evolutionary biologists mostly assume that polygyny increases sexual
dimorphism in size because, under polygyny, larger males monopolize
mating opportunities and pass on their ‘large male’ genes to their
sons. available data on parent–child correlations in height among
humans (homo sapiens) do not support the crucial
assumption that height is transmitted along sex lines. this paper
instead suggests that human sexual dimorphism in size emerged, not
because men got taller, but because women got shorter by undergoing
early menarche in response to polygyny. it further speculates that,
rather than genetically transmitted, the sexual dimorphism may
emerge anew in each generation in response to the degree of polygyny
in society. the analysis of comparative data supports the prediction
that polygyny reduces women’s height, but has no effect on men’s,
and is consistent with the speculation that the origin of human
sexual dimorphism in size may be cultural, not genetic.