While I’ve long been a critic of evolutionary psychology, I’m not stupid or woke enough—unlike some bloggers I won’t name—to dismiss the entire field as worthless. While it’s hard to test whether some behaviors in our species have evolved by natural selection, there are degrees of confidence we can get, and predictions one can make, to judge the likelihood that these behaviors are indeed “darwinian.” While nobody argues that behaviors like preferring your own children over others aren’t products of natural selection, there are those who claim that behavioral differences between men and women are not—and in fact cannot—be based on genes installed in our species by natural selection.
The two sex differences I find most evolutionarily convincing involve human sexual behavior—in particular the observation that males tend to be relatively indiscriminate in choosing someone to mate with, while females are pickier—and the fact that males are more aggressive than females. I feel that these behavioral differences are likely, at least in part, to be the result of sexual selection in our ancestors. I won’t talk about sexual behavior today, as I’ve written about it before, but I do want to highlight an article from last April discussing the evolution of male aggression. It’s by Steve Stewart-Williams, an associate professor of psychology at the University of Nottingham Malaysia Campus, and appeared online in in Nautilus. It’s a short but good summary of why the greater aggressiveness of men than of women almost certainly reflects, at least in part, natural selection in our ancestors. Click on the screenshot to read it, and you should:
I should first emphasize that while Stewart-Williams and I share the view of the evolutionary roots of some male aggression, we both agree that males can also be socialized into being more aggressive by being expected to conform to stereotypes of “masculinity” (remember the car race in Rebel Without a Cause?); and that even if males are more aggressive than females because of natural selection, that doesn’t mean that you can’t make them less aggressive—also by socialization. Any geneticist knows that, for nearly all traits, heredity is not destiny, and the environment can make a big difference.
Nevertheless, the SJW view of differences between men and women’s behavior is that all of those differences are due entirely to socialization, with no moiety due to genetics and evolution. That is an ideological stand that, in view of the substantial morphological differences between men and women, is pretty insupportable. And that view comes from the fear that if we do find evolution-based differences, it will lead to discrimination—usually against women. My own view is that any genetic differences we see cannot support any moral or legal inequality between the sexes, which is a philosophical position that shouldn’t depend on biology. (If it did, equality would change as our knowledge of biology changed.)
So I deplore those who try to pretend that differences either don’t exist, or can’t have an evolutionary basis, simply because it’s inconvenient for their ideology. (They always pretend that their criticism is based on science, but they don’t fool anybody with two neurons to rub together.) That’s why the same people who will admit that men are bigger and stronger than women because of genetics and evolution will also assert that there can be no behavioral or psychological differences due to genetics and evolution.
The caveats duly presented, Stewart-Williams gives several lines of evidence for an evolutionary origin of this behavioral difference. I’ll summarize them briefly; the indented sections are Steve’s writing.
1.) The behavior is consistent across different cultures, when one would expect different degrees and kinds of socialization.
An initial line of evidence is that it’s not only in the West that we find sex differences in aggression. Wherever in the world we look, men are more violent and aggressive than women, especially with other men. The clearest and most persuasive evidence for this comes from homicide statistics: In every country, without fail, men commit the vast majority of homicides (and are more likely to be the victims of homicide as well). If the sex difference in aggression is just an arbitrary product of culture, why does it rear its ugly head in every human group?
Now there are those, says Stewart-Williams, who argue that the difference in aggression is just a non-evolved byproduct of differences in size and strength. If you’re bigger and stronger (presumably for evolutionary reasons), then you can benefit by being more aggressive, and you get pigeonholed into social roles that involve more strength and aggression. But that raises the question of why men are bigger and stronger than women! While you’ll see social-justice warriors trying desperately to explain size and stength differences without invoking sexual selection, a reasonable explanation, based on observations below, including the behavioral differences in sexual behavior as well as parallels from animals like seals and gorillas, is that part of the size/strength differentiation involves men competing for women: to the stronger goes the reproduction.
The avoidance of sexual selection as an explanation is because that implies that there could be behavioral differences between men and women as well (sexual selection involves behavior), and to the Authoritarian Left that idea is to be avoided at all costs.
Here’s how Stewart-Williams rebuts the “byproduct” explanation for differences in aggression:
It’s a clever argument, and one worth taking seriously. On balance, though, I don’t think it flies. To begin with, the Eagly–Wood theory raises some awkward questions. Why wouldn’t natural selection create psychological sex differences as well as physical ones? The mere existence of the physical differences tells us that human males have been subject to stronger selection for aggression and violence than females. Why would this selection pressure shape our muscles, our skeletons, and our overall body size, but draw the line at our brains? And why would natural selection give men the physical equipment needed for violence but not the psychological machinery to operate it? This would make about as much sense as giving us teeth and a digestive system, but not a desire to eat.
That is a strong argument, and one that I haven’t seen rebutted by the haters of evolutionary psychology. Why are our brains the one organ that can’t be differentiated between men and women by selection?
