“Yes. Yes, let’s go on.”

The Ice Age valley disappeared, as if into mist, and only the human faces remained, falling away like the leaves of a calendar.

Still David felt he could recognize the faces of his ancestors: round, almost always devastatingly young when giving birth, and still retaining that signature of blue eyes and strawberry-blond hair.

But the world had changed dramatically.

Great storms battered the sky, some lasting years. The ancestors struggled across landscapes of ice or drought, even desert, starving, thirsty, never healthy.

“We’ve been lucky,” David said. “We’ve had millennia of comparative climate stability. Time enough to figure out agriculture and build our cities and conquer the world. Before that, this.”

“So very fragile,” Bobby said, wondering.

More than a thousand generations deep, the faces began to grow darker.

“We’re migrating south,” Bobby said. “Losing our adaptation to the colder climates. Are we going back to Africa?”

“Yes.” David smiled. “We’re going home.”

And in a dozen more generations, as this first great migration was undone, the images began to stabilize.

This was the southern tip of Africa, east of the Cape of Good Hope. The ancestral group had reached a cave, close to a beach from which thick, tan sedimentary rocks protruded.

It seemed a generous place. Grassland and forest, dominated by bushes and trees with huge, colourful, thistly flowers, lapped right down to the sea’s edge. The ocean was calm, and seabirds wheeled overhead. The inter-tidal shoreline was rich with kelp, jellyfish and stranded cuttlefish.

There was game in the forest. At first they glimpsed familiar creatures like eland, springbok, elephant and wild pig, but deeper in time there were more unfamiliar species; long-horned buffalo, giant hartebeest, a kind of giant horse, striped like a zebra.

And here, in these unremarkable caves, the ancestors stayed, generation on generation.

The pace of change was now terribly slow. At first the ancestors wore clothes, but — as hundreds of generations withered away — the clothing was of decreasing quality, reducing at last to simple skin bags tied around naked waists, and at length not even that. They would hunt with stone-tipped spears and hand axes, no longer with arrows. But the stone tools too were of increasing coarseness, the hunting less ambitious, often no more than a patchy attempt to finish off a wounded eland.

In the caves — whose floors gradually sank deeper over the millennia, as successive layers of human detritus were removed — at first there was something like the sophistication of a human society. There was even art, images of animals and people, laboriously layered on the walls with dye-stained fingers.

But at last, more than twelve hundred generations deep, the walls became blank, the last crude images scraped away.

David shivered. He had reached a world without art: there were no pictures, no novels, no sculptures, perhaps not even songs or poetry. The world was draining of mind.

Deeper and deeper they fell, through three, four thousand generations: an immense desert of time, crossed by a chain of ancestors who bred and squabbled in this unadorned cave. The succession of grandmothers showed little meaningful change-but David thought he detected an increasing vagueness, a bewilderment, even a state of habitual, uncomprehending fear in those dark faces.

At last there was a sudden, jarring discontinuity. And this time it was not the landscape that changed but the ancestral face itself.

David slowed the fall, and the brothers stared at this most remote grandmother, peering from the mouth of the African cave her descendants would inhabit for thousands of generations.

Her face was outsized, with her eyes too far apart, nose flattened, and features spread too wide, as if the whole face had been pulled wide. Her jaw was thick, but her chin was shallow and sliced back. And bulging out of her forehead was an immense brow, a bony swelling like a tumour, pushing down the face beneath it and making the eyes sunken in their huge hard-boned sockets. A swelling at the back of her head offset the weight of that huge brow, but it tilted her head downward, so that her chin almost rested on her chest, her massive neck snaking forward.

But her eyes were clear and knowing.

She was more human than any ape, and yet she was not human. And it was that degree of closeness yet difference which disturbed him.

She was, unmistakably, Neanderthal.

“She’s beautiful,” Bobby said.

“Yes,” David breathed. “This is going to send the palaeontologists back to the drawing board.” He smiled, relishing the idea.

And, he wondered suddenly, how many watchers from his own far future would be studying him and his brother, even now, as they became the first humans to confront their own deep ancestors? He supposed he could never begin to imagine their forms, the tools they used, their thoughts — even as this Neanderthal grandmother could surely never have envisaged this lab, his half-invisible brother, the gleaming gadgets here.

And beyond those watchers, still further into the future, there must be others watching them in turn — and on, off into the still more unimaginable future, as long as humanity — or those who followed humans — persisted. It was a chilling, crushing thought.

All of it — supposing the Wormwood spared anybody at all.

“…Oh,” Bobby whispered. He sounded disappointed.

“What is it?”

“It’s not your fault. I knew the risk.” There was a rustle of cloth, a blurred shadow.

David turned. Bobby had gone.

But here was Hiram, storming into the lab, clattering doors and yelling. “I got them. Bugger me, I got them.” He slapped David on the back. “That DNA trace worked like a charm. Manzoni and Mary, the pair of them.” He raised his head. “You hear me, Bobby? I know you’re here. I got them. And if you want to see either of them again, you have to come to me. You got that?”

David stared into the deep eyes of his lost ancestor — a member of a different species, five thousand generations removed from himself — and cleared down the SoftScreen.

Chapter 27

Family history

When she was forcibly restored to open human society, Kate was relieved to find she’d been cleared of the criminal conviction brought against her. But she was stunned to find she was taken away from Mary, her friends, and immediately incarcerated — by Hiram Patterson.

The door to the suite opened, as it did twice a day.

There stood her guard; a woman, tall, willowy, dressed in a sober business-like trouser suit. She was even beautiful — but with a deadness of expression and in her dark eyes that Kate found chilling.

Her name, Kate had learned, was Mae Wilson.

Wilson pushed a small trolley through the door, hauled out yesterday’s, cast a fast, professional glance around the room, then shut the door. And that was that, over without a word.

Kate had been sitting on the room’s sole piece of furniture, a bed. Now she got up and crossed to the trolley, pulled back its white paper cover. There was cold meat, salad, bread, fruit, and drinks, a flask of coffee, bottled water, orange juice. On a lower deck there was laundry, fresh underwear, jumpsuits, sheets for Kate’s bed. The usual stuff.

Kate had long exhausted the possibilities of the twice-daily trolley. The paper plates and plastic cutlery were useless for anything but their primary purpose, and a nearly useless for that. Even the wheels of the trolley were of soft plastic. She went back to her bed and sat desultorily munching on a peach.

The rest of the room was just as unpromising. The walls were seamless, coated with a clear plastic she couldn’t dig her nails through. There wasn’t even a light fitting; the grey glow that flooded the room — twenty-four hours a day — came from fluorescents behind ceiling panels, sealed off behind plastic, and anyhow out of her reach. The bed was a plastic box seamlessly attached to the floor. She’d tried ripping the sheets, but the fabric was too tough. (And anyhow she wasn’t yet ready to visualize herself garrotting anybody, even Wilson.)