In the beginning, there was nothing. And then, there were ticks.
They swarmed the earth, feeding upon anything they could find. Initially, they were herbivores, that is, they only ate green things. Like lettuce. Or green Jell-O. Or green crayons.
But one day, a tick named Reginald accidentally ate a zebra. It was painted green, and he had thought it was a normal meal. But he discovered that it had this weird red stuff on the inside. He liked it. He told all his ticky friends about it, and soon, there were no magical green zebras left. Deprived of a food source, they had to turn to normal-colored zebras, and eventually all sorts of mammals. They didn't care, as long as they contained the yummy red liquid.