Here Come The Dnasaurs

In 'Jurassic Park,' I scientists clone a theme park full of real dinosaurs from ancient DNA. Is that idea totally nutty-or could it actually happen?

Her graceful neck rises higher than the trees, like a giraffe in slow motion, her liquid eyes staring curiously, then dismissively, at the gaping humans; she returns to her grazing as if these late-model mammals were no more worthy of note than their scruffy shrewlike ancestors, with whom she shared the Earth 130 million years ago. The lack of interest is not mutual. The beast on that rolling meadow looks for all the world like a living dinosaur--a real, respiring, mothering, thundering, leaf-chomping Brachiosaurus. The awe-struck humans on screen are convinced that this monster of the Mesozoic has been brought back to life. We can tell they're convinced-by the actors' bugging eyes and dropped jaws.

OK, so not even the makers of "Jurassic Park," this summer's blockbuster-to-be, expect to achieve that crucial suspension of disbelief in the audience on the strength of the acting. And although director Steven Spielberg spent two years in preproduction-working with the computer maestros and modelmakers who created such wondrously realistic beasts as a Triceratops with a bad stomachache and a Tyrannosaurus rex with an appetite for cars carrying cherubic children (page 60)-special effects alone can't persuade audiences to pretend that dinosaurs have burst the coffin of extinction. There is only one hidden persuader in science fiction: a solid kernel of scientific plausibility. In Spielberg's $60 million "Jurassic Park," opening this Friday, this hard center is a theory barely 10 years old. It holds that snippets of the genetic material DNA, extracted from mosquitoes that sucked dinosaur blood and then became fossilized in amber, can bring dinosaurs back to life. "This movie depends on credibility, not just the special effects," Spielberg told NEWSWEEK. "The credibility of the premise-that dinosaurs could come back to life through cloning of the DNA found in prehistoric mosquitoes trapped in amber-is what allowed the movie to be made."

All great science fiction must be science first and fiction second. Even more, it must tap into the reigning scientific paradigm of its era. For Mary Shelley's "Frankenstein," that paradigm was electricity, the sizzling lightning bolts and arcing volts that were powering the nascent Industrial Revolution. For Godzilla, it was radioactivity and the Bomb. For "Jurassic Park," it is biotechnology. The manipulation of cells and genes has produced three cloned mice, pigs containing human DNA, tomatoes with flounder genes-and lots of people who fret about where it's all leading. According to the 1990 Michael Crichton novel that "Jurassic Park" is based on, biotech is headed toward using mosquitoes and bloodsucking flies to undo the dinosaurs' extinction.

Both book and film unfold in the world's greatest theme park: a gentle Brachiosaurus herd strides in meadows, rapacious Velociraptors eat oxen alive. The mastermind behind the park bankrolled paleontologists, geneticists and computer scientists to create the dinosaurs out of nothing more imposing than bugs in amber. The premise is that after insects fed on dinosaurs, they flew to a sap-oozing tree. In their postprandial languor, they got stuck. For good. Resin fossilized into the dusky gemstone amber, preserving intact the insect and, perhaps, its last supper. The rest of the dinosaur reanimation is, as they say, just biochemistry (diagram). First, dino blood is extracted from the belly of the mosquito and the DNA inside the blood cells is isolated. (The red blood cells of reptiles and mammals lack DNA, but "Jurassic Park" assumes that dino blood cells contain this genetic material.) Computers infer which parts of the genetic blueprint are missing. Scientists fill in the gaps with DNA from a frog. Finally, they implant the now complete genome into the ovum of a crocodile. That goes into a plastic egg, filled with all the requisite yolky nutrients. They incubate it, and wait.

Yeah, right.

But last September, two weeks into the filming of "Jurassic Park," biologists Raul Cano of California Polytechnic State University at San Luis Obispo and George Poinar Jr. of the University of California, Berkeley, announced that they had cloned DNA from a 40 million-year-old bee preserved in amber. Almost simultaneously, scientists at the American Museum of Natural History in New York reported that they had cloned the DNA from a 25 million-year-old termite trapped in the golden mineral. "'Jurassic Park' has at least one big toe in real biological research," says Poinar. "Ancient DNA is indeed being extracted and cloned from extinct organisms preserved in amber."

