For a species that’s been dead for a century, the passenger pigeon is having a pretty good year. A flurry of new books, features, and a major documentary has been roughly timed to commemorate the death of “Martha,” the last surviving member of the species that drew her final breath in the Cincinnati Zoo on Sept. 1, 1914. It’s a kind of national elegy for a bird that no one alive today remembers ever seeing, certainly not in the wild, where it was last spotted around the time shovels first broke ground on the New York subway system.
The bird was a cheap and easily procured source of meat in the 18th and 19th centuries due to its astonishing abundance (once numbering in the billions) and its unfortunate tendency to travel in massive flocks. Its fate was sealed by the 1850s with the expansion of the railroad and telegraph, which fueled an insatiable commercial appetite and profitable pigeon market by providing easy transport and rapid communication about the location of flocks. There were precious few attempts to save the species in that pre–Endangered Species Act era, and none that made a difference.
Less than 20 years following Martha’s quiet demise in Cincinnati, the sole surviving heath hen (a close relative of the Greater Prairie-chicken) made its last appearance in southeastern Massachusetts. Nicknamed “Booming Ben” for the bird’s distinctive vocalizations during its extravagant mating ritual, he was a relic of a population that was once common from New England to northern Virginia. Like the passenger pigeon, the heath hen was a plentiful and convenient source of protein (a “poor man’s turkey”) in the 18th and early 19th centuries. By the 1870s, however, the species had been hunted completely off the mainland. Only a few decades later there were fewer than 100 left, all of them hunkered down in a single flock residing in Martha’s Vineyard. Not a bad place to convalesce, unless you’re a small, genetically isolated, nonmigratory bird population.
Unlike the passenger pigeon, the heath hen had a few efforts to save it, including banning hunting and creating a sanctuary in the Vineyard in the early 1900s. But the die had been cast. Like Martha before him, Booming Ben—and the heath hen along with him—vanished into the evolutionary ether, mostly likely sometime in the spring of 1932.
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Although the public was slow to rally to the conservation cause in the early 20th century, not everyone greeted these losses with resignation. One of the strongest voices agitating for wildlife protection during these years was William T. Hornaday, the rabble-rousing wildlife crusader and founding director of the Bronx Zoo. Hornaday challenged the complacency of an American public unwilling to acknowledge the destructive game it was playing with its wild animals. In his conservationist manifesto, Our Vanishing Wildlife (1913), he tried to convey a sense of the biological stakes when a species was pushed to the brink of extinction.
“Let no one think for a moment,” he warned, “that any vanishing species can at any time be brought back; for that would be a grave error. ... The heath hen could not be brought back, neither could the passenger pigeon.”
What a difference a century makes.
It’s doubtful that even in his wildest dreams Hornaday would’ve envisioned that someday scientists and their allies would seriously be contemplating bringing long-extinct species—including the passenger pigeon and the heath hen—back from the dead.
Called “de-extinction,” the proposal taps into a range of established and still emerging techniques in cloning and genetic engineering, including the ability to rapidly sequence ancient DNA from preserved tissues of extinct animals to allow scientists to create approximations of lost species by “editing” the genomes of closely related (living) species. So, for example, the genome of a contemporary band-tailed pigeon could be altered to more closely resemble that of a passenger pigeon, and a population of the new birds could theoretically be bred and released into the wild.
The techno-environmentalist Stewart Brand is one of the driving forces behind the idea, which over the past 18 months has drawn considerable media attention and scrutiny. Brand’s Long Now Foundation is supporting scientific efforts to re-create the passenger pigeon—and exploring possibilities for the heath hen—within its “Revive & Restore” project, which has its sights on a range of candidates for resurrection, from the Tasmanian tiger to the woolly mammoth.
The de-extinction proposal has been met with no shortage of criticism, ranging from concerns about the misallocation of limited conservation dollars to a “vanity project,” to worries that the newly engineered species will wreak havoc when released into the environment, especially since we may no longer have the space to accommodate them. Fears have been raised that de-extinction will also lead to the relaxation of public commitment to conservation and to averting future species extinctions.
