Charlotte Pence

SEX DETERMINATION AND DARWIN

Tuesday’s class was a sex-education lecture that none of us had quite had before. Dr. Fritz opened it up by giving us a little reminder about what Darwin has contributed to our understanding of gender and sexuality. The simplest way to put it is this: Darwin cracked open the little nut of belief called essentialism, which is the idea that everything and everyone does not change, that there are a set of attributes essential to one’s identity and function. This comes partly from Plato, if we go way back in time. Plato proposed the idea of infinite time with a perfect universe in perfect harmony (whatever that might mean). And we see the Christian church later embracing this idea with two perfect people, ol’ Adam and his Eve, in a perfect sun-always-shining Eden. In this construct, organisms changing into other organisms (i.e. dinosaurs evolving into the yellow-bellied sapsucker outside my office window) are not a possibility. If you think about it a certain way, change is the opposite of perfection.

So, how does this relate to gender determination? For humans, and most mammals, one gene—the “y” chromosome—has to be turned on to go down the path to becoming male. When that gene turns on, it turns on a series of other genes. But until five or six weeks of age, a human embroyo has the materials to become either sex. The picture below gives a sense of what one’s anatomy looks like at this stage–and then how it develops. One can see how the same parts morph into something else later on in life.

But there are many different stages and different cells that have to be turned on all along the way. And there are various stages of sex, too. There’s genetic sex, gonadal sex, phenotopic sex, meaning that at each of theses stages, another type of development generally occurs. But not necessarily. As Dr. Fritz keeps reminding us, with slide after slide, there are examples of everything in the natural world. Women with penises, people born with both vaginas and penises, women with full beards, etc. Aside from physiological differences, there are all sorts of combinations of sexual preferences, too: men who feel like women but who prefer men; women who are attracted to men most of the time, but not all the time; men who primarily like women; and men and women who have no or very low sexual desire toward anything or anybody, etc.

His point was this: we as humans like categories. We have created the category of categories. But in biology, it’s all about recognizing how things generally work and accepting the shades of grey. Darwin helped us start to see that variation is not only natural, but a fact of life.

I’ve included here a chart, a very un-sexy chart, that shows various stages of development, just to give you a sense of the complexity of this thing often reduced to blue and pink ribbons.