In the process of evolution there were differences in most species of animals and plants. Divided and responsibilities among animals: one floor is engaged in the extraction of resources for survival, the other is the care of posterity. It is extremely rare species where the male and female are equally engaged in raising her baby. Is it possible to apply these laws to man? Biologists say "Yes".
Mothers invest more effort and devote most of the time the nurturing and education of their child. This phenomenon inherent process of evolution. While the father plays the role of breadwinner in the period of growth of the baby. Note that in modern society this role behavior may change.
Much depends on the fact that the mother or father copes better with certain functions. If the father likes to sit with the child, to educate him and teach new skills, it is likely that he can stand on the conventionally female role. This model provides the framework of the evolution of the best survival and is completely natural for the whole of the animal world, writes Proceedings of the Royal Society B.