Could Extinct Species Make a Comeback?
It's difficult to imagine that 10,000 years ago, right here in North America, there lived giant animals that are now the stuff of legends - mammoths and mastodons, ground sloths and sabretooth cats. They, and thousands of other species, have vanished from the Earth. And today, partly due to the expansion of one species - ours - animals are going extinct faster than ever before.
The very definition of extinct means gone forever, but what if we could change that? Scientists are making remarkable advances that are bringing us closer than ever before to the possibility of a true animal resurrection.
Who wouldn't be dazzled by an animal like the woolly mammoth, or the sabretooth tiger, the Irish elk or the giant sloth? Today they exist just as bones in museums, alive only in our imaginations and the recreations of artists and filmmakers. But what if that could change?
Web Extra: Frozen Zoo
Web Extra: The Tasmanian Tiger
Audubon Nature Institute
Sean Carroll
Smithsonian: Museum of Natural History
National Geographic Channel
Waking The Baby Mammoth
In the age of DNA, we now know that these vanished creatures, like all life on Earth, are ultimately nothing more than sequences of the four letters - A, C, T, and G - that make up the genetic blueprint or code of life. The codes for extinct animals were thought to have died along with them, until recently, when machines like one at the Smithsonian's DNA lab started working magic.
"Just the study of ancient DNA only broke onto the scene 20 years ago or so. The idea that we could harvest DNA from extinct creatures, from fossil bones, learn something about the past," Sean Carroll, a professor of molecular biology and genetics at the University of Wisconsin, told 60 Minutes correspondent Lesley Stahl.
Carroll says that like so many things in the field of DNA, the progress has been staggering.
One surprising discovery has been the value of ancient hair. Scientists recently discovered that the hair shaft seals DNA inside it like a biological plastic, protecting it, and making hair a rich and plentiful source of genetic information.
"Does that mean that you can take extinct animals, I mean, there's hair in museums? …And get the genetic sequencing?" Stahl asked.
"Possibly, and especially if those animals were preserved in any way, there's a good prospect of that. It's sort of like CSI, you know? How good is this forensic material? Can you get good DNA information from older and older and older material? That's pretty promising," Carroll replied.
So dusty old specimens that have been tucked away in the drawers of natural history museums like the Smithsonian are suddenly potential treasure troves of genetic information: just last year, using only a few clumps of wooly mammoth hair, scientists at Penn State were able to extract enough DNA fragments to figure out most of its genetic sequence, making the woolly mammoth the first extinct animal to have its genome decoded.
Which raises the question of whether resurrecting one of these creatures is really possible.
Scientists say one option would be genetic engineering: take a living animal that's related to the mammoth, like the elephant, figure out all the places where its DNA differs from the mammoth's, and then alter the elephant's DNA to make it match.
That's not possible just yet, but there may be another way: cloning.
"Is it possible that we're gonna get the full DNA of the woolly mammoth and be able to clone it?" Stahl asked.
"Yes, I think we'll be able to get much, if not all, of the woolly mammoth DNA. And the great advantage there is that a lot of the specimens are in permafrost. So they're sorta been conveniently frozen for us, which preserves DNA, preserves tissue better," Carroll said.
But for cloning, just knowing the DNA sequence from hair isn't enough. You'd need an intact mammoth cell, which Carroll says will be difficult to find, but not impossible.
"It could be a skin cell. It could be any particular cell that hopefully has been preserved well enough, stayed frozen for thousands of years and to transfer the nucleus of that cell into, for example an egg of an elephant," Carroll explained.
He told Stahl that the two species are "close enough" that maybe the elephant could serve as a surrogate mother.
It's called interspecies cloning: implanting DNA from one species into the eggs of another.
Anyone who wants to try it, with a mammoth or anything else, would be well-served to pay a visit to Dr. Betsy Dresser in New Orleans.
Tucked away on 1,200 acres of land that seem part Serengeti, part high-tech medical facility, she and her staff at the Audubon Nature Institute have been working quietly for years on the science and the art of interspecies cloning, and she'll be the first to tell you that, even with living animals, it isn't easy.
"You don't just clone some cells and then all of a sudden you have a baby. I mean, there's so many scientific steps along the way, knowing everything from hormones to the proper surrogate to, you know, length of pregnancy," she explained. "Because, see, we don't know how long a woolly mammoth, the gestation period. We can guess, but we don't know, really."
But Dr. Dresser's work on interspecies cloning is focused on the future, not the past. Rather than trying to resurrect extinct creatures, her goal is to keep the animals we have today from going extinct tomorrow.
