Sexual Selection in Human Evolution - Darwin's Hypothesis

Darwin's Hypothesis

Charles Darwin conjectured that the male beard, as well as the hairlessness of humans compared to nearly all other mammals, are results of sexual selection. He reasoned that since the bodies of females are more nearly hairless, the loss of fur was due to sexual selection of females at a remote prehistoric time when males had overwhelming selective power, and that it nonetheless affected males due to genetic correlation between the sexes. He also hypothesized that contrasts in sexual selection acting along with natural selection were significant factors in the geographical differentiation in human appearance of some isolated groups as he did not believe that natural selection alone provided a satisfactory answer. Although not explicit, his observation that in Khoisan women 'the posterior part of the body projects in a most wonderful manner' implies sexual selection for this characteristic. In the Descent of Man, Darwin viewed many physical traits which vary around the world as being so trivial to survival that he concluded some input from sexual selection was required to account for their presence. He noted that variation in these features among the various peoples of the world meant human mate-choice criteria would also have to be quite different if the focus was similar, and he himself doubted that, citing reports indicating that ideals of beauty did not, in fact, vary in this way around the world.