Charles Darwin (1809–1882)

Darwin's voyage aboard HMS Beagle gave him the raw material for a theory he sat on for two decades, wary of the storm it would unleash. On the Origin of Species argued that the staggering variety of life arises not from design but from natural selection acting on small inherited variations. He was a patient, exhaustive observer who trusted accumulated evidence over intuition, and who knew his idea would unsettle far more than biology.