Gender politics and science have never gotten along very well. The patriarchal system was—and in some cultures still is—based on the premise that women are more mercurial, less deliberative and physically less sturdy than men. Those are perfectly easy beliefs to hold—at least until you subject them to the least bit of intellectual scrutiny or real-world testing, at which point they fall apart completely.

In the 1970s, the script flipped, with the fashionable thinking being that gender differences are artificial constructs. Give little girls footballs or model rockets and little boys baby dolls or princess toys and they’d play perfectly happily with them as long as someone didn’t tell them otherwise.

But this too was mostly rubbish, as any parent who has raised both a boy and a girl can tell you—and as scientists confirm. The more closely they study brain structure, prenatal hormone exposure and more, the more they confirm that boys and girls are born fundamentally, behaviorally different.

The question gets a little murkier when it comes to one of the great dividing lines between the sexes: sports. On the one hand, both interest and participation in organized sports is still a predominantly male thing. On the other hand, when any culture makes the effort to level the playing field of opportunity, female participation rises dramatically. In 1972, before the enactment of Title IX, the landmark law that ensured gender equality in educational opportunities, only 7% of high school athletes were girls. Today it’s 42%.

Still, according to a thoughtful new study published in the journal Evolutionary Behavioral Sciences, the hard hand of evolution plays at least as much of a role in sports interest and participation as policy does—and quite possibly a greater one. And that, like it or not, tips the balance in favor of males.

The research, led by psychologist Robert Deaner of Grand Valley State University in Michigan, was more of a deep analysis of decades worth of other research, which is often the best way to get a high-altitude view of any social science. Deaner and his colleagues began by looking at the basic numbers.

One 2014 survey of 37 countries, for example, found that in every one, men were likelier to play some kind of sport than women. In a few countries, the difference was not statistically significant, but when the question was narrowed to specify competitive sports like basketball and exclude non-competitive ones like running, the men blew the doors off the numbers, besting women by nearly four-fold. A 2013 study conducted by Deaner and a colleague not involved in the current work found that males were twice as likely as females to be involved or interested in sports across 50 different countries or cultures.

The non-evolutionary explanations for the imbalance are familiar and numerous. Homemakers, goes one argument, who are still predominantly female, have less free time for sports than men do. In fact, however, research shows that both genders have about the same amount of free hours, but if the women are going to devote some of them to physical activity it’s likelier to be fitness training like yoga or Pilates or gym workouts. There is also the argument that even in a Title IX world, there still fewer well-organized sports leagues for girls than there are for boys. That may be true, but if the innate interest in sports were really the same across genders, the great leveler of sports in childhood—pick-up games that kids organize themselves—would be played more or less equally by all kids. But here the boys hold a ten-to-one edge.

As for the overwhelming gender disparity in sports spectatorship, the familiar non-evolutionary explanation is that there simply aren’t enough professional teams and leagues featuring female players to attract female spectators. But experience—if admittedly limited—doesn’t show that. The quality of play is first-rate in the 20-year-old Women’s National Basketball Association, but the league remains very much a ward of the much larger men’s NBA, with far smaller audiences and far less public interest as a whole.

Women’s professional soccer is taking off around the world, but it’s men who make up most of the viewership, not women. In Germany, the male share of the audience for women’s soccer is actually greater than it is for men’s, 64% to 58%.

So if it’s evolution that’s behind the gender divide—and Deaner and his colleagues take pains to say it’s not only evolution—what exactly are the survival advantages of playing a sport? And what in the world could be the advantage of simply sitting around and watching other people play.

Much of the answer is based on the phenomenon known as the spectator lek. Principally found in birds, but also in some species of insect and mammal, a lek involves males gathering in a single place and displaying their plumage, size or overall fitness, sometimes by engaging in mock—or not-so-mock—combat, while other members of the species observe. For females, the value of watching the displays is straightforward, since it helps them select the mates who have the fittest genes and can best compete for resources. For male spectators, it has equal, if different, value, allowing “nonparticipating males [to] monitor the performances so they can evaluate potential competitors and allies,” the researchers write.

The precise nature of athletic activities is important too, since so many of them—running, tackling, throwing projectiles, advancing across terrain (or even around a diamond)—are useful in warfare. This all serves to refine skills, reinforce alliances and intimidate potential rivals.

Social status matters too, and sports reliably confers it, enhancing both power and mating options for the participant. That’s a dividend exploited far more by male athletes than female. It is the rare women’s sports star who travels with a posse, spends extravagantly on the plumage that is bling or beds a partner in every city in which she plays. It’s too much to say it’s the rare male sports star who doesn’t do those things, but it’s certainly more common among the lads.

The function of sports as a kind of mortal combat for men is evident even in the way they approach a less directly competitive sport like marathon running, in which all but a tiny handful of participants are not actually contending to win. Overall, three times more males finish the race within 125% of the record time for their gender than females do for theirs, which suggests that the men were more focused on running to win than the women were. That’s a strategy that often backfires, since men were also three times likelier to slow significantly throughout the race, suggesting that their competitive impulses got out ahead of their abilities, whereas women tend to maintain a smarter, steadier pace.

None of this means that socialization, gender bias and all of the other cultural variables are not at work in the largely male world of sport. “An evolutionary approach is fully compatible with socialization playing a large role,” the researchers write, and so it is. Play has always been a big part of the life of all humans, and sports can be a big part of play. But that doesn’t mean the genders don’t still do it in many different ways—and for many different reasons.

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Write to Jeffrey Kluger at jeffrey.kluger@time.com.