Sex can be much more complicated than it at first seems. According to the simple scenario, the presence or absence of a Y chromosome is what counts: with it, you are male, and without it, you are female. But doctors have long known that some people straddle the boundary – their sex chromosomes say one thing, but their gonads (ovaries or testes) or sexual anatomy say another. Parents of children with these kinds of conditions – known as intersex conditions, or differences or disorders of sex development (DSDs) – often face difficult decisions about whether to bring up their child as a boy or a girl. Some researchers now say that as many as 1 person in 100 has some form of DSD.
Claire Ainsworth, Sex redefined, nature, 18 February 2015.
Today the SRY gene is understood as one among the many essential mammalian sex-determining factors that are involved in the genetic pathways of both testicular and ovarian determination. Mammals require cascades of gene product in proper dosages and at precise times to produce functioning male and female gonads, and researchers recognize a variety of healthy sexual phenotypes and sex determination pathways in humans.
Sarah Richardson, Sex Itself, University of Chicago Press.
In fact, the sex you develop as isn’t directly genetically determined at all, but instead depends on the action of gonadal hormones during the critical period when your prenatal development is taking place. All the X and Y chromosomes do is determine whether you develop testicles or ovaries, it’s the hormones produced by those organs that actually determine whether you develop as male or female.
Unfortunately, most doctors and pharmaceutical industry decision makers also subscribe to the myth that sex is genetically determined, which is why they’ve not appreciated the dangers of giving hormones to pregnant women, and why we’ve ended up in a situation we’re in today (where large numbers of people have been born who’ve undergone partial or complete opposite-sexed brain development, as a result of being exposed to hormone-disrupting drugs such as DES – find out more about DES studies on gender identity).
Hugh Easton, DES Son.
The influence of the XX/XY model of chromosomal sex has been profound over the last century, but it’s founded on faulty premises and responsible for encouraging reductive, essentialist thinking. While the scientific world has moved on, its popular appeal remains.