Narrator: This is Science Today. People often think of evolution as a very slow and gradual process. But researchers at the University of California , Riverside treated streams in Trinidad as giant test tubes to study the evolution of guppies in real time. Biologist David Reznick explains that they introduced guppies to environments they had not been exposed to before.
Reznick: We did things like measure mortality rates. We could show that if there's a predator, they died at a higher rate. We were also able to show that when there are predators there, the guppies are genetically predisposed to mature when they're younger and to have more babies, which is something that the theory predicted.
Narrator: Reznick says by manipulating the life span of guppies, they were able to show that these traits evolved rapidly.
Reznick: When I proposed this study originally in 1980, very often people would smile wanly and say it sounds like a great idea, we hope you live long enough to see something happen. It turns out that we were getting significant results in as little as four years and they may have actually changed much more quickly than that. So, it's become a model study for showing that evolution can be a very rapid process.
Narrator: For Science Today, I'm Larissa Branin.