Those 1992 triumphs were the culmination of a quest for what has been called "still life in amber." In 1982, Poinar and his wife, Roberta Hess, discovered that amber did not contain merely the imprint of insects, nor even just their dried-out remains. "The body of the organism itself was inside the amber," he says. They could see clearly, in an electron microscope, the muscle cells of a gnat immortalized in a hunk of amber. And to their amazement, they could also see, inside the muscle cells, the structures containing the gnat's genes. But when Poinar and colleagues set out to extract DNA from ancient creatures like those locked in amber, "granting agencies refused to fund us," says Poinar. "The project was considered too avant-garde."

Devoting weekends, evenings and their own money to the spurned project, Poinar and like-minded enthusiasts formed the Extinct DNA Study Group. In 1984, researchers led by Berkeley's Allan Wilson succeeded spectacularly in extracting DNA from the preserved skin of a quagga, a zebralike beast native to Africa that was hunted into extinction in the 1880s. The science of ancient DNA exploded. In the nine years since, researchers have recovered DNA from 40,000-year-old woolly mammoths frozen in the Siberian tundra, from 5,000-year-old Egyptian mummies, from the brain of a Florida Indian who died 7,500 years ago, from a magnolia leaf 17 million years old and from bees, termites and other insects that lived 25 million to 30 million years ago.

They haven't cloned any beings and brought Tut back to the Nile. But sci-fi writers and others have raised the possibility. Charles Pellegrino, a paleobiologist and rocket designer who lives on the fringes of science and evinces no desire to move toward the center, popularized this scenario in 1985, in Omni magazine. He wrote: "We could insert [genetic material] into a cell nucleus, provide a yolk and an eggshell, and hatch our own dinosaur." Yeah, right.

Except that a few years after Pellegrino's musing, Poinar's son Hendrik, working with Cano, figured out how to go beyond merely cracking the amber and extracting the DNA. He managed to rehydrate it, like so much instant mashed potatoes, returning to the wizened strands their ability to replicate. As a result, scientists can now "turn on" the ancient DNA and make billions of copies through a revolutionary process called polymerase chain reaction-biology's Xerox machine. Suddenly, biologists had enough DNA to read the letters that spell out, in part, how to make the bee or the mammoth or the quagga.

But they did not have the complete sets of instructions. DNA deteriorates over the eons. After 25 million years or so, less than I percent of the original blueprint survives. It was Pellegrino's suggestion, which Crichton borrowed for "Jurassic Park," that scientists back-and-fill to complete the genetic code. Since even flies and humans share 30 percent of their DNA, it might be possible to figure out which chapters the book of brontosaur DNA was missing, and fill them in with DNA from a modern relative.

Yeah, right.

Except that in 1992 Cano began using a powerful Sun Microsystems workstation to call up on his computer screen strands of ancient DNA, align them with DNA fragments from such relatives as living birds and reptiles, infer the similarities and differences-and, perhaps, figure out what is missing.

Having perfected the art of extracting DNA from amber-encased insects, Cano is using the same technology to fish for DNA directly from the fossils of duckbill dinosaurs. He calls it "molecular paleontology." Also on the trail of dino DNA from fossil bones is paleontologist Jack Horner-soft-spoken curator of the Museum of the Rockies in Bozeman, Mont., model for the hero of "Jurassic Park" and scientific adviser to the movie. Horner rocked paleontology with his discovery 15 years ago that maiasaurs ("good mother lizards") built nests and cared for their hatchlings, counter to dinosaurs' lay-'em-and-leave-'em reputation. "Getting DNA out of a dinosaur [bone] is real easy," he says. "But proving it's not [DNA from] bacteria or fungus contaminating the bones has never been done."

But the science rumor mill is buzzing with word that it's about to be done, by either Cano's lab or Horner's. "Someone will do it," says Cano. "And soon." (But not to clone a dinosaur: Horner and Cano are interested in comparing dinosaur DNA to that of living reptiles and birds to determine their evolutionary relationships.)

