Starting from the observed fact that humans construct themselves using information carried in two separate channels, one cultural and consisting largely of symbols, the other genetic and consisting largely of DNA, this book explores the consequences for human socio-cultural systems of the relationship between the two components of this dual inheritance model and of the key differences between them. Using a wide array of ethnographic cases, the book shows that while socio-cultural systems vary greatly, any one of them when analyzed will reveal the effects of the necessary tension between the two modes of information transmission across generations. The analysis of the ethnographic material shows that a dual inheritance model does a better job of accounting for distinctive characteristics of human societies than does an account based on either ordinary evolutionary theory or social-cultural construction theory alone. The key distinctions between the modes of transmission of the two types of information are that genetic information cannot produce exact replicas of itself, can only create a small number of close relatives, operates on an agenda based on the logic of inclusive fitness, and must be accomplished by copulation; while cultural information can inform large numbers of replicas of itself that can approximate to identity, operates on an agenda based on the establishment of wide-ranging groups united by symbolic kinship, and is transmitted in a public arena in which copulation is excluded or restricted. These differences generate many observed distinctive forms of human society.