The Social Instinct is full of memorable things like that. The only problem is Raihani’s fairly rigid application of Darwinian logic. She doesn’t get bogged down in the long-running debate about how much of human nature can be explained by evolution. Still, the book tends towards the approach that the philosopher-neuroscientist Raymond Tallis witheringly calls “Darwinitis”; interpreting all human behaviour in terms of how it helps us to survive or reproduce. The “ultimate explanation” of our habits, Raihani believes, is a Darwinian one.