Theory of evolution
English naturalist (1809-1882).
Set off at 22 as the Beagle's unpaid naturalist on a 2-year voyage that became nearly 5 circumnavigating the globe. Returned with a slowly-forming idea, then sat on it for 22 years terrified of religious backlash — until a letter from a young Wallace describing the same idea forced his hand. Origin of Species sold out on day one.
Charles Darwin is one of the historical characters you can play as in Rubicon, a trivia game where you answer in your own words and an AI judge reads what you meant. Charles Darwin is filed under Nature & Animals, and is strongest at Nature & Animals and Natural Sciences.