This book, and the series that it opens, neither follows nor precedes the books of the earlier Odyssey, but is at right angles to them: not a sequel or prequel, but an “orthoquel,” taking similar premises in a different direction.

The quotation from Rudyard Kipling’s “Cities and Thrones and Powers,” from Puck of Pook’s Hill (1906), is used by kind permission of AP Watt Ltd., on behalf of the National Trust for Places of Historical Interest or Natural Beauty.

For thirty million years the planet had cooled and dried, until, in the north, ice sheets gouged at the continents. The belt of forest that had once stretched across Africa and Eurasia, nearly continuous from the Atlantic coast to the Far East, had broken into dwindling pockets. The creatures who had once inhabited that timeless green had been forced to adapt, or move.

Seeker’s kind had done both.

Her infant clinging to her chest, Seeker crouched in the shadows at the fringe of the scrap of forest. Her deep eyes, under their bony hood of brow, peered out into brightness. The land beyond the forest was a plain, drenched in light and heat. It was a place of terrible simplicity, where death came swiftly. But it was a place of opportunity. This place would one day be the border country between Pakistan and Afghanistan, called by some the North—West Frontier.

Today, not far from the ragged fringe of the forest, an antelope carcass lay on the ground. The animal was not long dead—its wounds still oozed sticky blood—but the lions had already eaten their fill, and the other scavengers of the plain, the hyenas and the birds, had yet to discover it.

Seeker stood upright, unfolding her long legs, and peered around.

Seeker was an ape. Her body, thickly covered with dense black hair, was little more than a meter tall. Carrying little fat, her skin was slack. Her face was pulled forward into a muzzle, and her limbs were relics of an arboreal past: she had long arms, short legs. She looked very like a chimpanzee, in fact, but the split of her kind from those cousins of the deeper forest already lay some three million years in the past. Seeker stood comfortably upright, a true biped, her hips and pelvis more human than any chimp’s.

Seeker’s kind were scavengers, and not particularly effective ones. But they had advantages that no other animal in the world possessed. Cocooned in the unchanging forest, no chimp would ever make a tool as complex as the crude but laboriously crafted axe Seeker held in her fingers. And there was something in her eyes, a spark, beyond any other ape.

There was no sign of immediate danger. She stepped boldly out into the sun, her child clinging to her chest. One by one, timidly, walking upright or knuckle-walking, the rest of the troop followed her.

The infant squealed and pinched her mother’s fur painfully. Seeker’s kind had no names—these creatures’ language was still little more sophisticated than the songs of birds—but since she had been born, this baby, Seeker’s second, had been ferociously strong in the way she clung onto her mother, and Seeker thought of her as something like “Grasper.”

Burdened by the child, Seeker was among the last of the troop to reach the fallen antelope, and the others were already hacking with their chipped stones at the cartilage and skin that connected the animal’s limbs to its body. This butchery was a way to get a fast return of meat; the limbs could be hauled quickly back to the relative safety of the forest, and consumed at leisure. Seeker joined in the work with a will. The harsh sunlight was uncomfortable, though. It would be another million years before Seeker’s remote descendants, much more human in form, could stay out in the light, in bodies able to sweat and store moisture in fatty reserves, bodies like spacesuits built to survive the savannah.

The shrinking of the world forest had been a catastrophe for the apes that had once inhabited it. Already the evolutionary zenith of this great family of animals lay deep in the past. But some had adapted. Seeker’s kind still needed the forest’s shade, still crept into treetop nests each night, but by day they would dart out into the open to exploit easy scavenging opportunities like this. It was a hazardous way to make a living, but it was better than starving. As the forest fragmented further, more edge became available, and the living space for fringe-dwellers actually expanded. And as they scuttled perilously between two worlds, the blind scalpels of variation and selection shaped these desperate apes.

Now there was a concerted yapping, a patter of swift paws on the ground. Hyenas had belatedly scented the blood of the antelope, and were approaching in a great cloud of dust.

The upright apes had hacked off only three of the antelope’s limbs. But there was no more time. Clutching her child to her chest, Seeker raced after her troop toward the cool ancestral dark of the forest.

That night, as Seeker lay in her treetop nest of folded branches, something woke her. Grasper, curled up beside her mother, snored softly.

There was something in the air, a faint scent in her nostrils, that tasted of change.

Seeker was an animal fully dependent on the ecology in which she was embedded, and she was very sensitive to change. But there was more than an animal’s sensibility in her: as she peered at the stars with eyes still adapted for narrow forest spaces, she felt an inchoate curiosity.

If she had needed a name, it might have been Seeker.

It was that spark of curiosity, a kind of dim ancestor of wanderlust, that had guided her kind so far out of Africa. As the Ice Ages bit, the remnant forest pockets dwindled further or vanished. To survive, the forest-fringe apes would rush across the hazard of the open plain to a new forest clump, the imagined safety of a new home. Even those who survived would rarely make more than one such journey in a lifetime, a single odyssey of a kilometer or so. But some did survive, and flourish; and some of their children passed on farther.

In this way, as thousands of generations ticked by, the forest-fringe apes had slowly diffused out of Africa, reaching as far as Central Asia, and crossing the Gibraltar land bridge into Spain. It was a forward echo of more purposeful migrations in the future. But the apes were always sparse, and left few traces; no human paleontologist would ever suspect they had come so far out of Africa as this place, northwest India, or that they had gone farther still.

And now, as Seeker peered up at the sky, a single star slid across her field of view, slow, steady, purposeful as a cat. It was bright enough to cast a shadow, she saw. Wonder and fear warred in her. She raised a hand, but the sliding star was beyond the reach of her fingers.

This far into the night, India was deep in the shadow of Earth. But where the surface of the turning planet was bathed in sunlight, there was a shimmering—rippling color, brown and blue and green, flickering in patches like tiny doors opening. The tide of subtle changes washed around the planet like a second terminator.