Tuesday, March 28, 2006

The Biological Basis of Boys loving Boys: Part I

Part I of a three part article I've written for GayNZ on homosexuality and biology...

News that gay men can be sperm donors must be welcome to couples requiring assisted reproductive technology. However, evidence is accumulating that sexual orientation is the result of gene-environment interaction; sexual orientation has a heritable component.

Thus, using sperm from gay donors may have the potential of passing the gay gene(s) to the next generation. Patients requiring such service should be informed of such potential.

--Assoc. Prof. Frank Sin, The Press, 13 March 2006.

66 words, two paragraphs. It's hard to imagine that Sin's almost non-existent letter to the editor would have prompted the response that it did. Albeit brief, the ensuing attention in the news media, on talkback radio and its internet equivalent the blogs, seemed surreally disproportionate to what essentially was an innocuous letter...

Of course, the topic itself served merely as a catalyst to open up the ubiquitous can of worms (or indeed several cans) around not only the 'genetic' basis of homosexuality, but also the broader issues of personal liberties, rights to privacy, and the ominous spectre of 'designer babies' and neo-eugenics.

The issue is, naturally, an incredibly complex one. Like all issues that meet at the common vertex of science, ethics and the individual, it paradoxically becomes more complex, more troublesome, as our so-called 'knowledge' increases. As we gradually accumulate what we think we know, the boundaries become fuzzier, the grey areas become greyer, and our ability to make scientifically and ethically sound decisions becomes harder. It's not unique to the homosexuality debate; we see it in the euthanasia and abortion clashes that pop up like clockwork.

It is unfortunate that the public domain is not always well suited to complex debate. Instead of granting space for real discourse, a robust korero, everything is a soundbite, a simplistically absurd reduction of arguments, ideas and narratives to their most basic precepts. Suddenly everyone has an opinion, some more reasonable than others.

Sin didn't do himself any favours. Given he's an expert in genetics, I was surprised that he wrote the letter in the first place. Until of course one considers that Sin's field of expertise is human male infertility. Perhaps he could be forgiven for wanting to flag a warning about something that he perceived could undo the work to which he has devoted much of his research career. The response from Allan-John Marsh of the Wellington based Gay Association of Professionals (GAP) wasn't particularly helpful, or even correct either, implying that homosexuality was innate but neither inherited or heritable.

As could be expected, the mainstream media had a field day, frantically calling whoever they could to milk whatever controversy they could. Much huffing and puffing ensued, redneck opinions were aired, agendas were either pushed or defended, whichever 'side' of the debate you happened to be on. Somewhere in the middle of all this, the potential for the greater public to gain some understanding was lost.

So how then do we approach this topic? It appears that this issue has two distinct components: the biological basis of sexual orientation, and the ethical implications of 'choosing' a child's sexual orientation. Obviously the two are interrelated, but it is a good idea to work out what we think we know, and what we know we don't know about the first part, before trying to understand the basis for the second.

We need to be careful about this term ‘biological’. All too often it is confused with related but distinct terms like ‘genetic’, ‘innate’, or ‘inherited’, but the word biological also encompasses that which is ‘environmental’, ‘learned’ or ‘aquired’. Most, though not all, characteristics that make us human are a combination of many of these factors. When we enter the realm of behaviour, be it social or sexual, these interactions become even more complex and subtle. There are very few behaviours that are either genetic or environmental, innate or learned. Of those that are, it doesn't mean that one is more 'biological' than the other; at its very fundamental level, all behaviour is in some way biological, given that it involves the neurochemical processes of the brain - an essentially biological phenomenon.

A useful analogy is blinking and winking. Blinking is an entirely genetically, neurologically, innately controlled behaviour. It is universal across all human populations; we can all do it from birth without learning how to. Contrast this with winking, which is an entirely learned behaviour; there have been no studies which suggest that certain people have a predisposition to winking. We can often recall the period of our lives when we learned to do it. Winking isn't a human universal: not all cultures wink, and in the ones that do, it has different meanings, different contexts and different social responses. Both blinking and winking, however, are fundamentally biological. Although not innate, winking relies on our ability to learn, our behavioural flexibility, and our responses to environmental (social and cultural) stimuli, factors that do have strong biological, genetic and developmental bases.

