Charles Darwin

Charles Darwin provided the unifying explanatory framework for all of biology with his theory of evolution by natural selection. His five-year voyage on HMS Beagle provided observational evidence, but it was his synthesis of geology, paleontology, and biogeography that led to his revolutionary idea. In 'On the Origin of Species' (1859), he argued that species evolve over time through the natural selection of inherited variations that increase an individual's ability to compete, survive, and reproduce. This theory explained the breathtaking diversity of life without recourse to supernatural design, making biology a coherent science.

It connected all living things through common descent and provided a mechanism for adaptation. Despite initial controversy, evolution by natural selection is the foundational concept of modern biology, genetics, and medicine, influencing fields from psychology to computer science.