Evolution

by Stephen Baxter

  Perhaps it was the gathering light that inspired the singing.

  It began far away, a thin warbling of intertwined male and female voices, probably just a single mating pair. Soon more voices joined in the duo’s song, a chorus of whooping cries that added counterpoint and harmony to the basic theme.

  Noth moved to the end of the branch to hear better. He peered through banks of giant leaves that angled south toward the sun, like so many miniature parasols. You could see a long way. The circumpolar forest was open, and the trees, cypress and beech, were well spaced so their leaves could catch the low Arctic sunlight. There were plenty of broad clearings where clumsy ground-dwelling herbivores rummaged. Noth’s eyes in their mask of black fur were huge — like his remote ancestor Purga’s, well adapted to the dark, but prone to dazzling in the daylight.

  The song’s meaning was simple: This is who we are! If you are not kin, stay away, for we are many and strong! If you are kin, come home, come home! But the song’s richness went beyond its utilitarian value. Much of it was random, bubbling, like scat singing. But at its best it was a spontaneous vocal symphony, running on for long minutes, with passages of extraordinary harmonic purity that entranced Noth.

  He lifted his muzzle to the sky and called.

  Noth was a kind of primate that would be called notharctus, of a class called adapid, descended from the plesiadapids of the early millennia after the comet. He looked much like a small lemur. He had a high conical chest, long and powerful legs, and comparatively short arms with black, grasping hands. His face was small with a pronounced muzzle, an inquisitive nose, and pricked-up ears. And he was equipped with a long, powerful tail, laden with fat, his winter hibernation store. He was a little more than one year old.

  Noth’s brain was considerably larger than Plesi’s or Purga’s, and his engagement with the world was correspondingly richer. There was more in Noth’s life than the urgencies of sex and food and pain; there was room for something like joy. And it was a joy he expressed in his song. His mother and father quickly joined in. Even Noth’s infant sisters contributed as best they could, adding their tiny mewling voices to the adults’ cries.

  It was noon, and the sun was the highest it would travel today, but it was still low in the sky. Shafts of low green-filtered light slanted through the trees, illuminating the dense, warm mist that rose from the steaming mulch on the floor, and the tree trunks sent shadows striping over the forest floor.

  This was Ellesmere, the northernmost part of North America. The summer sun never set, but merely completed circles in the sky, suspended above the horizon, as the broad leaves of the conifer trees drank in the light. This was a place where the shadows were always long, even in high summer. The forest, circling the Earth’s pole, had the air of a vast sylvan cathedral, as if the leaves were fragments of stained glass.

  And everywhere the adapids’ voices echoed.

  Emboldened, the adapids began to clamber down the branches toward the ground.

  Noth was primarily a fruit eater. But he came upon a fat jewel beetle. Its beautiful carapace, metallic blue green, crunched when he bit into it. As he moved he followed the scent marks of his own kind: I came this way. This way is safe… I saw danger here. Teeth! Teeth!… I am of this troop. Kin, come this way. Others, stay away… I am female. Follow this to find me… That last message gave Noth an uncomfortable tightness in his groin. He had scent glands on his wrists and in his armpits. Now he wiped his wrists through his armpits and then drew his forearms across the trunk, using bony spurs on his wrists to embed the scent, and to cut a distinctive curving scar in the bark. The female patch was old; the brief mating season was long over. But instinct prompted him to cover the patch with his own multimedia signature so that no other male would be alerted by it.

  Even now, even fourteen million years after the comet, Noth’s body still bore marks of his kind’s long nocturnal ancestry, like the glands for scent marking. His toes were tipped, but not with nails, like a monkey’s, but with grooming claws, like a lemur’s. His watchful eyes were huge, and like Purga he had whiskers to help him feel his way forward. He retained a powerful sense of hearing and smell; he had mobile radar-dish ears. But Noth’s eyes, while wide and capable of good night vision, did not share the dark-loving creatures’ ultimate adaptation, a tapetum, a yellow reflective layer in the eye. His nose, while sensitive, was dry. His upper lip was furry and mobile, making his face more expressive than those of earlier adapid species. His teeth were monkeylike, lacking the tooth comb — a special tooth used for grooming — of his ancestors.

