Tiger feat?

June 28, 2002

The Australian Museum plans to clone the extinct thylacine from preserved DNA. Critics are sceptical, says Linda Vergnani.

Unlocking a metal cabinet, Sandy Ingleby pulls out a shallow drawer with an Alsatian-sized carnivore lying in it. The head of the marsupial thylacine, or Tasmanian tiger, rests on a white pillow. "This one was shot in the head in the 1800s," says Ingleby, collection manager in charge of mammals at the Australian Museum in Sydney. "The thylacine is among roughly 20 extinct Australian mammals species. We have the highest number of extinctions of any continent."

The museum's thylacine remains include about 25 boxes of skulls and three skins, one of a female with a well-preserved pouch. Exterminated as vermin in the wild, the last captive Tasmanian tiger died from cold and neglect in Hobart Zoo in 1936.

Now the Australian Museum has begun a controversial scheme to clone the thylacine from DNA taken from a preserved pup and other specimens. Critics point out that the team will have to overcome almost impossible obstacles, such as piecing together the thylacine genome from a jigsaw of DNA fragments and finding a surrogate marsupial mother in which to grow 21st-century thylacine embryos.

But Mike Archer, director of the museum, is optimistic. "We Europeans did a terrible thing by wilfully exterminating the thylacine. It was the largest land carnivore (in Australia), it was at the apex of the food pyramid. We just knocked it off cavalierly as if it were our God-given right. I do feel we have a moral imperative to bring back the thylacine and give it a second chance."

He says it can be returned to the wild. "The environment where it lived, where it was king of the roost, where its subjects still live, is intact."

Archer is concerned that if there is a delay in recreating the thylacine, there will be significant destabilisation of the Tasmanian ecosystem. Small, fierce Tasmanian devils are starting to take over the vacated niche. Archer, a palaeontologist, says the thylacine was the last of a family of marsupials that had existed for 24 million years. "The thylacine brings this hugely unique chunk of the genome back with it."

Archer believes the thylacine was "probably 50 per cent more gentle than dogs" and not the ferocious predator of sheep early Tasmanian farmers believed it to be. Contemporary accounts record that thylacines could be kept like dogs, which they resembled. Having raised various carnivorous marsupials, including a quoll, an endangered Tasmanian cat-like creature, Archer finds them surprisingly gentle. But he says his hand-reared quoll kitten instinctively knew how to kill a mouse. It is one reason he believes that cloned thylacines would have hunting instincts "hard-wired into their genes". Clones returned to the wild would instinctively hunt former prey species such as bandicoots.

Archer admits that although the project has been criticised, it has also been backed by scientists such as Bob Lanza of Advanced Cell Technology, part of a group carrying out cross-species cloning.

Don Colgan, head of the evolutionary biology unit at the Australian Museum and scientific project leader, rates their chance of success at just 4 to 10 per cent. "The goal is to bring thylacines back to the world. There is no point doing it if it is just going to be a circus freak, no point in bringing it back if it is going to survive only in captivity."

Colgan's involvement "stemmed from the time of the release of the film Jurassic Park". Journalists asked him then whether it was possible to resurrect the thylacine, and he replied: "It would require funding equivalent to the gross domestic product of the US to achieve it." But significant developments in DNA amplifying and analysing techniques plus cloning now make it seem feasible.

Colgan and conservation geneticist Karen Firestone, who is doing the DNA analysis, admit that mapping thylacine genes involves piecing together some 3.5 billion bases of DNA. They use samples drawn from an almost hairless pup, preserved in a jar of alcohol, plus bones and teeth from two other specimens. Colgan says they have extracted fragments of thylacine DNA with up to 2,000 bases. The sequences are being amplified and copied. He concedes that to sequence the genome resources would have to be increased greatly, and he hopes to get a "large-scale partner" involved.

Firestone, who previously worked at Taronga Zoo in Sydney researching quolls, says: "We've been looking at two families of animals related to the thylacine that we can use to reference the sequences." One marsupial carnivore family consists of numbats, the other includes species such as Tasmanian devils and quolls. One of these smaller predators could serve as a suitable surrogate mother if cloning succeeds.

Firestone claims they have taken samples from males and females. "It addresses one of the major criticisms that if we ever get to the stage of cloning the animal, it will be just one specimen." But the two scientists are frank that the success of the project will depend on new technological advances.

John Shine, executive director of the Garvan Institute of Medical Research in Sydney, says: "It would have to be a very brave and probably very foolish scientist who would say it's not possible if you look at what history teaches us about the exponential increase in our database on the genetics and cellular areas in the past several decades."

The Garvan Institute has offered the thylacine project advice and support. Shine, a professor of molecular biology and medicine at the University of New South Wales, says cloning with dead cells is not currently feasible, but he believes it will be eventually. He says the two big technical hurdles are joining together the DNA fragments and "packaging it in some way to put it into a viable cell or membrane". His institute backs the project because of potential spin-offs for human medical research. Also, he says: "We think this type of frontier science that captures the imagination of young people is very important for the future of science."

Among critics is Alan Cooper, director of the Henry Wellcome Ancient Biomolecules Centre at the University of Oxford, who led the team that sequenced the mitochondrial genome of New Zealand's extinct moa, a flightless bird. Cooper sees the thylacine project as "just a large publicity stunt designed to attract funding. The same phenomenon was seen in New Zealand over the moa and then the huia, another extinct bird. My concern is that such science fiction is doing a lot of damage to the field of ancient DNA - and getting us ridiculed."

He believes the project will fail because of the fragmented DNA, the lack of nuclear material and "the inability to use even a complete DNA sequence to make chromosomes". It would be better to use the money for conservation, he says. Even a "magically re-created species" lacks a habitat, a mate, parents and therefore all the knowledge passed on about things such as what to eat.

George Amato, director of the Science Resource Centre and senior conservation geneticist of the Wildlife Conservation Society in New York, says the "whole project seems like an enormous waste of time and money - and distracts from the real issues we are confronted with in conservation. No scientists currently can envisage a way of going from DNA sequence information to creating functional chromosomes and cells." He believes that even if a single thylacine could be resurrected, there is insufficient material to produce a population, "so it would just be a technological trick and not the recovery of an extinct species".

Archer is undeterred. He points to cross-species cloning and the recent production of a "rama" - a mixture between a guanaco and an African camel. His team has already "surmounted barriers people thought were impossible". With hundreds of museum specimens, there is the capacity to create a viable population, he says. "If you consider that every second specimen that was killed in Tasmania probably ended up on someone's mantelpiece or in a museum, there is an awful lot of thylacine DNA here and all around the world waiting theoretically to be reconstituted."

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