Essay: When "Ghost" Species Return From Extinction

Scott Wiedensaul
Special for National Geographic News
July 9, 2002

Earth is hemorrhaging. By some estimates, we lose three or four species per hour—perhaps 30,000 unique life-forms disappear every year—a rate of extinction the planet has not seen since an errant asteroid struck the Yucatán 65 million years ago and wiped out dinosaurs, toothed birds, ammonites and much else. But this time we're the asteroid, destroying habitats and altering ecosystems on a global scale.

Yet, not every loss is as permanent as it first seems. A number of times each year, scientists—by dint of hard work or dumb luck—rediscover species that they thought were extinct. Recently, researchers in Tanzania spotted a Lowe's servaline genet, a graceful, mongoose-like carnivore last seen in 1932, and widely considered to be extinct. Not long before that, the golden-crowned manakin, a South American bird, resurfaced for the first time since its discovery in 1957.

Not every search has a happy ending, though. A well-funded hunt for the ivory-billed woodpecker last winter in Louisiana produced a tape recording researchers thought captured the distinctive drumming of this huge and legendary bird. Further analysis of the tape, however, revealed that the sounds were actually distant gunshots, and the fate of the ivorybill remains unclear.

Ghosts from the Past

On occasion, the ghosts return after an absence that covers not decades, but centuries. The plump seabird known as the cahow, or Bermuda petrel, was considered extinct as early as 1620, eaten out of existence by hungry Europeans who plucked the tame bird from its nest burrows. Yet in 1951, a tiny colony was found on a rocky islet off Bermuda, where they had managed to avoid notice for more than 300 years. Nor is that the most extreme example. In the Canary Islands, a large species of lizard was rediscovered in 1999, a full five centuries after its supposed extinction.

In this era of grievous loss, such stories of rediscovery, while not balancing the accelerating biotic erosion, are nevertheless cause for hope. These lost-and-found species were not, of course, truly extinct, just overlooked. But what about animals and plants that are well and truly gone; does modern science hold a solution for even a fate as permanent and profound as extinction?

Cloning the Tasmanian Tiger

Researchers in Australia believe so, and they are trying to quite literally raise from the dead one of the most famous extinct species in the world—the surpassingly strange marsupial called the thylacine, better (and misleadingly) known as the Tasmanian tiger.

Not a cat at all, this wolf-like predator with a striped pelt is believed to have died out in 1936, after persecution by sheep ranchers. But two and a half years ago, a team of scientists at the Australian Museum in Sydney mapped out an audacious plan to remove tissue from a thylacine baby pickled in alcohol in 1866, sequence its DNA, reassemble its genetic blueprint in artificial chromosomes, and ultimately clone a live thylacine.

Recently, the team announced success in replicating the animal's DNA; not a groundbreaking achievement, as other researchers working with extinct DNA have accomplished the same task, but a crucial stepping stone toward their larger goal.

Continued on Next Page >>




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