Attempts have been made to deduce the social life of early hominids by means of the comparative study of non-human primates. But since social systems are strongly influenced by ecological conditions, it seemed that it might be more productive to compare hominids with animals which are ecologically but not necessarily phylogenetically similar, such as the social carnivores. The group dynamics, dominance hierarchies, land tenure systems, co-operative hunting techniques, and the like of the wolf, wild dog, hyena, and lion were compared with those of contemporary hunter-gatherers and, by inference, those of early hominids. It was concluded that the selective forces shaping human society were in many respects different from those that influenced non-human primates, especially with respect to co-operative hunting, food-sharing, and the division of labor. Field experiments were made in Tanzania to ascertain the relative importance of scavenging and hunting in the subsistence of hominids.