Evolution

by Stephen Baxter

  Far sat ten meters away, her legs folded before her, hugging her knees, fascinated by his toolmaking. It was like nothing she had seen before.

  In fact, Ax and Far had grown up in toolmaking traditions separated by millennia.

  Once they had put the trees behind them and moved definitively out onto the savannah, a new range of possibilities had opened up for the walkers. They were more than merely mobile. They migrated. But it wasn’t purposeful. For each individual, it was just a question of making a living. For people able to exploit new landscapes, it was often easier to walk to somewhere that looked a better place to live than to try to adapt to harsh conditions.

  But as the generations ticked by the people covered thousands of kilometers. They even walked out of Africa, into lands where no hominid had set foot before. Before the great clamp of the glaciations tightened, equable conditions had spread well out of Africa into southern Europe, the Middle East, and southern Asia. Walking into these familiar surroundings the people followed the easy living of the coastlines, west around the Mediterranean and diffusing inland, at last colonizing Spain, France, Greece, Italy — as did animals later associated only with Africa, like elephants, giraffes, and antelope. To the east, they worked through India to the Far East, suffusing through what would become China, even working south to reach Indonesia.

  It was not a conquest. Far’s kind had become far more widespread than any other ape species. But other animals, like the elephants, spread much further. And there were fewer of them. Their numbers in any given area were less than lions, say. Despite their tools the people were still just big animals in a landscape on which they had minimal impact.

  And the great wandering was not purposeful. One of Far’s distant grandmothers had reached as far as Vietnam; now, in Far’s time, chance and the endless walking had brought her lineage back to East Africa, to home.

  But here, in the ancient homelands, the returning migrants encountered new pressures.

  Some hominid populations had elected not to move, despite the climate’s treacherous fluctuations. To survive they had been forced to become smarter. Better tools — crucially, the hand axes — had been the key to their survival. The ax’s secret was its teardrop shape. A flattened bi-faced shape gave a long cutting edge for minimal weight. Though they would still use simple pithecine-like flake tools if they needed to — the flakes, easy to make, were “cheap” and were actually better for some tasks, like tackling small prey — the hand axes were used not just for butchering meat, but for hacking sticks and clubs from branches, sharpening wooden spears, opening up beehives, digging into logs to get at larvae, peeling off bark, shredding pith, and opening the shells of tortoises and turtles. It was from a group of these stay-at-homes that Ax was descended.

  Which was how Far, descendant of wanderers who had crossed southern Eurasia all the way to the Far East, now found herself confronted by the startlingly advanced technology of Ax and his kind.

  Ax worked patiently. Her gaze wandering, Far noticed now that the dry bed here was littered with hand axes: many of the rocks she had assumed were just cobbles had actually been shaped. They all had the characteristic teardrop shape, and were all worked to a greater or lesser degree to give that fine edge all the way around the tool.

  But these axes were strange. Some of the axes were tiny, the size of butterflies, while some were huge. Some of them were broken, some smeared with blood. But when she tried to pick up one of the larger axes, its edge cut into her fingers; it had hardly been used, if at all.

  Someone walked up to her. She cowered back.

  It was Scar-face, the man who had taught the children how to knap rock. He was looking at Far with a kind of hungry intensity. He had one of the huge axes in his hands. It was impractically large, too large to use to butcher. Still gazing at her he turned it over in his hands, and tapped at it with a hammer-stone, tidying up an edge. Then he scraped it over his leg, and removed a swath of the fine black hair that grew there. All through this he watched Far’s face and body, his half-covered eye gleaming.

  She had absolutely no idea what he wanted — none, that is, until she saw the erection poking out of his tuft of pubic hair.

  Ax had more or less finished the blade he was making: hand-sized, utilitarian, rough and ready, it was clearly a functional tool, manufactured in minutes. But when he saw what Scar-face was doing he threw down his ax angrily. He got up, scattering his spill of flakes, and punched the man’s shoulder. “Away! Away!”

  Scar-face snarled back, his erection subsiding. At last Ax grabbed the huge gaudy ax out of his hands, and threw it to the ground. Part of its beautiful edge sheared off. Scar-face looked at the ax, at Far, and, with a final glare at Ax, walked away.

  Far sat where she was, her knees tucked against her chest, fearful and baffled.

  Ax stared at her. Then he stalked up and down the dry stream again, surveying the stones. At last he came across a big malformed volcanic block, so heavy it took two hands to lift it. He sat down again, picked up a few hammer-stones, scattered more brush over his legs.

  He started to slam at the rock, displaying all his strength. Flakes and sheets of it began to fall away. But very quickly, thanks to his skill and strength, a crude hand ax teardrop shape emerged. Now he started to use a succession of smaller stones to shape the two lenticular surfaces, and to finish the edge to a fine blade.

  Where his first effort had come easily, borne out of a rock that had already had the rough shape of the final ax, this rock was much more difficult. He couldn’t have picked a tougher challenge — and he had chosen it deliberately. And all through this he made sure Far was watching him.

  The walking folk had already been making tools more or less like this for two hundred thousand years. Over such an immense span of time, the axes had become more than mere tools, more than functional.

