Johnson and Earle trace the evolution of human societies from family-level groups (foragers, horticulturalists; relatively peaceful and egalitarian), through local groups (farmers, pastoralists, some hunting groups like Eskimos or Northwest fishermen; where war is endemic and social life revolves around clan and tribe), and finally to regional polities (simple and complex chiefdoms, agrarian states; where aristocracies develop). The book is a bit dry and academically oriented. The authors provide 19 case studies which provide concrete support to their analysis. Each case study is broken up into a part on Economy & Environment and another part on Social Organization. The focus is quite materialist (and less focused on ideology or non-material culture). Social evolution is driven by population growth, technology, the intensification of production, the fight over access to better resources, the need to reduce risk, or the desire to benefit from trade and alliances with other groups. This is a vitally important topic in anthropology and history. However, one possible major drawback to their approach is the claim that "family-level organization is an elemental form of human society" (p.41). They briefly acknowledge that there is little direct archaeological evidence of the first human societies and that we cannot find the past in primitive societies that survived into modern times (though this assumption is the entire basis for using the case studies), leaving them to rely on certain universalistic assumptions about humans (p.45). Universal assumptions are fine when considering human biology, but they really should have delved more deeply into how the institution of the family might have evolved over time (like Lewis Morgan, Elman Service, or Eleanor Leacock do) rather than pretty much assuming the universality of the nuclear family. Of course, acknowledging this would significantly (but unavoidably) complicate at least Part I of the book. It would probably be more enlightening (as well as easier) to read those authors who do not take the nuclear family as elemental, even if this requires more speculation, especially since some uncertainty here is unavoidable.