The eyes of Piscator longidigitus polarize light, removing the bright reflections that normally prevent animals seeing below the surface of water. His brain automatically compensates for the refraction.	3 MILLION YEARS HENCE FISH-EATER Piscator longidigitus Three million years have passed and the results of constant natural selection and evolution are apparent. The temperate woodland-dwellers have diversified, and developed specialized body forms to fit different environments. Living by upland lakes and beside rivers, the fish-eater is equally at home on land and in the water. His pelt is smooth and glossy, his shape streamlined. Ears are small and close to the head, the neck is short and feet are broader than usual.
	The fish-eaters have evolved by natural selection the streamlined shape earlier engineered into the aquatics.

The figure has never noticed this. It is not part of his life and he is looking the other way. Sunlight, sparkling from the pool below him, casts ripples of light on his face and arms. He has the long limbs and the long face of one of the hunting people, but there is something a little different about him. His neck is shorter, his ears smaller, his fingers longer, and his feet broader than usual. Also, his eyes are strange – not in their appearance but in their function. The lenses smooth out the bright reflections from the water’s surface enabling him to see directly into the depths. His brain compensates for the refraction and distortion caused by the different densities of the water and the air. He uses these faculties to watch the bottom of the pool for his prey, for this creature feeds on fish.
In the temperate regions of the world, where the forests and woodlands still exist on the upland slopes, the hunting people still pursue their age-old lifestyle, just as they have done since they were engineered. However, as there are so many different food sources in the habitat, many of them have begun to specialize, and to develop bodily forms that are appropriate to their particular way of life. Most lie in wait for birds, or dig in the ground after burrowing mammals. Some even feed on nothing but insects that they remove from the layers of their wooden homes.
One group has developed as an almost exclusive fish-eater. Living mostly by the hilly lakes and rivers, these creatures spend most of their time on dry land, but enter the water to chase their prey. Their broad feet help them to swim, and their long fingers can spear their slippery prey with ease. Their pelt has become particularly smooth and glossy, and they are beginning to adopt a streamlined shape to their bodies, with a bulbous head tapering into the smooth shoulders without much of a neck. Their eyes work best above the water, but their focus can be adjusted to allow their use beneath the surface as well.
The individual beneath the overhang – so still that he appears to be asleep – suddenly focuses his eyes on a movement not far below the surface of the pool. A long fish swims in from the more turbulent area near the current, its deep tail whisking back and forth, moving its body lazily along with an ease that would make the watcher feel jealous if he had the capacity to feel such emotions. Taking his time, he watches the creature come closer and closer.
His hand cleaves the water so expertly that it hardly makes a splash. The pointed claws on the long fingers close around the scaly body, and pin it before the slippery shape can wriggle free. Then, with an almost reflex jerk, he yanks it from the water and onto the bank beneath the overhang.
With a swift blow he kills it.
Then he eases himself from his hiding place, straightening out the slight cramp in his muscles, and gathers up his catch to take it back to his mate and family.
No, he is not a fully-adapted water creature. There are other derived humans in the world who are more perfectly built for the water environment. Nevertheless he is good enough to survive and to continue his line.

The hand has evolved two strong fingers that allow the tree-dweller to hang from the underside of branches.
	3 MILLION YEARS HENCE TREE-DWELLER Arbranthropus lentus The long hooked fingers evolved to cling to the jungle canopy, but they can also break open insect nests under the bark. Small but slow, the tree-dweller moves with deliberation through the humid rainforest, clinging tightly to the underside of the great spread of branches. Fruit is plentify and insects abound. With no enemies and abundant food there is no need for speed, aggression or change. Without the need to adapt or develop, the sloth-like tree-dweller will remain in a state of statis, able to breed but unchallenged.

