Memes

Ideas are self-reproducing, and mutating -- so ideas evolve.
Culture is an idea.  Religion is an idea.
Organizations/corporations/governments are ideas.

Unguided Eugenics

To increase society's intelligence without sacrificing diversity, enforce 2-child policy -- dumb people are less likely to live long enough to reproduce.  Also halts overpopulation damage to environment & quality of life.

Unproductive Citizens

Successful/dominant civilizations are probably dragged down by the survival of their weak/lazy members.