2.) We don’t find, as expected under the socialization theory, larger amounts male aggression in societies that have stricter gender roles and less gender equality.
On top of that, if sex differences in aggression were all down to gender roles, the differences would be larger in cultures with stricter gender roles and greater gender inequality. That’s not what we find, though. On the contrary, it seems to be the other way round. A recent large-scale, multinational study revealed, for instance, that sex differences in adolescent physical aggression are smaller, rather than larger, in less gender-equal nations. Culture clearly matters when it comes to sex differences in aggression—but the effect of culture is apparently very different than the social role theory would lead us to expect.
3.) Males are more aggressive than females from the very beginning of childhood, presumably before they’ve had a chance to be socialized.
. . . the sex difference in aggression appears very early in life—usually before children take their first bite of their first birthday cake. From the moment they can move around under their own their steam, boys engage in more rough-and-tumble play than girls. The same sex difference is found in other juvenile primates, and appears to be related to testosterone exposure in the womb. In humans, the sex difference shows up long before kids understand that they’re boys or girls, so it can’t just be that they’re conforming to social expectations about how boys and girls ought to act. In any case, children are terrible at conforming to social expectations, as any parent who’s tried to persuade their progeny to sit nicely and quietly in a restaurant will readily confirm. And not only does the sex difference in aggression emerge early, it remains static until puberty. Absolute levels of aggression trend downward for both sexes; however, the gap between the sexes barely budges. If socialization creates the sex difference, why doesn’t continued socialization before puberty pry the sexes apart?
And here I should add that testosterone has a positive effect on aggression, whether injected or naturally circulating in people with abnormal levels of the hormone for their sex. That, too, points to an evolutionary explanation.
4.) The pattern of male aggression conforms to what we expect if it evolved to promote competition for females. Stewart-Williams reports that early differences in aggression remain static until puberty, when males suddenly become much more aggressive and much more willing to take risks. This would be expected because male aggression would be most adaptive when the reproductive benefits are greatest—during early reproductive years (in our relatives, of course, who probably began reproducing much earlier than modern humans). As Stewart-Williams argues:
How would the Nurture Only approach explain the violence gap that opens up between the sexes at puberty? Is there a sudden surge in gender socialization—a surge which, for some unknown reason, happens at exactly the same stage of life in every culture and in many sexually dimorphic species? Is it just a coincidence that this alleged surge in socialization comes at the same time as the massive surge in circulating testosterone that accompanies puberty in males?
He adds that after early adulthood, male aggression goes down steadily for the rest of a man’s life, something that the socialization hypothesis doesn’t explain but the evolutionary hypothesis does: why be aggressive when you get little reproductive payoff but risk being killed or injured by other, younger males?
5.) In many species of animals, including our closest relatives, males are more aggressive than females. If you have a “socialization” theory, you’d have to claim that what everyone accepts in other species as evolved differences in behavior just happen to be the nonevolved products of socialization in humans. What a remarkable coincidence!
A final line of evidence that sex differences in aggression have biological underpinnings is that these differences are not unique to human beings. Indeed, in some cases, the parallels across species are striking. Consider humans and chimpanzees. Among humans, males commit around 95 percent of homicides, and are around 79 percent of homicide victims. Among chimps, on the other hand, males commit around 92 percent of “chimpicides,” and are around 73 percent of chimpicide victims. In short, the sex difference in lethal aggression in the two species is remarkably similar in size.
That’s all I’ll say for now, except to add one more argument that is mine: the aggression difference also goes along with the sexual “choosiness” difference that has been repeatedly observed in psychological studies. Both bespeak a form of sexual selection in which males compete for females and females are choosy about who they select as mates.
I’ll also warn readers that many people who argue against any evolved behavioral difference between men and women are people who likely have an ideological agenda. And they often pretend that they don’t.
At the end, Steve tells us that it’s important to understand the roots of male aggression because it helps us reduce male violence that is harmful in today’s world (my emphasis):
None of this implies, by the way, that we’re necessarily stuck with male aggression, or stuck with aggression in general. As the psychologist Steven Pinker demonstrated in The Better Angels of Our Nature, levels of violence and warfare have fallen steadily over the decades, centuries, and millennia, despite the fact that aggression is part of human nature. In various ways, from policing and government to trade and moral norms, we’ve managed to pull ourselves, to a significant extent, out of the vortex of violence and bloodshed that characterized our species for the bulk of its tenure on Earth.
If we want to continue on this trajectory, however, or ideally to hasten our progress, our best bet is presumably not to delude ourselves about the true causes of our behavior. As policy wonks like to say: Wrong diagnosis; wrong cure. Let’s get the diagnosis right so that we can maximize our chances of curing the scourge of human violence.
I agree with the malleability bit in the first paragraph, but am not so much on board with the idea that we need to understand what causes our behavior because it will help us alter our behavior. After all, whether male aggression be due to socialization, evolution, or a combination of both factors, the treatment is the same: socialize men to be less aggressive! The reason I want to know what causes our behaviors is pure curiosity.