Cooperation: this time, between Man and Woman



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As I wrote in a previous blog, the first five weeks of this semester I spent away in Europe. During the first part of the trip I ran five Seshat workshops in Oxford, and then I went to Toulouse. What makes Toulouse and Oxford similar is that they are both homes to some of the earliest European Universities. All old European universities were initially schools of theology (as were the earliest American ones, like Harvard), and Toulouse was no exception. The University of Toulouse was founded in 1229 at the end of the Albigensian Crusades, to serve as a bulwark of orthodox Catholicism against the still largely heretic hinterland.

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Saint Sernin in Toulouse: even older than its university (photo by the author)

But that was not why I was visiting Toulouse. The actual reason was the invitation by Paul Seabright, the director of IAST (Institute for Advanced Study in Toulouse). Paul has been one of the pioneers in the new field of evolutionary economics, even before it became known as such. I have known his work since I read his excellent The Company of Strangers: A Natural History of Economic Life.

He has also written a very kind review of my Historical Dynamics. But we met for the first time last June, when he invited me to participate in a conference he organized in Toulouse. One thing led to another, and I decided to go to Toulouse for a longer visit in September. While I was there, Paul gave me his second popular book, which I read on the plane home. So this blog is about The War of the Sexes, which is, as Paul told me, part of the same trilogy as The Company of Strangers (with the third installment being currently written). The Company of Strangers is about how our day-to-day life depends critically on cooperation among huge numbers of strangers. We don’t think about it, but the reason that we can drive to a supermarket and buy all the food we want (well, can afford) – and that without getting killed along the way – is cooperation among huge numbers of strangers.

The title of the second book, The War of the Sexes, is somewhat misleading because, like the first book, it is also about cooperation. The subtitle, How Conflict and Cooperation Have Shaped Men and Women from Prehistory to the Present, describes it much better, but I suppose it’s war and sex that sell books, so the publisher must have decided to push both buttons in the title.



You might ask, isn’t war and cooperation strange bedfellows? Well, not to me – as readers of this blog know, my pet theory is that it was really war that created cooperation in large-scale human societies. More broadly, conflict and cooperation are intrinsically intertwined. Cooperation can be so hugely effective that it produces a lot of goodies, and dividing up these returns on cooperation between contributors can be a significant source of tension and conflict. Another, and very significant, source of tension is our striving to join the right coalitions (meaning, effective at cooperation), or not being excluded from the ones we wish to join. Just think of the angst associated with the annual sorority rush at American universities.

Much the same sources of tension are found in that elementary cooperative unit, the human family. Finding and keeping the right partner is what Jane Austen’s books, and much of the rest of world literature, are about.



Fair division of responsibilities and rewards between the partners becomes the next major source of tension once you solve the first problem.

So conflict is really the obverse of cooperation, in more ways than one. How did conflict and cooperation between the sexes play out during the evolution of Homo sapiens?

Paul starts at the ground zero of sexual selection, which is well known to evolutionary biologists. In biology, ‘females’ are the sex that produces a few large (read: expensive) gametes and ‘males’ are the sex that produces many small (read: cheap) gametes. Right there, this classification into expensive and cheap gametes sets the potential for an economic analysis.

I should note that using the economist’s tools to throw light on non-economic questions can be done well – or not so well. For example, I am under-impressed by the analysis in the wildly popular book Freakonomics. Paul’s books avoid various pitfalls affecting economist thinking when they venture outside their profession (for example, the automatic assumption of homo economicus whose decisions are guided only by material considerations).

You should read the book to appreciate the full argument, but here it is in an abbreviated form.

The asymmetry in offspring investment between females and males means that each female is quite precious, while most males are superfluous (one male can inseminate many females). The result is that males compete among themselves, while female choose. In most animal species a ‘high quality’ male (as judged so by the females) will mate with many females, while the majority of males will not pass their genes to the next generation. Paradoxically, females are the ones that wield power, because they control a scarce resource (there being an overabundance of sperm to fertilize all the eggs many times over).

In humans, however, the situation is quite different. For better or worse, some millions of years ago we went on the trajectory of growing ever larger brains and acquiring more complex social behaviors. But to build our energetically expensive and nutrient-demanding brains we needed meat.

