It remains controversial among biologists whether selection can operate at and above the level of species.

Natural selection operated savagely, with only 1 percent of each generation surviving.

Cultural traits alter the social and physical environments under which genetic selection operates.

They're based on simple qualitative calculus of what would happen if natural selection operated this way.

In general, selection operates most powerfully during times of famine or other privation.

Critics defended the idea that natural selection operates solely on individuals within a group.

Mutation is not the only way in which natural and artificial selection operate.

But such selection could operate on any highly social animal, whether or not it has language.

They accept that natural selection probably operates relatively infrequently.