For more than 100,000 years, H. sapiens lived as foragers, in small family groups with low reproductive variance. A minority of men were able to father children by two or three women; and a majority of men and women were able to breed. But after the origin of farming around 10,000 years ago, reproductive variance increased. In civilizations which began in Mesopotamia, Egypt, India, and China, and then moved on to Greece and Rome, kings collected thousands of women, whose children (...) were supported and guarded by thousands of eunuchs. Just a few hundred years ago, that trend reversed. Obligate sterility ended, and reproductive variance declined. For H. sapiens, as for other organisms, eusociality seems to be an effect of ecological constraints. Civilizations rose up in lake and river valleys, hemmed in by mountains and deserts. Egalitarianism became an option after empty habitats opened up. (shrink)

For more than 100,000 years, H. sapiens lived as foragers, in small family groups with low reproductive variance. A minority of men were able to father children by two or three women; and a majority of men and women were able to breed. But after the origin of farming around 10,000 years ago, reproductive variance increased. In civilizations which began in Mesopotamia, Egypt, India, and China, and then moved on to Greece and Rome, kings collected thousands of women, whose children (...) were supported and guarded by thousands of eunuchs. Just a few hundred years ago, that trend reversed. Obligate sterility ended, and reproductive variance declined. For H. sapiens, as for other organisms, eusociality seems to be an effect of ecological constraints. Civilizations rose up in lake and river valleys, hemmed in by mountains and deserts. Egalitarianism became an option after empty habitats opened up. (shrink)

Why do men and women compete? And what makes them compete more or less? An answer to the first question follows directly from Darwin. If Homo sapiens, like other species, is a product of natural selection, then we should have evolved to compete in order to reproduce. An answer to the second question follows from more recent versions of Darwinism. People, like other organisms, are likely to compete socially - to form dominance hierarchies - to the extent that it is (...) costly for subordinates to flee ecologically. This paper first reviews evidence that winners at political competition have consistently won at reproductive competition. Next, it documents the slow shift toward declining political competition - toward democracy, and toward declining reproductive competition - toward monogamy, in the course of Western history. Last, it offers a model of what might account for that change. (shrink)

Individuals give for two reasons. One is to get a benefit back. The other is to avoid a cost. “Cooperation” theories stress mutual benefits. “Conflict” theories stress costs. Hunters may give up part of their hunt because they get favors back, or because the recipients are stronger than they are and the hunting isn't as good anywhere else.

In Homo sapiens and other species, promiscuity, risk-taking, and aggression are less matters of sex (having XX vs. XY) than gender (giving PI vs. resources and/or genes). Classic role reversals include: sea-horses, polyandrous birds, and a few heiresses in England and Rome. Unlike other females, but like many males, they are assertive, they take chances, and they are not chaste.