It was a necessary skill. Committed to the open, Far’s kind had been pushed by a harsh winnowing to develop a new kind of awareness of nature. They had been forced to understand the habits of game, the distribution of plants, the changes of seasons, the meanings of tracks — to solve the endless puzzles of the complex, unforgiving savannah. By comparison, her remote ancestor Capo, who had lived and died thousands of kilometers northwest of this place, had learned the features of his generous forest world by rote: Unable to read the land, to figure out new patterns, he had been endlessly baffled by the unfamiliar.

Now the adults and their infants were coming back to the rock, carrying food. They were naked, and they carried only what they could cram into their hands and cradle in their arms. Most of them came back with mouths still full and chewing. The people ate as fast as they could, helping themselves, feeding only close family members, not averse to stealing when they thought they could get away with it. And they ate silently save for belches, grunts of pleasure or disgust when a bit of rotten food turned up — and an occasional word. “Mine!” “Nut,” “Break,” “Hurt, hurt, hurt…”

They were simple nouns and verbs, possessives and challenges, one-word sentences with no structure, no grammar. But nevertheless it was a language, the words labels that referred to definite things — a system far advanced over the jabbering of Capo’s time, and that of any other animal.

Here came Far’s brother, the Brat. He was carrying the limp corpse of some small animal, maybe a hare. And her mother, Calm, had an armful of roots, fruit, and palm pith.

Far was suddenly hungry. She hurried forward, mewling, her hands held out and her mouth open.

Calm hissed at her, theatrically holding her armful of food away from her daughter. “Mine! Mine!” It was a rebuke, and it was backed up by glares from the grandmother. Far was getting too old now to be fed like an infant. She should have come to help her mother rather than waste her energy running purposelessly about the landscape. Why, here was her brother, the Brat, who had been hard at work and had even returned with his own scrap of meat. All of that was conveyed in a word.

Life was not as it had been in Capo’s time. Nowadays the adults tried to coach the youngsters. The world had become too complex for children to be given the time to reinvent all the technology and techniques of survival from scratch; they had to be taught how to survive. And one of the roles of elders like Far’s grandmother was to drive such wisdom home.

But Far held her hands out again, making piteous animal mewls. Just once more. Just for today. I’ll help tomorrow.

“Graah!” Calm, as Far had known she would, dumped the food on the rock. She had gathered nuts, tsin beans, cowpeas, and asparagus bean tubers. She handed Far a fat tuber; Far bit into this quickly.

The Brat sat close to his mother. He was still too young to sit with the men, who were pawing through their own pile of food. The Brat had pulled apart his hare by main force, twisting off the limbs and head, and was using a chip of rock to lay open the chest. But as he performed this miniature butchery his gestures were tense, shivery.

None of his family knew it, but he was already gravely ill, through hypervitaminosis. A few days before one of the men had given him a few scraps of hyena liver, brought down in a brief battle over the remains of an antelope. Like that of most carnivorous predators, the liver had been full of vitamin A, and that subtle poisoning would soon become visible in the boy’s body.

In a month he would be dead. In twelve, forgotten, even by his mother.

But for now Calm cuffed him, reasonably gently, and grabbed some of his hare away from him, making him share with his sister.

Since Capo’s time the world had continued to cool and dry.

North of the equator, a great belt of taiga stretched right around the world, through North America and Asia, a forest of nothing but evergreen trees. And in the far north tundra had formed for the first time in three hundred million years. For the animals, the living offered by the taiga was meager compared to the old mixed deciduous and coniferous temperate forests. Similarly, the great grasslands continued to expand — grass was less thirsty than trees — but grass made arid plains, able to support only a much-reduced assemblage of animal species compared to the vanishing forests. As the slow desiccation continued, there were extinctions again.

But if the quality was diminished, the quantity of life was tremendous, astonishing.

The need to ride out periods of seasonal food shortages, and the need for guts able to process coarse diets all year round, favored the development of large herbivores. Giant mammals, a new “megafauna” on a scale not seen since the death of the dinosaurs, spread across the planet. Ancestral mammoths had already spread across northern Eurasia and, crossing the land bridges periodically exposed by the falling ocean levels, walked into North America. For now, living in equable climes, they were hairless and ate foliage rather than grass. They looked like typical elephants, but they had the high crowns and curling tusks of their woolly descendants.

Meanwhile there were giant camels in North America, and in Asia and Africa wandered the huge, mooselike sivatheres. A type of large rhino called an elasmotherium roamed across northern Eurasia. For a rhino it had long legs and a horn that could grow to two meters in length: It looked like a muscular unicorn.

And along with these huge packages of meat came new, specialized predators. The cats, freshly evolved, had perfected the technology of killing. They had side teeth like shears that could slice through skin, rip it aside, and get inside a body, where their incisors could nibble at the flesh. The saber-tooths were the acme. The saber-tooths would grow to twice the size of the lions of human times, becoming vast muscular predators built like bears, with short stocky limbs. They were built for power, not speed, and were ambush hunters, with mouths that could open hugely wide to crush prey. But all cats made even the dogs look like generalists by comparison; cats were perhaps the ultimate land predators.

But then, some half million years before Far’s birth, a new and dramatic worsening of the climate began. For the world’s creatures, the rules changed again.

There was a call from the plain. “Look, look! Me, look, me!” People stood up, gathering to see.

A man was approaching. He was tall, more heavily muscled than the rest, with a powerful, abnormally prominent browridge. This man, Brow, was dominant right now, the boss man in the tight, competitive world of the males. And he had a dead animal draped across his shoulder, a young eland.

The eight other adult men in the band began dutifully to whoop and yell, and they ran down the rocky slope. They slapped Brow on the back, stroked the eland respectfully, and ran and capered, kicking up a spectacular cloud of dust that hung, glowing, in the light of the descending sun. Together they hauled the eland up the slope and hurled it to the ground. The older children ran to see the eland, and began competing for its meat. The Brat was amongst them, but he was weaker even than others younger than himself, and he was easily pushed aside. Far could see a snapped-off wooden spear buried in the animal’s chest. That was how Brow had killed his prey, probably after an ambush, and perhaps he had left the spear in there to show how he had achieved this feat.

Brow, meanwhile, had sprouted an impressive erection. The women, including Calm, Far’s mother, made subtle signs of availability — a crooked hand here, thighs smoothly parting there.