Bringing Back the Thunder Beast

The freezer opens with a sound like a held breath released, and cold rolls out over the floor in a slow white tide. Inside, in racks of labelled vials, are fragments of animals that no longer exist.

The technician lifts one out with gloved fingers and turns it under the light. There is not much to see — a smear of frozen material, clouded, unremarkable. It came from a specimen collected more than a century ago, and it contains, in badly broken pieces, the instructions for building something the world has not contained since. She sets it back. The freezer closes. The cold withdraws.

"People imagine we've got a mammoth in here somewhere," she says, without looking up. "What we've got is a very expensive jigsaw with most of the pieces missing, and no picture on the box."

This is the first thing to understand about de-extinction, and almost nobody reporting on it says so plainly: nothing is being brought back. Ancient DNA does not survive intact. It shatters into short fragments, accumulates chemical damage, and after a few hundred thousand years gives up altogether. There will be no mammoth resurrected from a frozen carcass, no cloning of a creature from the permafrost. What can be done — what is being attempted, seriously and at considerable expense — is something subtler and stranger. Take a living relative. Identify the genetic differences that matter. Edit them, one by one, into the living genome until you have produced an animal that is not the extinct species but does the job the extinct species did.

For the mammoth, the living relative is the Asian elephant, which shares a common ancestor with it around six million years ago and differs across roughly a million and a half positions in the genome. Most of those differences are irrelevant. A few dozen govern the traits that matter for surviving a Siberian winter: a haemoglobin variant that releases oxygen efficiently at low temperature, a thicker subcutaneous fat layer, small ears that do not surrender heat, dense hair. Edit those into an elephant cell, and you have not made a mammoth. You have made a cold-tolerant elephant. Whether that distinction troubles you says a great deal about what you think species are for.

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Four thousand miles east, on a floodplain in the far north-east of Siberia, a very different experiment has been running for three decades, and it does not involve genetics at all.

The ground here is frozen to a depth of hundreds of metres, and it is thawing. Locked inside that permafrost is an enormous quantity of ancient organic carbon — the remains of grassland ecosystems that flourished during the last ice age. When it thaws, microbes get to work, and the carbon leaves as carbon dioxide and methane. The scale involved is difficult to hold in the mind: more carbon than exists in all the world's remaining forests.

The scientists here noticed something in the old sediment layers. During the Pleistocene, this landscape was not the mossy, shrubby tundra it is now. It was grassland — cold, dry, enormously productive — and it was full of large animals. Mammoths, bison, horses, musk oxen, all of them grazing, trampling, churning the soil, keeping trees and moss from taking over. Then, quite suddenly in geological terms, the animals disappeared, and so did the grass.

So they began putting animals back. Not engineered ones: ordinary horses, reindeer, bison, musk oxen, driven or flown in over years at enormous logistical cost, released into a fenced expanse of tundra and left to behave like animals. The results are legible in the soil. Where the herds graze heavily, the moss retreats and grasses return. Where they trample the snow in winter, they destroy the insulating layer that keeps the ground warm, and winter cold penetrates deeper. Ground temperatures in the trampled areas run measurably colder than in the untouched land beyond the fence.

It is a hypothesis about the whole Arctic, being tested on a few square kilometres by a handful of people, some horses and a herd of bison. The missing element, the founders freely admit, is an animal large enough to knock down trees. Hence the interest in elephants that can survive the cold.

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There is a case against all of this, and it is not a foolish one.

Restoration ecologists point out that the money involved would save a great many living species that are sliding towards extinction right now for entirely unmysterious reasons: habitat loss, hunting, disease. De-extinction, the argument runs, is a spectacular distraction — worse, a moral hazard, because it implies that extinction is reversible and therefore a little less urgent. Others raise the welfare question directly. An elephant's gestation lasts twenty-two months. The surrogate cannot consent, the calf cannot be asked, and the first generation of any such animal will be a subject of intense scrutiny for its entire life.

The strongest objection is the simplest. A mammoth is not a genome. It was an animal raised in a matriarchal herd, taught which plants were edible and where the water lay by mothers and aunts who had learned it from theirs. That knowledge is gone. You can synthesise the body; you cannot synthesise the culture that made the body functional. What walks out of the laboratory, however convincing its coat, will be an orphan in a landscape nothing has prepared it for.

The technician has heard all of this. She is not evangelical about the work, which is refreshing.

"The tools we're building get used either way," she says. "The same editing, the same reproductive technology, the same cryopreservation — it all applies to the species we're about to lose. If this ends up being a very public, very well-funded rehearsal for saving things that are still alive, I'd call that a reasonable outcome."

Outside, it has begun to snow. She pulls the freezer log towards her and enters the vial number, the date, the time. The instructions for the thunder beast go back into the cold and wait.