Evolution

And underneath the clay, one day, her mother had found a tooth.

'Joan, this isn’t just a tooth. I think it’s a Purgatorius tooth.'

'Say what?'

Her mother was big, bluff, her face coated with sweat and dust. 'Purgatorius. A dinosaur-era mammal. Found it right under the boundary clay.'

'You can tell all that from a tooth?'

'Sure. I mean, look at this thing. It’s a precise piece of dental engineering, already the result of a hundred and fifty million years of evolution. It’s all connected, you see. If you’re a mammal you need specialized teeth so you can shear your food more rapidly, because you have to fuel a faster metabolism. But if your mother produces milk, you don’t need to be born with your final set of teeth; the specialist tools can grow in place later. Didn’t you ever wonder why you had milk teeth? Joan, a lot of people are going to care a great deal about this. You know why? Because it’s a primate. This little scrap could be all that’s left of the most remote ancestor of you and me — and everybody alive — and the chimps and gorillas and lemurs and—'

And so on. The usual lecture, from the great Professor Useb. Joan, at age thirteen, had been a lot more interested in spectacular dinosaur skulls than ratty little teeth like this. But still, something about it had stuck in her mind. And, in the end, such moments had shaped her life.

'That’s the point of the conference, you see, Bex,' Alyce was saying. 'It’s a synthesis. We want to pull together the best understanding we have of how we got here, we humans. We want to tell the story of humankind. Because now we have to decide how we are going to deal with the future. Our theme is the globalization of empathy.'

That was true. The real purpose of the conference, known only to Joan, Alyce, and a few close colleagues, was to found a new movement, establish a new way of thinking, a new approach that might actually stave off the human-induced extinction event.

Bex shrugged. 'You think anybody’s going to listen to a bunch of scientists? No offense. But nobody has so far.'

Joan forced a smile. 'No offense taken. We’re going to try anyway. Somebody has to.'

'And there’s no point in all that stuff anymore, is there? Your archaeology.'

Joan frowned. 'What do you mean?'

Bex clapped her hands over her mouth. 'I shouldn’t say anything. My mother will be furious.' Her Martian eyes were bright.

Alyce had withdrawn into herself again; she gazed out of the window at the billowing debris of forest fires a thousand kilometers away.

Suppose I threw you down the strata, back into time, Joan’s mother had said to her. After just a hundred thousand years you’d lose that nice high forehead of yours. Your upright-walker legs would be gone after three or four million years. You’d grow your tail back after twenty-five million years. After thirty-five million, you’d lose the last of your ape features, like your teeth; after that you’d be a monkey, child. And then you’d keep on shrinking. Forty million years deep you’d look something like a lemur. And eventually -

Eventually, she would be a little ratty thing, hiding from dinosaurs.

Sometimes she had been allowed to sleep in the open, in the cool air of the badlands. The Montana sky was huge and crammed with stars. The Milky Way, a side-on view of a giant spiral galaxy, was a highway across the night. She would lie on her back, gazing up, imagining the rocky Earth had vanished, its cargo of fossils and all, and that she was adrift in space. She wondered if that little Purgatorius critter would have seen the same sky. Had the stars swum about the sky, across sixty-five million years? Did the Galaxy itself turn, like some huge pinwheel in the night?

But tonight, she thought, the smoke from the volcano would hide any stars.

ONE Ancestors

CHAPTER 1 Dinosaur Dreams Montana, North America. Circa 65 million years before present.

I

At the edge of the clearing, Purga crept out of a dense patch of ferns. It was night, but there was plenty of light — not from the Moon, but from the comet whose spectacular tail spread across the cloudless sky, washing out all but the brightest stars.

This scrap of forest lay in a broad, shallow lowland between new volcanic mountains to the west — the mountains that would become the Rockies — and the Appalachian plains to the east. Tonight the damp air was clear; but often mists and fogs blew in from the south, born over the great inland sea that still pushed deep into the heart of North America. The forest was dominated by plants that could extract moisture from the air: Lichen coated the gnarled bark of the araucaria trees, and even the low magnolia shrubs dripped with moss. It was as if the forest had been coated with a layer of thick green paint.

But everywhere the leaves were soured, the moss and ground cover ferns browned. The rains, poisoned by gases from the great volcanic convulsion to the west, had been hard on plants and animals alike. It wasn’t a healthy time.

Still, in the clearing, dinosaurs dreamed.

The thick night dew glistening from their yellow-black armor, ankylosaurs had gathered in a defensive circle, their young at the center. In the gentle Cretaceous air, these cold-blooded giants stood like parked tanks.

In the milky light Purga’s large black eyes had fixed on a moth. The insect sat on a leaf, brown wings folded, fat and complacent. With an efficient lunge Purga caught her prey in her paws. She severed off the wings with a couple of nips of her tiny incisors. Then, with a noise like the crunch of a tiny apple, she began to munch with relish at the moth’s abdomen. For this brief moment, with food in her mouth, Purga found a scrap of contentment in her crowded, difficult life.

