In the end, the Earth had been mended by the extinction of humanity, and time. Although a residual population of its descendants, much reduced in size and intelligence, had survived on one of the Caribbean islands for forty or fifty thousand years, the civilisation of old-style Homo sapiens had ended two hundred thousand years ago, its passing marked by the Burn Line laid down by the eruption of the Yellowstone volcanic field and the global convulsion of endtime wars. Little remained of its works. The corpses of a few satellites in Lagrangian orbits. Relics on the Moon and Mars. Fossils of humans, domestic animals and machines and other artefacts, the ruins of coastal cities crushed into thin strata under metres of mudstone and limestone, a litter of sea-changed glass and plastic preserved in the deepest parts of the oceans. And a suite of genes promoting brain growth, bipedalism and other traits which had been stitched into the genomes of a variety of animal species in what appeared to be a deliberate attempt to pass on the fire of intelligence.

Surprisingly, it had worked, and more than once. In Africa, Survey and Surveillance’s palaeontologists had discovered the remains of a species of ape which had constructed earthwork labyrinths some thirty thousand years ago; at around the same time, in what had once been Southern China, a species of monkey had created elaborate forest gardens; and in Australia, large flightless birds descended from a species of emu had built networks of desert oases and created murals depicting flowers, animals and enigmatic ceremonies that stretched for kilometres along cliff faces.

The labyrinth builders and forest gardeners had only briefly flourished; the emu civilisation had survived for several thousand years before a century-long megadrought wiped it out. Meanwhile, in the Americas, an intelligent species of bears had arisen, building mound cities, fighting endless territorial wars and enslaving another intelligent species, this one descended from the common racoon: tailless (apart from a few individuals born with a vestigial stump), smaller than bears and humans but much larger than their racoon ancestors, with an upright posture, a descended larynx and opposable thumbs. When the bear civilisation abruptly collapsed in a plague of madness, these slaves inherited the world.

Centuries later, according to legend, one of the seedships dispatched into the vasty deep of interstellar space in a last desperate attempt to preserve the human species returned from a two-hundred-thousand-year round trip, having failed to establish a foothold on the planets of a nearby star. The first generation of new humans, quickened in a lunar habitat by Mother, the seedship’s machine intelligence, found that the former slaves, industrious and endlessly curious, had multiplied and prospered. Their cities and settlements were scattered across South and North America, they had begun to colonise Africa and Europe, and they were on the brink of an industrial revolution based on wind- and water-power.