New study proposes that prosociality toward strangers initially evolves due to selection for social tolerance, allowing the expansion of individual social networks. Human social norms and language may subsequently extend this ape-like social preference to the most costly contexts. User DarwinDanger, in the Reddit Science subreddit, 04 Jan 2013
Altruism in other apes; bonobos will share with strangers more readily than with acquaintances User heidavey, in the Evolution subreddit, 03 Jan 2013