Rocks and sediments are really important for finding out  when our ancestors lived and what kind of environment they lived in. 

We learn a lot about fossils of our ancient ancestors by looking at the kinds of rocks and sediments they are found in. Those pieces of rock and sediments are called sedimentss and they tell us what kind of environments our ancestors lived in, where they died, maybe even how they died, and how fast they were buried.

For example, when we find fossils in sands or gravels we can figure out if they were on a beach or in a river when they were buried millions of years ago. 

To figure out when a fossil was buried, we can look at volcanic ash that lies above or below the fossil. Crystals in the ash can give us a precise date for how long ago it erupted from a volcano. Those dated ash beds can then be used to date how old the fossils that lie nearby.  

These are just a few of the many ways rocks and sediments can help us learn about our ancient ancestors!