Sexual orientation is an aspect of gender that emerges from the prenatal sexual differentiation of the brain," LeVay has been quoted as saying.  "Whether a person is gay or straight depends in large part on how this process of biological differentiation goes forward, with the lead actors being genes, sex hormones, and the brain systems that are influenced by them."

Essentially what LeVay is saying is that various maternal hormonal influences within the womb and the way a particular fetus’ brain develops along with the physical differentiation between what will become a male fetus and what will become a female fetus, are part of a "soup" of influences for the eventual sexual orientation of the individual.

During the development to a gendered being, the fetus encounters various hormonal activities which will determine if it develops as male.  Not to be overly simplistic but the ‘default’ position for fetal development is female and from there this is either fine-tuned or altered as a result of such things as testosterone.

While in the womb, what becomes a male fetus is bathed in testosterone and this, in turn, influences the development of external genitalia and various secondary sex characteristics.  This is one of the reasons men have nipples, for instance.  Ours just didn’t develop into mammary glands or develop the ability to, post puberty, produce milk; the testosterone bath arrested that development and channeled it down a completely different road.

The influence of testosterone also accounts for differences in brain structure between males and females, how we communicate verbally and non-verbally, and the fight or flight responses.

"If testosterone levels during a critical prenatal period are high," Levay has stated, "the brain is organized in such a way that the person is predisposed to become typically masculine in a variety of gendered traits, including sexual attraction to females.

If testosterone levels are low during the same period, the brain is organized in such a way that the person is predisposed to become typically female in gendered traits, including sexual attraction to males."

In the instance of bisexuality, and its various degrees, LeVay believes it results from "intermediate levels" of testosterone although he admits there is no direct evidence of this.

However, there is more going on than just the ‘either/or’ of hormonal influences.

There is a growing understanding that sexuality may be influenced by several combinations of genetic information.  If so - and it would seem probable - it would explain the different ‘types’ or ‘styles’ of homosexuality such as butch or femme lesbians, or hyper-masculine gay men.

Factor into all this predispositioning societal and environmental influences, and it is clear that human sexuality is...well...anything but clear.  We are a complex species and our sexuality and how we express that sexuality (and our sexualness for that matter) is likewise complex and still not totally obvious .

In 1996, when he published Queer Science, Levay cautioned "...[I]t is important to stress several limitations of the study. The observations were made on adults who had already been sexually active for a number of years. To make a really compelling case, one would have to show that these neuro-anatomical differences existed early in life - preferably at birth. Without such data, there is always at least the theoretical possibility that the structural differences are actually the result of differences in sexual behavior...." adding, "Furthermore, even if the differences in the hypothalamus arise before birth, they might still come about from a variety of causes, including genetic differences, differences in stress exposure, and many others."

He also acknowledged that since the brains he studied were those of gay men who had died of AIDS, there was the possibility, although he believed it to be unlikely, that the difference in hypothalamic size was the result of the disease.

"There is always the possibility that gay men who die of AIDS are not representative of the entire population of gay men," he wrote.

"For example, they might have a stronger preference for receptive anal intercourse....Thus, if one wished, one could make the argument that structural differences [in the region of the hypothalamus he studied] relate more to actual behavioral patterns of copulation rather than to sexual orientation as such."

In other words, the smaller region could be more tied in with behaviour than it was with sexual orientation generally.  It is possible, and LeVay acknowledged this, that if one could study the hypothalamus of living humans in some way other than dissection and pair that with in-depth interviews about their sexuality, we would have a far deeper understanding of the role biology plays in sexual orientation and sexual behaviour.