Excavators at the La Brea Tar Pits & Museum work to dig up fossils of mammoths, dire wolves, giant sloths and more out of the ground. They clean and piece together the bones, and prepare them for research and museum collections. With 4 million specimens already in scientists' hands, why keep excavating after more than 100 years?

The La Brea Tar Pits is one of the only paleontological sites on Earth that has preserved an entire ecosystem over time, from plants to camels to bugs. And every new fossil not only helps tell the story of the Los Angeles Basin over 50,000 years but also gives us clues about how current species, including humans, could weather climate change in the future.

We went to the La Brea Tar Pits to see how specimens are discovered, cleaned, and pieced together to build a record of the last 50,000 years.