Whimsical, queer exploration of all things gender.

Archive for the ‘Science’ Category

Is there a clear way to define a ‘biological’ sex?

One of the most fundamentally obvious things people might think when they’re asked what ‘Gender Studies’ actually is, is that it may look at differences between men and women… in some way. An interesting question to ask might be what actually is it that makes a man ‘a man’ and a woman ‘a woman’? It’s not as obvious as one may think.

When this question was first asked in a legal context (roughly 50 years ago), three factors were used to define ‘biological sex’: the chromosomes of an individual, what gonads (ovaries or testes) they possess, and their genitals. This is overly simplistic as it turns out that many different combinations of these three factors exist than the two categories everyone was assumed (or expected?) to fall into.

The rest of this post will contain science. For anyone apprehensive, I dare you to read on. I double dare you.

We are all told in school that with regards to chromosomes, men = XY and women = XX. For many people this is true. On the Y chromosome, which is a small, stumpy little thing, lies a gene called SRY, which stands for ‘Sex Determining Region Y’. It is responsible for unspecified gonads in a foetus to develop into testes. Seems pretty straightforward. However this area of the Y chromosome can in rare cases cross over to an X chromosome. If this X chromosome is then inherited, an individual who is XX but in all other ways ‘male’ (gonadally, genitally, and in appearance when older) will result. If the SRY-less Y chromosome is inherited, then the foetus will be XY, but otherwise ‘female’. Because sex on a birth certificate is decided just from someone taking a cursory glance, these conditions may be undiagnosed until the age of puberty, or sometimes not at all.

Individuals who possess a SRY gene will develop testes. Testes then produce testosterone, which is responsible for the development of typically male external genital structures (penis and scrotum) and internal genital structures (the bits needed for reproduction inside that aren’t the testicles themselves – mainly specific tubes).

Before sexual differentiation, all foetuses possess two structures where their internal sex organs will be, called the Müllerian and Wolffian structure. Testes produce a substance called ‘Anti-Müllerian Hormone’ (AMH), which causes the Müllerian structure to regress. The testosterone produced by the testes causes the Wolffian structure to develop into male internal structures. Lack of testosterone prevents the Wolffian structure from developing and causes it to regress, and lack of  AMH allows the Müllerian structure to develop into ‘female’ parts.

The ‘triggering amount’ of testosterone needed to cause penis and scrotum development is lower than the amount needed to make Wolffian structures develop – so if a foetus has a condition that results in lower levels of testosterone (and there are quite a few that can), the result will be someone without the corresponding male internal organs to match the external ones.

Whilst there are many, many different genetic conditions that can make fitting clearly into a ‘social sex box’† problematic, there are a couple that illustrate the potential ambiguity in defining sex very well.

The first of these is called CAH, or Congenital Adrenal Hyperplasia. This is a mutation in a gene which causes a particular enzyme the body normally produces, to not work. This enzyme is essential for the production of the substance cortisol, and so people with CAH cannot produce cortisol. The result of this is that the hypothalamus (the region of the brain which monitors certain hormone levels among other things) says:

“There is no cortisol! Release precursors!”

Various human brains (paraphrased)

In normal circumstances such precursors would get made into cortisol – but because the enzyme responsible doesn’t work, the precursors end up getting made into testosterone and other ‘masculising’ hormones – giving XX foetuses male genitalia. Due to not actually having testicles, no AMH gets produced, so female internal structures still form. Sometimes the genitals of such individuals are judged to be ‘ambiguous’, and tests are done at birth that reveal the condition. Some however look like entirely unremarkable boys, and may go completely undetected.

Another interesting condition is Androgen Insensitivity Syndrome, AIS. This is a mutation that occurs on the X chromosome, and happens in a gene that encodes a receptor (protein that senses when a particular thing is present) for testosterone. This means that in XY foetuses, even though testes are produced normally, and testosterone is then produced normally – none of the rest of the body can detect that the testosterone is there…so female genitalia develop. AMH is produced which prevents Müllerian structural development, but the Wolffian structures can’t develop either as the testosterone can’t be detected. AIS babies show no signs of being anything but female, though are XY and have testes. There’s no clearly agreed reason or way to decide whether possession of one trait or another is what indicates a foetus or babie’s ‘true’ sex, if such a truth can actually be said to exist.

AIS can be ‘complete’ or ‘partial’, with the ‘partial’ condition resulting in ambiguous genitalia. To quote from the book ‘Brain Gender’ by Melissa Hines:

The direction of sex assignment of individuals with PAIS depends to some extent on the appearance of the external genitalia; those judged to have a penis too small for success in the male role may be surgically feminized and raised as girls, whereas others are reared as boys and treated with andogens to try to stimulate penile enlargement and development of other male secondary sexual characteristics. In this syndrome and others involving undervirilization in XY individuals, however, additional considerations, such as the desire of the parents for a son versus a daughter can also influence the direction of sex assignment.

It’s fair to say that the result of accident or injury resulting in penile loss wouldn’t result in an individual who would be unable to have ‘success in the male role’, regardless of the fact that they have already been raised and socialised as male. This discussion hasn’t even touched on the importance of how personal understanding and identity of one’s gender can reflect on how one is defined. If an individual ‘feels’ strongly that they are a given sex, how is this necessarily any less biological? Whatsmore, is there even reason why choice of identity (particularly beyond the strongly binary male-female that is enforced by much of society) is ‘less valid’ as a way by which sex can be defined? It’s easy to get into some very tricky philosophical areas related to this, and certainly the arenas of biology and socialisation are virtually impossible to disentangle from each other.

When it comes down to it, none of these factors are how people judge the sex of people they see day-to-day. We look at what clothes people wear, their size, build, and where they have hair. We listen to what they sound like, and what their name might be. Most people rarely question what they’re presented with assuming they can easily put a person into one box or another. The questions asking why people feel the need to do this, and why people react the way they do when they can’t, are further huge areas to consider!

†If you’re into that sort of thing.

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