Males and females: The big little difference

Abstract

Our nearest relatives in the animal kingdom have an enormous variety in the relationships between and within the sexes. Single-male-multi-female and multi-male-multi-female species exist next to single-male-single-female. What are the evolutionary reasons behind? Reproduction is essential for not becoming a dead end. Cloning and asexual reproduction do not lead to unexpected outcomes, only sexual reproduction does. The essential difference between sperm and egg cells is associated with a specialisation in a female and male role that profoundly affects the relationships between individuals. Female mammals need not worry about whether they will be fertilized, but only about by whom, while males should have as their foremost worry whether they will ever fertilize a female at all. If not so his genetic material will get lost. If the female only has a small chance of successfully rearing the youngster(s) and if this chance is increased when the male stays to help he must consider the trade-off: whether paternal care wins (in number of healthy offspring) from polygamy. Ultimately, females determine which male strategies will be successful. Our own species does not resemble our closest relatives, the chimpanzee and the bonobo, at all. True enough, we share with them a modest degree of sexual size dimorphism, and, remarkably, a comparatively great intermale tolerance. It is difficult to maintain that the human socio-sexual pattern is a set of arbitrary cultural attributes that can vary without restraint. Our species fits in a grand global scheme of evolutionarily regulated adaptations: we weave a different texture, but follow the same laws. However we differ through paternal bonding to a male provider, which supports women to more successfully raise their infants who are more or less helpless for a relatively long period. © 2011 Springer Science+Business Media B.V.