To understand biological sex, look at the brain, not the body

There they are, in their Chevrolet Colorado, five dudes bouncing up and down as the truck grinds through the rugged American high country. Two guys up front, three in the back. Shania Twain is blasting. The fellow in the middle is singing along. “Oh, I want to be free, yeah, to feel the way I feel. Man, I feel like a woman!”

The other guys look deeply worried. But the person in the back just keeps happily singing away, even as the dude next to him moves his leg away. Just to be on the safe side.

This commercial aired back in 2004, and even now it’s not clear to me if it’s offensive or empowering, hilarious or infuriating. Twain says she wrote “Man! I Feel Like a Woman” after working at a resort where some drag queens were performing. “That song started with the title,” she said. “Then it kind of wrote itself.”

It’s a fun tune, and I admit I kind of loved seeing that commercial. But at its heart is an issue central to our current political moment.

When someone says they feel like a woman, what exactly does that mean?

Across the country, conservatives are insisting that — and legislating as if — “feeling” like a woman, or a man, is irrelevant. What matters most, they say, is the immutable truth of biology.

So what, then, is a biological male, or female? What determines this supposedly simple truth? It’s about chromosomes, right?

Well, not entirely. Because not every person with a Y chromosome is male, and not every person with a double X is female. The world is full of people with other combinations: XXY (or Klinefelter Syndrome), XXX (or Trisomy X), XXXY, and so on. There’s even something called Androgen Insensitivity Syndrome, a condition that keeps the brains of people with a Y from absorbing the information in that chromosome. Most of these people develop as female, and may not even know about their condition until puberty — or even later.

How can this be, if sex is only about a gene?

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