4. Nine Lives

It’s tough to be a wild animal on Earth today. The world is teeming with 7 billion humans, and our wants and needs – for housing developments, cheap food, and the latest and greatest electronic gadgets – are destroying what’s left of the wilderness. Almost a quarter of the mammalian species roaming the planet are at risk of extinction; the same goes for almost one in three amphibian species and one in eight species of birds. There have been five mass extinctions in history – the most recent is the one that wiped out the dinosaurs – and many scientists believe we’re at the beginning of a sixth. Conservationists have been doing what they can to preserve habitat, but it’s like trying to bail out a boat that’s constantly sprouting new holes; demographers estimate that, by 2050, there will be more than 9 billion people on Earth.

So it’s not surprising that scientists have started searching for alternatives, looking to biotechnology for potential solutions to the extinction crisis. A few iconoclastic researchers think they’ve found one in cloning. On the surface, the idea is simple: Animal numbers dwindling? Let’s just use science to make copies of the ones that remain! But it will not be nearly as easy as it sounds. That much has been apparent since the birth of the very first endangered-species clone: a little gaur named Noah, an exact copy of a rare wild ox native to India and Southeast Asia. His birth, in January 2001, proved that it was technically possible to mimeograph endangered animals. It was also a short-lived feat. Thirty-six hours after he was born, Noah began showing signs of a gastrointestinal infection; twelve hours later, he was dead. The researchers at Advanced Cell Technology, the Massachusetts company that brought Noah into being, said cloning had nothing to do with the calf’s tragic fate, but it’s impossible to say for sure, given the health problems that have been documented in other clones. Noah’s death suggested that wildlife replication would not be immune to the challenges and complications that have plagued those cloning pets and livestock. But when it comes to endangered species, there’s a pretty compelling rationale for forging ahead. Cloning these rare animals is about more than money or companionship – it’s about survival.

With these high stakes in mind, I decide to take a trip to New Orleans, where a small group of researchers have positioned themselves at the forefront of endangered-species cloning. Their remarkable facility is hidden inside nearly five hundred hectares of hardwood forest along the banks of the Mississippi River. At first glance, these woods look like any other slice of nature. But peek inside these thickets and you’ll find some surprising secrets: Some of the world’s most exotic animals – creatures that usually make their homes on the African savanna or in the mountains of Central Asia – are here, living quietly in this small patch of wilderness. Amble among these trees and you could find yourself face-to-face with a flock of preening snow-white ibises or a small spotted wildcat, pacing back and forth.

These are the grounds of the Freeport-McMoRan Audubon Species Survival Center. The entire compound sits at the end of a country lane, behind a locked gate. A guard checks my credentials, then allows me in. I drive slowly along a narrow gravel road that winds into the forest. Branches swoop over me, creating a lush canopy, and it’s impossible to see more than a foot or so past the trees that line the road. I half expect a leopard to leap out in front of my car at any moment.32

Suddenly, the forest opens up into a clearing, where a brick sign welcomes me to the sprawling Audubon Center for Research of Endangered Species (ACRES), the Survival Center’s 3,300-square-metre complex of genetic and veterinary laboratories. Each of the rooms inside is devoted to one small task in the much larger effort to save wild animals. Signs posted on the doors along one corridor announce, in succession: GAMETE/EMBRYO LABORATORY, MOLECULAR GENETICS LABORATORY, RADIO ISOTOPE LABORATORY, CRYOBIOLOGY ROOM. For a state-of-the-art research facility, it feels awfully homey, with its dark wood panelling and bucolic views. I have just settled down into a plush armchair when Betsy Dresser, the reproductive physiologist who directs ACRES, emerges from her office. Wearing a grey blazer the same colour as her closely cropped hair, she offers a warm handshake and a smile.

