Collaboration encourages equal sharing in humans, even in kids as young as 3, but one of humans' closest living relatives, chimpanzees, lack such sharing tendency, new studies have found.
Adult humans produce a vast majority of their resources in cooperative work with others.
Moreover, they generally try to distribute them based on norms of fairness and equity.
Now, recent studies show that even 3-year-olds do take note of whether or not rewards were produced collaboratively, which in turn affects their tendency to allocate the toys equally.
In these studies, children as young as three years of age were found sharing toy rewards equally with a peer when both collaborated in order to gain them, but not when worked individually.
Therefore, "the ontogenetically first sense of distributive justice may be that participation in a collaborative effort demands an equal division of spoils", said Katharina Hamann, who conducted the study with an international team.
But chimpanzees did not show this connection between sharing resources and collaborative efforts.
Also in the wild, they only rarely actively collaborate for subsistence.
Therefore, they may not have evolved a tendency to distribute resources more equally when those resources result from collaboration.
"Taken together, the primordial situation for human sharing of resources may be that which follows cooperative activities such as collaborative foraging, when multiple individuals must share the spoils of their joint efforts," concluded Hamann.