This study examines the relationship between sexual dimorphism and degree of polygyny. Authors test this relationship in both humans and non-human species. In non-human species, every correlation between sexual dimorphism (measured by body length) and degree of polygyny was significant. In human populations, sexual dimporhism was not related to degree of polygyny, however, there were some differences between populations with socially imposed monogomy and those with ecologically imposed monogamy.