>>12388684evolution
within a social species, tribes whose bad individuals kill themselves end up outperforming tribes whose bad individuals don't kill themselves.
why? resource/mate allocation. if bad genes in an individual spread, that harms the rest of the tribe. if scarce resources during a winter or famine don't go to the best individuals, that also harms the tribe
it's why you see depression and suicidal behavior in ethnicities that suffered famine's/winters in their evolutionary history.