Unlike Archimedes — who made one of his defining discoveries in a single flash, a Eureka moment — Darwin’s hypothesis about natural selection emerged slowly, over the course of decades. Empirical research conducted on a lengthy expedition aboard the HMS Beagle (1831-1836) percolated for many years before emerging as a fully articulated theory in The Origin of Species (1959). Indeed, it’s not really possible to specify where Darwin “discovered” evolution. Tom Chaffin tells the story.