Admittedly this is a simplistic analogy, and most behaviours are far more complex than blinking or winking. But it serves its purpose in our understanding of the fallacy of the false 'nature versus nurture' dichotomy which has seriously handicapped our ability to understand what it means to be human. As the author Matt Ridley points out, a more valid phrase would be 'nature via nurture', or possibly even 'nurture = nature'. Remember that in all of these discussions we do not assume any of these biological factors to be in some way immutable or deterministic (except perhaps blinking!). We can only talk, at most, about predispositions, about relative potentials to be inherited, about probabilities and trends. The very fact that there are individuals that break these trends, the fact that we can only work with statistical probabilities, means that these factors, social and non-social, are by their very nature not deterministic.

We must similarly exercise caution about what we mean by the terms 'sexual orientation', 'homosexuality', 'heterosexuality' and 'sexual identity'. The terms are very deeply embedded in our socialised classical Judaeo-Christian ideas and Victorian Protestant moral constructs, with a healthy dollop of modern pyschological, feminist and queer theories, not to mention theories of gender, thrown in for good measure. Everything that we 'learn' about sexual behaviour is constrained by the labels that we come up with, our classification system du jour. Our concepts of 'sexual orientation' are a product of current and historical cultural norms, which means that any 'answers' we gain are contingent on those norms. Our answers may not be very accurate, or even valid, but in this point in time it's the best we've got.

Given the variation we observe in sexual orientation, the hodge podge of behaviours, attractions and identities that we call human sexuality, we ask the question: are there any non-social biological factors that can be identified as playing a role in sexual orientation? The simple answer is yes: there are no 'gay genes', but there are factors, unrelated to social experience, that correlate with sexual orientation. Broadly these factors can be grouped into two categories: pre-natal developmental processes and genetic factors.

Raging hormones

There is substantial evidence that homosexuality is associated with 'atypical' pre-natal hormone levels, resulting in sex-atypical brain formation. We can hypothesise that foetal action of hormones (specifically testosterone) in laying down the brain structures which will play a role in sexual orientation is atypical in homosexuals. Specifically, lesbians are thought to be subjected to higher than average testosterone levels than straight women, while gay men experience lower levels than straight men.

Part of the evidence for this comes from the study of biological females, who through genetic mutation, express either massive or very little amounts of testosterone as foetuses (Congenital Adrenal Hyperplasia and Adrenal Insensitivity Syndrome/CAH and AIS respectively). As adult women, CAH individuals show a greater level of attraction towards other women than the population average, despite having received 'corrective' hormonal treatment, being raised as gendered females, and identifying as gendered females. By contrast, AIS individuals show a much lower level of attraction towards other women average. This suggests that the action of sex hormones in the womb is related to adult sexual orientation.

The problems with this are of course numerous. The vast majority of lesbians and gay men of course do not have these specific or identifiable genetic conditions resulting in increased/decreased testosterone levels; a mechanism by which they would be subjected to atypically high or low hormone levels is then unclear. Further, the specific markers which we know are the result of higher or lower testosterone levels, such as brain differentiation patterns, differences in the size of certain brain structures etc, are not consistently correlated with homosexuality in males or females. Some do show trends that we would expect, others do not.

The patterns of sexual orientation differ between males and females: males show a bimodal distribution, with the vast majority identifying as either entirely gay or entirely straight. In women it's the opposite: most identify somewhere in between, although not necessarily in the middle. There are also differences within homosexual groups. Gay men who identify as having 'feminine' childhoods exhibit some different markers than those with more 'masculine' childhoods. But then, is childhood gender non-conformity even a valid characteristic of sexual orientation? Similarly, there are differences between 'butch' and 'femme' lesbians in some of the neurological, hormonal and body markers that indicate differences in pre-natal testosterone levels.

So are we dealing here not only with different mechanistic 'causes' of homosexuality between men and women, but also between different types of homosexual men and women – types we've conveniently thrown together for labelling purposes? And where the hell do bisexual men and women fit into the picture?

Next Week: Part II - What is it with gay men and their mothers?