A human engineered to live on open grasslands needs the adaptations of a grass-eating nonhuman mammal. For the plains-dweller these include massive teeth that are replaced if they wear out chewing tough silica-rich grasses and, more importantly, a specialized stomach within the bloated abdomen containing engineered bacteria that can break down cellulose (a substance not normally digestible by the human frame). Cutting edges on the hands help to scythe the thick grass while the long legs enable the creature to move swiftly over the open landscape.
Gram stands shivering on the dusty plain, not shivering with cold but with apprehension. The spiky grass round about is familiar enough; he has been brought up on a diet of it since he was born, ten years ago. During that ten years, though, all the grass he knew had been grown in the habitat module. He was brought up and cosseted by Family, a group of creatures that saw to his every need and trained him for life outside.
Only in the last two years did he realize that he was not like the people of Family. He was not encased in metallic outer skins, he did not glide along the floor and cables and tubes did not spiral out of him, connecting him to glass and plastic devices - and his face! The faces were the only parts of Family that he could see directly, and his was nothing like theirs.
Now he is on his own and he knows it. Family cannot live out here, on the grassy plains, so they are all congregated together in the flying machine behind him. All this landscape before him is to be his.
Delicately he steps away from the flying module. Beneath his tapering foot the fibrous soil feels strange - not quite like the soil in the habitat. He can feel the eyes of Family on him, as he wades into the sharp waving grass, scanning him closely, as he knew they would. Not only are they watching him directly, but the little instruments that are strapped to various parts of his body are sending back signals, telling them how he is performing.He knows what he is supposed to do; he has been trained for long enough. As in the habitat, he reaches with his long arm and long hand and grasps a bunch of grass. The calloused cutting edge of his hand shears through the stems and leaves with a twisting motion, and he thrusts the bunch into his mouth and begins chewing. His big teeth grind into the stringy plant material, crushing it to a pulp and disrupting the fibers. He can feel the toughness, and knows that the wear on his teeth will be immense. He also knows that once a tooth is worn out another one will grow to replace it, and this will happen for the rest of his life, another thing that makes him different from the members of Family. He swallows the wad of grass, and down it tumbles into his voluminous stomach where it is met by specially-engineered bacteria that complete the digestion.
He scythes off another handful and eats it. This is working all right, he thinks, and hopes that Family think so too. He looks up to the horizon, a vast distance away. So this is to be his new home.
With sudden joy, Gram bounds away towards a clump of low bushes. He could be happy here, no matter what Family think. Suddenly he does not care what Family think: this is not their world - it is his.
Then in a first and final gesture of defiance he rips off the instruments that are strapped to his body and flings them away into the dusty grass.
By 1,000 years (the 30th Century)
The hazy grassland stretches away, green and yellow, to infinity, and a herd of grazing plains-dwellers moves gracefully across it. There are about 20 of them, the adults moving along on the outside of the group, with the youngsters in the center. This is some sort of instinctive arrangement, serving no real purpose, as there are no dangerous animals to defend against. They have no real speech, these creatures, since all their needs are simple and amply met. Food grows all around, there are no enemies, and they have the companionship of their own kind.
Towering clouds are building up overhead. The plains-dwellers are aware, but only dimly, that conditions are changing from year to year. There seems to be more rain than there used to be, but this is no problem. It only means that the grass (their food) grows more prolifically. It also means that new types of plants are beginning to grow: saplings that will develop into bushes and trees. Still, there will be plenty of grass left for them.
As they move slowly through the waving leaves and stems, they become aware of a distant humming noise. Looking up, their leader sees an oval spiky shape floating above the horizon away to one side. Such things go over now and again, but they have no effect on the plains-dwellers, who barely notice them.
However, this one is different. It is not pursuing its usual straight unwavering course but seems to be tilting to one side and descending in a very irregular manner. This is unusual enough for the herd's leader to stop and look at it, as does the rest of the herd.
The shape wobbles, and finally drops into the plain some distance away. Immediately it is engulfed in a white flash that fades into a billowing red and black ball, rising and spreading. A little time later, the explosion is heard as the sound sweeps across the open countryside, and the infants and parents alike start in alarm, but feel no fear. The leader, however, does see the danger. The burst of red has spread as a fire across the landscape and it is coming towards them.