But Brand argues that de-extinction offers something vital to conservationists today: an alternative narrative unburdened by the handwringing over extinction and ecological loss. If we were actually able to bring back the passenger pigeon, the heath hen, and other iconic species, he believes, “The conservation story could shift from negative to positive, from constant whining and guilt-tripping to high fives and new excitement.” (Earlier this year, Slate published an adaptation of Brand’s Issues in Science and Technology review of Cloning Wild Life, which conveys some of his thinking on the use of “high-tech genetic rescue” of both currently endangered and recently extinct species. The use of ancient DNA—as would be the case with the passenger pigeon, the heath hen, and the Tasmanian tiger—employs even more ambitious techniques in genetic engineering than somatic cell nuclear transfer)
I respect Brand’s long and impressive career as a tech-friendly enviro-maverick, but I think he’s wrong about this. De-extinction isn’t really a conservation strategy, and it doesn’t reflect a sound conservation ethic. In fact, I believe pursuing it will seriously undercut an important source of the value we attach to wild species. Even worse, it could undermine the moral lessons of extinction at a critical time in our environmental history.
Although a revived passenger pigeon, heath hen, or mammoth (setting aside the question of whether an engineered genome does an extinct species make) may have aesthetic, scientific, and even economic value to society, it obviously won’t share the natural history of the lost species. The evolutionary toil and historical richness of the forerunner species, including their co-evolution with other species over time, has been lost, replaced by a tale of technological manipulations in a 21st-century genetics lab.
In other words, the backstory is wrong, at least from a conservation perspective. A living species’ natural history is only one reason why we value them, but it’s a profoundly important one to conservationists (or at least it should be). In part, this is because our understanding of an unengineered species’ natural history encourages the adoption of an attitude of humility toward them. As the conservationist-philosopher Aldo Leopold reminds us, “Men are only fellow-voyagers with other creatures in the odyssey of evolution.”
That doesn’t mean that a novel natural history for the revived forms couldn’t be compiled over the coming centuries. There’s no “rule” specifying how many generations it takes for a species to accrue a distinctive (and hence valuable) natural history, or for one to lose it, as in the case of animals bred in captivity and reintroduced to the wild after an absence (e.g., the California condor). But there’s also no denying that many of the revived “fellow voyagers” would appear long after their unengineered analogues walked the earth or soared in the skies, and without the co-evolutionary narrative that partly defined the natural history of their progenitors. That is, they’ll simply lack the irreplaceable and unique evolutionary character that is part of why we valued the “originals” in the first place—an identity that vanished with them. If they’re fellow travelers, then, they’ll be arriving with suspiciously blank passports.
An even deeper cause for concern about species revival, though, is the well-meaning but still misguided attempt to erase the moral narrative of extinction. As Brand puts it in his defense of the resurrection of the passenger pigeon, “How fine it would be to reverse the founding human mistake that inspired modern conservation.”
If only it were that easy.
But we can’t reverse the “founding human mistake” by simply bringing back a few, or even a few scores of lost species (as difficult as that would be to pull off). That’s because wiping out the passenger pigeon, the heath hen, the Tasmanian tiger, and so on, as regrettable as these events were, wasn’t the real mistake. It was only the indicator of a deeper moral and cultural malady.
For more from Ben Minteer on de-extinction, visit the website of the Center for Humans & Nature.
This article is part of Future Tense, a collaboration among Arizona State University, New America, and Slate. Future Tense explores the ways emerging technologies affect society, policy, and culture. To read more, visit the Future Tense blog and the Future Tense home page. You can also follow us on Twitter.
The Revive and Restore Project is the brainchild of Long Now Foundation co-founder Stewart Brand and his wife Ryan Phelan, a serial entrepreneur who most recently sold her consumer genetic testing business DNA Direct to Fortune 500 company Medco. Their top candidates for de-extinction include the passenger pigeon and the woolly mammoth. Brand and Phelan promote the project as a way to restore lost genetic diversity with its mission of ensuring “deep ecological enrichment through extinct species revival.”
But some working on the front lines of biodiversity conservation are skeptical. In a commentary published in April, leading conservation scientists noted that few of their colleagues had considered synthetic biology’s potential effects on conservation, even though it might “transform...the prospects for maintaining biodiversity.” The authors outlined several ways that recreated extinct organisms could potentially affect strategic biodiversity goals—some positive, many negative. Their point was that no one knows, but conservation biologists better start paying attention (see chart, below).
