Evolution Read online

  But Boulder had been away just days, where Capo had expected weeks to pass. And from the look of his bristling aggression, his jaunt hadn’t made him any calmer.

  Capo was worried by the hunt, too. Monkey hunting usually happened only when other food was scarce, such as during periods of drought. Why hunt now?

  One of the clambering apes made a sudden leap. Cluttering, the monkey jumped the other way — straight into the arms of a waiting hunter. The watching apes hooted and barked. The hunter swung the screaming monkey around and slammed its skull against a tree trunk. Its cries were cut off immediately. Then the hunter hurled the limp carcass to the ground, its smashed head making a bright red splash in the forest’s green murk.

  That was Capo’s moment. He vaulted past Boulder to be first onto the body. He grabbed up the still-warm scrap, got hold of one ankle and twisted, hard, ripping the little limb loose at the knee.

  But, to his astonishment, Boulder challenged him. The burly male leapt at him feetfirst, ramming him in the chest. Capo fell sprawling, an ache spreading along his rib cage, the breath knocked out of him. Boulder deliberately picked up the monkey limb and bit into it, blood spurting over his mouth. All the apes were madly excited now, and they hooted and drummed and scrambled over one another.

  Ignoring the pain in his chest Capo leapt to his feet with a roar. He couldn’t let Boulder get away with this. He scrambled up into the lower branches of a tree, drummed ferociously, hooted loudly enough to disturb birds that roosted high above him, and vaulted back to the ground. He let anger surge through him so that he bristled, and a proud pink-purple erection stuck out before him: a nice touch that, his trademark.

  But Boulder kept his nerve. With the monkey limb wielded in his hand like a club, he began his own display, his stamping, leaping, and drumming just as impressive as Capo’s.

  Capo knew he couldn’t afford to lose this one. If he did, given Boulder’s circle of blood-stained hunters, he might lose not just his status but his very life.

  With an agility that belied his years, he leapt forward, knocked Boulder flat, and sat on his chest. Then he began to batter Boulder about the head and chest as hard as he could. Boulder fought back. But, save for youth, Capo had all the advantages: surprise, experience, and authority. Boulder couldn’t shift Capo’s weight, and he couldn’t bring his own powerful arms and legs fully into play.

  Gradually, Capo saw, he was winning the battle in the minds of the rest of the troop, which was just as important as subduing Boulder. The young male’s followers seemed to have melted away into the trees, and the whoops of excitement and approval Capo heard now seemed to be directed at him.

  But even as he battled to subdue Boulder, a slow deduction worked through Capo’s roomy mind.

  He thought of the dying trees he had glimpsed beyond the fringe of the forest island, the speedy return of Boulder and his wanderers, their apparent hunger, their need to hunt.

  Boulder had found nowhere to go. The forest patch was shrinking.

  That had been true all of Capo’s life, and now it was becoming unavoidable. There was no longer enough room for them here. If he tried to keep the group here, the tension between them, as they competed for dwindling resources, would become too intense.

  They would have to move.

  At last Boulder gave in. He lay limp under Capo, cupped the older male’s buttocks, and even briefly stroked his still-erect penis, all gestures of submission. To drive home his point Capo kept battering at Boulder’s head for long minutes. Then he clambered off the prone younger male. Still bristling, he made his way into the forest, where he could afford to limp and massage the pain in his chest and nobody could see how he hurt.

  Behind him the others fell on the vervet. Their stomachs could not digest flesh well, and later they would pick through their feces for lumps of meat to eat again. It was a digestive system that was going to have to improve, if the descendants of these rummaging creatures were to prosper on the savannah.

  II

  Since Roamer’s time, grass had remade the world.

  The great epochal cooling of the Earth continued. As water was locked up in the Antarctic ice cap, sea levels diminished, and inland seas shrank or became landlocked. But with more continental landmass exposed, there was less sea to buffer the climate from extremes of heat and cold, and the weathering rock drew carbon dioxide from the air, making it less able to retain the sun’s heat. Cooler and drier: The planet had developed a vast feedback mechanism, driving its surface to still more arid, chilly conditions.

