This article reports on an experiment conducted on different islands in the Bahamas to test the effect of predation and competition on lizards. They protected the some islands from birds (predators) by netting them off completely. They left some islands as a control, and finally they introduced snakes to a third group as an additional predator.
According to the researchers, predators seemed to kill lizards at the same rate, regardless of size or speed (random elimination from the gene pool). However, when predators were removed from the island, increased competition among lizards caused larger and faster individuals to be selected for.
This experiment displays an example of evolution that can be seen in a human lifetime.
Full article: http://www.sciencedaily.com/releases/2010/05/100510105033.htm