Paleontology explores ancient life by studying fossils and the rocks that preserve evidence of Earth's past.
Paleontology combines biology and geology to investigate organisms that lived long ago. Fossils can preserve bones, shells, leaves, tracks, burrows, and other traces of life. By comparing these clues with rock layers, modern organisms, and dating evidence, paleontologists build testable explanations of how life and environments changed through deep time.
Fossils are preserved remains or traces of organisms from the past.
Learn MoreRapid burial and special conditions can help preserve biological evidence.
Learn MoreRock layers and radiometric methods help scientists place fossils in time.
Learn MoreBody structures help scientists infer relationships, movement, and behavior.
Learn MoreFossils can reveal past oceans, forests, climates, and ecosystems.
Learn MoreThe fossil record documents both long-term evolution and episodes of mass extinction.
Learn MoreFossils include body fossils such as bones, teeth, shells, and plant remains, as well as trace fossils such as footprints, nests, burrows, and coprolites. Most organisms never become fossils because remains are usually broken down, eaten, or scattered. That means the fossil record is incomplete, but it still contains enormous amounts of evidence about organisms that no longer exist and about earlier forms of groups that survive today.
Fossilization is more likely when remains are buried quickly by sediment and protected from scavengers, oxygen, and weathering. Minerals may fill spaces in bones or replace original material, while impressions and molds can preserve an organism's shape. In rare cases, organisms or tissues may be preserved in amber, ice, tar, or very fine sediment. Different preservation processes capture different kinds of information.
Relative dating uses the positions of rock layers and fossils to determine which events are older or younger. Radiometric dating measures predictable changes in radioactive isotopes within certain minerals to estimate numerical ages. Paleontologists often combine several lines of evidence rather than relying on one method alone. This allows fossils and major events to be placed within the geologic time scale.
Scientists compare fossil bones and other structures with those of living and extinct organisms. Features such as joints, tooth shape, muscle attachment sites, and limb proportions can provide clues about diet, movement, and evolutionary relationships. These interpretations are hypotheses that can change when new fossils are discovered or new methods provide better evidence.
Fossils are not studied in isolation. The surrounding rocks, sediments, pollen, shells, and chemical signals can help reconstruct the environment in which an organism lived. Marine fossils found far inland may show that an area was once beneath an ocean, while fossil leaves can reveal information about ancient vegetation and climate. These clues help scientists rebuild entire ecosystems rather than focusing only on individual species.
The fossil record shows that species appear, change, spread, and disappear over time. It also records several mass extinctions in which unusually large numbers of species vanished across geologically short intervals. Extinction can result from many causes, including environmental change, volcanic activity, sea-level shifts, asteroid impacts, and ecological competition. Studying these events helps scientists understand both the history of life and the resilience of ecosystems.