A series of 'death pits' containing 300 bodies have been discovered in Russia. The grisly site, which was found in the city of Yaroslavl, northeast of Moscow, likely dates back to the Mongol invasion of Europe in 1238. During this time, Genghis Khan's grandson, Batu Khan, decimated entire communities in his brutal - and bloodthirsty - bid for power. Now, thanks to scientific advances, DNA evidence has revealed that three of the victims were related and killed together: a grandmother, a mother and a grandson.