Hank Greely, director of Stanford University’s Center for Law and the Biosciences, admits a longstanding fascination with the prospect of reviving extinct species, but couldn't decide whether it was really a good idea. So he organized a conference at Stanford last week and invited philosophers, lawyers, biologists, and wildlife professionals to think through the complex ethical, legal and political issues de-extinction raises.
“I think one of the reasons this issue has bubbled to the surface so quickly is that the technology is converging with the coolness of the idea of bringing things back, mixing with a sense of guilt we feel with driving things extinct,” University of Kansas law professor Andrew Torrance told me. But de-extinction raises several “definitional conundrums,” he said in this talk. Are de-extinct organisms GMOs? Invasive species?
And where would a resurrected species fit into environmental law? Conference co-organizer Alex Camacho, director of UC Irvine’s Law Center for Land, Environment and Natural Resources, said the Endangered Species Act has no framework for de-extinction, since its creators couldn’t possibly have imagined the prospect. Shortly after revival of an organism, a species could potentially be listed as endangered, but is it the same species? A new species? An endangered species? The ESA defines endangered as “in danger of extinction throughout all or a significant portion of its range.” But what is its range? Does it have a range? Presumably not, if you have one organism sitting in a lab, Camacho said.
Chuck Bonham, who directs the state’s Department of Fish and Wildlife agency but was not representing the agency at the conference, wrestled with the management implications of de-extinction. “How can you be extinct if you’re always available for revival?”
Technologies for recreating extinct species include back-breeding, cloning and genetic engineering. Though all have the potential to accomplish the task, said Beth Shapiro, an evolutionary biologist and ancient-DNA expert at the University of California at Santa Cruz, they also have drawbacks.
With back-breeding, scientists identify traits in the closest living relative and selectively breed offspring expressing desired traits until the animals resemble their extinct cousins. Sequencing bone and tooth fragments from extinct species speeds up the work of homing in on similar genome sequences in closely related descendants. Scientists in the Netherlands are using this approach to recreate the auroch, giant wild European cattle that went extinct in 1627, from domestic cattle. Cattle have a generation time of three to six years. Trying to revive mammoths from increasingly bigger and hairier elephants, which start reproducing on average at 20 to 25 years, could take centuries.
More problematic is cloning, where scientists remove the nucleus of an egg cell, replace it with the nucleus from a donor cell, tweak it to grow as an embryo and implant it in a surrogate mother. The process is highly fraught. Dolly, the famous cloned sheep, was the only lamb born out of 277 attempts—all the other clones died in utero or shortly after birth. In what’s considered the first successful de-extinction using this method, a Pyrenean ibex (a large wild goat that went extinct less than 15 years ago) carried by a hybrid ibex-goat, lived all of 12 minutes, and all in acute respiratory distress.
If researchers attempt this with elephants as surrogates, it’s likely that the much smaller elephant mother would not fare well carrying a mammoth to term.* That doesn’t account for the ethics of turning such highly intelligent social animals, who appear to grieve the death of their kin, into mammoth-resurrection machines.
Both methods, however, require intact genomes, which means you’d have to freeze cell lines taken from species before they went extinct. “If we’re going to de-extinct something that’s any older than something that we recently killed, we’re stuck with ancient DNA,” Shapiro said. And that means dealing with tiny fragments of DNA that are often tainted with bacteria and other contaminants.
That leaves genome editing, finding the sequences that code for traits of interest and pasting them into an existing genome. But researchers are still refining methods to find the right place in the genome and deliver the DNA without creating problems like cancer. An even bigger problem is figuring out which parts of the genome make a mammoth woolly, the sea cow so big or passenger pigeons flock together, Shapiro said. Even if you could reconstruct the genome of an extinct species, the jump to assigning function to sequences is enormous.
Given all these issues, Shapiro said, “I think we should consider deeply why do we want to de-extinct things.”
And that, for many working to conserve biodiversity, is the primary question. “Conservation biologists worry that if people think we can revive species they won’t care about protecting what’s left,” said Kate Jones, joint chair of ecology and biodiversity at University of College London and the Zoological Society of London.
Jones, who spent most of her career thinking about what makes species go extinct, told me she understands the appeal of de-extinction. “Who wouldn’t be excited about the prospect of seeing a mammoth?” she allowed. “But the practicalities of doing it are actually quite terrifying.” And as a conservation strategy, “it’s a bit useless. It’s dressed up as conservation, but it’s not.”
