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Mardi, 27 Septembre 2011 12:00

How to Hatch a Dinosaur

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Get a chicken, hijack its DNA, and stand back.
Photo: Dan Forbes; model maker: Jason Clay Lewis

People have told Jack Horner he’s crazy before, but he has always turned out to be right. In 1982, on the strength of seven years of undergraduate study, a stint in the Marines, and a gig as a paleontology researcher at Princeton, Horner got a job at Montana State University’s Museum of the Rockies in Bozeman. He was hired as a curator but soon told his bosses that he wanted to teach paleontology. “They said it wasn’t going to happen,” Horner recalls. Four years and a MacArthur genius grant later, “they told me to do whatever I wanted to.” Horner, 65, continues to work at the museum, now filled with his discoveries. He still doesn’t have a college degree.

What we’re trying to do is take our chicken, modify it, and make a chickensaurus.

When he was a kid in the 1950s, dinosaurs were thought to have been mostly cold, solitary, reptilian beasts—true monsters. Horner didn’t agree with this picture. He saw in their hundreds-of-millions-of-years-old skeletons hints of sociability, of animals that lived in herds, unlike modern reptiles. Then, in the 1970s, Horner and his friend Bob Makela excavated one of the most spectacular dinosaur finds ever—a massive communal nesting site of duck-billed dinosaurs in northwest Montana complete with fossilized adults, juveniles, and eggs. There they found proof of crazy idea number one: The parents at the site cared for their young. Judging by their skeletons, the baby duckbills would have been too feeble to forage on their own.

Horner went on to find evidence suggesting that, once hatched, the animals were fast-growing (crazy idea number two) and possibly warm-blooded (that would be three), and he continues to be at the forefront of the search for ancient bits of organic matter surviving intact in fossils (number four). Add in his work as a technical consultant on the Jurassic Park movies and Horner has probably done more to shape the way we currently think about dinosaurs than any other living paleontologist.

All of which means that people are more cautious about calling him crazy these days, even when he tells them what he plans to do next: Jack Horner wants to make a dinosaur. Not from scratch—don’t be ridiculous. He says he’s going to do it by reverse-evolving a chicken. “It’s crazy,” Horner says. “But it’s also possible.”

Over the past several decades, paleontologists—including Horner—have found ample evidence to prove that modern birds are the descendants of dinosaurs, everything from the way they lay eggs in nests to the details of their bone anatomy. In fact, there are so many similarities that most scientists now agree that birds actually are dinosaurs, most closely related to two-legged meat-eating theropods like Tyrannosaurusrex and velociraptor.

But “closely related” means something different to evolutionary biologists than it does to, say, the people who write incest laws. It’s all relative: Human beings are almost indistinguishable, genetically speaking, from chimpanzees, but at that scale we’re also pretty hard to tell apart from, say, bats.

Hello, chickensaurus!
Photo: Dan Forbes; model maker: Jason Clay Lewis

Hints of long-extinct creatures, echoes of evolution past, occasionally emerge in real life—they’re called atavisms, rare cases of individuals born with characteristic features of their evolutionary antecedents. Whales are sometimes born with appendages reminiscent of hind limbs. Human babies sometimes enter the world with fur, extra nipples, or, very rarely, a true tail. Horner’s plan, in essence, is to start off by creating experimental atavisms in the lab. Activate enough ancestral characteristics in a single chicken, he reasons, and you’ll end up with something close enough to the ancestor to be a “saurus.” At least, that’s what he pitched at this year’s TED conference, the annual technology, entertainment, and design gathering held in Long Beach, California. “When I was growing up in Montana, I had two dreams,” he told the crowd. “I wanted to be a paleontologist, a dinosaur paleontologist—and I wanted to have a pet dinosaur.”

Already, researchers have found tantalizing clues that at least some ancient dinosaur characteristics can be reactivated. Horner is the first to admit that he doesn’t know enough to do the work himself, so he’s actively seeking a developmental biology postdoctoral fellow to join his lab group in Montana. Horner has the big ideas, and he has some seed funding.

Now all he needed to make it happen, he told his TED audience, was a few breakthroughs in developmental biology and genetics and all the chicken eggs he could get his hands on. “What we’re trying to do is take our chicken, modify it, and make,” he said, “a chickenosaurus.”

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