Evolution

by Stephen Baxter

  As noon approached, the desultory stillness of this strange, heavy day deepened. The savannah, open and free, beckoned Far, as it had done yesterday. As the emptiness in her belly diminished, the pressures of survival and familial duty were overcome by her longing to get out of here.

  One spindly palm had survived the deinotheres’ attention, and it had a cluster of nuts at its top. A young man shimmied up the tree with a grace that came from his body’s deep-buried memory of earlier, greener times. Far watched his lithe torso working, and felt a peculiar ache at the base of her belly.

  She came to a kind of decision. She dropped the last of the food, clambered out of the thicket, and just sprinted off to the west.

  She felt a vast relief as her limbs worked, her lungs pumped, and she felt clean crisp dirt beneath her feet. For a time, as she ran without thinking, even the day’s heat seemed alleviated as the breeze of her passing cooled her skin.

  Then there was a deep, menacing rumble that echoed across the sky. She pulled up, crouched, and peered around fearfully.

  The bright sunlight dimmed. Thick black clouds were pouring across the sky from the east. She was startled by a flash of purplish light that lit up the clouds from within. Almost immediately there was a shattering crash and a deeper, drawn-out rumble that seemed to roll around the sky.

  Looking back at the rocky outcrop, which suddenly seemed very far away, she saw the people running, gathering up their infants. Her heart hammering, Far straightened up and began to head back.

  But now rain lashed down from the blackening sky. The drops were heavy enough to sting her bare skin and unprotected scalp, and they dug small craters in the dirt. The ground rapidly turned to sticky mud that clung to her feet, slowing her down.

  Light flashed again, this time a great river of it that briefly connected sky to ground. Dazzled, she stumbled and fell in the mud. Shattering noise pealed around her, as if the world were falling apart.

  She saw that the tall palm at the center of the trampled clearing had been split in two, and it was blazing, the flames licking at the fronds that dangled forlornly from its tip. The fire quickly spread through the rest of the smashed thicket — and then the dry grass on the plain beyond began to catch.

  A pall of gray-black smoke began to rise up before her. She got to her feet and tried to continue. But, despite the continuing rain, the fire spread quickly. The season had been exceptionally dry, and the savannah was littered with yellowed grass, dried shrubs, fallen trees ripe for burning. Somewhere an elephant trumpeted. Far glimpsed spindly forms fleeing through the murk: giraffes, perhaps.

  The hominids were safe, though. The flames would lap harmlessly around their rocky outcrop. Though they would all suffer from the smoke and heat, nobody would die because of this. And if Far could reach the outcrop, she, too, would be safe. But she was still hundreds of meters away, and the screen of smoke and flame cut her off. The flames were leaping hungrily over the long, dry grass, each blade of which burned in an eye blink. The air turned smoky, making her cough. Bits of burning vegetation drifted through the air, blackened, still glowing. When they fell on her skin they stung.

  She did the only thing she could do. She turned and ran: ran to the west, away from the fire, away from her family.

  She didn’t stop running until she came to a dense thicket of forest. Facing a blank, green wall, she hesitated for one heartbeat. Other dangers lurked here, but this place was surely invulnerable to the fire. She plunged inside.

  Crouched close to the root of a tree fern, surrounded by damp clinging fronds, she peered out at the savannah. The fire still swept voraciously through the long grass, and smoke billowed, seeping into the dense forest. But this forest clump was indeed too dense and moist to be under threat. And the fire was quickly consuming its fuel; the rain was starting to douse the flames.

  Soon she would be able to get out of here. She squatted down to wait it out.

  A scuttling movement close to her foot drew her attention. At the base of the tree fern’s textured root a scorpion moved with metallic precision toward her foot. Without hesitation, but taking care to avoid the sting, she slammed the heel of her hand down on the scorpion. Carefully she picked up the scorpion between two fingers, and lifted it to her mouth.

  Something rammed into her back. She was thrown forward onto her belly, with a mass on her back, hot, heavy, muscular. She was surrounded by screeching and hooting, and fists pounded at her back and head.

  Winded, summoning up her strength, she rolled over.

  A slim figure capered over her. It was not much more than half her height, with a skinny body covered with brown-black fur, long arms, an apelike head stuck over a narrow, conical chest, and a thin pink penis sticking out below its belly. Its fur was wet from the rain, and it stank, the smell musty and strong. And yet it — he — stood upright over her, like one of her own kind, like no ape.

  This was a pithecine: an ape-man, a chimp-man, a representative of the first hominids of all, Far’s remote cousin. And there were more of them in the jumbled branches above her, climbing down like shadows.

  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 lig
ht. 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.

  Before long the pithecines had overtaken her on both sides, and began to move closer.