Dresser has spent her life in the company of other species. As a child, she constantly begged her family to take her to the nearby Cincinnati Zoo, and as soon as she was old enough, she began working there, moving up through the ranks from teen guide to zookeeper to junior zoologist. When Dresser went to college in the 1970s, she discovered the field of reproductive biology. She read the latest work coming out of Duane Kraemer’s lab at Texas A&M, in fact, and watched as scientists learned to manage herds of cattle through careful breeding, artificial insemination and other reproductive technologies. But while scientists were fussing about with farm animals, populations of the world’s wild creatures were beginning to plummet. As Dresser recalls, ‘I saw the science and technology coming forward for our domestic animals, and I kept thinking, ‘Why can’t we do this with wildlife? Why can’t we apply some of this to at least try to save some species?” ’

After earning a PhD in animal reproductive physiology, Dresser established the Center for Conservation and Research of Endangered Wildlife (CREW) at the Cincinnati Zoo in 1981. At CREW, Dresser and her colleagues made a number of breakthroughs, including producing a Persian leopard cub through artificial insemination and creating the world’s first test-tube gorilla. Impressed by the research at CREW, the Audubon Nature Institute, which ran a zoo in New Orleans, asked for Dresser’s help in creating a similar programme. In 1996, Dresser found herself leading the brand-new Audubon Center for Research of Endangered Species (ACRES). ‘We exist because we want to see wildlife in the future’, Dresser says of ACRES. ‘I can’t imagine just seeing elephants and lions and tigers just in textbooks, like we see dinosaurs today.’

To make sure that these species stick around, Dresser, who directed ACRES for fifteen years and continues to consult with its scientific team, is willing to use whatever reproductive technologies are at her disposal. At first, the ACRES crew relied on the same techniques Dresser had honed in Cincinnati – embryo transfer, in vitro fertilization and the like – and the walls of the research facility are hung with photos of tiny kittens and newborn whooping cranes that the scientists brought into being. Dresser acts every bit the proud parent, showing off each creature. ‘Here’s a caracal’, she says, pointing to an image of two kittens she created using in vitro fertilization. The otherwise sand-coloured cats have tufts of black fur jutting straight out of the tips of their pointy ears. ‘Some people’, Dresser says, ‘call them Spock cats’.

Dresser goes down the line of photos, identifying each kitten: serval, fishing cat, Arabian sand cat and more. Nearly all of these felines are under threat, a result of poaching and habitat destruction. The ballooning human population is hurting these cats in other ways, too – our pet tabbies and Persians can’t seem to keep their furry little paws off their undomesticated cousins. This freewheeling interbreeding creates litters of cute little hybrids, but it doesn’t help boost the ranks of wild felines.

ACRES has made a name for itself for its work with these small exotic cats, and as the technology evolved, so did the scientists’ strategy. Though in vitro fertilization had allowed biologists to help exotic animals breed in new ways, the technique had limitations. Creating test-tube caracals, for instance, required harvesting sperm and eggs from wild cats, fertilizing the eggs in the lab, and then implanting them in surrogate mothers. Collecting and storing specialized reproductive cells is technically difficult – and potentially dangerous for the animals, since the females must be anesthetized and cut open in order for surgeons to recover their eggs.

Cloning has several distinct advantages. Scientists can get all the DNA they need for cloning from an animal’s skin cells; stealing a quick swipe of skin from a rare cat is a much easier proposition than surgically harvesting ova. Cloning also provides a way to propagate the genes of animals without viable sperm or eggs: old animals, infertile animals, even dead animals. To Dresser, the technique has an obvious role to play in rescuing endangered species. As she imagines it, scientists could collect skin samples from rare animals and then churn out new copies of them in the lab. Field biologists could take these creatures and release them into their native habitats, where the clones would mingle with their wild brethren – both socially and sexually – and the population would slowly rise again.

The prospect of using cloning to save endangered species is a big dream, one that will require many researchers and many years to pull off. So Dresser and her colleagues are beginning with the basics. They’re not running large-scale repopulation projects. They’re not even trying to produce hundreds of endangered clones. Instead, their role is to nail down the technology itself – to test cloning in different species, fine-tune the laboratory procedures and publish the results. That way, Dresser says, ‘If a habitat can’t be saved, and a population isn’t breeding naturally, and numbers dwindle to where there’re only five individuals left in a species, we can call on these tools.’

