Fossils sometimes form when a plant or animal is buried in or covered by rock or sediment, and some fossils are actual bones or even body parts that have become encased in rock or in preserving materials such as ice or amber. Other fossils form when a plant or animal creates an imprint in the soil that hardens over time and fills with new minerals, as a cast in a mold. Studying these and other fossil types presents a lot of evidence about the organisms and the time in which they lived.
Extinct Plants and Animals
Fossils can help researchers learn about plants and animals that became extinct a long time ago. For example, scientists learned everything about dinosaurs and saber-toothed tigers through research from fossils. Fossils can help scientists put together how the plant or animal looked based on its skeletal structure, and they also may help scientists understand what the animals ate, where they lived and how they died. Fossils are an important record of species that otherwise may not have been known because they died long before people began keeping records.
Evolution takes place over long periods of time, and the change can occur so slowly that it is difficult to know where one species ends and a new species begins. Fossils help provide that information. For example, fossils have identified the first amphibious creatures that developed legs, eventually leading to species that lived on land. The study of fossils also can identify some factors that influenced evolutionary change. For example, a drastic temperature shift may kill out some species or allow only those that adapted to the environment to survive.
The study of fossils can provide information about climate change. For example, one hypothesis about what killed the dinosaurs is that asteroids or other celestial bodies hit the earth, drastically changing the conditions for life. Another dramatic climate change led to the Ice Age, which killed off many species and changed life on earth. Scientists learn this information by determining the age of fossils that are discovered and studying other clues found in the same fossil layer.
Fossils can also help scientists understand how people of the past lived. The fossils of human remains and of plants and animals can provide these insights. For example, plant and animal fossils from a certain time can show what people ate. If signs of disease are found in plant or animal fossils, scientists can deduce that the people of the time period may have suffered the same disease. Understanding what people ate also provides information about how they lived, such as whether they were hunters and had to travel to find food. A fossil layer can also include artifacts from ancient cultures, such as tools or pottery.