  Like every species in the long evolutionary line that led from Purga to the unimaginable future, Noth’s was a species in transition, ladened with the relics of the past, glowing with the promise of the future.

  But his body and mind were healthy and vigorous, perfectly adapted to his world. And today he was as happy as it was possible for him to be.

  In the canopy above, Noth’s mother was taking care of her infants.

  She thought of her two remaining daughters as something like Left and Right, for one preferred the milk of the row of nipples on her left side, and the other — smaller, more easily bullied — had to make do with the right. The notharctus usually produced large litters — and mothers had multiple sets of nipples to support such broods. Noth’s mother had in fact borne quadruplets. But one of the infants had been taken by a bird; another, runtish, had quickly caught an infection and died. Their mother had soon forgotten them.

  Now she picked up Right and pushed her against the trunk of the tree, where the infant clung. Parked like this, her brownish fur blending into the background of the tree bark, Right would remain here until her mother returned to feed her. She was able to stay immobile for long hours.

  It was a form of protection. The notharctus were deep enough in the forest to be safe from any diving bird of prey, but the pup was vulnerable to the local ground-based predators, especially the miacoids. Ugly animals the size of ferrets, sometime burrow-raiders who scavenged opportunistically from the kills of other predators, the miacoids were an unprepossessing bunch, but nonetheless were the ancestors of the mighty cats and wolves and bears of later times. And they could climb trees.

  Now the attentive mother moved along the branch, seeking a comparable place of safety to leave Left. But the stronger child was happy where she was, clinging to her mother’s belly fur. After gentle pushing, her mother gave up. Laden with her daughter’s warm weight, she worked her way down a ladder of branches toward the ground.

  On all fours, Noth walked across a thick mulch of leaves.

  The trees here were deciduous, every autumn dropping their broad, veined leaves to cover the ground with a thick layer of decaying vegetation. Much of the mat on which Noth walked was made up of last autumn’s leaves, frozen by the winter’s hard cold before they could rot; now the leaves were mulching quickly, and small flies buzzed irritatingly through the misty air. But there were also butterflies, their gaudy wings making splashes of flitting color against the drab ground cover.

  Noth moved slowly, seeking food, wary of danger. He wasn’t alone here.

  Two fat taeniodonts grubbed their way across the ground, their faces buried in the rotting leaves. They looked like heavy-jawed wombats, and they used their powerful forelimbs to dig into the dirt, seeking roots and tubers. They were followed by an infant, a clumsy bundle pushing at her parents’ legs, struggling through the thick layer of leaves. A paleanodont scuffed for ants and beetles with its long anteater’s snout. And here was a solitary barylambda, a clumsy creature like a ground sloth with powerfully muscled legs and a stubby pointed tail. This creature, scuffling gloomily in the dirt, was the size of a Great Dane — but some of its cousins, in more open country, grew to the size of bison, among the largest animals of their day.

  In one corner of the clearing Noth made out the slow movement of a primate, in fact another kind of adapid. But it was quite unlike Noth himself. Like the loris of later times, this slow
, ground-loving creature looked more like a lazy bear cub than any primate. It moved slowly across the mush of leaves, making barely a sound, its nose snuffling the ground. This adapid generally stuck to the deeper forest where its slowness was not as disadvantageous as it would be on more open ground. Here, its slow and silent movements made it almost invisible to predators — and to the insect prey it sniffed out acutely.

  Noth wrinkled his nose. This adapid used urine as its scent marker; every time it toured its range it would carefully urinate on its hands and feet to leave its signature. As a result, to Noth’s sensitive nose it stank badly.