For all her optimism, Dresser is also a realist: She knows that cloning alone will not be enough to save a species. The ACRES team isn’t, for instance, tackling the environmental problems that are causing the extinction crisis in the first place, but Dresser believes that reproductive technology is an important piece of the puzzle. As she argues, ‘There is no one answer to saving endangered species or wildlife on this planet. There are many very good organizations in this world that work on saving habitat. And that’s what they do best. Why not do what we do best? My passion burns where I think we can be part of the solution – emphasis on part of the solution.’

For her first cloning project, Dresser chose the African wildcat (Felis silvestris lybica), a tawny-coloured feline with black rings circling its legs and tail. Native to northern and western Africa, the animals are thought to be the ancestors of domestic cats. Dresser decided to duplicate a three-year-old African wildcat named Jazz who already resided at ACRES, and technicians began by taking a tiny sample of the cat’s skin cells. To do the cloning, the researchers planned to employ nuclear transfer – the same technique that researchers had used to create Dolly, CC and others – but with a twist. Usually, scientists put the DNA of the animal being duplicated into an egg harvested from a female of the same species. When the scientists at A&M cloned Rainbow, for instance, they put her genes into an empty egg taken from another domestic cat.

Nuclear transfer presents extra hurdles for wildlife biologists, who may not be able to get their hands on enough females of an exotic species to provide eggs or act as surrogate mothers. And even if they rounded up a pack of wildcats, they’d be loath to put threatened animals through any unnecessary medical procedures. So when scientists clone endangered animals, they usually use a common, closely related species to serve as egg donors and surrogate mothers. This is known as interspecies nuclear transfer.

To clone Jazz, Dresser and her colleagues used everyday housecats. They collected ova from bog standard tabbies, removed the nuclei, and then used the standard nuclear transfer procedure to put Jazz’s genes inside. The eggs from the domestic cats now contained instructions for building a wild one.33 To maximize their chances of success, the researchers implanted the cloned embryos in fifty different lady housecats, and twelve ended up pregnant. The ACRES team carefully monitored the pregnancies, using regular sonograms to check on the developing kittens. Alas, cloning’s inefficiency reared its ugly head, and it was a long and sometimes heartbreaking slog. The first three cats miscarried. One went into premature labour; the kitten did not survive. Several kittens were stillborn. A few more survived their birth, but died within thirty-six hours.

The string of losses was eerily similar to what other cloners had faced, and the incomplete genetic reprogramming associated with nuclear transfer likely contributed to these poor outcomes. But the ACRES team kept at it, and on 6 August 2003, they extracted a tiny wildcat kitten – weighing less than a stick of butter – from the womb of a housecat named Brooke. The vet cleared the male kitten’s nose and mouth and watched him take his first breaths. As soon as Brooke was sewn up, the staff placed the kitten beside her, and the newborn started to nurse. The researchers watched and waited, hoping that when the anesthesia wore off and Brooke came to, she’d bond with the fuzzy ball of foreign DNA pressed up against her.

The odd couple thrived. Brooke took to her maternal duties like a champ, and the little clone continued to suck down her milk. After several uneventful days, Dresser and her colleagues let out a sigh of relief; it looked like the youngster would make it. In a nod to their New Orleans home, they named the kitten Ditteaux (pronounced, in the French fashion, as ‘Ditto’), and DNA analysis confirmed that he was, indeed, an exact genetic replica of Jazz.

Ditteaux soon had company. That November, Miles and Otis, two more clones of Jazz, were born, as was Caty, a copy of a female African wildcat named Nancy. Spring brought four more Nancy duplicates: Madge, Emily, Evangeline and Tilly. All the clones were raised by their surrogate mothers, and when they reached sexual maturity, they became swingers, mating in various combinations: Ditteaux and Madge, Ditteaux and Nancy, clone with clone. Their kittens were normal and healthy, and many were eventually sent to live at various zoos.

After these successes, the ACRES researchers moved on to other small exotic cats, cloning the caracal and the Arabian sand cat, the same species that Dresser so proudly showed off when we first met. Next up: lions and the Canadian lynx. They’ve created the cloned embryos already. All that’s left to do is implant them in surrogate mothers.

