Three years ago, evolutionary biologist Neil Shubin unveiled one of the most significant fossil finds of the century: Tiktaalik, a 375-million-year-old fish with “a neck, elbows, shoulders, even proto-wrists,” he says. An almost perfect link between fish and land vertebrates, Tiktaalik (unearthed in Nunavut) is our own distant cousin. Just as Larsson looks to dino bones to understand his embryos, Shubin used the fossil to design an experiment with modern-day paddlefish. He found that, even before limbed animals evolved about 365 million years ago, fish had the genes necessary to grow arms and legs. “Evolution doesn’t always rely on the development of new genes,” Shubin explains. “It’s redeploying old genes in new ways: changing their switches, or their time of activity.”
By tripping the right genetic switches at the right time, then, Larsson should be able to build a dinosaur inside a chicken egg.
While Larsson tinkers with the embryos in his lab, other scientists are on the hunt for dinosaur DNA, the so-called blueprint for life. In the movie Jurassic Park, researchers manage to extract it from a mosquito trapped in amber, then implant it into a frog’s egg; not long after, the park is swarming with velociraptors, triceratops, and even a bloodthirsty T. rex.
Harvesting DNA from bugs in amber worked just fine in the movies, but in real life, it hasn’t panned out. “Many people have tried, myself included,” says Blair Hedges, an evolutionary biologist at Pennsylvania State University, who says a sample could provide invaluable information on everything from a dinosaur’s appearance and behaviour, to the process of evolution. It could also theoretically be used to build a dinosaur, if enough were recovered—the first step, though, is to find some. So far, the oldest DNA ever recovered is under one million years old. The last dinosaurs died out 65 million years ago.
It isn’t necessarily the passage of time that ruins a DNA sample, so much as its surroundings, says Hendrik Poinar, director of McMaster University’s Ancient DNA Centre. Heat and humidity, for example, are both known to break down the molecule. “There’s no environment I can think of that would have remained constant enough to preserve dinosaur DNA,” he says. But “despite the fact I’m a disbeliever, I’m still a scientist. If you can find a bone that’s been in some weird cave for 65 million years, give it a shot.”
Finding that “weird cave” might not be so improbable. In 2005, Mary Schweitzer, a paleontologist at North Carolina State University, made an astonishing announcement: she’d discovered soft tissues in the leg bone of a 68-million-year-old T. rex. Her findings were, of course, controversial; yet in May, Schweitzer repeated the trick, this time with an 80-million-year-old hadrosaur. (The duck-billed dinosaur was sealed in dry, porous sandstone, which seemed to help with preservation.) “People just assume these tissues degrade,” she says, and because of that assumption, “no one bothered to look.”
None of Schweitzer’s soft tissues and proteins have so far yielded any dino DNA, but the discovery alone is enough to give hope. If these tissues can survive, Schweitzer suggests, maybe DNA can, too.
And if sandstone is a good preservative, so is the Arctic deep freeze. Each year in Siberia, the tusks, teeth and bones of ancient woolly mammoths (an elephant species extinct for over 4,000 years) can be found along the coast, shaken loose by erosion and the summer thaw. Mummified carcasses have even been uncovered, including one named Lyuba, a near-complete baby mammoth found in western Siberia in 2007. All of these, of course, could be rich sources of DNA.
Last year, researchers at Pennsylvania State University announced they’d managed to map 70 per cent of the woolly mammoth genome, the first time an extinct animal’s genome had been sequenced. The feat was accomplished using DNA from the hair of a 20,000-year-old mammoth found buried in the Siberian permafrost. Hair proved to be a great source, says Webb Miller, a professor of biology and computer science who worked on the project. “It locks out moisture and bacteria,” he says. “We just basically dunk it in bleach, open the hair shaft and take the DNA out.” Not only that, hair is easy enough to get: “Woolly mammoths have lots of it. We could literally buy pounds, if we wanted to.”
