Brains are a good place to begin because one thing that science has learned about them is that they’re in fact shaped by experience, cultural and otherwise. The part of the brain that deals with navigation is enlarged in London taxi drivers, as is the region dealing with the movement of the fingers of the left hand in right-handed violinists.

“You can’t pick up a brain and say ‘that’s a girl’s brain’ or ‘that’s a boy’s brain,’ ” Gina Rippon, a neuroscientist at Britain’s Aston University, told The Telegraph last year. The differences between male and female brains are caused by the “drip, drip, drip” of the gendered environment, she said.

THE drip, drip, drip of Ms. Jenner’s experience included a hefty dose of male privilege few women could possibly imagine. While young “Bruiser,” as Bruce Jenner was called as a child, was being cheered on toward a university athletic scholarship, few female athletes could dare hope for such largess since universities offered little funding for women’s sports. When Mr. Jenner looked for a job to support himself during his training for the 1976 Olympics, he didn’t have to turn to the meager “Help Wanted – Female” ads in the newspapers, and he could get by on the $9,000 he earned annually, unlike young women whose median pay was little more than half that of men. Tall and strong, he never had to figure out how to walk streets safely at night.

Those are realities that shape women’s brains.

By defining womanhood the way he did to Ms. Sawyer, Mr. Jenner and the many advocates for transgender rights who take a similar tack ignore those realities. In the process, they undermine almost a century of hard-fought arguments that the very definition of female is a social construct that has subordinated us. And they undercut our efforts to change the circumstances we grew up with.

The “I was born in the wrong body” rhetoric favored by other trans people doesn’t work any better and is just as offensive, reducing us to our collective breasts and vaginas. Imagine the reaction if a young white man suddenly declared that he was trapped in the wrong body and, after using chemicals to change his skin pigmentation and crocheting his hair into twists, expected to be embraced by the black community.

Many women I know, of all ages and races, speak privately about how insulting we find the language trans activists use to explain themselves. After Mr. Jenner talked about his brain, one friend called it an outrage and asked in exasperation, “Is he saying that he’s bad at math, weeps during bad movies and is hard-wired for empathy?” After the release of the Vanity Fair photos of Ms. Jenner, Susan Ager, a Michigan journalist, wrote on her Facebook page, “I fully support Caitlyn Jenner, but I wish she hadn’t chosen to come out as a sex babe.”