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Does female promiscuity level out the male-female height difference?

But a University of Arkansas researcher claims science has overlooked females' role in this. Females can reduce the size variance by mating promiscuously -- or, to put it more generously, resisting male "monopolization," says the researcher, Michael Plavcan. 

The reasoning is that in order for the males to grow in size over evolutionary time, their fight for dominance must actually be successful. In other words, the bigger male needs to get and keep the girl. But libertine females are able to frustrate that achievement, and thus reduce the amount by which males evolve to be larger.

He analyzed 35 primate species and found greater size variance strongly associated with less promiscuity, supporting the hypothesis, he says. The findings are to be published in a peer-reviewed book, "Sexual Selection in Primates" (Cambridge University Press). 

Plavcan says it's unclear whether his analysis applies to humans as well. Humans are generally classified as monogamous. However, among humans, the male-female size variance is small for primates -- as it is among the species with more promiscuous females. 

And "If you go around to hospitals, depending on the economic status [of a couple], between 10 and 15 percent of offspring are not that of the stated father," Plavcan adds.

—EJL