This chapter, presenting the main theoretical statements on social evolution, stems from the hypothesis of a sudden rise of spoken, syntactic language in Northeast Africa, 70,000 years ago. The youth among a small population of Founders formed a cohesive group through the shared efforts of developing agreed-upon syntax and vocabulary, and then formed a community of roughly 150 persons to sustain their language. These were the initial social institutions. These institution led to creation of others, such as for ritual and migration, and enabled processes of social and institutional evolution: innovation (through representation or modeling as a source of variation), inheritance (through social reproduction and regulation), and the assessment of the fitness of institutions for the community. These processes brought into existence the Human System. At the multiple scales of family, community, and cross-community networks, it underwent coevolution among biological, social, cultural, and environmental influences, yielding a “group-level human nature” that relied on emotions at group as well as individual levels.