He has seen this before (fires are commonplace on the grasslands), and is knowledgeable enough not to run away from it when it is sweeping towards the herd. He assesses the direction of the wind and moves his herd along at right-angles to it, so that the fire will eventually travel by them.
He need not have troubled. The clouds that have been building up throughout the afternoon now open, and a curtain of torrential rain appears between the herd and the fire drifting over them and soaking them instantly. By the time the downpour has passed nothing is left of the fire but a steaming black smudge on the distant landscape.
The erstwhile flying shape is steaming and black as well, but the plains-dwellers ignore it and continue their journey. It has nothing to do with them.
By 2,000 years (the 40th Century)
Larn strides across the grassy plains at the head of his tribe. Not far off he sees a thicket of bushes and thorn trees that he does not trust. Another group of plains-dwellers met danger at such a clump not long ago when a pack of some new kind of animal burst from within, taking them by surprise, and killing three of their number before the rest could escape.
Larn had thought about this incident for some time, and it made him uneasy. He had noticed that the other animals, the little animals of the grassy plains, had their enemies. There was always strife and death in the undergrowth, but not for the plains-dwellers. He had always assumed that this was because the plains-dwellers were the largest creatures around. They had no enemies. The plains were theirs, and theirs alone.
As a result the populations of plains-dwellers are growing and growing. As a lad, Larn could remember travelling with his tribe for days on end, and not meeting any others. Now other tribes are seen daily, and each one seems to be becoming bigger and bigger.
In one part of his mind Larn feels pride at this; his people are the masters of this landscape, and they should spread and fill it. Another, quieter part of him rebels, however. If there are more and more plains-dwellers as time goes by, will there always be enough grass to feed them all?
He turns and looks back at this tribe, and counts them: ten females, all his mates; five young males, that have latched on from other tribes; six of his children, almost adult; twelve of his juvenile children; and two old females, members of the original tribes of two of his mates. He took responsibility for these when he chose the females from those tribes.
It was the two old females that kept the tribe moving slowly. They all had the long legs with muscular thighs and tapering feet that allowed them to run quickly. However, they rarely had the chance to do so. Sure enough the youngsters would run about, very actively, but the older members had to remain close to one another, and so moved at a slow and sedate pace. It was so long since Larn had run that he thought he might have forgotten how (not that there was any real need for speed).
The children enjoy it, though, he muses as he watches them scamper and gambol through the long yellow grasses of the open plain.
Suddenly there is a hideous howling and baying noise from the suspicious thicket. He had let his mind wander and had forgotten the danger that the other tribe had faced.
With a yelled warning he brings the whole tribe together, but the youngsters are scattered too far. A crashing noise issues from the thicket and about ten indistinct forms burst out and streak through the grass. One of his children is brought down with a crash and a flurry of dust and broken plant stems.
Without thinking, for the moment, of his loss and grief he runs about, rounding up the others, trying to get them to crowd together, instinctively knowing that a large group is stronger.
He is dimly aware that the others are doing their best as well. The young males have rushed together in defense of the younger females and the juveniles. They stand shoulder to shoulder while the others sprint into the distance.
Then he comes across a horrible sight. One of the old females lies dead, her throat torn. Over her stands a hideous and misshapen, yet strangely familiar, figure. It is almost like a plains-dweller, but it does not have the long legs, its belly is not so round and its teeth are not so massive. These must be the strange new creatures that have moved onto the plains.
It is staring at him, the female's blood dribbling down its chin. Its eyes are grey and steady, it bares its teeth, and then it pounces. As a reflex, Larn brings down the cutting edge of his left hand, thrusting it into the soft flesh of the creature's neck, killing it instantly. So they are not invulnerable, Larn thinks with triumph; we can kill them.
Then another dark shape crashes into his back, sinking its teeth into his neck, and as he falls into the dust he realizes his mistake. He should have run, like the young females. These creatures have cunning and hunting skill, but they do not have speed.
If plains-dwellers are to continue to be the masters of the plains, they must learn to keep clear of these monsters. Speed is going to be their saving, but it is too late for him.
