Evolution Theory

Charles Darwin's theory of evolution by natural selection (On the Origin of Species, 1859) is the unifying theory of all biology — explaining the diversity of life, the fossil record, comparative anatomy, genetics, and biogeography within a single coherent framework. Combined with genetics (the 'Modern Synthesis', 1940s), it became the foundation of modern biology. Natural selection works through three requirements: heritable variation (offspring differ from parents and from each other), selection pressure (some variants reproduce more successfully), and deep time (enough generations for change to accumulate). Evidence for evolution is overwhelming and from many independent sources: the fossil record, comparative anatomy (whales have finger bones; humans have tailbones), DNA similarity, observed evolution in antibiotic resistance, and 200+ human vestigial structures.