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Reversing Extinction Through DNA Manipulation

By Wesley Fenlon

The pigeon comes first. Don't even think about what we might do with dino DNA.

Dinosaurs occupy an important role in education: In addition to being every kid's favorite creatures, they're often used to explain the concept of extinction. They're hardly the only extinct animals, of course--many, many species have been killed off since the days of the dinosaurs. And ever since Jurassic Park, dinosaurs have taken on another role that veers closer to science fiction. What if we could bring extinct animals back to life?

The fiction in that story is slowly fading, as Wired's story "The Plan to Bring the Iconic Passenger Pigeon Back From Extinction" proves. The story focuses on scientist Ben Novak and his research into "de-extinction," or the process of reviving an extinct species through cutting-edge DNA manipulation. It's Jurassic Park, except the focus of Novak's obsession is the North American passenger pigeon, which isn't quite as dangerous as a Tyrannosaurus Rex or raptor.

Image credit: Wikimedia Commons

Which isn't to say the passenger pigeon was totally harmless. Wired writes that flocks of several hundred million passenger pigeons roamed the east coast of the United States in the mid-1800s, destroying forests by landing on trees by the thousands and devouring acres of acorns and nuts. Their mass migration patterns made them easy picking for predators--including humans, who would stand below trees of the birds and fire guns into the branches, guaranteed to shoot down scores of birds. By the end of the 19th century, thousands of birds remained where there were millions decades before. And then they were extinct.

Novak's research focuses on reassembling the DNA of those birds to eventually recreate them. "Every cell in its fleshy toe pads contains the 1.5 billion base pairs of DNA that spell out the bird’s identity, from the color of its eggs to the sound of its voice," writes Wired. "But this DNA has seen better days. It has been broken apart by enzymes and oxygen, zapped with ultraviolet radiation and contaminated by other organisms."

Next-generation DNA sequencing makes it possible to analyze those DNA fragments. Modern sequencing led to the passenger pigeon's closest living relative, the band-tailed pigeon, which may provide similar enough DNA to allow scientists to piece together the passenger pigeon's missing pairs. But that's just the beginning of the de-extinction process.

From Wired report: "Here is Novak’s plan in broad strokes: Sequence the band-tailed and passenger pigeon genomes and find the significant differences between them. Edit the DNA from a band-tailed pigeon germ cell – the type that develops into sperm or eggs – to match that of the passenger pigeon. Implant this cell into the egg of another pigeon, perhaps a rock pigeon, which is easy to work with in the lab. Hope that the germ cell will migrate into the gonads of the developing chick. Allow the chick to grow up, and breed two such birds to create a passenger pigeon."

This is really just a piece of the story; Wired also writes about the difficulty of getting a DNA sample from a passenger pigeon, the organizations Novak's working with in his de-extinction effort, and the hurdles that remain in actually modifying a band-tail pigeon's genome. There's a successful process for modifying bacterial genomes, but a pigeon is vastly more complex.

And then there are the ethical and environmental issues of bringing a species back to life in a world far different from the one they left. Would the passenger pigeons destroy crops the way they once took out forests? Read the whole story; Novak's work is a long shot, but it seems possible that, within a decade, he'll be responsible for the renewed life of a bird that died more than a hundred years ago.

Image credit: Universal Home Video