At The Conversation, La Trobe University genetics prof Jenny Graves tells us,

When scientists compared the transcriptomes in postmortem tissue samples from hundreds of men and women in 2017, they found surprisingly different patterns of gene activity. A third of our 20,000 genes were expressed more in one sex than the other in one or several tissues.

The strongest sex differences were in the testes and other reproductive tissues, but, surprisingly, most other tissues also showed sex biases. For instance, a subsequent paper showed very different RNA profiles in muscle samples from men and women, which correspond to sex differences in muscle physiology.

A study of brain transcriptomes published earlier this year revealed 610 genes more active in male brains, and 316 more active in female brains.

“Hundreds of genes act differently in the brains of men and women,” November 5, 2025

And it’s baked in:

Another 2025 study examined 266 post mortem fetal brains and found more than 1,800 genes were more active in males and 1,300 in females. These sets of sex-biased genes overlapped with those seen in adult brains. “Act differently”

At this point, we can predict that at least some readers will divide into two contrasting groups: “It’s not possible!” vs. “I always suspected that… ”

The same patterns are noted across many animal species but Dr. Graves acknowledges that “we don’t know to what extent, or which functions” they govern. So we can’t be sure what they govern.

We can be reasonably certain, however, that this is yet another blow to the current effort to claim that humans are not sex binary.

Note: Does “post-mortem fetal brains” mean — to be honest — post-abortion fetal brains? If so, civilization has a long way to go.