Meanwhile, other labs and researchers have been busy making their own breakthroughs. Michael Clinton, a scientist at Scotland’s Roslin Institute, worked with Italian, Polish and Czech researchers to make a mouflon, a rare breed of wild sheep, using DNA extracted from a female found dead in a pasture, and Korean researchers cloned an endangered cattle species as well as the grey wolf. In India, Riaz Ahmad Shah of Sher-i-Kashmir University led a scientific team in creating Noori, a clone of the rare pashmina goat. And in 2011, Scottish embryologist Bill Ritchie, one of the scientists who brought Dolly into the world, turned his attention to a near-extinct species of Scottish wildcats. Like their African cousins, the Scottish cats are threatened by habitat loss and interbreeding with domestic cats, which could serve as egg donors and surrogate mothers in the cloning effort.

Alas, for every well-earned accomplishment, there are disappointing setbacks; nuclear transfer still produces failures and casualties, whether scientists are duplicating pets, livestock or wildlife. After making Noah, Advanced Cell Technologies went on to clone the banteng, another variety of endangered cow from Southeast Asia. The first such banteng, born to a domestic cow, was perfectly healthy, but its identical twin, born to a different cow two days later, was hugely oversized at birth. It was a classic case of the ‘large offspring syndrome’ that can plague cloned calves, and the second banteng was euthanized when it was a few days old. If we want to use clones to prop up a population, we’ll need to figure out how to produce healthy animals with less collateral damage and learn more about the long-term health of clones. (Ditteaux is still alive and well at age eight, and as scientists rack up more successes, and more clones come of age, we’ll have the chance to close this knowledge gap.)

These lingering challenges and unknowns mean that we’re not ready to launch any large-scale projects to restock the wild with clones. But if and when we are, what would such an endeavour look like? How would we go from a cloned kitten living in a lab to a sustainable wildcat population? In Dresser’s mind, the first task would be simply to create a lot of wildcats. Biologists would collect skin samples from as many of the felines as possible and send them off to a facility like ACRES. The laboratory scientists would turn the skin cells into cloned embryos, and a few months of gestation would turn the embryos into wide-eyed wildcat kittens. But researchers couldn’t just let the clones loose; repopulation projects are major undertakings, requiring long-term scientific, economic and political commitments. Captive-born wildcats would need to learn survival skills, such as how to hunt on their own, and biologists would need to work with African governments and agencies to secure a safe slice of land for the felines. That wouldn’t be an easy task given that it’s habitat destruction and other forms of human interference that got small exotic cats into trouble in the first place, and the clones might need to start their wild lives on a sanctuary or preserve. After the cats were released, scientists would need to spend years monitoring the animals, analysing mortalities and documenting how the lab-born cats were adjusting to their new lives. If all went well, the cloned felines would eventually integrate themselves into the wild population and begin to breed.

Many endangered-species reintroductions fail – reviews have turned up success rates that range from 11 to 53 percent – but there have been some important victories. Such programmes have boosted the wild populations of black-footed ferrets in the US, golden lion tamarins in Brazil and Arabian oryx in Oman, among others.

In addition, animal reintroductions can have ripple effects that help restore the environment itself. Every species is part of a complex ecosystem, and if an animal population suddenly disappears – or its numbers drop precipitously – it can throw the entire system out of whack. For example, some plants rely on animals to disperse their seeds; if these animals die out, the plants are vulnerable, too. When large herbivores disappear, dry shrubs and grasses accumulate, increasing the chance of wildfires. When predators disappear, herds of grazing animals swell, stripping the landscape of vegetation. Some scientists have proposed that by reintroducing animals to their native habitats, we can remodel landscapes and restore healthy ecosystems.

