As the light died, so the group settled toward sleep.
Far huddled against her mother’s legs. The ending day became just one of a long chain that stretched back to the beginning of her life, days dimly remembered, only vaguely linked. In the darkness she imagined running in the blinding brightness of day, running and running.
She had no way of knowing that this was the last time she would fall asleep close to her mother.
II
A million years ago, tectonic drift, slow but relentless, had caused North and South America to collide, and the isthmus of Panama was formed.
In itself it seemed a small event, Panama an inconsequential sliver of land. But, as with Chicxulub, this region had once more become the epicenter of a worldwide catastrophe.
Because of Panama, the old equatorial flows through the Americas — the last trace of the Edenic Tethys current — had been cut off. Now the only Atlantic currents were the huge interpolar flows, great conveyor belts of cold water. The worldwide cooling intensified drastically. The scattered ice caps covering the northern ocean merged, and glaciers spread like claws over the northern landmasses.
The Ice Ages had begun. At their greatest extent the glaciers would cover more than a quarter of all Earth’s surface; the ice would reach as far as Missouri and central England. Much was immediately lost. Where the glaciers passed, the land was scraped clean — down to the bedrock, which was itself pulverized and ground to dust — leaving a legacy of mountains with scored flanks, polished surfaces, scattered boulders, and gouged-out valleys. There had been no significant glaciation on Earth for two hundred million years; now a legacy of rocks and bones dating back deep into the age of the dinosaurs was comprehensively destroyed.
On the ice itself, nothing could live: nothing. Below the ice, great impoverished belts of tundra spread. Even in places far from the ice, like the equatorial regions of Africa, changes in wind patterns intensified the aridity, and vegetation shrank back to the coasts and river valleys.
The cooling was not a uniform trend. The planet tipped and bobbed in its endless dance around the sun, subtly shifting its degree of tilt, its inclination, and the fine-tuning of its orbit. And with each cycle the ice came and went, came and went; ocean levels fluctuated like the pumping of a heart. Even the land, compressed under kilometers of ice or released by its melting, rose and fell like a rocky tide.
Sometimes the climate shifts could be savage. Within a single year the amount of snowfall in an area could double, the average temperature fall by ten degrees. Faced with such chaotic oscillations, living things moved, or died.
Even the forests marched. Spruce proved a fast migrant, followed by pine, capable of marching at a kilometer every two years. The great chestnuts, massive trees with heavy seeds, could manage a pace of a hundred meters a year. Before the Ice Age the animals of the middle latitudes of the northern hemisphere had been a rich mixture of fleet grazers like deer and horses, giant herbivores like rhinos, and fast-running carnivores like lions and wolves. Now the animals were driven south in search of warmth. Populations of animals from different climatic zones were mixed up and forced to compete in fast-changing ecological arenas.
But some creatures began to adapt to the cold, to exploit the food supplies that still existed at the feet of the ice sheets. Many animals grew thick fur and layers of fat — large animals, like rhinos, and smaller animals, like foxes and horses and cats. Others began to take advantage of the huge temperature swings between the seasons. They migrated, moving north in the summer and south in the winter; the plains became a huge tidal wash of life, great mobile communities patiently stalked by predators.
There had been a catastrophe of mixing in the Americas. The two continents, north and south, had been separated since the shattering of Pangaea some one hundred and fifty million years ago. The fauna of South America had evolved in isolation, and was dominated by marsupial mammals and ungulates. There were marsupial “wolves” and saber-toothed “cats”; there were ungulate “camels” and trunked “elephants,” and giant ground sloths that could weigh three tons and stood six meters tall when they stood up to browse on palm leaves. There were still glyptodonts, not so dissimilar from the huge armored beast that had terrified Roamer, and the top predators were giant flightless birds, just as in archaic times. This exotic assemblage had been left alone to develop — though it was supplemented from time to time by waifs, brought by rafting or temporary bridges, like Roamer and her hapless companions, whose children had populated the South American jungles with monkeys.
But when the Panama land bridge was closed there was a massive migration from north to south of insectivores, rabbits, squirrels, mice, and later dogs, bears, weasels, and cats. The natives of South America failed to compete with these new arrivals. The extinctions took millions of years, but the empire of the marsupials was done.
For all the difficulty and dying, this time of fast and savage changes was, perversely, a time of opportunity. In the entire four-billion-year history of the Earth there had been few times more propitious for diversification and evolutionary innovation. Amid much extinction there was wild speciation.
And right at the center of this ecological cauldron were the children of Capo.
The next morning dawned brightly, with a washed-out blue sky. But the air was very dry and smelled oddly sharp, and the heat was soon stifling. The animals of the savannah seemed subdued. Even the birds were quiet; the carrion eaters clung to their tree roosts like ugly black fruit.
With their bare, sweating skin, the people were as well equipped for this hot, open dryness as any other species here. But they too began their day listlessly. They milled about their island of rock, picking at what was left of yesterday’s food.
This wasn’t a particularly rich area. The people didn’t discuss their plans — they never did, and anyhow they had no real plans — but it was obvious they shouldn’t stay here. Before long some of the men started to set off toward the water course to continue their walk to the south.
But the Brat’s condition had worsened overnight. The soles of his feet were cracked and oozing a watery pus, and when he tried to put his weight on them he cried out in pain. He wouldn’t be walking anywhere today.
Calm, Far’s grandmother, and most of the other women stayed close to the Brat. As for the men, the women just ignored their antics as they impatiently paced up and down the trail they had begun toward the south.
This conflict, all but wordless, over the day’s course was hurtful for them all. It was a genuine dilemma. The savannah was not like the bountiful, reliable forest of earlier times; you couldn’t just walk off in any random direction. Every day, in this sparse, changeable land, the people were faced with decisions about where to go to find food, water, what dangers to avoid. If they got it wrong, even once, the consequences were drastic. But the walkers had few children, and invested much effort in each one; you didn’t abandon one lightly.
At last the men gave up. Some of them returned to the rock to laze in the light of the high, hot sun. A handful of others set off under Brow’s leadership on the trail of an elephant herd, one of whose infants appeared to be limping. The rest of the men — and the women and older children — dispersed to the foraging sites they had explored yesterday.
The way these people were living — setting up a central home base, retrieving food, and sharing food and labor — was necessary. On the open plain the people had to work hard for food, and their slow-growing young extracted a high cost in care. They had to cooperate and share, one way or another. But there was no real planning. In many ways this was more like a wolf pack than any human community.