The first clue of life goes way back 4,500,000,000 years ago. That´s 4 and a half BILLION.

Who finds these clues and what do they look for? Why do they look for them?

A paleontologist is a person who studies the type of clues called fossils. A fossil is what is left from the skeleton of an old animal.

You may be wondering, how do they even find out how old those fossils are? Paleontologists use a trick they call "Relative Dating". By matching those fossils or rocks to other fossils or rocks they already know the age of.

Paleontologists also can tell how old a rock is because the Earth has layers underground. Usually the deeper underground the layer is, the older it is.

Why is all this so important to Paleontologists? Because studying those fossils lets them know how those animals were related to other animals. An example of this is how they agree that birds and dinosaurs are related.