Graeber / Wengrow: "New work on the demographics of modern hunter-gatherers--drawing statistical comparisons from a global sample of cases, ranging from the Hadza in Tanzania to the Australian Martu--shows that residential groups turn out not to be made up of biological kin at all [...] primary biological kin actually make up less than 10 per cent of the total membership of any given residential group." (280)
"There is an obvious objection to evolutionary models which assume that our strongest social ties are based on close biological kinship: many humans just don't like their families very much. [...] Many seem to find the prospect of living their entire lives surrounded by close relatives so unpleasant that they will travel very long distances just to get away from them."