And I don't see how guppies changing size is anything other than genetic variation. > > Again, it's something that I don't see as an issue, though you keep making it one... I still don't get it. Sexual recombination, pressure selection for smaller guppies... none of this refutes evolution by natural selection!-It is the issue. The guppies change themselves in a different river in a two year period to allow natural selection to protect them.No time to wait for chance mutations. Small guppies were out into a river where the predators like small guppies and big guppies were put in a river where predators liked big guppies. Look up Reznick's work, which I believe is ongoing.This is epigenetics preparing for trouble. The organism does the initial work and then natural sdlection takes over. Who is the prime mover??