Lesley Stahl Reports on Research that Could One Day
Resurrect Extinct Species and Save Endangered Ones
CBS 10 January 2010
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?
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
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 some thin' 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
"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
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.
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