  Meanwhile tectonic collisions created new mountain ranges: the Andes of South America, and the Himalayas of Asia. These new uplifts cast gigantic rain shadows across the continents; the Sahara Desert would soon be born in such a shadow. In the new desiccation, great belts of broad-leaved deciduous woodland spread from south and north toward the equator.

  And the grasses spread.

  Grass plants — huddling in their great crowds, able to rely on fertilization by windblown pollen — might have been designed for the new open, dry conditions. Grass was able to subsist on the sporadic rainfall that now fell, whereas most trees, with their roots delving ever deeper into the ground, found only dryness and could not compete. But the real secret of grass lay in its stems. The leaves of most plants grew from the tips of shoots, but not grass’s. Grass blades grew from underground stems. So grass could be cropped by a hungry animal, right down to the ground, without losing its power to regenerate.

  These unspectacular properties had enabled grass to take over a world, and to feed it.

  The new grass-eating herbivores developed specialized ruminant guts able to digest the grassy fodder over long periods and hence extract the maximum nutrient from it, and teeth able to withstand the abrasive effect of silica grains in grass blades. Many herbivores learned to migrate, because of the seasonality of the rainfall. These new mammals were larger than their archaic ancestors, lean and long-legged with specialized feet and a reduced number of toes to help them walk and run long distances and at speed. And meanwhile there was a sharp rise in the types of rodents, like voles and field mice, able to eat grass seeds.

  New carnivores rose, too, equipped to feast on the new herds of large herbivores. But the rules of the ancient game had changed. In the sparse cover of a grassland, predators could see prey from long distances — and vice versa. So predators and prey began a metabolic arms race, with the emphasis on speed and endurance; they developed long legs and quick reactions.

  A new kind of landscape began to spread — especially on the eastern side of the continents that were sheltered from the predominantly westerly winds and the rain they carried: open, grass-covered plains marked by scattered scraps of bush and woodland. And in turn animals who adapted to the new vegetation were rewarded with a guaranteed food source that could spread across hundreds of kilometers.

  But their specializations, and the stability of the grasslands, would lock in the grazers to the grasses, the predators to their prey, establishing a close codependency. In this period the deer, cows, pigs, dogs, and rabbits looked little different from their equivalents of human times five million years later — although many of them would have looked surprisingly large; they would later be outcompeted by their smaller, faster cousins.

  Meanwhile the opening up of land bridges, caused by the falling sea levels, led to a great crisscross migration of animals. Three kinds of elephants — high-browsing deinotheres, omnivorous gomphotheres, and browsing mastodonts — crossed from Africa to Asia. Along with them traveled the apes, cousins of Capo. And in the other direction came rodents and insectivores, cats, rhinos, mouse deer, pigs, and primitive types of giraffe and antelope.

  There were some exotica, especially on the islands and the separated continents. In South America the largest rodents that ever lived were flourishing; there was a kind of guinea pig as large as a hippo. In Australia, the first kangaroos appeared. And what would later be considered tropical animals could be found in Nort
h America, Europe, and Asia: In England, the Thames was broad and swampy, and hippos and elephants basked on its floodplain. The world had cooled greatly since Noth’s time, but it still wasn’t cold; the deepest chill would afflict later ages.

  But still the drying continued. Soon the older mosaic of grassland and woodland able to support a wide variety of animals lingered only in the equator-straddling Africa; elsewhere the grasslands opened up into arid plains, the savannah, steppe, and pampas. In these coarser, simplified conditions, many species fell away.

  This intense evolutionary drama was driven by the endless shifts in Earth’s climate — and the animals and plants were as helpless as bits of flux on a great terrestrial forge.

  The next morning there was no luxurious ball scratching. As soon as he woke, Capo sat up, hooted softly at the pain of yesterday’s lesions and bruises, and voided his bladder and bowels in a fast, efficient movement, ignoring the chitters of protest from below.

  He vaulted from his nest and began to shimmy down the tree. Just as yesterday he roused the troop by crashing into their nests, hooting, kicking, and slapping. But today Capo wasn’t interested in displaying; this morning his purpose was not dominance but leadership.

