The primates approach the cats deferentially, body language loud with tones of submission. The hunters flick ears at them, growl a little. Then all three stand, four-legged, thumbs held upwards to keep clear of the ground. When they amble off, the primates are following them, semi-bipedal, carrying the joints and slabs of meat like paid porters. You know the drill now: not your Earth and not your story. This world belongs to the cats.

These creatures are not what you’d call sabre-toothed tigers, but teeth like those turn up like a bad penny throughout the fossil record. Their ancestors in our histories are called barbourofelids: husky killers that terrorized the world for ten million years or so. They then died out before they could trouble the dreams of the earliest humans.

This species lives in prides and hunts a wide range of prey. The thumbs are lucky happenstance, a freak mutation. Over the next few million years these Miocene felids will languorously expand into a variety of habitats; prides will draw territorial lines that become diplomatic boundaries. Tool-making will be improved on, and in this the cats will be assisted by domesticated breeds of smaller animals. Various creatures come to live in their shadow and treat them with slavish deference. Ten million years back they had primates to pick fleas off them and fetch water in rolled leaves, look after kittens and bury the cats’ excrement. And sometimes to serve as a light snack. Yet they stayed, subservient to a fault. Meerkats and mongooses were their cleaners, honey badgers their guard dogs and monkeys their valets and artisans—weaving wicker, shaping stone, crafting bright masks or creating false manes of bone and feather.

Perhaps the primates are receiving protection from the association, though nothing that protects them from the cats, but this is not the symbiosis at work. The cats are only half the masters of the world. Their partners in crime are single-celled amoebae that infest both the cats and a wide variety of animals sharing a habitat with them. Far more than the disputed effects of Toxoplasma gondii in your domestic pets, this infection burrows into the brains of its non-feline victims. It instils in them a deep adulation for the cats, their scent, the sight of them, their needs. Tribes of primates, far from becoming world-striding hominids, are merely the servants, and the cats have evolved to make use of them.