TREE-DWELLERS

Far away, on another continent, a much smaller creature moves slowly, upside down, through the dripping branches of the tall trees. Her fingers and toes are permanently curved, and allow her to hang on the underside of the stoutest branches.
Slowly she turns her little head and looks about, seeking out the next piece of food growing in the humid air. There, on the next tree, is a bunch of fruit. Carefully she crawls along beneath the branch back to the trunk, where she can climb out amongst the branches closer to it. Dimly she sees that there is another creature, a male of her own kind, already on that tree, well above the branch with the fruit. He is moving slowly downwards. Whoever reaches the fruit first will claim it.
Her long fingers reach for the next hand-hold, and splinter through a weak thin layer of bark. The air is suddenly full of noise and aggression. A cloud of insects has burst from the hole and is thudding into her, jabbing through her pelt with pointed tail weapons. She feels the prick of the attacks, but there is no pain, as her line became immune to the poisons generations ago. She knows that there is good eating here, so ignoring the insects that are swarming and clustering around her hands she breaks up the bark covering the nest that she has disturbed. Combs of honey and grubs are stacked in there, vertically in neat rows. With her usual deliberate actions she breaks them from their hollow and chews contentedly.
Afterwards, with the nest empty, and the insects spent, exhausted or fled, she remembers the fruit on the next tree. With painfully slow movements she unwinds from her feeding position and begins to crawl along the branch once more.
Eventually she comes in sight of it, but she is too late. The male has already reached it and is eating. No worry. She has fed, and there is plenty of other sustenance around. She turns to crawl away again; but then she stops because the male has noticed her and is crawling along the underside of the thin branches towards her.
He obviously wants to mate. Does she want to let him? Yes, this is a good time since they have both eaten and will have the energy. It is also a long time since she gave birth, and her child has now matured and left, so she can take on the responsibility once more. Meekly she awaits the male’s approach.
The rainforests that still clothe the windward mountains of the moister parts of the globe and the great river basins along the equator still have tree-dwellers, which in most places have changed little over the millennia. The long arms and long-fingered hands that grasp branches allow them to hang firmly onto their high perches. The long legs with the prehensile toes allow trunks and boughs to be negotiated. The weak intellect that knows only about food and mating, and about those only enough to satisfy the basic drive for existence, allows the creature to survive. Food has always existed here, and, seemingly, will do so for ever; therefore the tree-dwellers have no need to change, unlike the creatures indigenous to the other habitats of the world.
The only change has occurred in the pace of their lives. With no enemies, the tree-dwellers in many areas have become slow and ponderous, moving sluggishly from one meal to the next, from one mate to another. There is no strife, either with one another or with different types of creature. Perhaps someday, when something unforeseen comes and takes away the forest, then perhaps the tree-dwellers will alter. That is, if they still have the genetic capacity for adaptation, if they have not lost the inherent ability through a long period of stasis and inbreeding.
Any change to the environment, however, will not take place for a long time yet.

ANTMEN

A long finger probes and gropes down the tiny tunnel into the nest. The loose soil and twigs are forced apart by the blade-like fingernail and the finger slides in, deeper and deeper. Ants, enraged by the intrusion, swarm out of side-chambers and tunnels, and mass against the attacker. Stings and jaws sink into the tough skin, but make little impression. Courageous fighters hang onto the invading flesh as their blind instincts dictate, while others climb over them to find other spots to attack. Soon the whole finger is a clump of swarming defenders.
Up above, the antman has gauged that enough time has elapsed, and pulls his hand with its long finger from the nest. It is a black mass of ants. He has judged the timing correctly - just enough time for the ants to attack his finger in sufficient numbers, but not enough for them to abandon the defence as useless. He did not feel the assault on his finger, since it has no nerves that would detect pain. The whole finger, with its attached ants, goes into his mouth and is then withdrawn slowly, his tiny teeth scraping the insects from the skin. He swallows the ants, a number of which saw the danger in time and abandoned the finger, and are now crawling over his face. They do not trouble him: he can close off his nostrils and his eyes as they come close, and when his mouth is empty he wipes them from his face with the back of his hand and his long tongue.
He turns back slowly to the nest. With the huge claws on two of his fingers (those that were once called the thumb and index finger) he rips the covering off another part of the nest. Patiently he waits for the defenders to swarm up once more, and inserts his long middle finger again into one of the passages.
He is rather a solitary creature. The ants that he eats are highly nutritious, but it takes a great deal of them to make a meal so a single anthill could hardly sustain two antmen. His movements are also very slow and deliberate. He has no natural enemies, although he evolved at the same time as many of his cousins developed into hunting, flesh-eating types. His defence is in the food that he eats. He is immune to the poisons of the formic acid in the ants’ stings, but his body does not break them down; instead it redeposits them in his tissues, making his flesh unpalatable to any meat-eater. His fine black fur has a glaring white stripe across the back and down the legs. Any meat-eater that sees this striking pattern realizes that its owner is not good to eat.
Once upon a time, millions of years ago, there were other animals that pursued this very way of life. They inhabited all the continents, but each place had its own unrelated species. The anteaters of old South America were no kin to the aardvarks of Africa, and they only looked like one another because they pursued the same lifestyle. They possessed similar bodily features that had the same functions – long sticky tongues, narrow mouths, heavy claws – but evolved independently. Likewise neither of these animals was related to the marsupial numbat of Australia, an ant-eating animal of similar appearance. The whole concept of the same shapes cropping up in unrelated animals that lived in the same way was what the zoologists once termed ‘convergent evolution’.
Now all the anteaters, the aardvarks and the numbats have been extinct for 3 million years, yet their food has remained: there are still ants and termites all over the world. It is the way of nature that if a food supply exists then a creature will evolve to exploit it, usually emerging from a group of fairly unspecialized animals. In this case, the most unspecialized animals around were the humans genetically engineered to live on the wide range of food of the temperate woodlands. Consequently, over the last few million years these omnivores have developed, under the natural influences of selection, to become specialized feeders in the various different environments present. One group has developed into the anteaters.