  His determination was still strong in his mind. The troop had to move. Where they should go wasn’t part of his unsophisticated decision making yet. But what was very clear in his head was the pressure of yesterday, his competition with Boulder, what he had sensed of the overcrowding of this little patch of forest.

  The troop gathered together on the ground, more than forty of them, including infants clinging to their mothers’ bellies or backs. They were sleepy, wary, scratching themselves and stretching. No sooner had Capo gotten them gathered, of course, than they were drifting apart again, plucking at bits of grass and moss on the ground, reaching for low-growing figs and other fruit. Even among the males he saw reserve, rivalry, resentment; they might resist him just to make their own points in the endless plays for dominance. And as for the females, they were a law unto themselves, for all of Capo’s noise and violence.

  How was he going to be able to lead this lot anywhere?

  He wasn’t conscious all the time, as a human was. He was conscious intermittently. He was only truly aware of his own thoughts, of himself, when thinking about others in the troop, because that was the primary purpose of consciousness, to model the thinking of others. He wasn’t conscious in the same way about other domains of his life, like food-gathering or even tool using: those were unconscious actions, as peripheral to his awareness as breathing or the working of his legs and arms when he climbed. His thinking was not like a human’s; it was simplified, compartmentalized.

  His mind was a sophisticated machine, basically evolved to handle complex social situations. And he had a good innate understanding of his environment. He had a kind of database in his head of the resources he needed to stay alive and where they could be found. He was even good at dead reckoning navigation, and could easily compute good shortcut courses from one site to another. It was his environmental awareness that had prompted his concern about the shrinking forest patch.

  It was hard for him to put together the elements of this puzzle: the danger posed by the shrinking forest, what he needed to do with his troop. But the danger was very real to him, and every instinct screamed at him to get away from here. The troop had to follow him. It was as simple as that; he knew it deep in the fibers of his being. If they stayed here they would surely die.

  So he roared to get his blood flowing, and threw himself into the most energetic display he could. He raced up and down among the troop, slapping, punching, and kicking. He tore branches from the trees and waved them over his head to make himself look even bigger. He swung and vaulted over branches and trunks, drummed ferociously on the ground, and — as a climactic gesture to reinforce his victory of yesterday — he threw Boulder to the ground and shoved his own puckered anus in the younger male’s face. It was a magnificent spectacle, as good as any Capo had mounted even in his younger days. Males whooped, females flinched, infants cried, and Capo allowed himself a glimmer of pride in his work.

  But then he tried to lead them away, toward the fringe of the forest. He walked backward, shaking branches and running back and forth.

  They stared. Suddenly he was behaving like a submissive junior male. So he displayed again, drumming, vaulting, and hooting, and went back to the follow-me routine.

  At last one of them moved. It was Frond, the spindly young male. He took a couple of tentative knuckle-walk steps. Capo responded with a chattering cry and threw himself at Frond, rewarding him with a burst of intense grooming. Now more came forward: Finger, a few more of the junior males, eager to be groomed in turn. But Capo noticed that Boulder aimed a sly kick at Frond’s backside.

  And then, to Capo’s intense relief, here came Leaf, her infant riding on her back, knuckle-walking grandly if a bit stiffly. Where this most senior female came, others followed, including Howl, the near-pubescent youngster.

  But not all the females followed — and not all the males. Boulder stayed behind, sitting squat under a tree with his legs ostentatiously crossed under him. Other males gathered around him. Capo displayed at them furiously. But they huddled and groomed each other as if Capo no longer existed. It was a deliberate snub. If he wanted to maintain his position, Capo was going to have to break up this knot of rebellion, perhaps even face down Boulder once more.

  But, almost to his own surprise, he gave up his displaying and stood back, panting.

  In his heart he knew he had lost them, that he had pushed them too hard, that his troop was fissioning. Those who chose to follow him would find their way, with him, to a new destiny — a destiny he himself couldn’t yet imagine. Those who stayed behind would just have to take their chances.

  He loped quickly away, out of the heart of the forest and toward the daylight, without looking back — although he was unable to resist a final valedictory liquid fart in the direction of the rebels.

  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, e
ven 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.