Searching for fossils gives clues to the past
Fossils are the remains of ancient plants and animals that have been preserved in minerals or rocks. The rock actually replaces the original animal or plant tissue.
Dinosaur bones, eggs and sea shells are typical fossils, but fossils also can be a cast of a preserved footprint, a groove where a fin marked the bottom of an ancient sea, scale prints from a prehistoric swimmer or the outline of a plant.
From microscopic organisms to giant trees, fossils unlock mysteries about the very distant past.
The people who examine fossils are called paleontologists. Archaeologists, who study ancient cultures, might find fossils as they uncover the remains of ancient towns.
“Archaeologists look for human-related items, including, sometimes, fossilized human bones. Paleontologists look for fossils in a wide variety of places, including deserts and in the foothills of mountains,” said Nancy O'Shea of Chicago's Field Museum in Chicago.
Normally, after a plant or animal dies, it decays. Once in a while, nature creates opportunities for objects to be preserved for millions of years. Plants and animals can become fossilized under certain circumstances if they are covered by certain mineral sediments.
These sediments actually penetrate the tissue and take the same form as the original object. While not fossilized, ancient people and animals have been found preserved for millions of years in ice, peat bogs and dry environments like desserts.
Fossils have been uncovered on every continent. The world's largest fossilized Tyrannosaurus rex, SUE, was discovered by paleontologist Sue Hendrickson in 1990 and is a main attraction at the Field Museum.
“SUE was found near the Black Hills of South Dakota,” O'Shea said.
The 28-year-old T-rex died 67 million years ago and was covered in water and mud, which became solid rock over time.
“We have scientists looking for fossils in Antarctica because millions of years ago it was much warmer and could support animal life. Any location where the bones might be preserved in rock, sand, mud, tar, etc., may contain fossils,” O'Shea said.
There's a story behind the evolution of fossil hunting. Scythian gold miners trekking through Asia's Gobi Desert were confounded by the dinosaur bones they discovered, so they spun fables about a half-eagle, half lion griffin.
“Many ancient myths are attributed to fossils that early humans found. For instance, the fossil of a mammoth skull has a hole where the trunk was attached. Early humans may have found such a skull and thought the creature was a giant with one eye. Hence, the myth of the Cyclops,” O'Shea said.
People in ancient China used dinosaur bones in medicines. Aristotle, the Greek philosopher who lived more than 2,000 years ago, saw a connection between shell fossils and shells uncovered at the beach, sparking the idea that fossils were once living creatures.
The word “dinosaur” dates to the early 1800s. It's a combination of the Latin words for “terrible” and “lizard.” Paleontologists are still digging through the story of the Earth's evolution with each fossil they uncover.
Future paleontologists might want to bone up on their skills by attending the Field Museum's Dino Camp, with sessions in late May and June, or the “Dozin' With the Dinos” museum sleepover May 6. The Evolving Planet permanent exhibit offers a close look at fossils.
For details, see the museum's website at fieldmuseum.org.