Peter Richerson reviews Samuel Bowles and Herbert Gintis's A Cooperative Species: Human Reciprocity and its Evolution, in Nature:
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.
Human societies are diverse and competitive, often violently so. Charles Darwin conjectured in The Descent of Man (John Murray, 1871) that the main evolutionary motor behind human cooperation was intertribal competition, and suggested that cooperation evolved in two stages. In ‘primeval’ times, well before the dawn of recorded history, our ancestors came under selection for cooperative instincts, such as sympathy and group loyalty. In more recent ‘civilized’ times, laws and customs have fostered cooperation on ever larger scales. Darwin contended that the primeval social emotions, more than natural selection, drove the evolution of civilization.
Michael Price takes more critical look in Evolutionary Psychology.