"Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and donkeys." Samuel 15:3
As you can see it existed before. The holocaust is a horror because it was industrialised mass murder, and the sheer number of people murdered in six years is staggering, but the idea of genocide is as old as the human race. Alas.