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The Key Creatures

The idea of de-extinction has been floating around lately, bringing to mind the possibility of saber-toothed cats and woolly mammoths roaming the lands that they once called home. Or, on a smaller scale, bringing back flocks of passenger pigeons that once darkened the skies.

"If we're talking about species we drove extinct, then I think we have an obligation to try to do this," Mike Archer, a paleontologist at the University of New South Wales, told Carl Zimmer at National Geographic in April.

Among the critics, the editors at Scientific American couldn't help but wonder whether such resources couldn't be put to a better use by trying to keep currently living species from going extinct or losing genetic diversity. " Already conservationists face difficult choices about which species and ecosystems to try to save, since they cannot hope to rescue them all. … Should we resurrect the mammoth only to let elephants go under? Of course not," they wrote in May.

George Church writes this week that that dismissal of de-extinction was "too hasty." Also in Scientific American, he says that "[t]he goal of reanimation research is not to make perfect living copies of extinct organisms, nor is it meant to be a one-off stunt in a laboratory or zoo. Reanimation is about leveraging the best of ancient and synthetic DNA."

Mammoths, for example, were keystone species lost from the tundra and bringing them back could help keep the region colder in light of global warming as they eat dead grass, allowing spring grass with deep roots to grow, knock down trees, which lets more light be reflected, and break through snow to let cold air reach the soil, Church says. He notes that the expense will not be trivial, but should be close to the scale of breeding livestock, particularly if genetic tweaks are made to boost the animals' immunity and fertility.

He adds that such reanimation efforts could also help species on the brink of extinction by injecting lost genetic diversity.

"Reanimation is not a panacea for ecosystems at risk. Preventing ongoing extinction of elephants, rhinoceroses, and other threatened species is critically important. By all means, we must set priorities for allocating finite conservation resources," Church says. "But it is a mistake to look at this issue as a zero-sum game."