His long strides take him swiftly across the scorching wadi and into the sharp blackness of the rock shadow at the other side. There he rests, looking out at the dazzling sand with his polarized dark-lensed eyes.

3 MILLION YEARS HENCE DESERT-RUNNER Harenanthropus longipis The fatty deposit across his shoulders is depleted but not yet exhausted. Bat-like ears radiate waste heat. Although similar in appearance to a hiver, the desert-runner’s ancestors originated in the temperate woodland. Through convergent evolution, the desert-runners are beginning to adopt the shape that was designed into the plains-dwellers all those millions of years before. However, the runners are carnivorous, unlike the hivers.

DESERT-RUNNERS

The sun burns blisteringly down, baking all the landscape and beating up from the sharp naked rocks and the pockets of dry dust that lie between. All is yellow and grey, and no plants are to be seen anywhere. In a wadi (a gushing torrent in the distant rainy season but now a parched gully) the sand lies deep and barren. The only sound is the distant hum of the wind, and the constant hiss of sand as it is blasted against the rocks and swirled about in the hollows. The monotony is broken by a faint scrabbling sound as a brown lizard scuttles amongst the loose stones and vanishes into their shadows, then all is stillness again. Few things venture out in the killing heat and dryness of the desert noon.
Yet in the distance something large is moving, and moving quite swiftly too. Its legs and arms are long and thin, and its head seems inordinately large, covered in white hair and surmounted by a pair of huge ears. It looks like one of the hivers, but it is travelling and hunting alone. It is, in fact, one of the hunters that has evolved and adapted to the harsh conditions of the desert – a desert-runner.
His long strides take him swiftly across the scorching wadi and into the sharp blackness of the rock shadow at the other side. There he rests, looking out at the dazzling sand with his polarized dark-lensed eyes. He sees things only in black and white, as the rod cells of his eye have developed at the expense of the cones, increasing his distant and night vision. He has just travelled many miles over the rocks and dust and will now rest a while to cool his body. Despite his adaptations to life in the desert he must still guard against the killing heat of the sun and the dryness of the wind. The fatty hump behind his neck is almost depleted, the store of fat having been turned into energy. Nevertheless, he knows that he will soon reach a fertile spot where his stores can be replenished.
The hump is only one adaptation to the dry heat of the desert. Greatly-enhanced kidneys distill and use every drop of water that enters the body. Waste heat is radiated from the body by means of the great bat-like ears, acting as heat-exchangers, and the long thin legs that give a very large surface area for the mass of the body. These are necessary, since no sweat exudes from the skin – all water is saved. The ears, eyes and nostrils have thick folds of skin that can close them off and keep out sand and dust when the winds get too high.
The sun has now passed its zenith, and the black desert shadows are lengthening. Rested now, the desert-runner creeps out to continue his journey. The first part of his travel was over sand, where he used his long legs, with their light elongated foot bones powered by the concentration of muscles in the thigh. Now his way takes him over naked rock, so his passage is slower, using his long toes and gripping fingers to find purchase in the cracks and joints of the hot crumbly stone. As the sun descends into the dusty haze of evening, his goal is in sight.
The hive looks like one of the rocky hills that surround it. Its vast roof slabs look just like the horizontal strata of the surrounding rocks, and the black entrances just like the wind-blasted caves of the dusty crags. Just as desert-living humans evolved along the lines of the desert animals, the desert cities of the hivers developed along the lines of their habitats. The vast thick roofs paralleled the flat stones that absorbed the heat of the sun and protected the creatures that existed underneath. The tunnels burrowed deep into the Earth, cool by day and insulated from the bitter cold of the night. Water was gathered by vast dew-traps in the surrounding sands, and food was gathered from wide areas and brought swiftly to the cities by the foraging teams.
The desert-runner will spend some time here. The hivers eat only plants, while he eats only animals, so they will not conflict with each other. The moisture that is generated in and around a hive and the food stored within attract all kinds of insects, reptiles and small mammals which the desert-runner will hunt, while the hivers, with completely different nutritional requirements, will tolerate his presence.

