Here is a fragment from A Game of Giants by Tim Urban: So while kindness, in all its manifestations—care, altruism, compassion—was an important survival trait in a world where well-functioning groups were necessary for survival, universal kindness probably wasn’t a great survival trait. Inevitably, other tribes would be selectively kind, shedding all of that kindness when dealing with other tribes. And when a kind tribe faces off against a ruthless tribe, the ruthless tribe usually wins.