Chimpanzees
and bonobos have been distinct species for around 900,000 years. Mr Wrangham says part of the reason for their differences is that, on their side of the Congo river, chimpanzees have always had to share habitats with gorillas; violence and hot-tempered aggression make sense when you have more limited food resources. Across the river, bonobos evolved with abundant fruit and foliage. Natural selection reduced their propensity for reactive aggression (the hot, impulsive type).
The kindness of strangers, The Economist May 4th 2019 人類の倫理観と社会性の起源(書評)
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