For Jones, this isn’t about de-extinction. “It’s about creating new species. They’re just flashy GMOs.”
Some senior conservation biologists refuse to engage with the topic because they think it’s not a legitimate debate, Jones told me. “But I think it’s kind of inevitable that this is going to happen whether it’s Stewart Brand or someone in their back garden.”
Then there’s the question of what you do with a species you’ve revived. Jamie Rappaport Clark, who served as head of US Fish and Wildlife under the Clinton Administration and now leads Defenders of Wildlife, urged de-extinction proponents to consider the politics of reviving species. De-extinction could justify stalling action on restoring habitat or saving species, for example. That would have doomed the Florida panther, which received an influx of genes from airlifted Texas cougars under her watch in a desperate move to save the big cat.
She’s also worried that de-extinction will provide political cover for defunding conservation. “They’ll say, ‘We shouldn’t be funding recovery and preventing the extinction of species because we have a way out.’ It will undermine the entire integrity of the ESA, which is already under serious distress now.”
During a roundtable discussion, Brand raised the prospect of bringing back the saber-toothed cat to California to replace lost ecological roles of predators, at which point Bonham leapt up from his chair, joking, “I’m out of here!”
He retrieved a piece a paper from his brief case and returned to tell Brand a story about the public’s uneasy relationship with predators. “We shot the last wolf in California about 100 years ago,” Bonham said. “One month after I came on the job, we got our first wolf back in California in 100 years.” Half the state wants him to create a wolf preserve. The other half wants to see history repeated. “We’re not ready,” he said.
Bonham read a passage from the 1982 Fish and Wildlife grizzly bear recovery plan. “This is an animal that cannot compromise or adjust its way of life to ours. Could not by its very nature, could not even if we allowed it the opportunity, which we did not.” The only place for the grizzly bear in California remains on the state flag. “How in the world do you expect a saber tooth to fare any better than...the grizzly bear?” he asked Brand.
Brand did not answer.
Jones asked Brand if any of the concerns conference participants raised about de-extinctinon had altered his vision. "Not yet," he answered. "It makes me more determined...that we make completely sure that everybody understands that de-extinction and conservation are in no way competitive." He said there's now a generation of kids who now want to see woolly mammoths in a zoo. "When they do I think they'll adopt a non-tragic relationship to nature and conservation with a sense that humans can...undo even serious damage like extinction."
Elizabeth Hadly, a Stanford paleontologist and Paul S. and Billie Achilles Chair of Environmental Biology, helped craft the recent call to action to policymakers. She thinks laboratory innovation rather than on-the-ground research is behind the de-extinction push. Funding for ecology and conservation pales compared to the big grants funding genomics and synthetic biology. Although she’s at Stanford, Hadly did not attend the conference. It pains her to think about what that money could do to protect the species already here—some hanging on by a thread.
The way we’re killing elephants now, we won’t have any more left in 10 or 20 years, she said. “And people are talking about mammoths? First of all, they were alive in an ice age. This is the completely wrong environment to bring them back to.”
She calls de-extinction “gee-whiz science at its worst” and thinks justifying it in terms of genetic diversity and ecosystem services makes no sense.
"Spending money to reintroduce recently lost existing species—even California’s grizzly bear—and restore habitat is a much better use of our time and energy", she said. "Without habitat restoration", she added, "the 750 mountain gorillas left on the planet won’t make it. I’d much rather combine the tiger subspecies together to create a better genetic reservoir than bring back some extinct organism.”
Clark, who spent her career working with species on the brink of extinction, offered a similar view. “The real question,” she told me, “is why would we spend all this energy and effort to bring back ancient animals but let so many others just disappear?”
She’s been spending a lot of time thinking about our moral obligation to future generations. “Is it to create a couple of sad woolly mammoths that live in a zoo? Or is it to save the wolves and the panther and the Delhi sands flower-loving flies and the fisheries?”
For Clark, there’s no question. “We need to do a better job of stewarding what we have," she said, "before we go rushing off after cool science experiments.”
*Note: Scientists think woolly mammoths were roughly the same size as Asian elephants, though the Columbian mammoth (which once lived in California) was bigger.