One researcher is putting this idea into action in the northern tundra of Siberia. Today, it’s a desolate place, the snow-covered ground featuring little vegetation beyond shrubs and moss. But it wasn’t always this way. During the Pleistocene epoch, which ended some twelve thousand years ago, the tundra was thick with wild grasses. Woolly mammoths, bison and wild horses roamed the land. According to Sergey Zimov, the director of Russia’s Northeast Science Station, these large herbivores played a key role in maintaining these grasslands. ‘In the winter, the animals ate the grasses that grew the previous summer’, Zimov wrote in Science. ‘All the while they fueled plant productivity by fertilizing the soil with their manure, and they trampled down moss and shrubs, preventing these plants from gaining a foothold. It is my contention that the northern grasslands would have remained viable . . . had the great herds of Pleistocene animals remained in place to maintain the landscape’.

Zimov is trying to turn back the clock by bringing the Pleistocene’s major herbivores – or their modern equivalents – back to the tundra. The animals will be deposited in Pleistocene Park, a large preserve that Zimov established in northern Siberia. Zimov hopes that these large herbivores will help convert the moss-covered landscape back into grassland and restore the diversity of plants and animals that have since disappeared from the region. The project will unfold over the course of decades, but reindeer, moose, musk oxen, bison and wild horses are already wandering the park and beginning to shape the landscape.

There are more radical proposals, too, such as ‘rewilding’ North America by stocking the Great Plains with wild horses, camels, elephants, cheetahs and more. (Elephants would serve as stand-ins for mammoths and African cheetahs as proxies for the extinct American cheetah.) According to the scientists championing the idea, these exotic animals will help convert weedy, rat-infested landscapes into lush, biologically diverse grasslands. (And, one imagines, turn a simple trip to Walmart into a drive-by safari.)

The ultimate effects of these ambitious projects are unknown, but even a small-scale reintroduction can help restore an ecosystem. Take the once-abundant grey wolf, which had disappeared from America’s Yellowstone National Park by the mid-1920s. The park’s elk populations exploded in the decades that followed the grey wolf’s disappearance, and these hungry ungulates spent their days chomping on the park’s aspen, willow and cottonwood trees, stripping branches of their leaves and chewing through saplings.

In 1995 and 1996, officials took a few dozen wolves from Canada and released them into the park. The wolf population slowly grew, and the elk population shrank back to a sustainable level. Today, the vegetation is recovering as well: the trees are taller, and the leaf canopies are thicker. This, in turn, has made the area more hospitable to other species. Songbirds are more abundant, and beavers, which had all but vanished from the park, are returning. What started out as a modest reintroduction project has been restoring Yellowstone to a place where all sorts of species can thrive together.

In the long run, boosting population size is just part of the task for scientists such as Dresser, since many endangered species are also handicapped by a lack of genetic diversity. Consider the enormous variation among human beings, all the different traits possessed by the people in your family, or in your county, or in Mozambique, Sri Lanka and Iceland. Imagine that a meteor hits Earth and spares (miraculously!) only the people living on your block. Whole family trees, and their unique genetic variants, have been wiped out. You and your neighbours are the only people who can repopulate the planet, and even if you reproduce in every possible combination, your descendants will not be as genetically diverse as the human race was before the meteor.

This reduced diversity creates all sorts of problems. It means a rare and devastating mutation might proliferate. If, purely by chance, the genetic mutation that causes Huntington’s disease is hiding in your neighbour’s genome, your block’s descendants could suffer from the disorder in staggering numbers. And if there are only a few families contributing their DNA to the communal pool, there will inevitably be a lot of inbreeding, which can cause problems of its own. A small gene pool also invites other disasters; if an infectious disease comes roaring along, and everyone’s equally susceptible to it, it could wipe out humanity in one fell swoop.

This is essentially what happens to a species whose numbers have dropped precipitously, such as the cheetah. Evidence suggests that some unknown catastrophe wiped out most of the planet’s cheetahs about ten thousand years ago, leaving just a small number of the cats to pass their genes along. The cheetahs alive today are a remarkably homogeneous bunch, with very little genetic variation. Their low levels of fertility and high rates of sperm abnormalities may be a result of generations of inbreeding.

Cloning, which just makes twins of the creatures that are already out there, won’t solve the genetic-diversity problem for cheetahs or any other species, but we could use the technology to prevent a gene pool from shrinking further. For instance, if scientists learn to clone the cheetah – something they have not yet attempted – they could create carbon copies of the animals that don’t reproduce. If one of the wild felines dies in infancy, and scientists can get their hands on a skin sample, they could clone the youngster, giving it another chance to pass along its genes. They could do the same with cheetahs that reach old age without ever having little ones. In a small population, every genome counts.