"I feel like we're in the emergency room of the wildlife business, really," she told Stahl. "I don't want to see elephants in textbooks or, you know, the way we see dinosaurs. We're going to lose a lot of species if we don't do somethin' about it."
Dresser and her team are trying to increase the populations of endangered animals by putting their DNA into the eggs of their non-endangered relatives.
On the day we visited, they were laparoscopically removing eggs from an ordinary housecat, then sending the eggs down the hall to have the housecat DNA literally sucked out of them.
"What she's doing is she's removing the DNA from this domestic cat egg. And she can see it by what we call fluorescing it," Dresser explained, while observing the procedure with Stahl. "It becomes just very blue, and so now she knows where it is. And now you'll see her go in there and be able to remove it."
Once the housecat DNA is deposited outside of the egg, they will replace it with the DNA of an endangered Arabian sandcat, a completely different species, gathered from a tiny piece of skin.
"And there you see it being inserted into the domestic cat egg," Dresser explained.
"And you made that from just skin?" Stahl asked.
"Just from skin cells, right," Dresser said.
An electrical pulse starts the egg dividing, and if all goes as planned, the now sandcat embryo will be put back into the domestic cat to grow to term.
It has worked before -- with African wildcats; the research has resulted in some interspecies offspring. These interspecies clones were so normal that they even mated the old-fashioned way and produced kittens.
"Eight kittens altogether. We had a couple litters," Dresser told Stahl. "Totally African wildcats, totally healthy. And it said to us, 'Hey this works.' And now that we know we can do it, we can say to the world, 'These animals do develop. They do reproduce naturally.' And we can use this as a tool for endangered species."
And Dresser is working her way up. Her next interspecies cloning project will use the non-endangered caracal cat as a surrogate mother for an endangered lynx; and after that, the Eland antelope as a surrogate for its endangered cousin, the bongo.
"You know, there are still people who get nervous at the idea of cloning. They think there's something wrong about it," Stahl remarked.
"I'll tell you what, if you have to choose cloning or extinction, I'm gonna choose cloning. But I wanna be darn sure that I know how to do it. And if we don't do it while we have the animals now to be able to learn how to do it, then we're not gonna have a choice. It's not gonna be an option," Dresser said.
So to keep her options open while she's mastering interspecies cloning, she's also putting as many animals as she can on ice, literally.
Dresser is the keeper of a new kind of zoo - a frozen zoo - where she's collecting tiny skin samples from thousands of different animals, representing hundreds of species, and is storing them at 343 degrees below zero in tiny canisters inside tanks filled with liquid nitrogen.
"We've got lions and tigers, we've got gorillas and rhinos. We've got little frogs. All of the animals…that people know in zoos," she explained.
Asked how long a piece of skin can be viable, Dresser said, "We think these cells can sit here for hundreds, maybe thousands of years."
"So, if any one of these animals were to go extinct, you could bring them back?" Stahl asked.
"In theory, I believe we can," Dresser said.
And she agreed that her frozen zoo is kind of Noah's Ark.
"Do you think we're at the stage where we should be taking every single wild animal, even if they're not endangered, and putting them in a frozen zoo?" Stahl asked.
"Yes. I absolutely do," Dresser said. "What have we got to lose? I think we should put every species in that we can, while we have the opportunity."
Which raises the question: with so many living animals today threatened, why think about resurrecting extinct ones, like the mammoth?
"To bring the woolly mammoth back, we don't have enough space for the big animals we already have," Stahl told Sean Carroll.
"These projects, like the woolly mammoth, they inspire people to think about the meaning of what we're doing here. And why would you invest years and years of your life in trying to bring back a woolly mammoth, or taking care of them if you did," he replied.
"That's an excellent question," Stahl said.
"I think it would fire up people's imaginations. And I think somewhere there's a 9-year-old girl watching this program and listening to this saying, 'That's what I wanna do. I wanna bring back these creatures that are extinct. Or I wanna protect creatures that are now threatened from going extinct.' So in many ways, I think the woolly mammoth can sort of be a poster animal for a general effort of being more conscious of our activities on the planet," Carroll explained.
No one has yet found the intact cell it would take to resurrect that poster animal, but in Siberia, two years ago, a reindeer herder discovered a remarkably well-preserved one month old baby mammoth that had lain frozen in permafrost for 40,000 years.
Its DNA was in better shape than any previously found, raising hopes that between new finds and new technology, it may just be a matter of time.
Produced by Shari Finkelstein and Meghan Frank