She turned to get up. But something slammed against her head, and she fell into blackness.

When she came to she was flat on her back. Her chest, legs, and buttocks ached.

Pithecines were all around her.

Some of them had clambered into pod mahogany trees in search of fruit. Others were digging in the ground, pulling out corkwood roots. They were active, foraging bipeds, working wordlessly. But, unlike her, they were short, hairy, their skin slack like chimps’.

Somebody was screaming. Far turned her head to see.

A pithecine was crouched in the dirt. It — she — was straining, her face contorted, her slack breasts heavy with milk. Far, blearily, saw a small solid mass emerge from her rump: mucus-covered, hairy, it was the head of a baby. This pithecine woman was giving birth.

Other females surrounded her, sisters, cousins, and her mother. Chattering and hooting softly, they reached between the new mother’s legs. Gently they fumbled with the baby as, moistly, it was pushed out of the birth canal.

The new mother faced problems no earlier primate had endured, for the baby was being born facing away from her. Leaf, a female of Capo’s time, would have been able to see her baby’s face as it emerged, and would have been able to reach down between her legs to guide her baby’s head and body out of her birth canal. If this pithecine were to try that she would bend the baby’s neck backward and risk injuring its spinal cord, nerves, and muscles. She could not cope alone, as Leaf could have — but she did not have to.

When the baby’s hands were free, it grabbed at its mother’s fur and began to pull. Even now it was strong enough to aid in its own delivery.

It was all a consequence of bipedalism. A quadruped supported its abdominal organs with connective tissue hung from its backbone. The pelvis was just a connecting element that translated the pressure on the backbone down and outward to the hips and legs. But if you decided to walk upright your pelvis had to support the weight of your abdominal organs — and the weight of a growing embryo inside you. The pelvises of the upright pithecines had quickly adapted, becoming like a human’s basin-shaped supporting structure. The central opening for the birth canal changed too, becoming larger side to side than front to back, an oval shape to match a baby’s skull.

This pithecine mother’s birth canal was narrower in comparison to her baby’s head than any previous primate’s. Her baby had entered the canal facing its mother’s side, to let its head through. But then it had to turn so its shoulders lined up with the canal’s widest dimension. Sometimes the baby would finish up in the easiest position, facing its mother, but more often than not it would turn away from her.

In the future, as hominid skulls increased in size to accommodate larger brains, still more elaborate redesigns of the birth passageways would be required, so that Joan Useb’s baby would have to twist and turn in a complicated fashion as it headed for the light. But even in these deep times, the first bipedal mothers already needed midwives — and a new kind of social bond had been forged among the pithecines.

At last the baby emerged fully, falling to the leaf-strewn ground with a plop, its small fists closing. The mother fell to the ground with a gasp of relief. One older pithecine picked up the child, cleared plugs of mucus from its mouth and nose, and blew into its nostrils. At the hairy little scrap’s first wail, the midwife peremptorily thrust the baby at its mother and loped away.

Suddenly Far felt strong hands around her ankles. She was jolted, leaves and dirt scraped under her back, and she lost sight of the mother and baby.

She was being dragged over the floor. Every time her head clattered on a rock or tree root pain exploded. Hooting, screeching creatures were all around her. These were all males, she saw now, with knotty pink genitals half-buried in their fur, and astonishingly large testicles that they would scratch absently. When they walked their gait was oddly awkward, the joints of their hips peculiar.

She realized dimly that they were hauling her deeper into the forest. But she seemed to have no strength, no will to fight.

Suddenly another bunch of pithecines came rushing out of the deeper green, howling angrily. The males who had taken Far rose to confront these newcomers.

For a time there was a festival of yelling, hooting, and displaying. The pithecines bristled their fur, making some of them look twice their usual size. The larger ones crashed through branches, ripped leaves from the trees, and leapt and slapped at the ground. One of Far’s group sprouted an immense pink erection that he waggled at the interlopers. Another leaned back and pissed over his challengers. And so on. It was cacophonous, baffling, stinking, a skirmish between two groups of creatures who looked identical to a bewildered Far.

At last Far’s captors drove off the intruders. Bristling with leftover aggression they hurled themselves around the trees, screeching and snapping at one another.

Now, calming, the pithecines began to forage on the ground, their long fingers raking through the debris of leaves and twigs. One of them found a chunk of black rock, a cobble of basalt. He quickly found another rock, and he turned the first over and over in his hands, his pink tongue comically protruding from his mouth.

At last he seemed satisfied. His eyes on the basalt rock, he set it on the ground, holding it precisely between thumb and forefinger. Then he slammed down his hammer-stone. Splinters sprayed away from the target rock, many of them so small they were barely visible. The pithecine rummaged in the dirt, rumbling his disappointment, then he turned back to his rock and started to turn it over in his hands once more. The next time he struck it, a thin black flake the size of his palm sheared off neatly. The pithecine hefted his flake in his hand, turning it around between thumb and forefinger while he studied its edge.

This stone knife was just a cracked-off splinter of stone. But its manufacture, involving an understanding of the material to be shaped and the use of one tool to make another, was a cognitive feat that would have been far beyond Capo.

The pithecine eyed Far. He was aware that Far was conscious, but he was going to begin his butchery anyhow.

His arm flashed out. The stone flake sliced into Far’s shoulder.

The sudden sharpness of the pain, and the warm gush of her own blood, brought Far out of her passive shock. She screeched. The pithecine roared in response and raised his flake again. But, just as she had crushed the scorpion, Far slammed the heel of her hand into his face. She felt a satisfying crunch of bone, and her hand was covered in blood and snot. He recoiled, blood gushing.

The pithecines fell back, startled, hooting their alarm and slapping their big hands on the ground, as if reassessing the strength and danger of this large angry animal they had brought into their forest.

But now one of them bared his teeth and began to advance on her.

She forced herself to her feet and ran, deeper into the forest gloom.

She clattered against tree trunks, got lianas and roots wrapped around her legs, and pushed through dense knots of branches. Her long legs and powerful lungs, designed for hours of running over flat, open ground, were all but useless in this dense tangle, where she couldn’t take a step without tripping over something.

And meanwhile the pithecines moved like shadows around her, chattering and hooting, climbing easily up trunks and along branches, leaping from tree to tree. This was their environment, not hers. When they had committed themselves to the savannah, Far’s kind had turned their backs on the forest — which had, as if in revenge, become a place not of sanctuary but of claustrophobic danger, populated by these pithecines which, like the sprites they resembled, would inhabit nightmares long into the future.