Fossils & Extinction

A fossil is the remains or impression of prehistoric life (that includes plants and animals).

When plants and animals die, they usually leave nothing behind. However, sometimes those living things die in a watery environment and they become buried in the mud. Once buried, skin and muscle break down, leaving only bones or shells behind. Over thousands or even millions of years, sediment builds on top of them and hardens into rock. Then something like erosion brings the remains to the surface where scientists called paleontologists can dig them up and study them.

A plant or animal that is extinct could once be found living on Earth but is now gone.

A scientist who studies fossils.

Many animals became trapped in a thick, sticky liquid called asphalt that seeped through cracks at the Earth’s surface. They got stuck and died and their bones were preserved.

Dental picks are used to carefully scrape away small amounts of rock from the fossil. Other tools include brushes to sweep away dirt and a chisel and hammer, which is used to chip away at harder surfaces.

When fossils are dug out of the ground, they still have rock or asphalt around them. The fossils are taken to a lab to be further cleaned before they are categorized and studied.

Fossil Preparators receive fossils that come from the dig site and clean them! At the La Brea Tar Pits, asphalt can be dissolved from the fossils using a special liquid. For types of rock other than asphalt, Fossil Preparators must clean fossils using additional tools.

Animal fossils found at the La Brea Tar Pits include horses, saber-toothed cats, short-faced bears, mammoths, giant sloths and dire wolves. In total they have found over 1 million fossils.

Zoe notices that the teeth from one of the skulls are flat and the teeth from the other one are sharp. She knows that animals that exist today that have flat teeth (like cows or horses) eat grass and that animals with sharp teeth, like cats, eat meat.

From animal fossils (especially skulls) we can learn about what an animal ate, its size and shape, and the strength of an animal (based on muscle attachments). We can also learn about whether an animal was predator or prey (based on eye socket placement) and even how good its sense of smell was (by the size of the nasal cavity).

Tiny fossils called microfossils provide evidence of a range of animals and plants that lived alongside the bigger animals. Examples of microfossils include pieces of leaves, seed, and bark from plants and also bones from small animals like lizards and rodents. All this information together can help us know about the environment from the past.