Every species becomes extinct eventually. Some leave descendants that continue the evolutionary proliferation of life that kicked off on this planet over 3.5 billion years ago, but no parent species is immortal. Life on Earth is in continual flux, with new lineages emerging as others die back.

But what if we could resurrect lost species? And even if we developed the technology to do so, are such efforts wise during a time when the same attention and energy could be applied to preventing extant species from slipping away? This Friday, researchers are going to converge at the TEDX DeExtinction symposium, partnered with National Geographic, to discuss the possibilities and pitfalls of reviving species that have been lost over the past 12,000 years.

The woolly mammoth – the shaggy Ice Age icon that persisted until a scant 3,700 years ago – is probably the most charismatic “deextinction” candidate. For decades now, scientists have been considering how the lost proboscidean might be brought back through cloning, and we’re continually told that the necessary advances to accomplish the task are just around the corner. (Although, much like a Windows software release, the debut of woolly mammoth 2.0 has long been delayed. I’m not optimistic about estimates that we’re only four or five years away from squeeing over the photos of the first cloned baby mammoth.) But the woolly mammoth may be more of a symbolic conversation-starter that has obscured other Lazarus-wannabes, including the Tasmanian tiger, passenger pigeon, Steller’s sea cow, and the Xerces blue butterfly.

These candidate species, the “Revive & Restore” project says, were selected according to three sets of criteria. These requirements run the gamut from the squishy and snuggly – “Is the species missed?” – to matters of technological knowhow and whether the species is “rewildable.” What seems missing, or at least glossed over, are the ecological and ethical implications of reviving these lost species, and the focus on charismatic species has skewed attention towards animals that may not actually be good selections for resurrection.

Just as the woolly mammoth symbolizes the great hope of species revival, the proboscidean also highlights the lack of attention ecology receives in such proposals. The challenge of deextinction is almost always framed in technological terms – can we bring back species? – but what will happen to the animals after they have been recreated has received comparatively little attention.

Let’s say that scientists are able to clone a woolly mammoth within their ambitious five year time frame. Where would such an animal live? The woolly mammoth’s natural habitat – the cold, dry mammoth steppe of the last Ice Age – does not exist anymore. Perhaps there are modern ecological proxies in scattered refugia, but should we really strive to bring back an animal that might only exist in zoos, or may face shrinking habitats in the wake of future climate change?

To bring back a species that no longer has a place in the world would be irresponsible and undercuts the moral imperative that deextinction advocates so often rely on to make their case. Indeed, one of the primary arguments for deextinction is that we must pay penance by restoring animals that previous generations of humans have wiped out, yet we’d only repeat our mistakes if we brought back a species without consideration of the creature’s future survival on a changing planet. Trying to replicate the Ice Age doesn’t make much sense when our species is hurtling the planet towards a greenhouse world.

View Images The long-fanged gape of Smilodon, on display at the Page Museum. Photo by Brian Switek.

Smilodon, a sabercat also listed as a top candidate, is an even worse choice. Wildlife specialists in and around Yellowstone National Park have enough trouble trying to get the public to accept the presence of wolves – carnivores that were extirpated from the area within recent history before being reintroduced two decades ago – and conservationists continue to struggle with the persistent conflict between jaguars and ranchers in South America. Can you imagine the uproar over sabertoothed cats being returned to the western United States or South American grasslands? There may not be a country for revived sabercats.

A simplistic argument could be made that Smilodon de nouveau would be necessary to keep cloned mammoths and mastodons in check at some future date, but such a position relies on the assumption that the cat actually hunted the large herbivores. Thanks to geochemical and anatomical evidence, paleontologists have found that Smilodon preferentially targeted camels and bison, not the giant proboscideans of its time. This isn’t just technical nitpicking. If we’re not only going to restore species, but try to recreate communities and interactions from deep time, we must heed the evidence of the fossil and historical record and not just restore species because we think it would be cool to see them.

The Shasta ground sloth might be a better deextinction candidate. Chris Clarke recently made a case for bringing back the trundling herbivore. Thankfully, Clarke totally avoided the guilt trip that deextinction advocates often use to insist that we have a duty to bring an extinct species back, and instead considered how the sloth might resume its role as a seed disperser within imperiled Joshua tree habitats. I’m not entirely convinced that reviving the Shasta ground sloth would be a worthwhile endeavor, especially since we don’t know exactly why the species died out nor whether the sloth would be able to cope to environmental changes that are already underway due to climate change, but I believe Clarke made a far better case for his favorite sloth than woolly mammoth or sabercat advocates have made for their candidates of choice. (And, I must admit, seeing baby sloths cling to the backs of their plodding mothers would be absolutely adorable.)

View Images The passenger pigeon is one of the top deextinction candidates, but would the revived birds be able to thrive in the wild? Image from Wikipedia.

Of course, the Ice Age megamammals are extreme examples. Most of the candidate animals were wiped out much closer in time. But the same questions still apply. The best candidates for deextinction may not be the biggest, most beautiful, or famous, but species that will be resilient and adaptable to the altered nature of their old haunts and to future ecological fluctuations. More than that, some of the candidate animals might face the same threats to their existence that exterminated them in the first place. Human conflict might be just as bad, if not worse, for revived species, particularly carnivores such as the Tasmanian tiger and sport animals that require populations of staggering size to survive, such as the passenger pigeon.

Conjuring extinct species back into life will require a great deal of care, planning, and management. Is all the effort worth it, especially when conservation efforts worldwide are suffering from a lack of funding?

One way that deextinction advocates could make a stronger case for their projects would be to identify applications to threatened and endangered species that are still living. Perhaps genomic engineering could add variation to populations of animals suffering from the effects of population decline and inbreeding, such as cheetahs. And maybe cloning could help keep a truly critically-endangered species afloat long enough to have a chance to keep adapting and evolving. Some of these techniques are already being used, or at least considered.

I’m not totally against deextinction efforts. Some, such as Clarke’s Shasta ground sloth proposal, may actually have significant benefits for ecosystems that are at risk of deteriorating. But the conversation needs to move beyond charismatic characters and details about technology to the ecological consequences of reviving lost creatures – not only for the species in question, but for the ecosystem it might be reintroduced into and still-living animals that are nearing extinction.