Checking DNA Against Elephants Hints At How Mammoths Got Woolly

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Mammoths had a distinctive version of a gene known to play a role in sensing outside temperature, moderating the biology of fat and regulating hair growth. That bit of DNA likely helped mammoths thrive in cold weather, scientists say. (Courtesy of Giant Screen Films, 2012 D3D Ice Age, LLC/Penn State University)
Mammoths had a distinctive version of a gene known to play a role in sensing outside temperature, moderating the biology of fat and regulating hair growth. That bit of DNA likely helped mammoths thrive in cold weather, scientists say. (Courtesy of Giant Screen Films, 2012 D3D Ice Age, LLC/Penn State University)

Scientists say they've found a bit of DNA in woolly mammoths that could help explain how these huge beasts were so well-adapted to live in the cold of the last ice age.

Woolly mammoths had long shaggy fur, small tails and ears to minimize frostbite, and a lot of fat to help stay warm as they roamed the tundra more than 12,000 years ago.

"They have this weird hump on their back, which is thought to be something like a camel hump — sort of a fat deposit that stored water and energy for the cold, dark winters," says Vincent Lynch, an evolutionary biologist at the University of Chicago.

He and some colleagues recently compared the DNA of woolly mammoths to DNA of the modern Asian elephant, which dwells in warm tropical forests and is their closest living relative.

"We wanted to identify the genetic changes that happened in woolly mammoths that make them mammoth-like," explains Lynch.

The scientists got some of their DNA from mammoth fur they bought on eBay for around $100, recalls Webb Miller of Pennsylvania State University.

"We were collaborating with Russian scientists at that time, and learned from them that the supplier was well-respected," notes Miller. "Of course, after we got a little sequence data we would have identified a fake."

In the journal Cell Reports, the research team says that when they compared this ancient DNA to the DNA of Asian elephants, they got a long list of genes with mammoth-specific changes.

But, Lynch says, here's the trouble: "We know that most genetic differences between species actually are neutral. They have no function."

To see what might be significant, they reviewed what was already known about each gene. They found one gene that was intriguing.

"Based on what we know in humans and mice, it had three functions," says Lynch. "It functions in sensing the external temperature. It functions in fat biology. And it functions in regulating hair growth."

Previous studies had shown that when you disable this gene in mice, says Lunch, "they actually prefer to live in colder environments."

The scientists did some lab experiments to see if the mammoth-specific genetic change actually did anything potentially meaningful. And it did — it turned down the activity of the protein produced by the gene.

"My perception of what's novel in the paper, as compared with other ancient genome papers (and indeed most extant-genome papers) is that we go beyond simply running computer programs and reporting the results; we make computational predictions and verify them with laboratory experiments," Miller told NPR in an email.

But could you use this information to help re-create a woolly mammoth?

"I have no interest in 'de-extinction' of the mammoth," says Miller.

Neither does Lynch.

"You could change this one gene in an elephant and maybe make it woolly mammoth-like with respect to some things," Lynch says. But to claim you'd re-created a mammoth, he thinks you'd need to make millions of changes to the Asian elephant's DNA. You'd have to put in every mammoth-specific change, plus take away everything that's unique to Asian elephants.

"And even then it's not really a woolly mammoth," he says. "It's a transmutated Asian elephant. You can never actually bring back a woolly mammoth."

Lynch thinks scientists shouldn't try — that it would be unethical. "Elephants are intelligent species. They have complex social groups. They learn from each other," he notes. "So if we bring back a woolly mammoth, who's it going to learn how to be a woolly mammoth from?"

"They're gone," Lynch says. "And who are we to bring it back?"

Copyright 2015 NPR. To see more, visit http://www.npr.org/.

Copyright NPR. View this article on npr.org.

Transcript

DAVID GREENE, HOST:

And we're covering everything this morning, including woolly mammoths who roamed the frozen tundra over 12,000 years ago during the last Ice Age. Their closest relative alive these days is the Asian elephant, which lives in warm, tropical forests. NPR's Nell Greenfieldboyce reports that scientists have now compared the DNA of these two mighty beasts to try and figure out how woolly mammoths got to be so, well, woolly.

NELL GREENFIELDBOYCE, BYLINE: The woolly mammoth had long, shaggy fur, a small tail and ears to minimize frost bite and a lot of fat to help stay warm.

VINCENT LYNCH: And they have this weird hump on their back, which is thought to be something like a camel hump, sort of a fat deposit that stored water and energy for the cold, dark winters.

GREENFIELDBOYCE: Vincent Lynch is an evolutionary biologist at the University of Chicago.

LYNCH: We wanted to identify the genetic changes that happened in woolly mammoths that make them mammoth-like.

GREENFIELDBOYCE: Mammoths are extinct, but thawing ice means bits of them turn up from time to time. You can even buy mammoth hair on eBay. These researchers did. Then they extracted the DNA. In the journal Cell Reports, they describe how they compared it to the DNA of Asian elephants. They found a long list of genes with mammoth-specific changes. But Lynch says here's the trouble...

LYNCH: We know that most genetic differences between species actually are neutral. They have no function.

GREENFIELDBOYCE: Still, they spotted one gene that seemed intriguing.

LYNCH: Based on what we know in humans and mice, it had three functions. It functions in sensing the external temperature. It functions in fat biology, and it functions in regulating hair growth.

GREENFIELDBOYCE: Lynch says previous studies have shown that if you disable this gene in mice...

LYNCH: They actually prefer to live in colder environments.

GREENFIELDBOYCE: The scientists wanted to see if the mammoth-specific change in this gene would alter the protein it makes and have a similar effect. And some lab experiments suggested maybe so.

LYNCH: We found that the mammoth protein was much less active. It's sort of like if you had a dimmer switch on a light that was kind of like turning down the activity of the protein.

GREENFIELDBOYCE: But Lynch says don't think you can take this information and use it to transform an Asian elephant into a mammoth.

LYNCH: You could change this one gene in an elephant and maybe make it woolly mammoth-like with respect to some things.

GREENFIELDBOYCE: Trying to re-create a mammoth in all its woolly glory would require a ton of other genetic changes, so many that scientists don't have the technology to do it. And even if it was possible, Lynch thinks they shouldn't try it. Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.