Abstract
In many indigenous societies, people are categorized into several cultural groups, or clans, within which they believe they share ancestors. Clan attributions provide certain rules for marriage and descent. Such rules between clans constitute kinship structures. Anthropologists have revealed several kinship structures. Here, we propose an agent-based model of indigenous societies to reveal the evolution of kinship structures. In the model, several societies compete. Societies themselves comprise multiple families with parameters for cultural traits and mate preferences. These values determine with whom each family cooperates and competes, and they are transmitted to a new generation with mutation. The growth rate of each family is determined by the number of cooperators and competitors. Through this multi-level evolution, family traits and preferences diverge to form clusters that can be regarded as clans. Subsequently, kinship structures emerge, including dual organization and generalized or restricted exchange, as well as patrilineal, matrilineal and double descent systems. These structures emerge depending on the necessity of cooperation and the strength of mating competition. Their dependence is also estimated analytically. Finally, statistical analysis using the Standard Cross-Cultural Sample, a global ethnographic database, empirically verified the theoretical results. Such collaboration between theoretical and empirical approaches will unveil universal features in anthropology.
Highlights
We aimed to reveal the emergence of various kinship structures and descent systems from family interactions depending on environmental conditions
By tracing the marriage and descent relationships of the emergent clans, we demonstrate the evolution of kinship structures and descent systems
Families within a cluster are recognized as cultural kin, and marriage occurs only among families from different clusters
Summary
Kinship relationships, including marriage, descent and cultural relatedness, stipulate the alliance of families and organize social structures. We introduce a simplified model suitable for studying the evolution of both kinship structures and descent systems, together with analytical estimates and empirical tests on a cross-cultural database. We introduced cooperative relationships with cultural kin and mates (blue and orange solid lines in figure 1b) Families cooperate with those who have traits similar to their own, and those who prefer (or are preferred by) them. Ns number of societies in a system dc decline in mortality with cooperation variable dm increase in mortality with competition variable t cultural traits of family evolve p preferences for groom traits evolve assumption is set to demonstrate that society-level structures, which determine the marriage rules of families, can evolve, even when starting from an initially homogeneous state. The notations and parameter values adopted in the simulations are summarized in table 1
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