Historian Jared Diamond: "If Genghis Khan had been born 10 years later or 200 miles further away, we wouldn't know anything about him."

Jared Diamond: "Genghis Khan created the largest land empire in world history, all the way from China to Poland. And yet, there were other people who tried—Attila the Hun and Tamerlane the Turk. Why did Genghis Khan succeed?

Well, within the last 10 years, students of tree rings have figured out that on the Mongolian steppe, the wettest time in the last 2,000 years was the decade of Genghis Khan's birth. If he had been born 10 years later or 200 miles further away, we wouldn't know anything about Genghis Khan. But he happened to have been born at the right time and place because with all that rain, that meant hay to feed sheep and goats, to feed Mongol babies, and it also meant hay to feed Mongol horses to ride into battle.

So Genghis Khan was someone at the right time and place, but he had no idea, and we didn't have any idea until this tree ring study of the last decade."