The Decline of Polygyny: An Interpretation

Polygyny is thought to be more prevalent where male wealth inequality is greater; however, the decline of polygyny in most of the world occurred with the emergence of capital-intensive farming with unprecedented wealth disparities. The distinction between rival wealth—divided among ones offspring—and non-rival wealth—transmitted to all children irrespective of their number (like a public good)—may resolve this “polygyny puzzle.” Our model’s marital matching Nash equilibrium replicates the observed incidence of polygynous marriage among the Kipsigis, an African agropastoralist population. We then simulate a hypothetical transition to monogamy among the Kipsigis following an increase in the importance of rival wealth.