It was males who specialized on hunting game. The reason is obvious: it’s kinda hard to stalk the antelope through the bushes with a squalling infant on your back. And even older children require constant supervision and defense against predators. It’s simply impracticable for females to specialize in hunting, and once this division of labor arose, evolution further optimized males for hunting ability with larger upper body mass for strength and slimmer build for long-distance running (and, perhaps, better spatial intelligence, one of the few cognitive domains where men are better than women).

Females specialized in gathering, and even though they are probably better (more efficient) at it, and plant foods typically provide more than half of calories in most foraging societies, their inability to hunt resulted in their losing a great degree of power in their dealings with the males. In Chapter 4 Paul provides a very clear explanation of how this logic works – those who control the scarce resource (in this case, meat) are the ones who can drive the best bargain.

Still, things were not that bleak for women during the Pleistocene. All evidence we have suggests that in foraging societies women retain a great degree of power, much more than in agrarian societies, in which stringent control by men (fathers and husbands) was the rule. Richard Wrangham in Catching Fire points out that for men, who spent a lot of time out hunting, it became critical to have a woman caretaker at home, who might not even be a sexual partner.

You come back to the camp after an exhausting day of searching for game, empty-handed (because hunting is a high-gain but high-risk occupation). Having a partner who has got the fire going and roasted some tubers for your dinner is a big deal, even if your partner is a post-reproductive older widow.

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A scene from the Cahokia museum (photograph by the author)

But of course it’s even better if she is your wife in all senses of this word!

So yes, relations between sexes are full of tension and conflict, but for humans it’s really cooperation that defines it. There are a multitude of ways in which a marriage can go sour (as Tolstoy said, each unhappy family is unhappy in its own way), but the majority of humans somehow manage to muddle along, so that there are plenty of happy families around. The twin messages in The War of the Sexes are that we shouldn’t expect this (having a happy family) happen automatically, but we have also been provided by evolution the psychological predispositions to make it so.

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The picture of hunter-gathers here is based on ethnographically known people. I think when considering the evolutionary long run, we need to go beyond the ethnographic model. The ecology of ancient Homo species are not known in any detail, but their stone toolkits were relatively simple. Given that the paleoanthropology record throws big surprises in our laps two or three times a decade, it is a good bet that if we could study lower and middle paleolithic people in the flesh, we’d Likely meet multiple major surprises. For example, there is evidence from damage to skeletons that both male and female Neandertals hunted big game using up close and personal techniques that resulted in bone fractures similar to what rodeo cowboys suffer. Maybe the old, recuperating, and crippled of both sexes looked after the kids while healthy younger adults of both sexes hunted. Or maybe Neandertal males were just major spouse abusers. Or maybe . . . .

Population densities of all Homo species in the Pleistocene seem to have been very low even compared to Holocene H-Gers. I suspect that they were often or generally so low that they experienced the Allee effect. That is, population growth rates increased with population density rather than decreased. Humans were worth more as potential mates, trade partners, sharers of information and the like than they cost in terms of competition. Running across a band of strangers led to parties not fights. The other megafauna predators were perhaps our main competitors; people were friends in a hostile world. Populations did seem to increase fairly steadily after 50 kya as anatomically modern humans spread out of Africa, very late in the history of the genus.

Brain sizes and toolkit complexity complexity increased more or less steadily over the 2 million years of our genus’ history and even last glacial anatomical moderns don’t look exactly like Holocene people or behave like them. For example, Pleistocene folks seem to have been rather more carnivorous than low latitude H-Gers who are over-represented in the ethnographic record. California records a considerable increase in population densities and intensities of plant use over the Holocene. The early people were mobile foragers emphasizing hunting, and later people got heavily into using stone grinding slabs and mortars to mill grass seeds and acorns.

There is a sort of “human nature” trope that I think we need to get past. People will say that we have been hunter gatherers for 2 million years and then trot out the Kalahari San or the Shoshone as an ethnographic model. We are by nature hunter-gathers. Nuts! Whatever Homo erectus was doing (likely rather different things at different times and places) it was not what the San or Shoshoni were doing, perhaps not even close. No doubt some things that they were doing departed from ancestral ape behavior in the direction of ethnographic H-Gers but aside from stone tool manufacture, we can say very little with any certainty. The paleoanthropology record is very, very frustrating regarding most of the Big Questions. Some ancient Homo might have”experimented” with forms of social organization that are quite deviant from a straight-line extrapolation from chimps to ethnographic H-Gers. Who can say? There is no harm in telling stories about what might have been going on in the Pleistocene. The danger comes if you believe them and try to build a scientific argument on such a foundation of quicksand.

