Men who have lots of babies with lots of different women seem to be having a moment right now. Between Elon Musk’s outspoken pronatalism and Andrew Tate’s penchant for sexual aggression, it’s easy to see how somebody might think that we may be about to enter a new social phase: the death of monogamy. And indeed, it’s trivially easy to find discussions of emergent polygyny in the more manospheric corners of Reddit and in incel Discord servers, which describe “Chads” with numerous sexual partners as just one manifestation of this dynamic.

This all raises an interesting question for a demographer like me: is polygyny the future? Will we see, as we did during the expansion of steppe ancestries in the Bronze Age, a dramatic increase in the inequality of male reproductive success, with a few men having dozens of children by many women, while twenty, thirty, or perhaps even fifty percent of men have no descendants at all?

Humans have pretty much always been monogamous. We’ve been coupling up since before we were even humans. We know this from numerous different sources. Across mammalian species, the ratio of male-to-female body mass is a strong predictor of the intensity of male competition for mates, which in turn is a strong predictor of whether males tend to be monogamous or polygynous. Humans have male-to-female body mass ratios most like those of other monogamous primates. Likewise, animal species in which single alpha males maintain harems of females tend to have prominent built-in weaponry: horns, antlers, claws, extra bone plates on the skull, extremely sharp teeth. Humans have none of that. Instead of claws, we have fingernails that break easily, and hunter-gatherer communities rarely even show ethnographic evidence of boxing traditions: humans appear to be physically adapted not to fight to the death over mates. There is more such biophysical evidence: human testosterone levels, penis sizes, sex ratios at birth, and displays of aggression all support the idea that humans have been more-or-less monogamous for as far back in our genetic record as one can go, probably even before the advent of Homo sapiens.