Primates' Fertilization Systems and the Evolution of the Human Brain

Abstract

Since the time of Darwin and Wallace, the origin of the human brain has been a controversial issue in evolutionary biology. The development of the human brain has been a matter of dispute between those who attribute it to the forces of natural selection and those who emphasize the role of sexual selection. Building on Darwin’s original insights, in this paper we argue that the uniquely human cognitive capabilities are likely to have been initially spurred by sexual selection. We consider the incentive properties of fertilization systems and, pursuing this ‘economic’ perspective, we compare human gender relations with those of other primates. We argue that, because of its potential egalitarian nature and its consequent quasi-monogamic gender relationships, the human fertilization system is much more likely to have given selective advantages to investments in emotional and rational intelligence, thus favoring the development of many fundamental human capabilities. Even if our brain was initially spurred by sexual selection, after some time, unlike the famous case of the peacock’s tail, it proved extremely useful also in the domain of natural selection. Thus, differently from explanations based on the effects of either natural or sexual selection alone, we show that favorable selection complementarities may have had a crucial role in the evolution of the human brain.

Keywords: Gender Relations, Sexual Selection, Emotional and Rational Intelligence