At last the mother took over. As her great jaw closed around his skull — as he felt a prickle of biting teeth around his scalp, like a crown of thorns — the last thing Elephant heard was that remote purring growl.

When the morning came, everyone knew that Elephant had been taken.

Capo peered with fascination at the scuffed, hair-strewn gravel patch where Elephant had briefly struggled, at the line of bloody paw marks, already dried to brown, that led away into the distance. He felt a vague regret at the loss of Elephant. It seemed baffling that he would never again see that clumsy youth with his stiff, awkward attempts at grooming, his clumsy fumbling as he tried to figure out how to get the flesh out of an oil palm nut.

But before the day was done, only Elephant’s mother would remember him. And when she was dead in her turn, there would be nothing to say he had ever existed, and he would be gone into the final blank darkness that had swallowed up all of his ancestors, every one.

Elephant had paid the price of the troop’s survival. Capo felt a cold relief. Without hesitation, without even performing the follow-me display, Capo moved down the slope and out onto the salt flats.

The next day they had to cross the salt. Under a washed-out blue-white sky the pan spread almost to Capo’s horizon, where hills, trees, and marshes crowded. It was as if this gray sheet were a flaw in the world.

The salt, lying over hard, grayish mud, was broadly flat, but the surface had texture, streaked here and there by swooping concentric lines that crowded to central knots. In one place an underground spring had caused the salt to billow up in great blocks that the apes had to clamber over.

But nothing grew, here on the salt. There weren’t even any tracks. Nothing moved save the apes, no rabbits or rodents, not even an insect. The wind moaned across this hard mineral stage, nowhere broken by the rustle of bushes and trees, the hiss of grass.

But still Capo kept on, for there was nothing else to do.

It took hours to cross the salt pan. But at last, his feet and hands aching, Capo found himself reluctantly climbing a ridge. At the crest of the ridge there was a belt of forest — even if it was a dense, uncomfortable-looking kind of forest.

Capo hesitated, facing the forest. He was overheated; his legs and feet were bleeding from a dozen small lesions. Then he pushed forward awkwardly and entered the forest’s green gloom.

The ground was hidden by a tangle of roots, branches, moss, and leaves. Wild celery grew in clumps everywhere. Although it was around noon, the air here was cold, made damp by a faint mist like a morning fog. The tree trunks were clammy, and thick lichen and moss left uncomfortable green streaks on his palms. The dampness seemed to dig through his fur. But after the aridity of the salt pan he relished the close, comforting tangle of green around him, and he devoured the leaves, fruit, and fungi he was able to pluck from the ground around him. And he felt safe from predators. Surely there was nothing that could strike at the hungry, weary band in this green density.

But now he saw hulking brown-black shapes just ahead, dimly visible through the tangled green. He froze.

A huge arm reached out to a branch wider than Capo’s thigh. Muscles worked in a great mound of shoulder, and the branch was snapped in two as easily as Capo might snap off a twig to clean his teeth. Giant fingers plucked leaves from the nearby branches and pushed them steadily into immense jaws. The whole head worked as the big animal chewed, heavy muscles working the skull and jaw together.

The nearest creature was an ape, as Capo was, a male — and yet unlike Capo. The big male watched the odd, scrawny little apes without curiosity. He looked powerful, threatening. But he didn’t move. The male, and a small clan of females and infants, did nothing but sit around and feed on leaves and the wild celery that carpeted the forest floor.

This was a gorilla: a remote cousin of Capo’s. His kind had split off from the broader lineages of apes a million years ago. The split had come in a period when another forest had fragmented, isolating the populations it supported. As their habitat shrank to the mountaintops, these apes had turned to a diet of leaves, endlessly abundant even here, and became huge enough to resist the cold — yet they remained oddly graceful, able to move silently through this dense forest.

Though populations of gorillas would later adapt back to lowland conditions, learning to climb trees and subsist off fruit, in a sense their evolutionary story was already over. They had become specialized in their environments, learning to eat food that was so well-defended — covered in hooks, spikes, and stings — that no other creatures competed for it. They could eat nettles, for example, with an elaborate maneuver that involved stripping leaves from a stem, folding in the stinging leaf edges, and popping the whole packet into their mouths.

Sitting in their montane islands, lazily eating their leaves, they would survive almost unchanged until human times, when the final extinction would overtake them all.

When he was sure the gorillas were no threat, Capo crept away, leading the others onward through the forest.

At last Capo emerged from the far side of the forested ridge.

They had at last clambered out of the arid lowland basin. When he looked south across the plateau he had reached, he faced a rocky, rubble-strewn valley that scoured its way down to lower ground. But there, beyond the valley, he could see the land he had hoped to find: higher than the plain he had left behind, but well watered, glistening with lakes, coated green by grass, and studded with pockets of forest. The shadowy forms of a great herd of herbivores — proboscideans, perhaps — drifted with stately grandeur across the lush plain.

With a hoot of triumph Capo capered, vaulted over rocks, drummed on the stony ground, and shit explosively, spraying the dry boulders with his stink.

His followers responded to Capo’s display only listlessly. They were hungry and dreadfully thirsty. Capo was exhausted himself. But he displayed anyway, obeying a sound instinct that every triumph, however small, should be celebrated.

But now he had climbed so high that the remote, persistent growling from the west had grown louder. Dimly curious, Capo turned and looked that way.

From this elevated place he could see a long way. He made out a remote turbulence, a white billowing. It seemed to hover above the ground like a boiling cloud. He was actually seeing a kind of mirage, a very remote vision carried to him by refraction in the warming air. But the billowing steam clouds were real, though their suspension above the ground was not.

What he was glimpsing was the Strait of Gibraltar, where even now the mightiest waterfall in Earth’s history — with the power and volume of a thousand Niagaras — was thundering over shattered cliffs and into an empty ocean basin. Once the plain from which Capo had climbed had been covered by water two kilometers deep, for it was the floor of the Mediterranean.

Capo had been born in the basin that lay between the coast of Africa, to the south, and Spain, to the north. In fact, he was not very far from the place where a clever dinosaur called Listener, long ago, had stood at the shore of Pangaea and gazed out on the mighty Tethys Sea. Now he had climbed out of the basin to reach Africa proper. But if Listener had seen the birth of the Tethys, Capo was witnessing something like its death. As the ocean levels dropped, this last fragment of the Tethys had become dammed at Gibraltar. Landlocked, the great ocean had evaporated — until at last it emptied, leaving behind a great valley in places five kilometers deep, littered with salt pans.