“Second, if the idea of friendship as a cooperation device seems strange, that may be because of the unusually good times in which we live. In the feast-and-famine world of our hunter-gatherer ancestors, having friends who were willing to have you over for dinner wasn’t just a nicety but a matter of life and death. The world of our ancestors was also a lot more violent. In our world, few friends can say that they’ve saved one another’s lives, but that might not have been true in the past.”