  To Ax, this feat of toolmaking was a kind of courtship. He was displaying his fitness as a mate to Far. By making the tool he was showing her in one clear demonstration the strength of his body, the precision of his working, the clarity of his mind, his ability to conceive and see through a design, his skill for locating raw materials, his coordination of hand and eye, his spatial skills, his understanding of the environment around him. All of these were traits he expected she would want to pass on to her offspring — and that was why such displays had acquired a logic of their own, divorced from the utility of the hand axes.

  Driven by lust and longing, men and boys would make dozens of axes, over and over. They would labor for hours over a single ax, seeking perfect symmetry. They would make tiny axes the size of their thumbnails, or they would make huge unwieldy affairs that would have to be held in two hands like an open book. They would, as Ax had, seek out particularly difficult raw materials and go ahead and carve out axes anyhow. Sometimes they would even throw away their axes, deliberately, to show how rich they were in strength and skill.

  It was even worth trying to cheat, as Scar-face had done. It didn’t work very often — women quickly learned they had to see the most impressive ax being made before them — but occasionally it paid off, and the liar got a chance to pass on his genes at very low cost.

  This mixing up of toolmaking with sexual courtship would have a profound effect on the future. As no male could afford not to make axes just as his forefathers had done, it was a recipe for stultifying conservatism. These people would make the same tool to the same plan, over and over, across several continents, despite several glacial cycles, for a million years. Even the different species who followed them would continue with the same technology. It was a continuity and a consistency that no institution, no religion would ever match. Only sex had a strong enough hold on the human mind to have achieved such a vast freezing.

  When he worked on his tools, Ax had to think, to some extent, like a human. Unlike the pithecine stone-slammer who would take whatever shape and size of flake his cobble offered him, Ax had to have an image of the final artifact in his mind. He had to
select the raw materials and hammer-stones to match that vision, and he had to work systematically toward his goal. But his mind was divided as no human’s could be. Ax made his tools like a human, but he attracted mates like a peacock or a bower bird.

  When Ax was done, he turned the tool he had made over and over in his hands, showing her its fine faces, its smoothly finished edge. It was magnificent, if impractical.

  Far, brought up in a subtly different culture, had no clear idea of what he was doing — and she was just as baffled by Scar-face’s attempt to cheat. But she did sense Ax’s interest in her, and a warmth in her belly spread in response. And a more calculating corner of her mind was aware that if she mated with Ax, if she became pregnant, then she would become part of this group, and her future would be secured.

  But she had never had sex, not with anybody. Longing, fearful, she sat there at the edge of the streambed, her legs still tucked against her chest. She didn’t know how to respond.

  At length he dropped the beautiful ax, among so many others. Baffled, casting backward glances at her, he walked away.

  Speciation — the emergence of a new species — was a rare event.

  One species did not morph smoothly into another. Rather, speciation relied on a group of animals being isolated from the larger population and put under pressure to survive. The isolation could be physical — say, if a group of elephants was cut off by a flood — or it could be behavioral, if, for instance, one group of hominids that had adopted a particular way of scavenging was shunned by another group that hadn’t.

  Variation was implicit in the genome of every species. It was as if every species, at any given moment, was contained in a field, fenced off by the habitable limits of its environment. Every viable variation would come into play, to fill up every available corner of the field. An isolated group was stuck in a fenced-off corner of the field. But perhaps a little of the outer fence came down, opening up a new and empty field, into which they began, slowly, to diffuse. More variation might be necessary to fill the newly available space — and if the necessary variation wasn’t available in the genome, perhaps it could be generated by mutation.

  In the end, those who reached the furthest corner of the new range might have gone a great distance, genetically, from those who had remained in the old field. If the distance became too great for the old and new kinds to crossbreed, a new species was born. Later, when the isolating barriers came down, the evolved kind might interact with the parent type — perhaps to supplant them.

  Some three hundred thousand years earlier, in another part of Africa, a group of nondescript forest-fringe pithecines had found themselves cut off from their home range by a lava flow, cast out of their forest once and for all.

  There were many challenges to be met. The old pithecine habits of forest-fringe hunting had been a start, something to build on. But out on the savannah the food supply was very different from that in the forest. Whereas the forest had provided a steady supply of fruit, the main savannah food was meat. Meat was high-quality nutrition, but it came in packages scattered sparsely over an arid, inhospitable landscape, packages you had to be smart to spot, get hold of, and use. And stranded out on the savannah, away from the trees’ shelter, a new kind of body was needed to cope with the aridity and the heat, new kinds of behavior needed to extract the resources needed from the new environment — and to survive in predator hell.

  Within a mere few dozen generations Far’s ancestors had adapted drastically.

  The ancient primate body plan had been rebuilt, stretched tall almost to human proportions. Far’s body was much bulkier than that of the ancestral apes. She was twice as heavy as an adult gracile pithecine. That bulk was an adaptation for openness: a larger body was more efficient at storing water, a key advantage on a plain where there could be many hours’ walking between water sources.

