Read a little of The World Until Yesterday by Jared Diamond and you'll get some surprising answers to this question. tl;dr in many places people who couldn't pr

Read a little of The World Until Yesterday by Jared Diamond and you'll get some surprising answers to this question. tl;dr in many places people who couldn't prove consanguinity would essentially have to attack each other due to a prisoner's dilemma dynamic. The idea of seing a stranger and just walking past them is actually quite new.