Not so selfish (via Samuel Bowles)

A prescription for how human cooperation evolved will provoke much-needed debate about the origins of society, finds Peter Richerson.
Humans are capable of remarkable feats of cooperation. Warfare is an extreme example: when under attack, hundreds or even millions of people might join forces to provide a mutual defence. In A Cooperative Species, economists Samuel Bowles and Herbert Gintis update their ideas on the evolutionary origins of altruism. Containing new data and analysis, their book is a sustained and detailed argument for how genes and culture have together shaped our ability to cooperate.
Modern hunting and gathering societies offer clues as to how human cooperation evolved. They are typically organized into tribes of a few hundred to a few thousand people. Each tribe is composed of smaller bands of around 75 individuals united by bonds of kinship and friendship. Formalized leadership is often weak, but cooperation is buttressed by social norms and institutions, such as marriage, kinship and property rights. The tribal scale of social organization probably evolved by the late Pleistocene (126,000–11,700 years ago), or perhaps much earlier.

If you have 5 minutes, you can check everything here: http://tuvalu.santafe.edu/~bowles/