By stockpiling DNA from exotic animals, we can also prevent other species from developing such crippling diversity problems in the first place. At ACRES, these DNA samples are kept behind the door labelled ‘Cryobiology Room’, and Dresser takes me inside. The room is cold, dark and unimpressive. There is no obvious high-tech lab equipment, just a cluster of metal tanks, the approximate size and shape of kegs, lined up along the wall. But appearances can be deceiving. ‘That is years of science in there’, Dresser says, gesturing at the tanks.

This is the Frozen Zoo, where an entire wild kingdom is packed into a few square feet. Dresser opens one of the tanks, which are kept at a frigid -225 degrees Celsius, and nitrogen vapour comes swirling out. Suspended in the fog is a metal rack packed with tiny yellow straws. Each straw contains a cell sample from a different animal. They hold skin cells, sperm, eggs and whole embryos from thousands of different individuals, including gorillas, elephants, rhinos, monkeys, buffalo, frogs, storks, cranes, lions, tigers and bears. If Dresser is a modern-day Noah, these tanks are her ark. (Indeed, the story of Noah pops up again and again in the world of endangered-species cloning, from the little cloned gaur that was named after the biblical figure to the researchers who invoke the tale when discussing their DNA banking projects.) When the samples are frozen just so – pumped full of a cryoprotectant that prevents cells from bursting as the temperature drops – they can survive indefinitely.

Frozen zoos provide us with the opportunity to preserve the genetic diversity of a species before catastrophe strikes. If they had existed when the cheetah population was at its most robust, scientists could have packed the tanks with hundreds or thousands of cheetah skin samples. If we had these cells available today, we could look through them for genetic variants that have disappeared from the wild. We could clone these animals back into existence, and set them free on the African savanna, restoring genetic lineages that had died out.

According to Duane Kraemer – who established his own project to bank wildlife DNA after his students showed an interest in species conservation – what we really need to do is store cells from animals that are not endangered, preserving their diverse DNA for the future. ‘We should be systematically sampling populations and putting their cells into storage’, he says. ‘Our species has a tendency to wait until we’re in trouble until we look for solutions.’

Frozen zoos are popping up all over the planet. The San Diego Zoo in California has a particularly well known one, and eighteen institutions in eight countries are participating in the Frozen Ark Project, run out of the University of Nottingham. Together, these institutions have collected and preserved 48,000 DNA samples from more than 5500 species; the collective goal is to hit 10,000 species by 2015. If we store these samples properly, we’ll be able to use them to pull off remarkable scientific feats, including resurrecting species that die out in the wild. For example, the San Diego Zoo’s ice-cold collection includes cells from the po’ouli, a small Hawaiian songbird believed to be extinct. (The last known po’ouli died in 2004.) Scientists haven’t yet figured out how to clone birds, but if they do, the po’ouli DNA is sitting there in liquid nitrogen, ready to be brought back to life – and to give the fabled phoenix a run for its money. (Who needs a mythological bird that rises from the ashes when we’ve got a real one?)

The closest that scientists have got to species resurrection is the cloning of the Pyrenean ibex, a Spanish mountain goat. By 1999, there was only one Pyrenean ibex left in the world. Her name was Celia, and the rest of her kind had been hunted to extinction. One day in January 2000, Celia found herself under the wrong tree in Spain’s Ordesa National Park. The tree toppled, crushing Celia and officially snuffing out the Pyrenean ibex for good – or so it seemed.