SLOTHMEN AND SPIKETOOTHS

A huge mound of fur-covered flesh, an indistinct lump in the luxuriant undergrowth, pushes its way through the bracken and brambles. It makes contented burbling noises to itself as it goes. Insects, small mammals and birds burst from cover to get out of the path of the great creature as it crunches slowly through the greenery. It is quite harmless, but its immense weight causes a great deal of damage as it passes.
It stops by a tree and looks slowly upwards. There are appetizing fresh green leaves up there. Using its fore-limbs against the trunk, it slowly pulls itself upright. Now it begins to look more like a human being, to be precise the tundra-dwelling human being, that was its distant ancestor.
From the bushes beyond, a number of other creatures stop feeding and move out of the way. They are also descendants of the tundra dwellers and have grown large, but not nearly as big as this great creature. Nor have they changed much in the last million years or so: they still produce the huge quantities of superfluous fat, and are still infested by the tiny parasites that live on the excess.

In carnivores it is normally the pointed canines that develop as killing teeth. The spiketooth, however, has a jaw that drops down to allow the teeth to be used efficiently, and it is the upper incisors that have become the weapon.	3 MILLION YEARS HENCE THE SPIKETOOTH Acudens ferox Large plant-eating animals inspire the evolution of meat-eating creatures to feed on them. Acudens ferox is heavier than other hunting species. It can afford to be, needing neither speed nor stealth to hunt the slothmen. It has slashing front teeth able to penetrate the thick fur and tough skin of its prey.

Although much larger than the tundra-dweller, the slothman retains the proportions of the species from which it evolved. The fat layers are still in place and heavy claws are needed to pull the huge body upright.

3 MILLION YEARS HENCE SLOTHMEN Giganthropus arbrofagus Temperate climates encourage the evolution of large creatures, bulk retains body heat and large leaf-eaters can find enough nourishment to support their mass. By a process of convergent evolution the slothman is now similar to the giant ground sloth of South America from pre-human times. But two factors were needed to allow the tundra-dwellers to evolve into slothmen – plentiful food and no enemies. Sustenance is still there but now they face a newly-evolving predator.

Tree sloth form, parasite host with parasite and spiketooth. All come from the same basic stock.

The tundra-dwellers that adapted to woodland life did so very successfully. Their heavy bodies were well supplied by the voluminous plant life of the habitat. Evolution had produced the right shapes by trial and error; man copied them, and then evolution took the copies and modified them further. If these big creatures have a parallel – a convergence – with any creature from the fossil past it would be with the giant ground sloths of ancient South America. Like these, firstly, they developed successfully, even with their great bulk and sluggish habits, because there was the food supply to sustain them and they had no natural enemies; secondly, they spend most of their time on all fours, so that their bulk can be well supported, but they can also rise to their hind legs to feed from tall trees; and, thirdly, they have become about three times as tall, and so about ten times as heavy, as their ancient ancestors.
Like the giant ground sloths, too, they are succumbing to a newly-evolving predator.
The hunters have been evolving into many specialized types, each one hunting a specific type of prey: some hunt birds, some hunt small mammals, some hunt fish. One, however, has evolved to hunt the descendants of the big tundra-dwellers. 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 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 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.
The slothman munches placidly at the leaves and twigs, unaware of the approaching danger. Away below him in the undergrowth the parasitehosts have already left, their dim wits sensing the approach of a 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 spreadeagled on his back with his enemy crushed to death beneath him. However, this makes him vulnerable to the 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.

CONTENTS