Joseph Henrich

Just the simple physical link.

Well, one of the key elements of human history that is really emerging now is that a lot of the interesting aspects of our physiology, anatomy, and biology were actually driven by selection pressures created by cultural evolution.

So one of the best studied cases of gene culture coevolution is the spread of fire, making of fire and cooking.

And so if you look at our anatomy and physiology, our digestive tract, and you compare it to other species, our fellow apes and stuff, we seem to have stomachs that are too small, colons that are too small.

We have these tiny teeth.

But these actually make sense once you realize that we've long been a primate that cooks its food.

Because cooking acts as a kind of pre-digestion, food processing more generally.

And then this allowed natural selection to reduce the size of our stomachs, shrink our colons, give us these small teeth, because we do the digestion in this cultural way by taking advantage of fire and cooking.

But of course, we don't innately know how to make fire or cook.

So this is something that is completely culturally transmitted, but then has dramatically shaped our physiology and anatomy.

Yeah, so this is one of these things where the assumption that everybody was monogamous, people began to make generalizations.

And one of the things that they generalized is that testosterone declines over men's lives.

But then anthropologists began to study other societies and looking and comparing what happens to men's testosterone in polygynous versus monogamous societies.

So the standard result from monogamous societies is that men's testosterone declines after they marry, and then it declines again after they have their first child.

And this makes good sense in comparisons with other species because declines in testosterone are associated with fatherhood in other species.

You're beginning to engage in the nest, you've stopped your pursuit of mates, and you're not engaging in much competition with other males at this point because you're moving into a fatherhood phase.

But in polygynous societies, we don't see the decline, which fits the theory really well.

But it just shows how institutions, whether you're going to have polygamy or monogamy, affects the endocrinology of human bodies.

And so you need to think of cultural endocrinology.

So the institutions affect the hormonal life cycle patterns.