“This freedom of movement allows for both men and women to recruit help from their families when necessary. The main result from our computer simulations and co-residence data was that although both husbands and wives try to maximise the number of family members living close by, neither sex has the upper hand. This implies that neither one ends up living with their relatives but instead reside with a small proportion of relatives and in-laws and a large number of unrelated individuals. Rules of sharing are therefore extended to unrelated co-residents, and movement between camps is frequently used as a way to avoid the less cooperative individuals.

These populations could not have evolved in harsh environments without placing cooperation between the sexes and families at the heart of their lifestyle. In a nutshell, this means that egalitarianism, food sharing, large-scale cooperation and sex equality are all a matter of necessity in hunter-gatherers.

The Evolution Of Fairness

Our simulations are a simple mechanistic answer for the puzzle of why modern hunter-gatherers live with so few kin, but they have huge implications for our understanding of human evolution, and also of human nature.

The fact that we are able to live, interact and cooperate with unrelated individuals and not only with kin has been recently identified as the most fundamental difference between human societies and other animal societies.

Of course, humans have the capacity to be anything, from the most cruel and unequal species, with sex slavery and warfare, to the most cooperative and caring animal, with people donating blood to complete strangers. Good and evil are just the two extremes of our malleable nature. However, the few surviving hunter-gatherers groups show us that without the equality and cooperation between sexes that they share with our distant ancestors many of the characteristics that we like to call “uniquely human”, such as caring for others and fairness, would probably not have evolved.”

via Why Our Ancestors Were More Gender Equal Than Us | IFLScience.