In the end about half the males and rather more of the females stayed behind. It was a drastic diminishing of Capo’s domain. And as he walked toward the bright light of the plain he could hear the whoops and howling of the males. The battles over the new hierarchy had already begun.

At the forest’s fringe, on the edge of emptiness, Capo paused.

Just as yesterday, gomphotheres grazed on damaged, half-drowned trees. To the north the grassy plain stretched to its misty horizon, littered with glimmering lakes and marshes, herbivore herds passing like shadows. To the south, beyond a kilometer or so, the ground gleamed white as bone. The salt pan would be a difficult place to cross. But Capo could see how the land rose, up toward a green plateau, where — it seemed to his poor eyes, adapted for the short focuses of the forest — a thick blanket of trees lay draped over the rock.

South, then, across the dry land, to the new forest on the plateau. Without glancing back to see if the others were following, he set off on knuckles and feet, pushing through grass that waved around him, shoulder-high.

The land rose, quickly becoming drier.

There were some trees here, but they were just thin-trunked pines clinging to arid ground, with none of the comforting density and moistness of the forest clump. So there was little shelter to be had from the high sun. Capo was soon panting hard, baking inside his thick fur, his knuckles and feet rubbed raw. He could not sweat, and his knuckle-walking gait, effective for clambering around the complex, crowded environment of the forest, was inefficient here.

And Capo, a creature of the forest, was intimidated by this great sweep of openness. He hooted softly and longed to cower, to hold his arms over his head, to hurl himself into the nearest tree.

There were animals to be seen, scattered over the dry plain: There, were deer, some species of dog, and a family of grubbing animals like spiky-furred pigs. The larger animals were very few. But as Capo blundered on, many smaller creatures scampered away underfoot: lizards, rodents, even primitive rabbits.

The twenty or so of the troop who had followed him toiled painfully up the slope after him. They moved slowly, for they stopped frequently to feed, drink, groom, play, argue. This migration was more like a slow walk made by easily distracted children. But it was not in Capo’s instincts to hurry them. They were what they were.

Capo crested a shallow, eroded hill. From here he looked back across the wet, glistening landscape with its islands of forest and crowding herbivores. But when he looked ahead, to the south, he could see the great dryness they approached. It was a broad, high, dry valley, scattered with thin trees and bits of vegetation. It was kept arid by an accident of geology which had left it cupped in a great subterranean bowl of rock, barren of springs, shadowed from rainfall.

It was an intimidating sight; the valley was exposed, utterly open. And yet he must cross it.

And from here, now that there was no forest to soak up the noise, he could make out that great, mysterious roaring from the west. The remote noise sounded like the groaning cry of some huge, pained, angry beast, or like the thunderous hoofs of some great herbivorous herd. But when he looked to the west he could see no dust clouds, no black wash of animal bodies. There was nothing but the roaring, continuing just as it had all his life.

He began to clamber down the rocky slope, still heading south.

The ground became bare. Still trees clung to life here, their roots wormed into faults in the rock. But these pines were sparse, their leaves spiky, jealous of their water. He stopped under one of these trees. Its branches and leaves offered him virtually no shade. He could find no fruit, and the leaves he plucked were sharp and dry in his mouth. He made a grab for a small mouselike creature with long, levered hind legs; his mouth watered at the thought of biting into its soft wet body, its small bones crunching in his mouth. But here on this rocky ground he was clumsy and noisy, and the mouse thing evaded him easily.

Now the ground changed again, becoming a broad slope of broken stone that spread out before him, a road leading to the depths of the dry valley. The going got even harder as Capo slid and slipped on the loose rubble. Hot, thirsty, hungry, scared, he hooted his protest and threw bits of the rubble around, tramping and kicking it. But the land was not to be intimidated even by Capo’s mighty displays.

Meanwhile the chasma watched the ragged group of anthropoids as they struggled down the uneven, treacherous slope.

She had never seen creatures like this before. With a predator’s cold interest, she made unconscious calculations of their speed, strength, and meat yield, and began categorizing the individuals — here was one who seemed wounded and limped a little; here was an infant, clasped tightly to its mother’s chest; here was a juvenile straying, foolishly, from the tight group.

This chasmaporthetes was actually a kind of hyena. But, long legged, slim, she looked more like a cheetah. She did not have all of the true cats’ suppleness and speed, not quite; her kind had more adapting to do in the fleet conditions of this emerging world of grass. But her range was huge in this barren valley. She was the top predator here, and she was well equipped for her grisly work.

To her, the apes were new meat on the savannah. She waited, her eyes glowing like captive stars.

At last, exhausted, Capo gave up. He slumped to the ground. One by one, what was left of his troop joined him. By the time they had all arrived, the sun had started to set, filling the sky with fire and casting long, stark shadows along the floor of this gravel-littered bowl.

A kind of dull indecision raged within Capo. They shouldn’t stay here, out in the open; his body longed to climb a tree trunk, to pull together branches to make a cozy, warm, safe nest. But there were no trees here, no security to be had. On the other hand they couldn’t cross the valley floor in the dark. And they were all hungry, thirsty, exhausted.

He didn’t know what to do. So he did nothing.

The troop began to disperse, following their own instincts. Finger picked up a cobble-shaped, palm-sized rock, perhaps hoping to use it in some future nut-cracking project. But a scorpion scuttled out from beneath the rock, and Finger fled, hooting.

Frond was sitting alone with his back to the rest of the group, assiduously working at something. Capo, suspicious, loped up as quietly as he could on this loose, scattered gravel.

Frond had found a termite mound. He was sitting before it, clumsily poking sticks into it. When he saw Capo he cowered, screeching. Capo delivered brisk, perfunctory blows to his head and shoulders, as Frond would have expected. He should have hooted to the rest on discovering this bounty.

Capo ripped open a shrub. All of its branches were spindly and bent, and when he stripped a branch by passing it through his mouth, the hard, spiky leaves hurt his lips. But it would have to do. He sat alongside Frond. He pushed his stick into a crevice in the mound, and worked it until it had slid in deep. It was not ideal; the stick was too short and bent to be truly effective, but it would have to do. He jiggled it around, waiting patiently. Then he withdrew the stick, centimeter by centimeter. To the stick clung soldier termites, sent to defend the colony from this invader. Capo took great care not to dislodge this cargo. Then he swept the stick through his mouth, enjoying a mouthful of sweet, moist flesh.

When they saw what was going on the rest of the troop crowded around, the older ones making their own fishing sticks. Very quickly a rough pecking order established itself, lubricated by kicks, punches, hoots, and sly grooming. The more senior male and females alike got closest to the mound while the young, who didn’t understand what was happening anyhow, were excluded. Capo didn’t care. He just concentrated on holding his own position close to the mound while working assiduously at the termites.