As we mark Charles Darwin’s birthday on February 12th, our culture is riding a wave that should take us back to his theory. The #MeToo and #TimesUp movements are the crest of the wave, which may represent a turning point against men’s chronic exploitation of women. It’s one aspect of the decline of male supremacy predicted and fought for by Elizabeth Cady Stanton, the pioneering women’s rights activist born just a few years after Darwin.

Stanton, like Darwin, was a realist when it came to gender differences. She thought that some were intrinsic and fundamental, but that these were to women’s advantage. Indeed, in a powerful 1869 speech, she held that the strongest argument for women’s equality was “the difference between man and woman.”

This founding feminist leader did not seriously entertain the view that behavioral differences between the sexes are purely cultural and easily changed. Her speech contains a litany of male abuses of power that are neither deniable nor exceptional, and she persuasively argues that women should be given a chance to do better. They are slowly but surely being given that chance.

A decade before her speech, in The Origin of Species, Darwin had written “a few words about what I call Sexual Selection,” which have proved true throughout the animal and human worlds. But they are true in different ways for different species.

Take the cassowary, a large flightless Australian bird. One sex is about as tall as a man, very aggressive—they have killed people—and has distinctive adornments around the head. The other is smaller, less adorned, and much less violent. The larger ones are females, who fight each other to gain harems of males. The males brood the eggs and nurture the chicks for nine months while the female goes off to her next conquest.

Darwin’s theory says that many sex difference arise because one sex competes for the other, and over many generations becomes larger, more aggressive, adorned with flashy features or built-in weapons, and sexually exploitative.

In our own species, men are somewhat larger, more muscular, adorned with facial and body hair, more aggressive and  often sexually abusive. Growing evidence on brain differences suggests that men have more trouble inhibiting aggression and separating it from sex. These traits come from a deep evolutionary history in which our two (main) genders have tended to have roles very different from those of cassowary males and females.

Of course, women can be muscular, aggressive, or exploitative. The gender difference is statistical. But it’s a very large one, grounded in biology—although, surely, exacerbated by some cultures. At this writing, for instance, the White House is in turmoil over a high-ranking advisor to the President who is a known wife beater—in two different marriages. He was finally forced to resign, but the administration’s culture protected him for more than a year. This unfortunately has been true of male-dominated hierarchies throughout history.

This does not mean we have to knuckle under to our evolutionary past; we can’t derive ought from is. But it does mean  that working against and around it may be harder than we thought. The good news is that the extremes of male supremacy, violence, and sexual exploitation we see in recorded history—see Homer and the Bible, for instance—were greater than those seen in hunting-gathering societies, which represent our deeper prehistoric adaptation.

Later, large-scale despotic regimes encouraged powerful men to amass wives and concubines and soldiers to view women as spoils of war. Rape was a standard weapon. In Central Asia and Ireland genetic traces of those depredations exist today.

While men have always tended in these directions, the small face-to-face groups among hunter-gatherers made women less easy to exploit, control, or shunt aside. They were always there, supporting each other, offering opinions around the fire, and keeping a lid on male abuse. In these respects hunter-gatherers were more like our close ape relatives, the bonobos, and less like our other close relatives, the chimpanzees.

Rates of men’s violence (including rape) have been in decline for generations, although they are still far too high. Our current leap forward  in consciousness about sexual harassment is part of that very healthy trend toward restraint. But it is hard to imagine it happening if it weren’t preceded by a steady increase in women’s power.

Darwin was not a Social Darwinist; he did not invent the phrase and he explicitly rejected the callous policies associated with it. He firmly separated moral choice from evolutionary history. While he was a man of his time on women’s issues, not a feminist, he encouraged women scientists and considered men generally more selfish. He would have recognized the fundamental differences Stanton and other feminists were describing, and would surely be impressed with women’s gains a century and a half later.

But he would not be surprised to see us still struggling against our evolutionary legacy. As women take their rightful place in positions of power, and as their coalitions grow smarter and stronger, we can look forward to a less violent  and less sexually abusive world—not despite sex differences, and certainly not because they don’t exist, but because women are less motivated than men to commit abuse. Stanton would surely be pleased.