Have to remember the world population was much smaller. Maybe 150 million in Alexander's time and 400 million in Ghenghis Khan's. They'd have had to do a much m

Have to remember the world population was much smaller. Maybe 150 million in Alexander's time and 400 million in Ghenghis Khan's. They'd have had to do a much more efficient butchery to reach the same raw numbers. That said, a little googling seems to indicate that the Mongols do, in fact, win that competition. They were pretty big on genocide.