  She stumbled suddenly into a twilight-dark clearing — where a new monster reared up before her, bellowing. She squealed and fell flat in the dirt.

  For a heartbeat the monster stood over Far. Beyond it squat forms sat; broad faces turned toward her, incurious, huge jaws chewing.

  The monster was another hominid: another pithecine, in fact, a robust form. This big male, with an immense swollen belly, was taller and much bulkier than the gracile types who had captured her. His posture, even when he stood erect, was much more apelike; he had a sloping back, long arms, and bent legs. His head was extravagantly sculpted, with high cheeks, an immense, rocklike jaw filled with worn, stubby teeth, and a great bony crest that ran down the length of his skull.

  Exhausted, in pain, her shoulder bleeding heavily, Far curled up on the ground, expecting those immense fists to come slamming down on her. But the blows never came.

  The blocky creatures on the ground behind the big male huddled a little closer together. They were all females, with heavy breasts over those giant bellies, and as they stared at Fur, they pulled their tubby infants toward them. But still they sat and ate, Far saw. One female picked up a hard nut — so hard Far would have had to use a rock to crack its shell — placed it between her teeth and, pushing up on her jaw with her hand, cracked it easily. Then she began to crunch it down, shell and all.

  But now the skinny pithecines came hurtling into the clearing. When they saw Big Belly they clattered to a halt, stumbling over one another like clowns. Instantly they began to display, stalking to and fro with their fur erect; they slapped the ground and hurled twigs and bits of dried shit at their new opponent.

  Big Belly growled back. The truth was this gorilla-man was a vegetarian, forced by the low quality of his diet to spend most of his day sitting still while his vast gut strove to process his food. But this immense brute with his stumps of teeth, powerfully muscled frame, and cowering harem seemed a much more intimidating proposition than the skinny pithecines. He dropped to a knuckle-walk posture with a slam that seemed to make the ground shake, his huge gut wobbling. He stalked back and forth before his little domain, his own fur bristling, roaring back at the impertinent graciles.

  The pithecines backed away, hooting their frustration.

  Far scrambled out of the way and blundered on, still deeper into the seemingly unending forest. This time, she wasn’t pursued.

  She couldn’t see the sun, not directly; there was only a scattering of green-tinged dappled light to mark her way. She had no sense of how long she plunged on through the forest, how far she had come. The deep cut in her shoulder had crusted over, but still she lost blood. Her head ached from the slamming it had taken from the pithecine’s rock, and her chest and back were just masses of bruises. And shock and bewilderment at losing her mother, and the small band of people who had made up her world, began to overwhelm her.

  Exhaustion crept up.

  At last she tripped over a root. She fell at the foot of a tree fern into soft, frond-littered loam.

  She tried to push herself up, but her arms seemed to have no strength. She got to her hands and knees, but the color leached out of the world, its dee
p swallowing green turning gray. Then the ground seemed to tilt, the loamy ground swiveling up to slap into her face, hard.

  The earth was cool under her cheek. She closed her eyes. The aches of her bruises and cuts seemed to fade, rattling into the distance like the storm’s thunder. A clamor filled her head, monotonous and loud, but somehow comforting. She let herself sink into the noise.

  After Capo had come the great divergence from the chimps. The new kinds of apes that followed were hominids — that is, closer to humans than chimps or gorillas.

  In the grand drama of the evolution of the hominids, learning to walk upright had been the easy part. Millions of years of apelike tree-climbing had seen to that. Now, as Capo’s descendants adapted to their new life on the interface between forest and savannah, to become more bipedal actually meant less body reorganization than needed to revert to all fours.

  Their feet, no longer required to grip branches at odd angles, became simplified into compact pads that lost much of their flexibility, and their big toes no longer worked as thumbs — but their new arched feet served as shock absorbers that enabled them to walk long distances without injury. Knee joints and thigh bones were redesigned to absorb the new upright load. The uprights’ spines became longer and curved to push their centers of gravity forward so it lay over their feet, and on the center line of their vertical bodies. New, specialized hip joints arose, a design that enabled them to lift one leg off the ground without losing their balance, as chimps would, so that they could walk without swaying. Their hands no longer had to combine manipulation with support and so became more flexible: their knuckles slimmed; their thumbs were freed up for more complex and delicate grasping. They became less strong, weight for weight, now that they didn’t need to haul themselves through the trees all the time.

  Bipedalism helped the new savannah apes by allowing them to walk or run long distances between scattered sources of food and shelter, and by enabling them to reach fruit and berries at higher levels. As time went on they became more upright and taller, succumbing to the same pressures that had shaped giraffes. Bipedalism was such a major advantage, in fact, that it had already evolved independently in other ape lineages — although all of those creatures would succumb to extinction long before true humans appeared.