“These data not only suggest a technological shift, but also the early development of social exchange networks. It is plausible that when the environmental and social conditions called for it, such groups could have decided that the use of collective force would have been occasionally necessary. Having the cognitive abilities necessary for such complex forms of planning and culture would have also allowed for sophisticated ways to identify in‐ and out‐groups, such as the use of bodily ornamentation, which likely would have been key in determining appropriate allies or adversaries. We see no reason to conclude that these ancestral human populations lacked the capacity to choose when to use violence and when to refrain from its use.
“The migration signal makes good sense in terms of climate. For most of the last few hundred years, different parts of Africa have been out of step with each other in terms of the aridity of the climate. Only for a brief period at 60,000-70,000 years ago was there a window during which the continent as a whole experienced sufficient moisture to open up a corridor between the south and the east. And intriguingly, it was around 65,000 years ago that some of the signs of symbolism and technological complexity seen earlier in South Africa start to appear in the east.