The gender disparity in the police force, argues Feminist Majority executive director Katherine Spillar, comes from the way policing is marketed. Would-be cops are recruited with promises of car chases and helicopter rescues, which fit traditional masculine values, while most of police work is nonviolent beat-walking and working with communities, with appeal to traditionally feminine values. Additionally, testing still has a physical strength component, while it should focus more on the ability to de-escalate potentially violent situations, which appears to be the direction of progress in policing. But there’s something even more basic at work here as well: Research on how elite companies like law firms and consultancies hire has found that if there isn’t a rigorous, standardized protocol for evaluating potential candidates, hiring managers just use themselves as the proxy of worthiness for a position, so people end up hiring people who are just like them, and thereby organizations replicate themselves.

Which makes the gender differences in predispositions to aggression and violence goddamn frightening. Back in the 1970s, psychologists were concluding that there weren’t many differences in psychology traits between men and women, except for aggression. A 2004 meta-analysis on sex differences in aggression found that men are more aggressive than women at every age, particularly so in their 20s, and this held in every country the analysis looked at, from the U.S. to the U.K. to Canada to Spain to New Zealand to Japan to Finland to Australia to the Netherlands. Indeed, as psychologists Hal Arkowitz and Scott O. Lilienfeld reported in Scientific American in 2010, men are more likely to be “aggressive in their mental lives,” fantasizing about revenge and homicide and dreaming more frequently of violent acts. A 2007 study of babies found that at 17 months, 5 percent of baby boys will bite you, kick you, or do other physically aggressive acts, compared with 1 percent of girls. And those differences hold at 29 months, which makes you think that the male disposition to violence is not wholly a matter of socialization to traditional gender roles, or, more bluntly, acculturation to toxic masculinity. Even more astounding, there’s evidence that humans aren’t the only one with gender disparities in aggression: “Males are the more belligerent sex in virtually all mammalian species that biologists have studied,” write Arkowitz and Lilienfeld. “Even the one marked exception to this trend — the spotted (“laughing”) hyena — may prove the rule. The female hyena, which is more physically aggressive than her male counterpart, has higher testosterone levels than the male does.”