Like big kids everywhere, I would love to see it happen. The idea of resurrecting woolly mammoths fires the imagination on all cylinders. Last week, Ian Wilmut, the man who cloned Dolly the sheep, ruminated about how it might be done. The answer, in brief, is that it pushes at the very limits of plausibility, but there is a tiny chance that, within 50 years or so, it could just happen.
Even if this minute chance is realized, please do not mistake de-extinction (as the resurrection business is now known) for reviving lost faunas and habitats. At best, it will produce a public cabinet of curiosities, at worst new pets for billionaires. There is an obvious, fatal, but overlooked problem with de-extinction. The scarcely credible task of resurrection has to be conducted not once, but hundreds of times, in each case using material from a different, implausibly well-preserved specimen. Otherwise the population will not be genetically viable.
For a species to have a reasonable chance of survival, across decades and centuries, it needs a wide genetic base: a minimum of several hundred individual genomes. The European bison, or wisent, is considered a great success story: It was almost extinct a century ago; now there are 3,000. However, it remains acutely vulnerable because the entire population has been bred from the 54 animals to which the species was reduced by 1927. The bison are plagued by problems associated with inbreeding, and a single cattle disease could finish them off, as a small genetic spectrum is less likely than a large one to offer resistance.
Last week, the Born Free Foundation doused the excitement over the birth in Chester Zoo in northwest England of two Sumatran tigers, a species that is critically endangered. It said that the global population in captive breeding programs is too small to be genetically viable: If tigers become extinct in the wild, they will soon become extinct in captivity.
So the painting published by National Geographic in April, depicting tourists in safari vehicles photographing a herd of Siberian mammoths, is pure fantasy: The animals it shows are mumbo-jumbos. And that is a great shame.
As experiments by the Russian scientist Sergei Zimov show, mammoths could play a key role in restoring the ecosystems that once supported them. Perhaps 15,000 years ago, hunters using small stone blades moved into the Siberian steppes. Their technologies allowed them to wipe out the mammoths and most of the musk oxen, bison and horses that grazed there. As a result, the great Siberian grasslands turned to mossy tundra, and have remained that way ever since.
These species sustained their own habitats. They recycled the soil’s nutrients through their dung. Their grazing made the grass more productive and prevented it from growing long enough to kill itself. Long grass in Siberia flops over and insulates the soil, which then becomes too cold and wet for grass to grow. It is quickly replaced by moss, which is an excellent insulator, keeping the soil cold enough to prevent the grass from returning. Zimov has shown that when large animals are brought back, their trampling quickly breaks up the fragile layer of moss and lichens, allowing the grass to dominate again within one or two years. The grazers, in other words, are keystone species: animals that exert disproportionate impacts on their environment, creating conditions that allow other species to live there.