This layer marked the boundary between the Palaeozoic and Mesozoic eras, a boundary in time marked by the greatest extinction of life in Earth’s history. The ancient spasm of death, recorded in rock, had been obvious to the first modern geologists, the gentlemen-scientists from Edinburgh.

Even now, nobody knew how it had happened. The more famous extinction pulse at the end of the Cretaceous, the one that had killed off the dinosaurs, had attracted a great deal more study, but that event had involved far fewer species. The best explanation was a slow deterioration of the climate, accompanied by a lowering of sea level, that had created conditions inimical to most life existing at the time.

That was plausible. But nobody knew.

The answer was surely embedded in these rocky layers somewhere, in the bones and skulls eroding out of the Karroo. But Henry could grab all the samples he liked; he was sure the answer would never, now, be found.

Henry had grown up believing that the future was, more or less, infinite, and that there would be time — for generations to come, if not for him — to figure out answers to most of the great questions. Earth itself held the clues to the great puzzles of geology and palaeontology, and Earth would always be there…

But the future wasn’t infinite any more, and Earth wasn’t going to last forever.

There just wasn’t time for the slow processes of science to unpick the secrets of Earth’s past. When the evidence was gone, it would be gone forever, and they would never know.

So, here was Henry clambering over the Karroo, grab-bagging bones out of the ground.

Field work was now the only game in town, in all the sciences.

Nobody was doing analytical science any more. The only people working in labs were directing the others, out in the field.

Most of the effort, in fact, was in biology. In what was left of the rain forests, half-trained researchers were wrapping entire giant trees in plastic and drenching them with bug spray, hoovering up the stiff little bodies into nitrogen-cooled collection flasks, for eventual shipping to the great Arks that were flying to the Moon.

The National Institutes of Health’s Natural Products Repository in Maryland — fifty thousand samples of plant, microbial and marine material from thirty tropical countries, stored in forty-one walk-in freezers — had been compactified, roughly catalogued and fired off to a cryogenic store in some deep-shadowed crater on the Moon. Some of the big bioprospecting drug companies, like Merck which had spent years trawling the flora and fauna of Costa Rica for resources for new products, had had similar repositories impounded and shipped off-Earth, though not without bloody battles over compensation.

And so on.