 And so scientists did not really spend that much time, because it was very complicated, very messy. But now we are beginning to look at it, and we're beginning to realize that, like you said, it's like a rainforest, a jungle down there. It's survival of the fittest. So some people think that evolution does not take place on time scales that you can measure. Therefore, they doubt whether or not evolution is correct. But actually, evolution takes place in your gut.