  Noth found a fallen beehive. He inspected it curiously, hesitantly. Hive bees were relatively new arrivals, part of an explosion of new forms of butterflies and beetles and other insects. The hive was abandoned, but there were whole handfuls of delicious honey to be had inside it.

  But, before he attacked the honey, Noth listened carefully, sniffing the air. His sensitive nose told him that the others, high in the trees above, were still far away. He ought to be able to devour this food before they reached him. But he shouldn’t. There was a calculation to be made.

  Noth was low-ranking among the males in his group. What Noth was expected to do was to call out, letting the rest know he had found food. Then the other males and the females would come, take as much honey as they wanted, and — if Noth was lucky — leave him a little for himself. If he stayed silent and was caught with the honey, he would be severely beaten, and any food left would be taken away, leaving him nothing at all. But on the other hand if he got away with it he might get to eat all the honey, and be spared any punishment…

  The choice was made. Soon he was working the honey with his small hands, licking it down as fast as he could, eyes flicking around to check on the others. He had finished the honey and wiped away any traces on his muzzle by the time his mother reached the ground.

  She still had her pup, Left, clinging to her belly. She began to scrabble at the floor, her fat-ladened tail held out behind her, silhouetted against the bright shafts of light that pierced the forest’s higher layers. She quickly uncovered more chunks of the fallen hive. Noth made a play of grabbing at the honey, but his mother pushed him away with a sharp shove and fell on it herself.

  Noth’s father now tried to join in the bounty, but his mate turned her back on him. Here came two of Noth’s aunts, his mother’s sisters. They immediately rushed to their sister’s side and, with screeches, bared teeth, and handfuls of thrown leaves, drove Noth’s father away. One of them even grabbed a chunk of honeycomb from his hand. Noth’s father fought back, but, like most adult males, he was outsized by any one of the females, and his struggles were futile.

  It was always the way. The females were the center of notharctus society. Powerful clans of sisters, mothers, aunts, and nieces, together for life, excluded the males. All this was a behavioral fossil: The dominance of females over males, and the tendency of male-female pairings to endure after mating, were more common in nocturnal species than those able to live in the light. This powerful matriarchy was making sure that the sisters had first call on the best of the food, before any male.

  Noth took his own exclusion calmly. After all, the taste of illicit honey still lingered in his mouth. He loped away in search of more food.

  Purga and Plesi had lived isolated lives, usually as females with pups, or as half of a mating pair. Solitary foraging was a better strategy for nocturnal creatures; not being part of a noisy group made it easier to hide from night hunters, who would wait in silent ambush for their prey.

  But animals active by day did better to keep to groups, with more eyes and ears on the alert to spot attackers. The notharctus had even evolved alarm calls and scents to warn each other of different classes of predators — birds of prey, ground predators, snakes — each of which required a different defensive response. And if you were part of a group there was always the chance that the predator would take the next guy, not you. It was a cold-blooded lottery that paid off often enough to be worthwhile adapting for.

  But there were disadvantages to group living: mainly, if there were large numbers of you, there was increased competition for food. As that competition resolved itself, the inevitable result was social complexity — and the size of the adapids’ brains had increased so that they were capable of handling that complexity. Then, of course, they were forced to become even more efficient at searching for food to fuel those big brains.

  It was the way of the future. As primate societies became ever more complex, a kind of cognitive arms race would continue, increasing smartness fueled by increasing social complications.

  But Noth wasn’t that smart. When he had found the honey, Noth had applied a simple behavioral rule: Call out if the big ones are close by. Don’t call if they aren’t. The rule gave Noth a good chance of getting away with maximum food and minimal beating. It didn’t always work, but often enough to be worth trying.

  It looked as if he had lied about the honey. But Noth was incapable of telling genuine lies — planting a false belief in the minds of others — for he had no real understanding that others had beliefs at all, let alone that their beliefs could be different from his, or that his actions could shape those beliefs. The peekaboo game played with human infants — if you want to hide, just cover your eyes; if you can’t see them, they can’t see you — would have fooled him every time.