The moth quickly died, its sparklike awareness incapable of recording much pain.

The moth consumed, Purga moved on. There was no grass cover here — the grasses had yet to dominate the land — but there was a green covering of low ferns, mosses, ground pine, horsetails, and conifer seedlings, even a few gaudy purple flowers. Through this tangle, scuttling between scraps of cover, she was able to progress almost silently. In the dark, solitary foraging was the best strategy. Predators worked by ambush, exploiting the shadows of the night; no group could have been as invisible as a lone prowler. And so Purga worked alone.

To Purga the world was a plain picked out in black, white, and blue, lit up by the uneasy light of the comet, which shone behind high scattered clouds. Her huge eyes were not as sensitive to color as the best dinosaur designs — some raptors could make out colors beyond anything that would be visible to humans, somber infrareds and sparkling ultraviolets — but Purga’s vision worked well in the low light of night. And besides she had her whiskers, which fanned out before her like a tactile radar sweep.

Purga looked more rodentlike than primate, with whiskers, a pointed snout, and small folded-back ears. She was about the size of a small bush baby. On the ground she walked on all fours, and she carried her long bushy tail behind her, like a squirrel. To human eyes she would have seemed strange, almost reptilian in her stillness and watchfulness, perhaps incomplete.

But, as Joan Useb would one day learn, she was indeed a primate, a progenitor of that great class of animals. Through her brief life flowed a molecular river with its source in the deepest past, its destination the sea of the furthest future. And from that river of genes, widening and modifying as thousands of millennia passed, would one day emerge all of humanity: Every human ever born would be descended from the children of Purga.

She knew none of this. She didn’t give herself a name. She was not conscious like a human — or even like a chimp or monkey; her mind was more like a rat’s or a pigeon’s. Her behavior was made up of fixed patterns, controlled by innate drives that constantly shifted in balance and priority, reaching a new sum each moment. She was like a tiny robot. She had no sense of self.

And yet she was aware. She knew pleasure — the pleasure of a full belly, the safety of her burrow, the snouts of her pups as they nuzzled her belly for milk — and, in this dangerous world, she knew fear very well.

She crept among the feet of dreaming ankylosaurs. As she moved beneath the immense bellies Purga could hear the huge rumble of the dinosaurs’ endless digestion, and the air was thick with their noxious farts. With their crude teeth, all the work of processing and digesting their coarse food had to be done in the dinosaurs’ vast guts, which labored even as the ankylosaurs slept.

The ankylosaurs were herbivorous dinosaurs. But this was a time of huge, ferocious predators. So these animals, larger than African elephants, were covered with armor, a fusion of bones, ribs, and vertebrae. Great yellow-black spines were embedded in their backs. Their skulls were so heavily reinforced there was little room left for brain. Their tails ended in heavy clubs that could smash legs or skulls.

The dinosaurs were too huge for Purga to comprehend. Hers was a small world, where a fallen log or a puddle was a major obstacle, where a scorpion could be a significant predator, where a fat millipede was a rare treat. To her, the dozing ankylosaur herd was a forest of immense stumpy legs and drooping tails that had no connection to each other.

But for Purga there was a rich prize here: dinosaur dung, immense heaps of it scattered in the muddy, trampled ground. Here, in fibrous mountains of roughly digested vegetation, she might find insects, even dung beetles, laboring to destroy the tremendous turds. She burrowed into the steaming stuff eagerly.

Thus had been the role of the ancestors of humanity, all through the long dinosaur summer: relegated to the fringe of the reptiles’ great society, emerging from their burrows only at night, foraging for a living from dung, insects, and the small pickings of the forest.

But tonight the rewards were meager, the droppings watery and foul-smelling. The volcano-damaged vegetation had provided poor fodder for the ankylosaurs, and what came out the other end was of little value to Purga.

She moved across the clearing and into the forest. Here conifers towered grandly, rising to spreading mats of leaves far overhead. Among them were smaller trees a little like palms, and a few low bushes bearing pale yellow flowers.

Purga scrambled briskly into the angular branches of a ginkgo tree. As she climbed she used the scent glands in her crotch to mark the tree. In her world of night, scent and sound were more important than sight, and if others of her kind found this mark, any time within the next week, it would be a sign like a neon light, telling them she had been here, even how long ago she had passed.

It was pleasing to climb, to feel her muscles work smoothly as they hauled her high above the dangerous ground, to use the delicate balance afforded by her long tail — and, most of all, to jump, to fly briefly from one branch to another, using all her body’s equipment, her balance, her agility, her grasping hands, her fine eyes. She was forced to shelter in burrows on the ground. But everything about her had been shaped by an existence in the complex three-dimensional environment of the trees, where almost all primate species, throughout the family’s long history, would find refuge.