By Cynthia Mills
©Dean C. Kalmantis/images.com
Could be guilt, or simply loss, but people hope with mythic zeal for the resurrection of extinct or nearly extinct species. Regard the passion aroused by recent sightings (and soundings) of the ivory-billed woodpecker in Arkansas swamps. Check out the websites showing a blurry video of what may be a thylacine (also known as a Tasmanian tiger or Tasmanian wolf), footage reminiscent of the short take of Bigfoot. If only—the most painful phrase in any language—if only we had a second chance to save the creatures we’ve destroyed. Our feelings are not simple—not intellectual nor wholly emotional, but some amalgam of both. In many ways, we are the same people who once promoted the intentional elimination of these and other species.
So is cloning a good idea—redemption, perhaps? It could be the Holy Grail of conservation or it could be the ultimate folly. Opinions divide along familiar lines—the technophile versus the technophobe: one cheers invention and possibilities, the other points out it was just these things that put us into our present muddle. But science is all about letting the genie out of the box—Pandora’s box, some say, but even restoration ecologists admit we can no longer reasonably hope to separate human impact from nature. The fact is, cloning works—mammals can be produced from the transfer of an adult cell nucleus into the egg of another, related species. And if we can do that, we can save genetic diversity. But does that translate into saving a species? And what if we think it can, yet it can’t?
For the most part, conservation professionals have expressed their opinion of cloning by ignoring it, says Eileen Crist, Associate Professor of Science and Technology in Society at Virginia Tech, Blacksburg. At a recent restoration ecology meeing in Zurich, Switzerland, she bucked that trend by presenting cloning as a conservation strategy that is gaining a foothold in modern conservation thinking. She described cloning research as spanning a spectrum from science fiction to intriguing possibility to actual practice and talked about three different endeavors: cloing the long-extinct, the recently extinct, and the currently endangered animals. These divisions are instructive: once seen in this light, cloning research reveals itself as three very different ventures with profoundly different implications.
Dolly is dead, and Dolly was only six years old. Cloning is still a new, inexact technology and expensive to boot. Although there may be hundreds, even thousands, of living clones of mice, cattle, sheep, and cats, it still takes dozens of embryos to produce a single surviving clone. Success rates vary with the species cloned and the depth of understanding of each species’ reproductive biology; efficiency can be as low as a 0.0006 percent chance of producing one live embryo. We can run these odds with domestic species, of which we have plenty, but not if we are working with species where there are at most a few dozen reproductive individuals out there.
The mechanisms underlying cloning’s shortcomings are just now being unraveled. In mammals, parental imprinting is a factor: some genes are routinely shut down in one parent; the wrong combination of gene turnoffs results in lethal consequences. Then there are epigenetic effects, those mysterious glitches that come from bad timing—genes turned on or off at the wrong time during development. Fetuses grow to massive size and placentas outgrow their usefulness. Animals are born with failing respiratory or immune systems or never develop normal behavioral patterns.
Those are the problems facing regular cloning. Cloning endangered species means using different species not only as surrogate mothers but also as surrogate eggs (oocytes). This adds another layer of complexity and brings new sources of incompatibility, because we are putting a nucleus from one species into the cell of another species with its own cytoplasm and mitochondria. Cell metabolism requires that the nucleus and mitochondria interact; what if they don’t speak the same language? Finding closely related species helps, indeed makes cloning possible, but often does not result in normal, healthy animals.
On the other hand, reproducing a genetically unique individual, particularly one that can pass on those genes, does make sense. That is just what Oliver Ryder, geneticist with the center for Conservation and Research of Endangered Species for the San Diego Zoo, has done in partnership with others, including a private enterprise, Advanced Cell Technology. Although their first, widely publicized, attempt ended with the death of the gaur calf, Noah, at three days, they did succeed in cloning a male banteng. The bull is now two years old and healthy enough to be out acting as a herd bull at the San Diego Wild Animal Park. Ryder picked this bull carefully. Imported from Europe three-quarters of a century ago, the original bull died in 1980 from fight wounds that had become infected. Now he’s back as a clone, and according to the Species Survival Plans (created by the American Zoo and Aquarium Association), he’s the most genetically valuable male banteng in the world. So what, if he isn’t perfectly normal?
