For all her cold adaptations Dig was still a primate. She still retained the agile hands and strong forearms of her ancestry. And, though her brain was much diminished from her ancestors’ — in this straitened environment a big brain was an expensive luxury, and animals were no smarter than they needed to be — she was smarter than any lemming.

But the climate was getting colder yet. And every year the remnant animals and plants were crowded into an increasingly narrow strip of tundra close to the coast.

The endgame was approaching.

Dig found herself laboring for breath.

In a sudden panic, she scrabbled at the snow above her, hands evolved for climbing trees now digging their way through a roof of snow.

She pushed her way out of the burrow and into a thin spring light, shockingly bright. A gush of fetid air followed her, steaming in the cold — fetid, and laden with the stink of death.

She was a bony bundle of urine-stained skin and fur on a vast, virgin snowscape. The sun was high enough above the horizon to hang like a yellow lantern in a purple-blue sky. Spring was advanced, then. But nothing moved: no birds, no raptors, no dwarf allo chicks erupting from their wintry caves. No other burrower emerged onto the snow; not one of her own kin followed her.

She began to work her way down the bank of snow. She moved stiffly, her joints painful, a ravening hunger in her belly, a thirst in her throat. The long hibernation had used up about a quarter of her body mass. And she was shivering.

Shivering was a great failure of her body’s cold-resistant systems, a last-resort option to generate body heat with muscular movement that burned up huge amounts of energy. Shivering shouldn’t be happening.

Something was wrong.

She reached the bare ground that fringed the sea. The soil was icebound, still as hard as a rock. And despite the lateness of the season nothing grew here, not yet; spores and seeds still lay dormant in the ground.

She came across a group of leaellynasaurs. In the cold, they had intertwined their limbs and necks until they had formed a kind of interlocked, feathery sculpture. Instinctively she flattened herself against the snow.

But the leaellyns were no threat. They were dead, locked in their final embrace. If Dig had pushed, the assemblage might have toppled over, frozen feathers breaking off like icicles.

She hurried on, leaving the leaellyns to their final sleep.

She reached a little headland that overlooked the ocean. She had stood in this place at the end of last summer, under a small stand of fern, watching raptor and frog battle. Now, even the fern’s spores were locked inside the bare ground, and there was nothing to eat. Before her the sea was a plain of unbroken white, all the way to the horizon. She quailed before the lifeless geometry: a horizon sharp as a blade, flat white below, empty blue dome above.

Only at the shore was there a break from the monotony. Here the sea’s relentless swell had broken the ice, and here, even now, life swarmed. Dig could see tiny crustaceans thrusting through the surface waters, gorging themselves on plankton. And jellyfish, small and large, pulsed through this havoc, all but translucent, lacy, delicate creatures that rode the swell of the water.

Even here, at the extremes of the Earth, the endless sea teemed with life, as it always had. But there was nothing for Dig.

As the great global cooling downturn continued, so the great clamp of the ice tightened with each passing year. The unique assemblage of animals and plants, trapped on this immense, isolated raft, had nowhere to go. And in the end, evolution could offer no defense against the ice’s final victory.

It was a gruesome extinction event, hidden from the rest of the planet, drawn out over millions of years. An entire biota was being frozen to death. When the animals and plants were all gone, the monstrous ice sheet that sat squat over the continent’s heart would extend further, sending glaciers to grind their way through the rock until the ice’s lifeless abstraction met the sea itself. And though the deeper fossils and coal beds of ancient times would survive, there would be no trace left to say that Dig’s world of tundra, and the unique life that had inhabited it, had ever existed.

Dispirited, she turned away and set off over the frozen ground, seeking food.

As light leaked into the sky, Capo woke. Lying in his treetop nest he yawned, his lips spreading wide to expose his thick gums, and he stretched his long, furry limbs. Then he cupped his balls in one hand and scratched them comfortably.

Capo looked something like a chimpanzee, but there were not yet any chimps in the world. He was an ape, though. In the long years since the death of Roamer, the burgeoning families of primates had diverged, and Capo’s line had split off from the monkeys some twenty million years ago. And yet — still some five million years before the rise of true humans — the great age of the apes had already come and gone.

Capo squinted into the sky. The sky was gray blue and free of clouds. It would be another long, hot, sunny day.

And a good day. He rubbed his penis thoughtfully. His morning erection felt tight, as it always did. Some of the most troublesome of the subordinate males had sloped off into the deeper forest a few days ago. It ought to be weeks before they were back, weeks of relative calm and order. Easy work for Capo.

In the stillness of morning, sound carried far. Lying here, his thoughts rambling, Capo could hear a distant roaring, like the endless grumble of some vast, wounded beast. It came roughly from the west. He listened for a few heartbeats, and his hairs prickled at the sullen majesty of the never-ending, baffling rumble; it was a sound of awesome power. But there was never anything there, nothing to see. It had been there in the background all his life, unchanging, incomprehensible — and remote enough not to matter.

He felt a nagging unease, but not about the noise. A vague concern crept up on him in such reflective moments.

Capo was more than forty years old. His body bore the scars of many battles and the patchy baldness of endless grooming. He was old enough and smart enough to remember many seasons — not as a linear narrative but in glimpses, shards, like vivid scenes cut out of a movie and jumbled up. And on a deep level he knew that the world was not as it had been in the past. Things were changing, and not necessarily for the better.

But there was nothing to be done about it.

Languorously he rolled over onto his belly. His nest was just a mass of thin branches folded over and kept in place by his weight. Through its loose structure he could make out the troop scattered through the tree’s foliage, primates roosting like birds. With a soft grunt he let his bladder go. The piss sprayed messily from his penis, still half erect, and rained down into the tree.

It splashed Leaf, one of the senior females, who had been asleep on her back with her infant clutching her belly fur. She woke with a start, wiping thick urine from her eyes, and hooted her protest.

His time of reflection over, the last of his erection shriveling, Capo sat up and vaulted out of his nest.

Time to go to work. A great black-brown ball of fur, he proceeded to crash through the tree. He smashed nests, punched and kicked their occupants, and screeched and leapt. He kept this up until the whole tree was a leafy bedlam, and there was no possibility of anybody staying asleep, or not being aware of Capo’s dominant presence.

He made one very satisfactory hard landing right in the middle of the nest of Finger, a stocky younger male with a very agile brain and hands. Finger curled up, chattering, and tried to lift his backside in a gesture of submission. But Capo targeted the backside with one well-aimed kick, and Finger, shrieking, went tumbling down through the foliage toward the ground. It was high time Finger was taught a lesson; he had been getting too cocky for Capo’s liking.