survival **
survival of the fittest
natural selection
selection ***

Who could ask for a better example of natural selection in action?

Natural selection has given us another look at the human race.

It is, I think, only a matter of natural selection.

Was there a natural selection involved in not speaking up?

On the other hand, like natural selection, sometimes the results were not what had been intended.

I also believe that natural selection was the means by which man came into existence.

This desire is also thought to have been a result of natural selection.

If it does not, the human race will have been one of natural selection's dead ends.

He rather preferred the last two terms to natural selection.

He also anticipated in general terms the idea of natural selection.