By 5,000 years (the 70th Century)
Plenty of fruit is available in the tropical treetops, so there is nothing to worry about here. Like the extinct monkeys and nonhuman apes, the tropical tree-dweller (he has not the wit to consider himself as an individual let alone as a being with a name) climbs the vertical trunk through the luminous green of the leafy canopy, and scampers four-footed along a broad bough, forking onto a thinner branch and finally along slender waving twigs to reach the point where the bunches of fruit dangle invitingly. Hanging upside-down now, he reaches outwards with his narrow prehensile fingers and delicately pries the bunch free from its stalk. Some fruits drop off, falling with a fading plop, plop through the layers of leaves and twigs below, away to the forest depths. These are immediately forgotten, as he has secured enough for his needs.
This is his whole life. It is of no relevance to him that the equatorial tropical forest belt of Earth is narrower now than it has been at any time within the last million years, that the cooler climates have been encroaching from the north and the south, bringing their windy grasslands and barren deserts with them. The only significance to him is the fact that when he is in the gloom of the lower branches he often sees, on the forest floor, bands of strange creatures moving purposefully in a particular direction. Since he rarely ventures down onto the floor anyway, he just ignores them.
The lost fruits, dented and bruised by their fall through the branches, at last thump softly down into the decaying plant matter of the forest soil. A group of gaunt long-legged plains-dwellers, uneasy and out of place in this strange environment, but driven from their grasslands by increasing cold and ravening packs of wild creatures, starts at the sudden noise. Then, when they see the fruit that has fallen, all four of them pounce upon it, scratching and tearing at one another in their attempts to reach it first.
This drama is completely irrelevant to the tropical tree-dweller. There is always plenty to eat up in the sunny heights and he can leave the lower shades to those strange beings.
It is in the far north and the far south that the ice age is causing its havoc. Fluctuating ice sheets and glaciers, together with unstable weather patterns, are forcing highland middle-latitude inhabitants to resort to drastic measures and changes in lifestyle just in order to continue living, and encouraging genetic changes in body and mind that could not have endured if the environment had remained constant and unchanging. Here, in the tropical forest, however, things have not altered for thousands of years. The tropical tree-dwellers have a constant supply of fruit and insects in their leafy canopies, so there is no need for them to move to new areas or to change in any way.
By 10,000 years (the 120th Century)
Rain falls. It now falls for long periods and the grasslands are losing their character. Instead of one short rainy season in the year followed by long periods of dryness, there is now more rain all year round.
The grasses thrived under the old conditions. Their tops were shriveled off by the Sun, grazed away by animals and burned by periodic bushfires, but they survived because of their protected underground stems, and grew again from ground level. Few trees or bushes flourished under these conditions, but the plains-dwellers also did well here. Their exclusive diet of grass meant that they could live here where no other large creature lived. They could spend the dry seasons in the thorn thickets that bordered the grasslands and separated them from the humid tropical forests of the Equator, and they migrated out over the grasslands proper during the wet season, feeding as they went. Other large creatures could not cope with this existence.
Now, with the more frequent rains, the thorn forest is spreading over the plains, and trees are growing where once there was only grass. With the new conditions different creatures, ones that hunt meat for food, are creeping out of the tropical forests. More and more often the plains-dwellers have to take themselves off out of danger. With their immensely long legs they can quickly outpace any enemy, but this is becoming more and more frequent. It is wasting a great deal of energy and eroding valuable eating time.
Over the past few thousand years the plains-dwellers have faced problems like this, many times. Sometimes, when it seemed as if the grasslands were going to disappear, herds of them went through the thorn thickets and into the depths of the great rainforests, in the hope of finding new pasture. None ever returned. Few went the other way, where the grasses became shorter and sparser, where food became harder and harder to find, and where even small creatures became rarer and more difficult to see. The grasses in this direction eventually gave way to rocky and sandy wastes, where the rainy season was even shorter and less reliable than it was on the plains. In these previous times of crisis, however, the problem was never long-lived: the grasslands established themselves once more.
Now, with the increased rainfall, the grasses as the plains-dwellers knew them are becoming obliterated by thorn forest. The only reliable expanses of grass seem now to be found in the once-desert areas, and even these un-beckoning wastes are changing because of the increased moisture. Grasses and other low plants are finding purchase in the harsh rocky soil that once they found uninhabitable. Perhaps in this direction lies the future home of the lanky plains-dwellers.
By 50,000 years (the 520th Century)
After 40,000 years in which the climate has been relatively settled, in which seasonal rains have been enough to sustain sufficient vegetation for the herds of plain-dwellers, the food chain is becoming unstable once more. Over the years the plains-dwellers have changed, now being the communal plains-dwellers.