The Times has a chat on the timeline of human brutality. Encouragingly, the overall picture appears to be that (compared to past periods) less people – as a percentage of the total – die from violence. Here is the Times on the top three most deadly human conflicts:

The savagery of the Mongol conqueror Genghis Khan may have culled the global population by about 11 percent; two bloody upheavals in China — the An Lushan Rebellion and the collapse of the Xin Dynasty — each may have felled about 6 percent of humanity. Those are but 3 of the 100 worst atrocities in history, as cataloged by Matthew White in “The Great Big Book of Horrible Things,” an amusing (really) account of the murderous ways of despots, slave traders, blundering royals, gladiators and assorted hordes.

More on this here.