Evolution

Further north still, coniferous forests grew, evergreen trees whose spiky leaves were always ready to take advantage of the sun’s thin ration of light. Browsing animals lived on the young twigs and needles in the summer, and on bark, mosses, and lichen the rest of the year. Many of them were goats. Especially common were the hadrosaur-like duckbill forms. Their predators included the ubiquitous mice and rats — but there were also carnivorous squirrels and huge birds of prey that seemed to be trying to emulate the pterosaurs of the oxygen-rich Cretaceous skies.

On the northern fringes of the continents a belt of tundra had formed. Here the descendants of pigs and goats cropped the thin foliage of summer, and huddled together to endure the winter. Like the vanished mammoths, some of these creatures had grown huge, the better to retain their warmth, until they were great round boulders of flesh. On the tundra the predatory rats had grown their incisors into huge stabbing instruments, the better to penetrate those thick layers of fur and fat. They looked something like the saber-toothed cats of earlier times. There were even populations of migrant bats who had learned to subsist on the vast swarms of insects that formed during the brief tundra spring.

None of these new species, of course, would ever bear a human name.

There was one key difference in this latest recovery of life, compared to its last great trauma after Chicxulub. The rodents had not evolved until some ten million years after the comet impact. This time, though, when the days of recovery came, the rodents were everywhere.

Rodents were formidable competitors. They were born with incisors ready to gnaw. These great teeth were deep-rooted in powerful jaws: Once rats had been able to gnaw through concrete. Their teeth enabled them to eat food hard and tough enough to be inaccessible to other mammals. But the rodents’ ability to proliferate and adapt was more fundamental. Rodents lived fast and bred young. Even among the giant species like the rat-cheetahs, females had short gestation times and produced large litters. Many of those kits would die, but every one of those dead babies was raw material for the relentless processes of adaptation and selection.

Given empty spaces to fill, the rodents evolved quickly. In the grand recovery after the disappearance of man, the rodents had been the big wi

All this had left little room for the descendants of humans.

Crowded out by increasingly ferocious and confident rodents, the posthumans had given up the strategy — superior intelligence — that had brought them such success, and disaster. They had retreated, seeking sheltering niches and passive strategies. Some had become small, timid, fast-breeding ru

The elephantine humans had tried another approach: becoming so huge they were protected simply by their immense size. But this had not been entirely successful. You could tell that from the design of their gazellelike back legs. Elephants could not have run very quickly, but they had not needed to; in their day no predator existed that could have taken on a full-grown proboscidean. Facing the power of the rodent predator families, the elephantine posthumans had had to retain the power to flee.

But even this had not been enough.

The mouse-raptors were social creatures. Their sociability was deep rooted, reaching back to the colony structures of the marmots and prairie dogs, which had lived in hierarchical “towns” of millions of animals. They scouted, seeking prey or water. They kept sentry watch for each other. They hunted cooperatively. They communicated: The adults called to each other continually with cries, squeals, and the drummings of those powerful tails that sent long-range shudderings through the ground.

For the posthumans, the sociability of these raptors made them simply too effective as predators. The numbers of the big herbivores had steadily dwindled.

But that was bad for the raptors too. And so, in time, the elephantines and the mouse-raptors had developed a kind of symbiosis. The mouse-raptors learned to protect the herds of slow-witted elephantines. Their presence would deter other predators. By their behavior and signals they could warn the elephantines of other dangers, such as fires. They could even guide them to water and good grazing.

All the raptors asked for in return was to take their share of meat.

The elephantines passively accepted all this. They had no choice. And over enough time, selection had shaped the elephantines to fit the new conditions. If the raptors chased away the other predators for you, why be fast? And if they did your thinking for you, why be smart?

As their bodies had bulked up, the people’s minds had shriveled, casting off the burden of thought. They were like domesticated chickens, whose brains had been sacrificed to make longer guts and a more effective digestive system. It wasn’t so bad when you got used to it. Under the mouse-raptors’ unthinking guidance their numbers had even increased. It wasn’t so bad, so long as you turned away when your mother or your sister or your child was taken.

Not such a bad life, to be farmed by rodents.

The light began to leak out of the sky. So Remembrance found another stand of acacias, and crawled gingerly into the branches of the tallest tree. It would have to do. At least she was off the ground.

As the light died, so the stars appeared — but it was a crowded sky.

The sun, in its endless swimming around the Galaxy, was now passing through a wisp of interstellar dust and gas, a wisp mighty enough to span light years. Human astronomers had seen this coming. It was the vanguard of a mighty bubble blown in the gas by an ancient supernova explosion, and at its heart was a region where stars were being built. And so the new sky was spectacular, full of bright, hot new stars.

But there was nobody on Earth who might understand any of this. Remembrance spent a sleepless night listening to the squeals, thrums, and roars of predators, while u

III

The first few hundred asteroids the astronomers discovered had orbited in their orderly belt between Mars and Jupiter, comfortably far from Earth. These space rocks had been a curiosity, nothing but a theoretical challenge to students of the origins of the solar system.

It had been quite a shock when Eros was discovered.

Eros was found to sail within Mars’ orbit — in fact at its nearest to Earth, it came to within less than a quarter of the closest approach of Mars and Earth. Later, more asteroids were found that actually crossed the orbit of Earth, making them candidates for eventual collision with the planet.

Eros, that first rogue, was never forgotten. As long as people cared about such things, the asteroid became a kind of mute hero among its kind, better known than any other.

At the begi

But under the circumstances the asteroid’s name could not have been more inappropriate.