Fossils play a crucial role in supporting the theory of common descent, which posits that all living organisms have a shared ancestor. This theory is backed by the examination of the fossil record, which is the collection of preserved remains or traces of ancient life.
One of the main pieces of evidence that fossils provide comes from the observation of transitional forms. These are fossils that exhibit characteristics of two different groups, demonstrating how species have evolved over time. For example, the fossil record shows a progression of transitional forms leading from early land-dwelling mammals to modern whales, indicating how a species can evolve from one form to another.
Additionally, fossils can show changes in specific traits over long periods, which reflect the adaptive changes that species undergo in response to environmental pressures. This gradual change in traits aligns with the concept of descent with modification, where species evolve from common ancestors while adapting to their surroundings.
Moreover, the geographic distribution of fossils often mirrors the evolutionary relationships among organisms. For instance, similar fossils found in different parts of the world can suggest a common ancestry, particularly when these species are now separated by vast distances but once shared a land connection. This supports the idea that species diverged from a common ancestor as they spread out over time.
In summary, fossils provide tangible evidence of the historical changes in life forms, illustrate the process of evolution, and support the idea of common descent by showcasing transitional forms, adaptations, and geographic distributions of species that indicate shared ancestry.