It had long been believed that Eros, with its eccentric orbit taking it endlessly across the orbit of Mars, was in no danger of collision with the Earth. In fact, it seemed much more likely to collide with Mars itself.

But Mars was gone.

And, over long enough periods, as it responded to the subtle tweaks of the planets’ gravitational pulls, the spinning of the sun, and its own intricate, intrinsic dynamic instabilities, the orbit of the asteroid evolved. One million years after the demise of mankind, Eros had sailed close to Earth — very close, close enough to be visible to a naked eye, had anyone been looking.

Some twenty-nine million years after that, it was coming closer still.

Stuck in her acacia tree, Remembrance itched. She scrabbled at her fur, hunting for the ticks and bugs that loved to feast on your blood, or lay their irritating eggs under your skin. But there were places she couldn’t reach, like the small of her back, and naturally the bugs congregated there.

It was a painful reminder of how alone she was. As language had declined, the habit of grooming had returned to serve its old function of social cement. (It had never really gone away anyhow.) But Remembrance had had no grooming since before her last sleep, when she had huddled with her mother in her nest.

Hot, itchy, hungry, thirsty, lonely, Remembrance waited in her acacia stand until the sun had once more climbed high in the sky.

Then, at last, she clambered down.

The elephant people and their rodent keepers had gone. Across the empty, dust-strewn grassland, little stirred. The silence was as heavy as the heat. Through dusty haze, she could see a dark smudge to the east that might have been a herd of elephantine pigs or goats, or even hominids. To the west there was a little pocket of motion, a glimpse of brown fur. Perhaps it was a predatory rat with her kits.

To the north, where the mountains loomed purple, she could see that splash of dull greenery. She still had no other impulse than to make straight for the forest’s alluring comfort.

Naked, her hands empty, she set off across the plain, slumping every now and again to let her knuckles carry some of her weight. She was a tiny figure crossing a huge, bare landscape, accompanied by nothing but the shadow under her feet.

She found no water, nothing to eat save handfuls of sparse grass. As she lumbered on, she was increasingly distracted by thirst. The silence settled still more heavily. Soon it was as if there were nothing in her life but this walk, as if her memories of a life of green and family were as meaningless as her dreams of falling.

She found herself walking down a shallow slope into a broad bowl of land kilometers across. Before this great depression she hesitated.

A valley was incised across the heart of the bowl — a valley once cut by a river — but even from here she could see that the valley was dry. The vegetation was different from that in the plain beyond. There were no trees here, few shrubs, and only occasional splashes of grass green. Instead, there was a broad mass of rustling violet leaves.

To distrust anything new was a good rule of thumb. But this great bowl lay right across her path, cutting her off from her forested slope, still far away. She could see there were no animals here, no herbivores, no prowling predators.

So she set off, wary, watchful.

The belt of violet purple turned out to be flowers growing in thick clumps, some tall enough to reach her waist, amid spindly, pale blades of grass. She walked on until she was surrounded by the clamoring purple. But there was still no water.

Once there had been a city here. Even now, so long after the city’s fall, the soil was so polluted that only metal-tolerant plants could survive here — such as the violet-petaled copper flowers that waved over the soil.

Eventually the purple flowers grew thinner. At the very heart of this strange place she came to the river’s shallow bank. The channel was dry, filled only with drifting dust: Ancient geological shifts had long since diverted away the water that had cut this channel. Remembrance clambered down the eroded banks and tried digging into the dusty substrate, but there was no moisture to be had here either.

As she climbed out of the shallow bowl it wasn’t long before Remembrance came to another obstacle.

There were trees here — twisted, stubborn-looking trees — and termite mounds, and broad, low ant colonies, scattered like statues over an otherwise dry and lifeless plain. It was not a forest — it wasn’t crowded enough for that — it was more like an orchard, with the individual trees well spaced, surrounded by their little gardens of termite mounds and ant nests. These were borametz trees, the new kind. The orchard stirred deep, instinctive feelings of unease in Remembrance. Something inside her knew that this was not the kind of landscape within which hominids had evolved.

But this stark landscape of trees and termites was another barrier across her path, stretching to left and right as far as she could see. And, as the sun began its swift descent to the horizon, she was growing ever thirstier and hungrier.

Tentatively she walked forward.

Something tickled her foot. She yelped and jumped back.

She had disturbed a double line of ants. They were walking to and from a nest — she could see the holes in the ground — along a trail that led to the broad roots of one of the trees. She crouched down and began to swipe at the ants with her cupped palms. She scooped up more dust than insects, but she managed to cram a few of the ants into her mouth and crunched the gritty goodies. More ants clambered around her feet, intent on their task, oblivious to the sudden fate of their fellows.

The tree that was the destination of these ants was unspectacular: It was low and squat, with a thick, gnarled trunk, branches coated with small round leaves, and broad roots that spread across the ground before plunging into it like digging fingers.

Remembrance walked up and inspected the borametz tree skeptically. No fruit clung to its low branches. There were what looked like hard-shelled nuts growing in clusters from the base of the trunk, close to the roots of the tree. But there were very few of the nuts, less than a dozen. When she tried to prize them off, she found they were bound too strongly for her fingers, and the shells were too tough for her teeth. She pulled off a few leaves and chewed them experimentally. They were bitter and dry.

She gave up, dropping the last of the leaves, and made her way to a more promising food source. The nearest termite mound was as tall as she was, a great rough cone of hardened mud. She went back to the tree to look for a twig. She’d done a little termite-fishing in the past, though she was not as good as Capo had been. She was not even as expert as chimps had been in the age of man. But she might be able to get enough of the squirming goodies to allay her hunger -

She glimpsed a lunging head, incisors like blades scything through the air. Rat. She leapt upward, reaching for the branches of the borametz. The branches were narrow, tangled, and hard to grasp. But she forced her way into them, for they were all the cover she had.

It was a mouse-raptor: one of the colony that had herded the posthuman elephantines to the lake. Squealing its high-pitched rage the raptor reared up on its huge hind legs, slashed at the lower foliage with its blood-stained incisors, and rammed the borametz’s trunk with its massive skull.

Young, restless, inquisitive, the raptor had never hunted this kind of animal. Tracking Remembrance this far had been a good game. But now the raptor had played enough, and had become curious about how she would taste.

The borametz’s gnarled bark scraped Remembrance’s skin painfully. The raptor couldn’t reach up into the branches. But under the battering of its huge head the whole tree shook, and Remembrance knew she would soon fall, like a piece of fruit. Growing frantic, she squirmed through the branches, trying to get further away from the raptor.