An interesting and provocative argument that culture has influenced human evolution since one million years. The authors propose that the variable climate of the Pleistocene provided the conditions for favoring culture in pre-humans, since it allowed our ancestors to adapt more quickly than genetic evolution would have allowed. However one views that argument, I think that their (partly) independent argument about the importance of culture in human history is solid. The fundamental observation is that cultural evolution affected human genetic evolution in the long term, and the development of different forms of society in the short term. The authors also propose that modern global society is a "giant field experiment in which the social instincts adapted to smaller-scale societies are subjected to a wide range of new environmental conditions." They make an interesting observation that "social innovations that make large-scale society possible, but at the same time effectively simulate life in a tribal-scale society, will tend to spread." This was written before Facebook became a global phenomenon.