All About Dinosaur Fossils and Carbon Dating

Somewhere out there, even as you read this, a team of scientists is hot on the trail of a dinosaur fossil that might add greatly to our understanding of the natural world. Or perhaps they have already found the fossil and are analyzing it in the lab, determining what clues about an ancient creature's behavior still remain embedded in it. Virtually any ancient organism that once lived can leave behind evidence in the form of a fossil. But exactly what is a fossil, anyway? Fossils aren't like rings, other jewelry, or other signs of human life; they can be even more mysterious.

All About Fossils

A fossil is any remnant of a plant or animal that lived in a past epoch of geological history. Geological history, time as thought of as the lifespan of the Earth or even of the entire universe, is measured in millions or even billions of years. The oldest fossil ever recorded was more than 3.4 billion years old! It was a cytobacteria, a microfossil that lived in the Paleoarchean Era. During this time, the Earth's atmosphere had little or no oxygen.

The discovery of any fossil can expand our knowledge of life not only on Earth but throughout the observable universe. For example, the discovery of cytobacteria from an oxygen-free era of Earth's past gave many scientists hope that life could have appeared on Mars, even though there is no evidence that its atmosphere has ever been like Earth's is today. Fossils do not need to be recognizable multi-celled creatures: In fact, trace fossils are just as valid as body fossils.

Dinosaur Fossils

Trace fossils are impressions or other disturbances in the environment that suggest a creature was once present. Tracks are common trace fossils. Items like jewelry, such as rings, might be traces of humans, though not technically fossils. By comparison, body fossils consist of a creature's remains. Dinosaur fossils have been known to mankind since at least the Middle Ages, when Europeans and Asians alike believed they were the bones of dragons. However, no one realized these creatures actually lived millions of years ago until the very recent past.

In fact, there was no such thing as a "dinosaur" until 1676, as far as people knew, and even then, the discovery of a gigantic leg bone didn't enter scientific literature until 1763. It wasn't until 1824 that remains of a megalosaurus, a huge, carnivorous beast that first appeared about 181 million years ago, were unearthed. Its discoverer, British adventurer William Buckland, considered himself a fossil hunter. However, even he couldn't have imagined he would find such a magnificent animal!

Then, as now, the existence of the dinosaurs captured the popular imagination. Throughout the 1800s and early 1900s, there was a race to find and classify them. The name "dinosauria," a combination of Greeks words for terrible and lizard, caught on in 1841, around the same time scientists concluded that they were looking at reptiles of the past. Unlike human artifacts, however, it was difficult to date these fossils.

Carbon Dating

The answer was provided by carbon dating. Carbon dating measures the decomposition of carbon-14, an isotope of the extremely common element carbon, within biological remains. Unlike other isotopes of carbon, carbon-14 is always undergoing a natural form of decay. The rate of this decay is constant under all circumstances, so the radioactivity of carbon-14 can be measured to provide a time frame in which a formerly living thing was alive and well.

Even fossil fuels, called such because they are produced when biomass is subjected to substantial geologic pressure over a long period of time, once had carbon-14. Fuels and other samples that no longer have detectable amounts of carbon-14 activity are called "radiocarbon dead." Fossil fuels take so many eons to form that they no longer exhibit measurable radioactivity, but other samples of biomass continue to emit radiation at a fixed rate based on carbon-14 levels.

Radiocarbon dating was first used by the American scientist Willard Libby, working in 1947. His early work demonstrated that due to photosynthesis, any plant would naturally absorb carbon-14 until the plant's death. By measuring the diminishing presence of carbon-14 within a dead plant, he showed it was possible to determine its approximate date of death. This discovery spread to other sciences, including paleontology, and Libby won 1960's Nobel Prize in Chemistry.