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Tiger From a Jar?

Could Cloning Bring Back Tasmanian Tiger and Other Species?

By Lee Dye

July 8, 2004 ? A mysterious predator in a far-off corner of the world, hunted to extinction decades ago, has emerged as the central character in what is likely to be a prolonged and bitter scientific debate.

The Tasmanian Tiger, which wasn't really a tiger, is being asked to answer questions of staggering implications. Is it possible to bring extinct species back to life through cloning? And if we can, should we?

This is not an academic exercise. The prestigious Australian Museum, under the directorship of Mike Archer, has vowed to do just that, using DNA from animals that have been dead for more than a century. Some say it can't be done. Archer himself says he isn't sure, claiming that success would be the "biological equivalent of the first walk on the moon."

The effort has taken on almost religious overtones, modern humans seeking a way to atone for the sins of their forefathers. Or as Archer puts it, it's a chance to "redress our immoral actions when we willfully and wrongly exterminated this animal."

Cloning the tiger would require so many scientific breakthroughs that success would be a "technological miracle," Archer maintains, and others agree.

"It would be a miraculous birth, a clone from aged DNA," writes David Owen, author of Tasmanian Tiger, The Tragic Tale of How the World Lost its Most Mysterious Predator, recently released by The Johns Hopkins University Press. Owen, a Tasmanian novelist, has chronicled the plight of the tiger from the years when it roamed across much of Australia and the southern island state of Tasmania to the present. It has reached a mythical status with sightings still being reported despite convincing evidence that the beast no longer survives.

But as Owen meticulously points out, all the hoopla over the possibly of cloning an extinct animal may just make it easier for us to ignore the desperate need to protect the habitat of endangered species that are barely hanging on.

The lead character in this ongoing drama is a strange beast indeed. The Tasmanian Tiger is actually a marsupial, with a pouch to carry its young. It has also been called a wolf, a dog and a hyena, but its lineage is clearly revealed in its kangaroo-like hind quarters, and the shape of its ears and muzzle, as well as the pouch. It is about the size of a Dalmatian.

It is officially named "thylacine," and it is the largest carnivorous marsupial known in modern times. But most references still call it a tiger.

Its end began thousands of years ago when humans introduced dogs to Australia. Wild dogs competed with the tigers for food, and the tigers gradually disappeared from mainland Australia. They thrived in the rugged terrain of Tasmania for centuries, but in the 1800s they found themselves accused of killing sheep, an economic crime that the people of that era could not tolerate.

There's precious little evidence to support that, Owen argues. It's far more likely that sheep were killed by wild dogs, not tigers that avoided human contact. But by then the animal's reputation was established as a vicious killer with a vampire's taste for blood and internal organs. It was a thrill killer, according to the legends of the day, sometimes wiping out entire flocks of sheep just to watch them die.

In 1886 the Tasmanian government passed a law that mandated the destruction of the species, and bounties for dead tigers led to feverish hunting expeditions over the next 50 years. The only known surviving tigers ended up in zoos, despite a gradual awakening to the fact that the tiger was not a demon and should be protected.

In 1936 legislation was passed by the parliament declaring the tiger to be wholly protected, but it was too late. Two months later, the last known survivor died in a Tasmanian zoo.

Myths about the tiger continued to grow, with frequent reports of sightings in the wild, but little evidence to support them. Owen has documented eight official expeditions between 1957 and 1966 in search of remaining tigers.

"What they had in common was justified optimism at the outset and negative results at the end," he writes.

So does the tiger still thrive somewhere in the dense forests of Tasmania, as so many residents claim? The museum's Archer describes himself as "sadly unconvinced. Without a single hair, dropping or any tangible evidence, I have to remain skeptical."

Extinct species have long fascinated Archer, and his courting of the tiger began about 15 years ago when he discovered a pickled tiger pup in the museum. It had been preserved since 1866 in a jar of alcohol rather than the more commonly used formalin, which would have destroyed the DNA.

That was long before Dolly ruled the headlines but even then Archer began thinking about bringing the tiger back.

But its one thing to clone a living species, with an abundance of specimens from which DNA can be extracted, and it's quite another to create a clone from ancient DNA. In all, museum researchers have extracted DNA from three different preserved tigers, but that still leaves enormous gaps in the animal's genome.

The last step in this long and tortured scientific journey will be to put a complete set of the tiger's chromosomes in a living cell, and implant that cell in another animal, probably the closely related Tasmanian devil, which would serve as a surrogate mother.

But in the end, even if it all works, that may not be enough. Owen notes that no tigers reproduced while in captivity, and any cloned animals would likely be quite different from those that once roamed across Tasmania.

The museum has targeted the year 2010 for completion of the project. Even if it fails, Archer maintains, it should lead to numerous scientific breakthroughs, possibly paving the way for cloning extinct animals sometime in the future.

The nightmare in that dream, of course, is that the prospect for cloning might lead to a relaxation of the effort to protect species that are still living.

Uncounted thousands of species have perished at human hands. Bringing the tiger back would be thrilling, but it won't lift that burden. Protecting what we have left must remain our first priority.

[original article]

Posted by thinkum at July 8, 2004 04:36 PM