Scientists Say: Fossil

This is any preserved trace left from an ancient living thing

dragonfly fossil

Fossils preserve the traces or bodies of ancient life, such as this dragonfly.

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Fossil (noun, “FAH-sul”)

This word describes the remains or traces of ancient life preserved in rock. Fossils can be animal body parts, like bones or teeth. They can also be ancient footprints or the impression of a leaf left in stone. Even poop, from dinosaurs or other animals, can become a fossil.  

Fossils provide a record of life on Earth, millions and even billions of years ago. This fossil record can reveal how organisms lived and evolved, or changed over long periods of time. The scientists who study fossils are called paleontologists (Pay-lee-en-TOL-oh-jists).

The traces of living things don’t usually last long. Leaves decay and footprints wash away. And most organisms that die will rot. But under some conditions, evidence of ancient life can be preserved. For instance, if an animal’s body is quickly buried by sand, soil and rocks on the seafloor, it can partially turn to stone. Over time, more of this material, called sediment, can pile up. Its weight squishes the sediment at the bottom, turning it to rock. In this process, minerals replace the body’s tissue, bones or shell to make a fossil. Something similar can happen to buried leaves or other plant parts. Or only an imprint may be preserved. 

Fossils can also form from the resin secreted by trees. This sticky stuff can catch insects, leaves or feathers. When the resin fossilizes, it can even preserve soft tissue. As the resin fossilizes, it turns to a stone called amber. 

In a sentence

Fossil teeth from Neandertals suggest they ate a variety of foods. 

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Carolyn Wilke is a former staff writer at Science News Explores. She has a Ph.D. in environmental engineering. Carolyn enjoys writing about chemistry, microbes and the environment. She also loves playing with her cat.

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