As Ryder admits, “Most clones are abnormalÖin general, developmental problems are not infrequent or uncommon in clones. So long as it is not a germ-line mutation, as long as it is a developmental problem, an epigenetic effect, not a genetic effect, it won’t have a negative consequence on the gene pool. The question is, can clones produce completely normal offspring; and I think the answer is yes.” Sure, he has the mitochondria of a Holstein cow, but that will not be part of what he will pass on.
Ryder advocates using cloning judiciously under carefully selected circumstances where conservation is served by reproducing individuals who carry genes that few (or no) other surviving animals carry. These individuals need to be special—veritable grab bags of diversity, created and birthed for no other reason than to distribute their rare and special genes. Like salmon swimming upstream, their whole purpose is to procreate, creating a new generation of genetic diversity.
Betsy Dresser, reproductive physiologist at the Audubon Center for Research of Endangered Species (not connected to the National Audubon Society) in New Orleans, is another cloning advocate. At the Audubon Center, researchers have cloned African wildcats and are working on cloning African sand cats, black-footed cats, and various antelope species. Of these, only the black-footed cat, with fewer than 10,000 reproductive individuals, is considered vulnerable, although the other two cat groups also have dwindling numbers. Their (relatively) comfortable status helps justify trying out new technologies on them rather than eliminating them as candidates for cloning.
For Dresser, cloning is a new tool in the Assisted Reproductive Technology (or ART) toolbox. She compares the present state of cloning technology with early efforts using in vitro fertilization to produce human babies. “When Louise Brown, the first test-tube baby, was born, the success rate was down around one percent. Well, now it is up to 75 to 80 percent in some labs. I think the day is going to come when that is going to happen with cloning.”
For Dresser, the abnormalities clones exhibit are just puzzles looking for solutions. “What we’re trying to do, as a team of scientists, is to methodically, [in a sense], disprove some of the fears. Not by just talking about it, but by going ahead and showing that we can produce normal healthy offspring from clones. I think the only way those theories can be disproved is to see normal healthy offspring.”
So although she applauds the laboratories that are saving cells and tissues from endangered species, she chastises those who stop there. In all the frozen zoos and museum collections of the world, there may be over a million samples representing at least 700 different species; yet fewer than a handful of scientists have tried cloning. Dresser insists that isn’t enough. “You can freeze all you want, but if you don’t produce babies, then you don’t know whether the cells are viable or not.”
It was this sort of outlook that inspired the thylacine project, the so-called attempt to clone a Tasmanian tiger. The thylacine was a marsupial predator native to Tasmania. European colonists of the island suspected the predator would attack their livestock and thus set about eliminating the species completely, succeeding in 1936 when the last known representative died.
With the success of Dolly, scientists at the Australian Museum announced their intention to produce a thylacine by using DNA scavenged from a pup preserved in alcohol since 1866.
Karen Firestone, who worked on the cloning attempt and is currently a conservation biologist for the Australasian Conservation Genetics Center, remembers it as a very interesting time. “The public was just engrossed with the idea. We’d get emails from people from around the world—from kids who wanted to be the first thylacine keeper at the zoo.”
Her boss, Michael Archer, now dean of the Faculty of Science at the University of New South Wales, well expressed the dreams of people when he wrote, “It never occurred to me that anyone would doubt that this would be a good thing to do if it’s possible. We were the cataclysm that exterminated the thylacine for all the wrong reasons, not a geological or cosmological disaster. Its world is still alive and well in Tasmania. The green throne of the “King of Australian beasts” is still there, waiting for the King’s return . . . as for us, we would be given a second chance to value a restored world whose natural order we should not have violated in the first place.”
The thylacine project was unique, not just in the far-sighted nature of its vision—the scientists, at least, knew a living clone was decades or more in the future—but also because there actually might still be a place for the animal to live. Much of the criticism leveled against cloning for conservation is the same as that leveled against captive breeding of endangered species in zoos. What is the point, after all, of producing animals when there is no habitat left for them? Do we do it just to produce a population we can gaze at in a zoo, or just to satisfy some human longing? What about the animals themselves—is it fair to create them only for a life in captivity?
