Large plant-eating animals inspire the evolution of meat-eating creatures to feed on them. The spiketooth is heavier than other hunting species of human. It can afford to be, needing neither speed nor stealth to hunt the leaf-and-twig-eating slothmen. It has slashing front teeth able to penetrate the thick fur and tough skin of its prey.The hunter human species have been evolving into many specialized types, each one hunting a specific type of prey: some hunt birds, some hunt smaller mammals, some hunt fish. The spiketooth, however, has evolved to hunt the slothmen. The spiketooth is larger and heavier than the other hunters, not needing stealth or speed for its hunting since its prey is large and slow-moving. What it does need, however, is a specialized killing weapon, and this it possesses in the shape of its front teeth.
Amongst the traditional carnivorous mammals, of which there are only a few small nonhuman species left, the killing teeth were normally the pointed canines. In extreme types, like the sabre-toothed cats, they developed into long slashing blades that were able to penetrate the thick hides of very large animals. In the spiketooth the weapons have developed instead in the incisor teeth at the front, rather like the only remaining teeth of the parasites that also feed on the flesh of the descendants of the tundra-dwellers. The spiketooth's mouth is very large, allowing its jaw to drop clear of the upper teeth so that they can be wielded efficiently. The hands are large and powerful, with strong fingernails that allow the spiketooth to hang onto the fur of the slothman while it stabs at the neck, or onto the fatty rolls of the parasitehost while it slashes its way through the blubber.
This may seem like cannibalism, since both predator and prey are descended from modern human beings; but their common ancestor existed so far back in time that the creatures involved now comprise entirely different species. The preying of one upon the other is merely the natural result of the development of a stable ecological system.
A male slothman munches placidly at the leaves and twigs, unaware of the approaching danger. Away below him in the undergrowth a group of parasitehosts have already left, their dim wits sensing the approach of a mated pair of spiketooths. If the distant crashing caused by their lumbering flight through the thickets causes any concern to the slothman, he does not react to it. He does not react at all until the familiar form of a spiketooth steps out from the shade of the forest and he suddenly recognizes the shape and the smell. Slowly he turns away from the tree, turning his back on his enemy, and begins to descend to all fours.
The first spiketooth, less experienced than the other, leaps for the broad back, hooks onto the long fur, throws up his head and drops his jaw ready for the strike. This is a mistake, as it enables the slothman to use his only weapon - his weight. He slowly topples backwards, while the attacking spiketooth tries frantically to untangle his claws from the fur. Remorselessly the attacker is pressed back down into the bracken and the soil of the forest floor, and the slothman lands spread-eagled on his back with his enemy crushed to death beneath him. However, this makes him vulnerable to the dead spiketooth's mate. She now leaps upon the unprotected chest and plunges her long killing incisors into the slothman's neck.
The kill is a success, which is all she knows. There is no grief for her dead mate. The spiketooth has evolved so far from the original human state that she feels no emotion at all.
By 5 million years (the 50020th Century)
They are wiped out by the travelers of the stars.