Historical migration patterns and the evolution of culture

• New cultures emerge when groups of diverse people intermingle over history. • The ancestral diversity of the world’s countries and regions varies on a continuum. • Regions high in ancestral diversity are societies in which people have to interact with others who do not initially share a common language or social norms. • Members of ancestrally diverse societies tend to be open to experience, relatively more sanguine toward outgroups, and able to become “social brokers” in new environments. • New cultures of emotion emerge in ancestrally diverse societies over generations. • Cultural adaptations include accepted non-verbal emotional expressiveness, easily interpreted non-verbal expressions of emotion, a frequent use of smiles, and the development of a physiology to support these challenging interactions. • Language in ancestrally diverse societies becomes increasingly simple to facilitate high numbers of new adult language learners. . Cultures change, but new cultural systems and practices also emerge over history. The socio-ecological factors that exert pressure on human values and practices to evolve in dynamic ways are numerous. We examine the evolution of culture due to conditions created by long-history migration. The populations of today’s countries and other geographic regions have descended from an uneven influx of people from different cultural and linguistic traditions. We suggest that the challenges of social living in contexts of historic intergroup mingling over long timescales, which include social unpredictability, linguistic variability, and a collision of conflicting social norms, constitute contexts that encourage new cultural adaptations. We show that societies of high ancestral diversity are marked by social unpredictability in that they involve greater relational mobility and normative looseness than societies of low ancestral diversity. In these contexts, outgroup attitudes are somewhat more sanguine, and perhaps consequently, people are more open to new experiences and relationships. To manage this social complexity, we show that cultures of emotion that emerge in ancestrally diverse societies involve 1) emotional expressiveness and 2) expressive accuracy, 3) the frequent use of smiles potentially to communicate preferences and establish trust, and 4) regular exercise of the balance between sympathetic and parasympathetic nervous systems to support a high level of non-verbal communication and informational exchange. We also present evidence to motivate the hypothesis that languages evolve in predictable ways in ancestrally diverse societies. Specifically, features of language that facilitate language acquisition by adult learners, such as compressibility, should become more common in ancestrally diverse contexts. We end by raising questions about the time course for the of cultural evolution of emotion practices and the effects of power dynamics between interacting groups on the content of new cultural practices. .