Even if we could find habitat for them, would they be able to survive in it? They would be odd misfits—not just chimeras of cells from two species, but chimeras of two different animal experiences or cultures. Not raised by their parents, they would have to learn survival skills from domestic animals or humans. How could they be expected to succeed under those circumstances?
All this laboratory-based conservation costs money, after all—lots of money. Wouldn’t this money be better directed toward protecting habitat, preventing extinction in the first place? Karen Baragona of the World Wildlife Fund (WWF) worries that the “dazzle factor” of cloning appeals to the media and public more than the more prosaic “muddy-boots, on-the-ground” conservation efforts aimed at protecting whole spaces with their myriad of species. Also, cloning and ART put the focus on reproduction, which is often not the real problem. Pandas, WWF’s policy statement notes, have a reputation for being difficult to breed in zoos, but females in the wild typically produce eight cubs in their lifetimes. Protect them in the wild and all the IVF, ART, and cloning will not be necessary.
When it comes to resurrecting extinct species, Baragona states, “We’ve lost these species. It’s a tragic lesson in the permanence of extinction. When an ecosystem loses a species, its place in that ecosystem is taken over by other species. Even if an extinct species were reintroduced, the conditions that supported it before have changed, and it’s quite unlikely that the species could thrive. Whether it would or not, it’s a pretty expensive and frivolous experiment.”
There is also the danger that the public will be given a false sense of security, that technology will advance so that we can put everything right in some more perfect future. Few biologists feel comforted by such visions.
Other critics, such as Naida Luskutoff of Omaha’s Henry Doorly Zoo, worry about more insidious threats. What if, for example, in the cloning of a gaur or banteng, a prion lurked in the cow’s oocyte or slipped across the cow’s placenta? Then the clone could become a sort of suicide bomber, introducing fatal diseases into a dwindling, vulnerable population.
These could all be considered merely technical problems, problems we need time and experience to solve. Deeper issues and philosophical difficulties remain. Environmental ethics philosopher Eric Katz of the New Jersey Institute of Technology considers clones to be something other than natural, in an existentially lethal way. He cites the the Book of Job, where Job’s faith is tested to settle a wager between God and Satan. His wealth and farm are taken away and his family killed. When Job does not lose faith and God wins the bet, God rewards Job with a new farm and new wealth. God can’t give Job his family back—they are dead, after all—so he gives him a new family, too.
Most of us would say that the new family is fine, but not quite right—there are some things that are irreplaceable. The same, Katz says, is true of wild animals. “It may look like a Bengali tiger—it may act exactly like one and it may reproduce—it’s not. It’s something that we created and in that sense it’s no different from the hundreds of millions of chickens we produce for food each year.” Nature, inherently, cannot be recreated by man.
Still, there exists a cadre of what might be called eternal optimists. Ryder and Dresser accede with sighs to the criticisms. But the money they get would not go to habitat in Malaysia, the donors wouldn’t agree to a brick or plaque in a faraway place. The history of habitat protection is littered with failures, and even protected lands suffer the pressures of a burgeoning population of hungry and desperate farmers and poachers.
To them, cloning is at least one sort of last resort, one more hopeful tool. In answer to criticism, Ryder says, “I would join in those who long for the preservation of the most wild and the most primeval, but I think that may be a luxury in our times. I think that the future will be thankful for what we can save, not for what we say isn’t worthy for them to receive. I think that is a hubris of ours—that the future would like to reserve some judgment about.”
A naturalist once described the California condor in the wild as a masterpiece of art—because it was unique and it fit so well into its own skin. The same could be said of many lost species and, even more so, the lost relationships—the complex, emerging networks of species in their homes. The speaker was trying to make the point that, as with the Mona Lisa or the Sistine Chapel, experiencing the original is so much more than being exposed to a copy. Is this what we fear about cloning? Would a copy—albeit a living, breathing, behaving, copy—ever fill the gap? That is the question we are all being forced to answer.
About the Author
Trained as a veterinarian, Cynthia Mills has been writing about animal and wildlife issues for over ten years. Recently she turned from clinical practice to fieldwork, looking at the impact of biodiversity on human diseases in wildlife. Her writing has been included in the Best American Science and Nature Writing anthology.