Charles Darwin was the original crowd-sourced scientist. He may have reputation as a recluse who hid away on his country estate, but he actually turned Down House into the headquarters for a massive letter-writing campaign that lasted for decades. In her magisterial biography of Darwin, Janet Browne observes that he sometimes wrote over 1500 letters in a single year. Darwin was gathering biological intelligence, amassing the data he would eventually marshall in his arguments for evolution. In the letters he wrote to naturalists around the world, Darwin asked for details about all manner of natural history, from the color of horses in Jamaica to the blush that shame brought to people’s cheeks.

Given the skill with which Darwin used the nineteenth-century postal system, I always wonder what he would have done with the Internet. A new paper offers a clue: he might have enlisted thousands of citizen scientists to observe evolutionary change happening across an entire continent.

Darwin used his Victorian crowd-sourcing to collect evidence that was consistent with his evolutionary theory; he didn’t expect that he could actually document evolutionary change happening in his own ...