- - Monday, October 24, 2011

In “Jurassic Park,” the 1991 novel about a wildlife preserve for dinosaurs, the late Michael Crichton raised the specter of the resurrection of extinct species using preserved DNA specimens. It seemed far-fetched two decades ago. But we live in an era now when yesterday’s science fiction is today’s banner headline on the Drudge Report.

With Tuesday’s Blu-ray debut of the “Jurassic Park” movie trilogy, the time is right to ask: How far has science advanced toward realizing the underlying premise of the franchise?

Well … nobody said it was going to be easy.

DNA usually only survives for a few thousand years in the fossil record, and finding older samples is an extremely rare occurrence. Professor John Horner, the paleontologist who served as technical adviser for the “Jurassic Park” series, believes that if long-dead creatures are ever revived, the most likely candidates aren’t dinosaurs but more recently extinct animals like the dodo or mammoth.

“In the case of mammoths,” he says, “we do have living elephants, which are their close relatives, so reviving them might be possible in the not too distant future.”

Indeed, scientists have even speculated that we might be able to “regrow” dinosaurs by fiddling with the DNA of their modern descendants, such as birds, although this seems a remote prospect at present.

More immediate success might be obtained on a smaller scale, including a kind of reverse “Jurassic Park” scenario, where scientists use ancient DNA evidence to ascertain that a species thought to be extinct is, in fact, not so.

This occurred most recently in New Zealand where a kind of storm petrel thought extinct since 1850 was discovered to be alive and well.

Also in New Zealand, the plumage of the extinct giant bird known as the moa has been reconstructed using DNA extracted from 2,000 year-old feathers. The DNA was taken from the shaft and barb of the feathers, something not previously thought possible.

Another creature that could be “revived,” albeit far less glamorous than the moa, is the humble bacterium.

When a human body is preserved after death, the DNA of its microorganisms, including disease-causing pathogens, can often survive intact alongside traces of the human DNA, preserved within human tissues.

Biomolecular scientist Mike Bunce, who heads the ancient DNA research lab at Australia’s Murdoch University, thinks that this kind of DNA is essentially a genetic time capsule.

“It means we can go back and see what a disease looked like in the past,” he says.

Diseases mutate much faster than human DNA does, so even going back a decade or two can reveal a lot about how a disease has evolved.

As Mr. Bunce puts it, “the human genome is in a constant arms race with its pathogens.”

Ancient DNA from a medieval cemetery in London was recently used to prove that the plague pathogen Yersinia pestis was definitely responsible for the Black Death of the 1300s.

And tuberculosis-causing bacteria have also been found in a 9,000 year old mummy from Atlit-Yam, a submerged Neolithic village off the coast of Israel, where DNA traces were preserved because of flooding.

This raises the subject of DNA’s potential misuse in germ warfare or terrorism; and no doubt many biotech firms will be keen to unlock the potentially lucrative secrets ancient DNA can reveal.

This subject was broached in a recent film starring Willem Dafoe called “The Hunter,” which concerns an American bounty hunter’s attempts to track down and kill the last surviving Tasmanian tiger for a European biotech firm.

In reality, the Tasmanian tiger is thought to have been extinct since the 1930s, but it is not inconceivable that it could one day be brought back to life, as could other species such as the dodo or the quagga, a subspecies of the zebra.

DNA has also been extracted from hair in woolly mammoths, but Nicolas Rawlence, an expert in ancient DNA and the head of the team that extracted the moa DNA. doesn’t believe that research of this kind will lead to the reconstruction of extinct species a la “Jurassic Park.”

“No matter how fast molecular technology increases it cannot get around the fact that as soon as we die, our DNA starts to degrade, making reconstruction of extinct species very difficult, if not impossible,” he says.

Mr. Horner, who was the partial inspiration for “Jurassic Park’s” protagonist Dr. Alan Grant, is equally skeptical. “Quite frankly,” he says “we’re no closer to reviving a dinosaur than we were in 1993 [when the first film came out], because we have yet to find even the smallest piece of DNA.”

While it is true that DNA has been extracted from dinosaur bones, this DNA hasn’t come from the dinosaurs themselves but rather from organic matter present in the soil, which rains down onto the bones from above.

In addition to the difficulty of obtaining pristine, non-degraded DNA, another major problem would be the fact that extinct animals’ natural habitat will have changed considerably in the time since they died out.

This would mean they would have trouble living anywhere outside of a specially prepared wildlife sanctuary — the very premise behind “Jurassic Park.”

Faced with an eternity of captivity, some might argue that the creatures would be better off extinct.

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