Peter Turchin

Pete, we have to work with what evidence we have – and as data accumulate, our interpretations will change. As you of course know, all knowledge in science is tentative and liable to change. Having said this, I want to mention that Paul’s argument is not based just on ethnographic data on modern hunter-gatherers. He also brings other evidence to the table. It’s in the book, and I couldn’t give justice to his argument in a short review.


Fair enough.

Gene Anderson

All very interesting and broadly plausible. A couple of cautionary notes though. Even today, women often hunt and men very often gather. It occurs also that a lot of birds have very rigid sexual division of activity during nesting (some hornbills wall the female up in a hole with the eggs) but don’t evolve cooperation or intelligence, while other birds don’t have much division of labor but are highly intelligent and social–crows and ravens for example.

Peter Turchin

Gene, I am not making the case that division of labor between men and women drove the evolution of intelligence. And neither does Paul – as I remember, in the book he takes it as given, and then traces the consequences. I am with Pete and Rob (Boyd) on this issue – it was Pleistocene climatic chaos that created a niche for a very smart and culture-capable species.

Ross David H

I would be interested to hear what you or Paul Seabright would predict the long-term consequences would be of cases like India where the male:female birth ratio has changed in recent years. It would seem to to alter the relative bargaining positions, although sometimes things don’t turn out in the way one expects. Also on the other hand what happens in cases (e.g. Europe post-WWI) where so many young men have died that the young adult male:female ratio is significantly different than 1:1.


Joe Henrich reviewed a lot of data on this topic with a modest amount of help from Rob Boyd and me.

Henrich, J., Boyd, R., & Richerson, P. J. (2012). The puzzle of monogamous marriage. Philosophical Transactions of the Royal Society B: Biological Sciences, 367(1589), 657-669. doi: 10.1098/rstb.2011.0290


Some just-so input of my own: When speculating that those other than mothers are providing a great deal of child care (e.g., Peter’s “Maybe the old, recuperating, and crippled of both sexes looked after the kids while healthy younger adults of both sexes hunted.”), it’s important to remember that someone among those care-givers needs to be lactating. Although I suspect a good deal of wet nursery was going on, the first 6 months of a baby’s life is not a time when the biological mother can be absent for long – for her own sake and the child’s. Of course, birth intervals might have been long enough for this 6 month period to have constituted a small fraction of the total time a female might have spent hunting.


But that assumes that lactation couldn’t evolve. Perhaps lactating Neandertal moms nursed at long intervals and produced relatively concentrated milk. Then they could hunt all day and nurse when the got home at night and again in the early AM just before they went off for the day.

Peter Turchin

Paul Seabright responds to Ross David H:

As it happens I am on record nine years ago as making a prediction about exactly this:

and I don’t think anything that has happened since has made that prediction seem less likely.
The corrollary of this prediction is that after wars which kill many young men there should be a fall in violent crime – something which was certainly true after WW2 and I think probably true after WW1 (though I’m less sure about the latter).

There would also be consequences for the age difference between husbands and wives and for the frequency of polgynous arrangements (a shortage of males leading to more women being willing to marry older husbands or to have affairs with already married men).


i find it rather wierd that there was the concept of a family mentioned. and that necessarily females are mentioned as the caretakers. yes there is suckling the youngs, for which are females irreplaceable, but it takes about until the age of 18 even for pleistocene conditions. until a human gathered enough calories to sustain him self. so there is a long timespan of provisioning for offspring after the period kids are weaned, where males can take care as well.

further humans are very flexible in their pattern of social organization, even hunter gatherers, so why project the idea of a family (at least when i got the idea that something like a core family, so father, mother, children) onto something where it simply does not apply and try to use it as the basis for modeling? this will just result in a very faulty explanation.

and also mothers didn’t have to leave their kids in camp, when they go gathering tubers or berries, they very often took their offspring with them, that’s at least how it goes with alot of hunter gatherers even nowadays

so in conclusion i think there are some simply wrong stereotypes about male and female roles used as a basis for modeling.

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