  Noth was one of the most intelligent creatures on the planet. But his intelligence was specialized. He was a great deal smarter concerning problems about the others of his kind — where they were, their potential for threat or support, the hierarchies they formed — than about anything else in his environment. He couldn’t, for example, associate snake tracks with the possibility that he might stumble on a snake. And though his behavior looked complex and subtle, he obeyed rules as rigidly as if they had been programmed into a tribe of robots.

  And still the notharctus spent much of their lives as solitary foragers, just as Purga had. It was visible in the way they moved: They were aware of each other, avoided each other, huddled for protection, but they did not move together. They were like natural loners forced to cooperate, uncomfortably imprisoned by necessity with others.

  As Noth worked the forest floor, a troop of dark little creatures scurried by nervously. They had ratlike incisors, and a humble verminous look compared to Noth and his family, their black-and-white fur patchy and filthy. These little primates were plesiadapids: all but identical to Purga, even though she had died more than fourteen million years before. They were a relic of the past.

  One plesi came too close, snuffling in its comparative blindness; Noth deigned to spit a seed at it; the seed hit the scuttling creature in the eye, and it flinched.

  A lithe body, low-slung, slim, darted from the shade of the trees. Looking like a hyena, this was a mesonychid.

  Noth and his family cleared off the ground quickly.

  The plesi froze. But it was hopelessly exposed on this open forest floor.

  The mesonychid hurled itself forward. The plesi squirmed and rolled, hissing. But the meso’s teeth had already taken a chunk out of its hind leg. Now more of the meso’s pack, scenting blood, came jostling toward the site of the attack.

  The mesonychid was a kind of condylarth, a diverse group of animals related to the ancestors of hoofed animals. The meso was not an expert killer or a meat specialist but, like a bear or wolverine, it was an opportunistic feeder. All the condylarths were doomed to extinction ten million years before the age of mankind. But for now they were in their pomp, top predators of the world forest.

  The other inhabitants of the forest floor reacted in their different ways. The lorislike adapid had a shield of thickened skin over bony bumps on its back, beneath which it now tucked its head. The big, dull barylambda concluded it was under no threat even from a pack of these small hunters; like the hyenas of later ages, the mesos were primarily scavengers and rarely attacked an animal much bigger than themselves.
The taeniodont, however, decided that caution was called for; pompously it trotted away, its gaping mouth showing its high teeth.

  Meanwhile the plesi fought on, inflicting scratches and bites on its assailants. One of the mesos was left whining, the tendons of its right hind leg badly ripped, blood leaking from torn flesh. But at last the plesi succumbed to their teeth and weight. The mesos formed a loose circle around their victim, their slim bodies and waving tails clustered around their meal like maggots around a wound. The rising stink of blood, and the fouler stench of panic shit and stomach contents, overwhelmed Noth’s sensitive nose.

  Though some of the ancient plesiadapids had specialized, learning how to husk fruit like opossums or to live off the gum of trees, they remained primarily insect eaters. But now they faced competition from other insectivores, the ancestors of hedgehogs and shrews — and from their own descendant forms like the notharctus. Already the early-form plesis had become extinct across much of North America, surviving only in fringe areas like this marginally habitable polar forest, where the endless days did not suit bodies and habits shaped during the nights of the Cretaceous. Soon the last of them would be gone.

  Noth, high in the cathedral calm of the trees, could see the family as they climbed up toward him, their lithe limbs working smoothly. But something disturbed him: a shift in the light, a sudden coldness. As clouds crowded past the sun, the great forest-spanning buttresses of light were dissolving. Noth felt cold, and his fur bristled. Rain began to fall: heavy misshapen drops that clattered against the trees’ broad leaves and pounded like artillery shells into the mud below.

  It was because of the onset of the rain, and the overwhelming stink of the bloody deaths below, that Noth did not detect the approach of Solo.

  Hidden in a patch of shadow, his scent blowing downwind, Solo saw the notharctus troop scurrying to safety.