This book seems both too early and too late. Too early, in that a Darwinian group-selectionist view of human society has only really been systemized or well-explored in the past couple of decades, too late in that most of it seems like second-hand William Graham Sumner, with whom Keller studied. That said, there is some meat here; his discussion of the influence of "ghost-fear" on group behavior is quite good, and his endorsement of a materialist basis for cultural development (although he is careful to distance himself from the rest of Marx's theorizing) is also interesting. But this book is largely speculation.