Isolated from mainland evolution, island-dwelling temperate woodland-dwellers have developed a high-protein diet and reduced in size. Now, as a new species, the islanders return to the mainland, where the tundra-dwellers have adapted as a leaf-eating forest people.

The islander, Homo nanus, (also known as the island voyager or the island person) is a small-sized human from 50,000 years (the 520th Century), descended from the temperate woodland-dweller (those of the Island Clan), that has a mostly carnivorous diet and is downsized due to insular dwarfism, from Man After Man: An Anthropology of the Future.

The icecaps and glaciers are in full retreat now, melting away to the poles and withdrawing up the mountains. The climate is becoming warmer, changing the conditions not only in the arid tropics but over every climatic and vegetation zone of every continent. The retreat of the ice changes not only the climate but the geography as well. Meltwater, gushing from the rounded ice-tunnels and widening crevasses, floods into intertwined rivers that wash across the gravel plains and empty into the ocean, causing sea levels to rise over the whole world. In some places, however, once the unimaginable weight of ice is removed, the land surface rebounds like a slow spring, lifting it above its former level, and causing the sea level to fall back. Then there is the volcanic activity, mostly at the edges of continents and in strings of islands arcing across the oceans, producing new lands and destroying others.

All in all, it is a time of appearing and disappearing islands, of continents joined by land bridges which then submerge, and of lowlands engulfed by the seas and shallow seas that become plains bounded by the banked shingle and sand of former beaches.

The islanders have always found it easy to move from island to island, floating upon the trunks of trees wrenched from their forest stands, or on rafts built from the stems of smaller trees lashed together by vines and creepers. They have used vessels like this to support them while they dived for fish in the straits of the archipelagos. Now, however, this activity is dangerous. The changing weather patterns are producing unfamiliar winds and frequent storms, and changing the sea currents between the islands. More than one raft of island voyagers has disappeared in recent memory.

One has found itself on the beach of the mainland - a region the existence of which was only guessed at by the island people. After the rigors of the accidental voyage the new country may be either an unending source of plenty to the small hungry group of five islanders or deceptively barren. The islanders' original digestive systems allowed them to eat almost anything, but millennia of island-dwelling on crags and slopes that supported few nutritious plants have changed all that. Now they can only subsist on the high-protein diet that they gained from birds and their eggs, and the fish and shellfish of the sea. No birds seem to nest on accessible crags here, and the shingle beach gives little purchase for shellfish.

There may also be enemies. Some huge figures are moving about down the beach. In build, they are somewhat like the islanders, but they are more than twice their size, and very slow-moving. There are about ten of them.

The islanders do not know these creatures for forms of the tundra-dwellers. The tundra is dwindling away now, but for many thousands of years groups of its inhabitants have been spreading southwards, changing their diet and adapting their lifestyle as they went, through the coniferous forests and into the zone of deciduous woodlands. Because they have been forced to change all the time they have a better chance of survival than the groups of their relatives who remain static on the tundra. Now they are massive leaf-eating forest-dwellers (dim of wit but quite adaptable to changing conditions). However, they do retain the thick deposits of fat that are now superfluous to their purposes, and indeed could be disadvantageous to them in the hot times that may come. Nor do the islanders realize that the difference in size between them comes from the fact that the tundra-dwellers were created large by the ancient genetic engineers as a precaution against heat loss in the cold north, and the islanders have become small over the past few thousand years as an evolutionary adaptation to their limited resources.

The islanders have no fear of the great creatures. They see them, as they see all living things that are not their own kind, as food. Nimbly they sprint down the beach towards them. Alerted by the crunching and rattling of the shingle under the tiny feet, the big tundra-dwellers see the little figures coming, and dimly perceive that there is some kind of danger. They turn to lope back into the forest, but they are too slow.

Two of them are caught by the legs and brought down with a crash. One is knocked senseless by the impact, the other is killed by quick bites to the neck and face. The killing is not easy. The hide is thick and covered with a woolly pelt, and there are deep layers of fat beneath.

It is the blood that the islanders want, and they gorge themselves on that of the slain tundra-dweller, balancing their feast with the carbohydrates from the fatty deposits. The corpse carries more food than the group of islanders can eat at one time, and having satisfied themselves they leave the remains to the white seabirds that have gathered on the shingle to watch the feast. This seems to the islanders to be a waste of food.

Together they pull the corpse of the second tundra-dweller up the shingle and into the shade of the forest, before it begins to decay in the Sun or is eaten by scavengers. If only there were some way of keeping such a big creature alive while feeding from it. Then there would not be so much waste.

The massive form stirs; it is not dead at all, merely stunned. The islanders seize it by the limbs and pin it to the ground. They are not letting this one get away, nor are they going to let it die and rot before they need the food again.

By 1 million years (the 10020th Century)

The islanders have evolved parasitic feeding habits that rely on the tundra-dweller's metabolic need to produce surplus fat. They also do not understand the harvesting aquatics.

There is a massive compound and basic tundra-dweller, bloated and misshapen, lumbering through the forest with four or five spindly little islanders attached to it, embedded in it, seeming to live off its flesh. The tundra-dwellers cause no trouble to the land-visiting aquatics; in fact, they sometimes blunder out into harvesting parties where they are particularly vulnerable. In the open they are easily brought down and the moving reef of flesh can be killed by blows from an agile aquatic or drowned by being dragged within a membrane. The small attached islanders (tiny wizened bodies with spindly crablike legs and enormous mouths) become strangely pathetic without their mounts and scuttle clumsily for cover.

By 2 million years (the 20020th Century)

They evolve into the parasites and the tundra-dwellers they parasitically live off of become the hosts.

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