The year before Celia’s death, some forward-thinking researchers had swiped a sample of her skin and stored the cells in liquid nitrogen. Then, after the elderly goat was gone, the scientists thawed out her cells and used nuclear transfer to get the ibex DNA into a whole clutch of domestic goat eggs. For their surrogate mothers, the researchers used hybrids – female crosses between the domestic goat and the Spanish ibex, a subspecies closely related to the Pyrenean variety. After the five-and-a-half-month gestation period, one hybrid was still pregnant. Researchers opened her up and delivered Celia’s clone. The newborn kid opened her eyes and moved her legs, but she struggled mightily for air, and died just a few minutes after her birth. A necropsy revealed lung abnormalities, a defect that’s been observed in other young clones. It was the briefest of resurrections, but the return of the Pyrenean ibex gave scientists hope that cloning could indeed bring back other extinct species.34

Several labs have embarked upon projects to clone species that died out long before Celia. Mike Archer, a palaeontologist at Australia’s University of New South Wales, has long dreamed of reviving the thylacine, one of the many strange creatures that evolved in the land down under. Like a kangaroo, the thylacine was a marsupial that carried its young in its pouch, but it looked more like a hyena, and the dark brown stripes running down its back earned the animal its other name: the Tasmanian tiger. The mammal has been extinct since 1936, when the last thylacine died at the Hobart Zoo. The technology used to painstakingly preserve cells in frozen zoos was not around when the thylacine disappeared, but we’ve held on to a few strange souvenirs: dried thylacine skins and wrinkled, hairless thylacine pups floating in alcohol-filled jars.

Clearly, these are not ideal conditions for DNA, which degrades over time, but a few Australian scientists think that they can use these samples to clone the Tasmanian tiger. They haven’t done so yet, but other researchers have managed to get some decent DNA from these thylacine samples. In 2008, one team of scientists isolated a piece of DNA from a baby thylacine that had been stored in alcohol a century ago. Then they put the thylacine fragment, which controlled bone and cartilage formation in the animal, into the genomes of mice. The DNA jumped right back into action, performing its normal regulatory duties in the bodies of these transgenic mice. Triumphant, the scientists wrote: ‘[W]e have restored to life the genetic potential of a fragment of this extinct mammalian genome’. The following year, a different group of researchers got their hands on some thylacine hair and published the complete sequence of two Tasmanian tigers’ mitochondrial genomes. These were exciting developments for those who dream of seeing packs of striped marsupials hunting down wombats and wallabies. But let’s not count our Tasmanian tigers before they hatch; the deterioration of the DNA in our thylacine samples means that bringing the animal back to life is still a long shot.

The longer a species has been extinct, the more difficult the resurrection. That makes the oft-cited goal of cloning a woolly mammoth – last seen alive circa ten thousand years ago – an especially daunting one. In recent years, several mummified specimens have been discovered under the Siberian permafrost. The ice has helped preserve the carcasses and, scientists hope, the DNA they contain. Russian, Japanese and Korean researchers – including the (in)famous cloner Hwang Woo Suk – have joined forces to extract DNA from these carcasses and re-create the prehistoric giants using elephants as egg donors and surrogates. (During his 2006 trial for fraud, embezzlement and other alleged offenses, Woo Suk admitted that he’d spent some of his research funding trying to buy mammoth tissue from the Russian mafia.)

They have a truly mammoth task ahead of them. To use nuclear transfer, they’ll have to find a cell in pristine condition. That will be difficult to find; the passage of thousands of years, cycles of freezing and thawing, and the presence of various microbes can all damage genetic material, and the DNA in even the best mammoth specimens unearthed so far has shown evidence of degradation. The other option – to sequence enough different genetic fragments to yield a complete, error-free genome and then build a set of chromosomes from scratch – is even more daunting. Add to that all the normal challenges that accompany cloning, plus the difficulties of working with the elephant reproductive system. (Among other obstacles, researchers will need to navigate more than 2.5 metres of reproductive tract to get a cloned embryo inside an elephant’s uterus.)

If that doesn’t sound tough enough, we could try going back even further, to the Jurassic era. Dinosaur DNA is way too far gone for cloning, but the famed palaeontologist Jack Horner has a different proposal for bringing back the reptilian beasts. Birds, scientists now know, are the modern descendants of dinosaurs. In fact, the genomes of birds and dinosaurs are so similar that Horner thinks we can reverse-engineer the reptilian beasts from chicken embryos. To make a ‘chickenosaur’ that looks like a prehistoric raptor, we wouldn’t even have to add new genes to a chick embryo – we’d just have to alter how its current genes were expressed, Horner says. Put a bird cell in a dish and bathe it in just the right growth factors, and we might be able to run evolution in reverse, prodding chicken DNA to build something that looks like it belongs in a real-life Jurassic Park.

