Medieval mapmakers, with their limited knowledge of distant lands and uncharted seas, sometimes depicted dragons on the far edges of their maps. Hic sunt dracones (“Here be dragons!”), they warned. Dragons do not appear on our modern maps. But bodies on the rail lines of Madrid and the streets of Fallujah leave no doubt that Something Ferocious stalks the edges of our political and religious maps. Nationalism, tribalism, empire and religion mutate in draconian forms, and we sometimes fail to recognize the beastly genes in our own DNA.