It's a type of natural selection called "group selection", and it's taboo, because it's very tempting to invoke it to explain away all sort of apparent paradoxe

It's a type of natural selection called "group selection", and it's taboo, because it's very tempting to invoke it to explain away all sort of apparent paradoxes - but it requires very tricky circumstances to work at all, if it even can, and it's rare for the explain-away-ers to bother to show why it works in their particular instance. https://en.wikipedia.org/wiki/Group_selection https://en.wikipedia.org/wiki/Group_selection