Of course, even if someone retrieved dinosaur DNA, Disneyland wouldn't have to worry about competition from a real-life Jurassic Park. None of the ancient DNA harvested from amber or fossils, notes the Natural History Museum's Ward Wheeler, is longer than 250 of the units (called base pairs) used to measure DNA. The human genome contains 3 billion base pairs. Dinosaurs might have had between 1 billion and 10 billion, estimates the museum's Rob Desalle, who with Wheeler helped isolate the 25 million-year-old termite DNA. Even if scientists discover every single one of the base-pair chains, joining 40 million of them in the right order would be like taping together a book that has been chopped into individual letters. "And even if we could splice them all together," says Desalle, "there are all sorts of development things that happen in the egg that we don't know about."

Here's where the prospects for re-creating Triceratops dim. You need a lot more than DNA to build a dinosaur, says David Botstein, chairman of the genetics department at Stanford University, who gets a brief mention in Crichton's book. You need a cell. Only in the cell, with its still-not-understood biological signals that tell genes to turn off and on, can DNA direct the creation of an embryo. "Otherwise," says Botstein, "it's as if you have discovered the instructions to build an automobile, but you have no tools, no parts, no metal, no machinery. That's where we are in DNA technology." Spielberg, for one, is not dismayed. "I believe, without a doubt, [that science is capable of re-creating dinosaurs through genetic engineering]," he says. "It could be 40 years from now. But I don't think our collective imagination can envision the world that science will give us."

Yeah, right.

Except that the science establishment also once doubted the possibility of cloning animals of the nonextinct variety. "Cloning" means duplicating an organism exactly-producing its identical twin. In principle, that should be possible using any cell of the animal you want to clone. Every cell (except sperm and eggs) contains the same, complete genetic instruction manual as in the original fertilized egg. A human liver cell contains the complete specifications for making an entire person; a dinosaur's muscle cell contained the full code for making a whole brontosaur. But not all those instructions are carried out. Some of the DNA is switched off so that in a liver cell, only the genes for liver-ness are active; genes for muscles and neurons and the rest are inactive. The trick to cloning an individual from a single cell is to wake up all the genes in the cell. In the 1950s, biologists did that in amphibians. They transplanted a cell from a young tadpole's intestine into a frog egg. The egg grew into a tadpole identical to the first. In 1978, when a book purported to tell the true story of a tycoon who had himself cloned, researchers dismissed the idea by saying mammals could not be cloned. Three years later biologists in Geneva cloned three mice, starting with the cell from a very early embryo.

The challenge to cloning a dinosaur, assuming one had a cell full of DNA, is that cells from anything but an embryo seem to have forgotten how to make the complete animal. It is adult DNA, of course, that is the raw material for "Jurassic Park" and the likely discovery of scientists looking for dinosaur genes in fossils. Scientists do not know when the DNA in dinosaur cells forgot how to make the complete creature.

Clearly, high hurdles stand in the way of bringing dinosaurs back to life through genetic engineering. Researchers have not found an amber-trapped insect containing dinosaur blood. They have no guarantee that the cells in the blood, and the DNA in the cells, will be preserved intact. They don't know how to splice the DNA into a meaningful blueprint, or fill gaps with DNA from living creatures. And they don't have an embryo cell to use as a vehicle for cloning.

None of this is banned by any law of nature. And in science, the saying goes, what is not strictly prohibited is, in principle, possible. "Jurassic Park's" vision of hubristic scientists determined to shape the future, damn the consequences, recalls the physicists of the Manhattan Project. When they set off the Trinity test in Alamogordo, N.M., in 1945, they were not sure that the atomic bomb would not ignite the planet's entire atmosphere, consuming Earth in a world-ending holocaust. They did it anyway. Crichton sees in "Jurassic Park" a reflection of science's delusion of control. "Biotechnology and genetic engineering are very powerful," he says. "The film suggests that [science's] control of nature is elusive. And just as war is too important to leave to the generals, science is too important to leave to scientists. Everyone needs to be attentive." Right.

Scientists in "Jurassic Park" re-create dinosaurs by extracting the extinct reptiles' DNA from mosquitoes preserved in amber. Here's the theory:

Here Come The Dnasaurs | News