Evidence for Evolution

Fossil Records as Evidence for Evolution

• Fossils offer concrete evidence of creatures that once inhabited the earth, affirming that life on earth has existed for billions of years and has undergone a series of physical transformations.
• Various trends can be observed within the fossil record, including the transition from simple to complex organisms, and the emergence of new anatomical features and species.
• The fossils of transitional species are powerful pointers towards evolution. The Archaeopteryx, an ancient creature showing features of both dinosaurs and birds, is a key example.
• Fossil layers, or stratigraphy, further show species’ evolution over time, as older fossils are typically more primitive than their younger counterparts.

Comparative Anatomy and Embryology as Evidence of Evolution

• The study of homologous structures, distinct features shared by species of common ancestry, supports the theory of evolution. For example, the similar bone structure in the limbs of humans, cats, whales, and bats suggests common ancestry.
• Vestigial organs, like the human appendix, present in an organism but reduced in function, serve as evidence that a species has evolved over time.
• Embryology reveals similarities in early developmental stages in different species, suggesting a shared ancestor. The pharyngeal pouches in human and fish embryos, for example, show a common evolutionary starting point.

Molecular Biology as Evidence for Evolution

• Comparisons of DNA sequences across different species can provide profound insights into shared ancestry. The closer the match between the sequences, the more recent their last common ancestor.
• Proteins are also used to track evolutionary relationships. The cytochrome c protein, for example, varies very little amongst species, suggesting a common ancestor.
• The presence of pseudogenes, genes that have lost their function through mutations, provide evidence of evolution at a molecular level.

Biogeography as Evidence for Evolution

• The geographical distribution of organisms around the world showcases evolutionary adaptations. For example, isolated islands often house unique species that have adapted to specific environments, such as the varying Finch species in the Galapagos.
• Endemic species, limited to a specific geographical area, offer insights into evolution through adaptive radiation, a process whereby species diversify rapidly to fill available ecological niches.

Evidence from Artificial Selection

• Humans have, over centuries, practised selective breeding to enhance desirable traits in plants and animals, showing that traits can be chosen and promoted through generations - a microcosm of natural selection.