At last, humanity is on the scoreboard. After three consecutive losses, Go world champion Lee Sedol has beaten Google's DeepMind artificial intelligence program, AlphaGo, in the fourth game of their five-game series. DeepMind founder Demis Hassabis notes that the AI lost thanks to its delayed reaction to a slip-up: it slipped on the 79th turn, but didn't realize the extent of its mistake (and thus adapt its playing style) until the 87th move. The human win won't change the results of the challenge -- Google is donating the $1 million prize to charity rather than handing it to Lee. Still, it's a symbolic victory in a competition that some had expected AlphaGo to completely dominate.