I heard recently that humans have essentially stopped natural selection in the traditional sense. The idea behind the statement is that we live in a world where people who are not "best suited to the environment" are able to reproduce causing subsequent generations to carry on unhelpful traits, like very poor eyesight. Nature without modern intervention would leave a significant portion of the population in a position to never reproduce allowing for the natural evolution that accompanies advantageous mutations to be passed on through generations. The statement, of course, is a generalization. We have really changed the game. Only in upcoming generations will humans know what the cumulative effect will be. Maybe it should be called "the age of unnatural selection."