  And her metabolism had become efficient at creating and storing subcutaneous fat, for fat was a key fuel reserve. Ten kilograms of fat would be sufficient to see her through forty days without food, enough to ride out all but the most severe seasonal fluctuations. The fat had fleshed out her body, giving her swollen breasts, buttocks, and thighs, a much more human shape than the pithecines’ chimplike slackness. But Far was not a round ball; instead she was tall and thin, so that her body was also an efficient radiator of waste heat, and when the sun beat down from above, comparatively little of her skin was directly exposed to its radiation.

  More heat adaptations: Apart from her head, with its grooming patch of hair, her skin was all but bare. And she sweated, unlike Capo, unlike any other ape outside her species family, for bare, sweating skin was a better temperature regulator than hair for creatures destined to spend their lives in open tropical sunlight. Sweating was a paradox, for it meant Far lost water. So she had to be smart enough to find water sources to make up for that, and, unlike some of the true savannah creatures, her kind would always be tied to some extent to water courses and the coasts.

  The most apelike characteristics of the pithecines — their grasping feet, long arms, and stooping gait — had soon been abandoned. Far’s feet were best fit for running and walking, not climbing: her big toe was now a toe, not a thumb. But Far’s rib cage was a little high, her shoulders a little narrow: even now her body still carried with it traces of its vanishing adaptation to the trees — as would modern humans’, as would Joan Useb’s.

  Meanwhile her brain had grown to more than three times the mass of a pithecine’s, the better to handle the puzzles of a difficult landscape and the intricacies of still more complex societies of large groups of savannah foragers. That big brain was very energy-hungry, but Far’s diet was much richer than any pithecine’s, with plenty of high-protein foods like meat and nuts, which in turn required greater intelligence to gather. Thus her smartness had been driven by a virtuous circle of development.

  All these changes were drastic, and yet they had been achieved by an evolutionary strategy of remarkable economy. It had been heterochrony — different timing. Walker infants looked much as their more apelike ancestors had — as would human babies — with relatively large skulls, small faces and jaws. If you wanted to become Capo, you grew your jaw large and kept your brain relatively small. But Far’s brain had grown large while her jaw had stayed small. Even the much larger size of her body had been achieved by stretching out growing phases: her body had something like the relative dimensions of a fetal Capo, inflated to adult size.

  But that large body size and big brain came at a price. She had been born with her development incomplete, because that was the only way her head would have squeezed through her mother’s birth canal. She had been born premature. Unlike the apes and even the pithecines, walker infants could not forage for themselves until long after weaning: aside from their physical immaturity, the ability to exploit food sources like hunted meat, clams, and heavy-shelled nuts was not innate in the newborn, and so had to be learned. But at the same time the children of the walkers were being born into the predator hell of the savannah. So, while they were young, kids needed a lot of care.

  These costly, dependent children made it difficult for the walker types to compete with the fast-breeding pithecines, with whom they often shared the same habitats. And that was why the walkers began to live longer.

  Most pithecine females, like the apes before them, died not long after their fertility ended — indeed, few long outlived their last birth. Walker women, and men, began to live for years, even decades after their reproductive career was apparently over. These grandmothers and grandfathers began to play a crucial role in shaping walker society. They helped with the division of labor: They helped their daughters care for the children, they helped gather food, they were essential in passing on the complex information required by the walkers to survive.

  All this had required a new efficiency in body design. Walker bodies were much better than pithecines’ at maintenance and longevity — all save their reproductive systems; a forty-year-old wa
lker woman’s ovaries were as badly degenerated as would be the rest of her body at age eighty, if she lived that long.

  Crucially, the grandmothers’ support meant their daughters could afford to have children more often. That was how the walkers outcompeted the pithecines and apes. Almost all walker children survived long after weaning. Almost all pithecine infants did not.

  For the pithecines the emergence of this new form was a disaster. Walkers and pithecines were too close cousins to share the ecology easily. There were few direct conflicts between the types of people: Sometimes pithecines hunted walkers or walkers hunted pithecines, but they found each other too smart and dangerous a prey to be worth the trouble. But in ages to come the walkers — big-brained, flexible, mobile — would slowly drive their smaller-brained cousins to extinction.

  Toolmaking and even consciousness were, ultimately, no guarantee of survival.

  Of course it need not have happened. If not for the fluctuation of the climate, the chance isolation of Far’s ancestors, there might have been no mankind: nothing but pithecines, upright chimps screeching and making their crude tools and waging their petty wars for millions of years more, until the forests disappeared altogether, and they succumbed to extinction.

  Life always had been chancy.

  Far spent the night alone, cold, drifting through an uneasy sleep.

  The next day, as she tried to join in the group’s activities, a woman, heavily pregnant, glared into her eyes, an ancient primate challenge. Was Far here to take food that might otherwise reach the belly of her unborn child?

  Far felt more isolated than ever. She had no ties with anybody here. There was no reason why they should share their space, their resources with her. It wasn’t as if this place was brimming with riches. And now even Ax seemed to be rejecting her.

  As the afternoon wore on she was the first to return, alone, to the hollow in the sandstone outcrop. She tucked herself into the peripheral corner she had come to think of as her own.