. >> we can't cleanaway the outside, so we save the microfossils, so we focus on the stuff. >> reporteryou are able to get better apps from the things you -- answers from the things you find. >> that's right. the more evidence you have, the better the story you can tell. >>> so i have to say, i visited the la brea tar pits when i was little with my parents. the one thing i wanted to do, that i didn't get a chance to do is touch the tar. i'm jealous. >> playing with the tar. it was sticky, it took my about 10 minutes to get it off my hands, i can see why it would get an animal stuck. >> these tar pits seem to be good at preserving the animals, is that because the tar. >> the asphalt and the bacteria, you don't get feather or hair, so that made it difficult to get d.n.a., but as far as preserving the structure, they can tell a lot about an animal based on the skeletal structure. it's thanks to the asphalt. >> what is amazing is that you really see in the tar pits how much the climate changed. l.a., essentially, was under water once upon a time, and the tar pits are evidence of that. >> ab