Even if we can surmount all the technical issues, bringing extinct animals back might prove to be more cruel than kind. What would become of a resurrected mammoth or a Tasmanian tiger – or even two or three? They would be mere curiosities, carnival creatures confined to labs and zoos. Life in the wild likely wouldn’t be much better. Though Zimov has kindly offered up Pleistocene Park as a potential refuge for any future mammoth clones, we’d be sending the animals out into a world vastly different from the one they once knew. We might be setting the animals up for a miserable existence on a planet that can no longer give them what they need.

Cloning concerns environmentalists for just this reason – because the technology allows us to just churn out new animals without restoring or repairing their habitats. To many biologists, cloning is all sizzle and no substance, a high-tech spectacle that fails to address habitat loss, poaching, pollution and the other human activities that put wildlife at risk in the first place. David Ehrenfeld, a biologist at Rutgers, raised this concern in an article in Conservation Biology. Cloning, he wrote, ‘is a glamorous technology, and there is the danger of creating the false impression in the mind of a technology-infatuated public that it offers an easy, high-tech solution to the problem of extinction. Not only can this divert resources from conservation methods that have a much better chance of success, but repeated cloning failures may disillusion the lay supporters of conservation’. Cloning, he concluded, ‘should never be a conservation strategy of first resort’.

But the time for first resorts has come and gone, and safeguarding species is an all-hands-on-deck enterprise. Indeed, for cloning to have a real shot, laboratory scientists must work with conservationists; researchers can make all the fauna facsimiles they want, but the lab babies will need somewhere to live. The prospect of unleashing a thousand clones in the planet’s forests and prairies may be pure fantasy, but it’s not so far-fetched to imagine using cloning to accomplish more modest goals, such as duplicating select animals from select populations to keep certain genetic lineages alive. Cloning could help us maintain species in captivity until we can restore their habitats or add crucial genes back into a group of animals about to be released into the wild. Cloning won’t be a cure-all, but given the state of the planet, it can’t hurt to have options.

That’s why frozen zoos represent the ultimate safety net, a genetic savings account for the future.35 A century from now, scientists might have cloning down pat, or they might have an even better way to bring these ‘frozen cells’ back to life. One tantalizing possibility involves stem cells, which can morph into any of the body’s specialized cell types. Take a stem cell from an African wildcat and you may be able to coax it, in the laboratory, to grow into brand-new eggs or sperm. Scientists have managed to take the frozen skin cells of two highly endangered species – the white rhinoceros and the drill (a monkey) – and transform them into stem cells. The next step is to turn these cells into sperm and eggs, and then create test-tube rhinos and drills. The approach may turn out to be more efficient than cloning or a better option for species in which nuclear transfer has proved difficult. What’s more, because using eggs and sperm to create new embryos leads to genetic remixing, it will yield rhinos with new combinations of genes and should be a better way to maximize genetic diversity. This stem cell work is still in early stages, but Dresser is thrilled by the promise it holds. ‘I may not live long enough to see some of the stem cell stuff applied to tigers or lions or elephants’, she says, ‘but that’s okay, because somebody had to start that process.’

After spending years pioneering so many lab techniques, Dresser is passing the torch to the next generation of researchers, moving out from behind the microscope and into a more public role. She wants to make a forceful case for the need to develop reproductive technologies for endangered species – and to do so before it’s too late. She’s been travelling all over the country and batting ideas around with other experts. She’s visited labs that specialize in livestock breeding and talked with scientists about how their research might be applied to more exotic animals.

The technology is moving quickly, and wildlife biologists have to stay on their toes. Breakthroughs in any number of fields – livestock breeding, companion animal medicine, human reproductive technology – can spark strategies for saving endangered animals. Even advances in computing and electronics could play a role: Just ask the brigade of biologists who are fighting for threatened species with an arsenal of high-tech tracking devices.