The fossil record provides evidence for evolution in several key ways:
- Chronological sequence of fossils: Fossils are found in sedimentary rock layers arranged in a chronological order, with older fossils in lower layers and younger fossils in upper layers. This sequence shows a progression from simpler to more complex organisms over time, consistent with evolutionary theory. For example, prokaryotes appear before eukaryotes, and invertebrates appear before vertebrates in the fossil record
- Changes in organism features over time: Fossils show that organisms from the past differ from those alive today, demonstrating a progression of evolutionary changes. Comparing the anatomy of extinct and modern species reveals how traits have changed and diversified through descent with modification
- Transitional fossils: These fossils exhibit intermediate features between ancestral species and their descendants, illustrating evolutionary transitions. Examples include fossils linking land mammals to whales, dinosaurs to birds (e.g., Archaeopteryx), and fish to amphibians. Transitional fossils help fill gaps in the evolutionary lineage and confirm gradual changes over time
- Law of fossil succession: Different species appear in a consistent order in the fossil record across the world, indicating a natural sequence of development without reversals (e.g., amphibians never appear before fish). This pattern supports the idea of common ancestry and evolutionary branching
- Evidence of common ancestry: The fossil record supports the concept that all species are related through a "tree of life," showing how species diverged from common ancestors over millions of years
In summary, the fossil record provides a detailed historical archive of life on Earth, documenting the gradual changes in species, the emergence of new forms, and the presence of transitional forms that collectively support the theory of evolution
