What Are Fossils

Thanks to the character Ross Gellar on the popular television show "Friends," most people know that a paleontologist is a scientist who studies fossils. However, since Ross's area of expertise was dinosaurs, the general populous might be misled to think that all paleontologists study dinosaurs. In reality, only a small fraction of recorded fossils are from dinosaurs; the vast majority is from plants and other animals, and these fossils are of greatest interest to most paleontologists.

What Are Fossils and How Are They Formed?

The word "paleontologist" comes from paleo- (meaning ancient) and -ologist meaning one who studies. Therefore, a paleontologist is one who studies ancient fossils. A fossil is the preserved remains of a prehistoric plant or animal, usually one that is now extinct. Most fossils are found in layers of sedimentary rock, which is rock formed from sediment (consisting of smaller rocks, clay, mud, sand, etc.)

There are six ways that fossils were created, each of which requires different techniques for locating and excavating the fossil. You may recall the movie "Jurassic Park," where a fly was perfectly preserved in amber (hardened tree sap), which is considered amberization or unaltered preservation. Fossils can also be created when parts of the plant or animal have broken down or dissolved over time, and only certain elements or minerals remain. For example, carbonization or coalification occurs when only carbon remains, and when the specimen's bone and hard parts have been replaced over time by calcite, pyrite, iron or other minerals, this is considered replacement. A similar phenomenon occurs when these minerals replace the organism's original tissues and actually preserve parts of the specimen, which is known as permineralization or petrification (such as petrified wood). Recrystalization occurs in one of two ways: either when the specimen's hard parts crystallize into smaller, more stable minerals or when small crystals become bigger crystals. Finally, authigenic preservation is frequently seen with plants that dissolved, leaving a cast or mold of the original specimen.

As humans, our fascination with fossils stems from a desire to go back in time, to understand our beginnings. Fossils give us a way to look back at the past, before humans existed and before history was written. By studying fossils, paleontologists can begin to understand these prehistoric plants and animals, and speculate on the causes for their extinction. Whether or not "Jurassic Park" could become a reality with today's advancements in science and research remains to be seen.