Coren Apicella, a research fellow in the Christakis lab at Harvard Medical School, spent the summer of 2010 traveling around the remote Lake Eyasi region of Tanzania with the Hadza, one of the last remaining populations of hunter-gatherers on the planet. Their lives offer a window into our past—and clues about the evolution of cooperation. Within the Hadza community, cooperators cluster together, preventing self-interested individuals from destroying the social fabric. What’s more, the architecture of the Hadza social network matches that of modern social networks. These findings were published January 26, 2012, in Nature.