The passenger pigeon was once widespread across North America. When the Europeans came to the New World, there were between three and five billion passenger pigeons roaming the skies. But the bird went extinct in 1914, due to a combination of deforestation and hunting (they were a popular source of meat, considered to be pests, and were relatively easy to hunt down because of their flocking behavior). Passenger pigeons lack the ancient mystique of dinosaurs and giant ground sloths, but they’re uniquely accessible—it’s not that strange to imagine a world where passenger pigeons once again rule the skies. And that might be less miraculous than it sounds.
All of a sudden, it seems like de-extinction—the act of bringing extinct species back to life—is a feasible thing, something that reasonable people can seriously discuss. I first discovered Revive and Restore, the Long Now Foundation’s ambitious project to revive extinct species, months ago while poking around on their website. Then, on March 15th, Revive and Restore partnered with the National Geographic Society for TEDxDeExtinction, a day-long look at the implications of de-extinction (sample discussion topic: "Restoring Europe’s Wildlife with Aurochs and Others"). And finally, National Geographic launched an exhaustive multimedia exploration of the topic, centered around a cover story entitled "Reviving Extinct Species."
For Ben Novak, a 26-year-old former genetics student at McMaster University’s Ancient DNA Center, de-extinction has been a pressing topic for a lot longer than a couple months. These days, Novak is leading Revive and Restore’s efforts to bring back the extinct passenger pigeon—the initiative’s first de-extinction effort. But his interest in de-extinction began in earnest at age 13, when he did a case study on what it would take to bring the dodo (a relative of the pigeon) back from extinction. "That kind of sparked the pigeon bug," he says.
Novak began working on population studies (with an eye towards de-extinction) while studying evolution and ecology at Montana State University, but he encountered some resistance to his passenger pigeon ideas while applying to grad school. "Every time I’d submit an application, part of it was discussing that I’d like to work with passenger pigeons, population genetics, and designing a project looking at specimen collections—collecting as much background data and research as I could," he says. "Nothing worked, nothing ever persuaded anyone back then." That was five years ago.
There were some false starts—Dr. Beth Shapiro, who was at Penn State at the time, was interested in Novak’s pigeon genome sequencing ideas. She was even beginning passenger pigeon work herself, but the academic department had the final say on Novak’s application, and it was a no-go. Novak was even accepted to McMaster University for his passenger pigeon studies, but he couldn’t get his requests for tissue approved and eventually settled on a different thesis project.
Fast forward to 2011. Novak managed to score passenger pigeon samples from Chicago’s Field Museum of Natural History. He had already sequenced the DNA once with help from an outside lab and $2,500 from family and friends, but he needed to sequence it one more time. Revive and Restore agreed to donate some money. In November, Novak joined the initiative full-time.
Right now, he says, his focus is on "bringing together the right materials to design a long-term project, putting together budgets, approaching funders. There’s a great deal of social networking among scientists who could be interested in background research." But Novak, who currently works with Shapiro in her UC Santa Cruz lab, has a multi-step vision for bringing back the passenger pigeon.
First, Novak and other researchers need to compare passenger pigeon genome and band-tailed pigeon genome sequences. Ancient DNA is degraded and hard to work with, so the band-tailed pigeon (a modern species with a common ancestor) will act as a kind of reference genome. By scrutinizing the mutations that differentiate the two birds, Novak hopes to "produce a theoretical genome sequence of the band-tailed pigeon genome with all of the introduced mutations that we predict will be necessary to make the passenger pigeon."
The next step is synthesizing the spots of DNA that need to be swapped out to make a passenger pigeon. As Novak explains it: "You swap out the band-tailed chunks at site and splice in the passenger pigeon chunks so you end up with a genome that has all the passenger pigeon bits that you want having replaced the band-tailed bits." Doing that will be incredibly difficult, and Novak isn’t sure yet what method the lab will end up using. Molecular geneticist George Church’s research on altering bacterial genomes could be helpful, but animals are obviously different. Says Novak: "We will have a better idea in a year or two as to how we’ll be doing our cell work." Eventually, though, that cell work should allow the researchers to create a hybrid pigeon.
Once baby passenger pigeons start popping out of eggs, Novak and whatever researchers are still working on the project will begin captive breeding in an environment that simulates an actual habitat, as opposed to a domesticated aviary setting. "No matter what type of bird we produce first, it will be a hybrid/chimeric mix of a band-tailed or rock [pigeon] and passenger pigeon," says Novak. Surrogate adult birds that have been painted to look like passenger pigeons will ensure that the chicks are raised with right diets and in the right time frames.
Novak imagines that scientists will set up multiple sites—perhaps state forests, national forests, and private land—along the passenger pigeon’s traditional migration route. Trained homing pigeons will fly from aviary to aviary, simulating an adult flock that knows the pathway for the chicks to join. In order to protect the chicks from accidentally escaping, they’ll be set up with GPS chips and other monitoring tools. If data indicates that the birds aren’t getting lost, the first generation can start to fly on their own—and eventually, ferry the juveniles without help from homing pigeons. Finally, Novak anticipates taking down the aviaries and letting the pigeons fly free.
This process won’t be completed in the near future. Novak estimates that it will take 50 to 75 years to get to the point where the passenger pigeons can fly free—25 years if we’re really lucky. Just getting to the point where humans can breed captive passenger pigeons could take at least 10 to 15 years. This is all assuming that Revive and Restore (or whatever initiative exists in 2050) can even secure enough funding to make this happen.
There are any number of ethical issues to consider—something that Novak was eager to discuss. "Anything that could be morally wrong about this is something we would create out of doing it the wrong way, and not intrinsic to the process," he says.
But what of the habitat changes to the passenger pigeon’s environment since the species went extinct? Surely all those new roads, cell phone towers, railways, new plants, and new tree species will cause some issues. Novak is confident that the passenger pigeon—an "opportunistic feeder"—would find plenty of food to eat. As he points out, other bird species have figured out how to adapt to the modern environment. And what if the pigeons, known for their heaviness and ability to fell branches, decided to perch on power lines? Novak dismisses the issue: "It’s probably not a problem foreseeable for a hundred, a hundred and fifty years, and I’m pretty confident at that point that power lines will be underground anyway."
Many scientists challenge the morality of bringing back extinct species in the first place. "There is clearly a terrible urgency to saving threatened species and habitats," explained John Wiens, an evolutionary biologist at Stony Brook University in New York, in the National Geographic cover story. "As far as I can see, there is little urgency for bringing back extinct ones. Why invest millions of dollars in bringing a handful of species back from the dead, when there are millions still waiting to be discovered, described, and protected?"
Says Novak: "No one doing this work that I’ve met is thinking this is going to replace current conservation efforts or is going to be more important. Extinct species like this can be an integral part of restructuring the future of biodiversity and how we interact in the world."
There is always the danger that a reintroduced species will become a pest, wreak some terrible unforeseen havoc on the environment, or just fizzle out, unable to survive in today’s harsh conditions. These are risks that some scientists are willing to take. After all, it’s human development that has caused many extinct species to disappear. Perhaps we should be the ones to bring them back.