3D DNA Preserved for 52,000 Years in Freeze-Dried Woolly Mammoth Remains

Some 52,000 years ago, a female woolly mammoth with a shaggy, mullet-like mane died in a cave in Siberia. The region’s dry, cold climate freeze-dried the hulking creature’s body, transforming its flesh and skin into what amounted to woolly mammoth jerky.

Now, the well-preserved creature—nicknamed Chris Waddle, after the retired English soccer player known for his business-in-the-front, party-in-the-back-style haircut—is giving up some of the extinct species’ secrets. Using a piece of skin from near the animal’s ear, scientists have reconstructed the three-dimensional architecture of its DNA, according to a new paper published this week in the journal Cell.

This unprecedented feat, which involved more than 50 international scientists, offers new insights into how the animal’s genes behaved while it was still alive. More broadly, their methods may help support the conservation of today’s living animals and, possibly, aid in efforts to “de-extinct” the woolly mammoth.

“To get as close to a real mammoth as possible, one needs to know how the [genetic] architecture differs from an Asian elephant,” says Hendrik Poinar, a biologist at McMaster University in Hamilton, Ontario, who was not involved with the research, to NewScientist’s Corryn Wetzel.

Usually, after an animal dies, its DNA molecules begin to break down and spread out, leaving behind a jumbled mess of genetic material. When researchers later try to study that DNA, it’s like trying to read the scattered pages of a book that’s been turned upside down and shaken. They can still learn a lot, but this heap of genetic information gives them an incomplete picture.

However, because of the way the 52,000-year-old woolly mammoth was preserved, the geometry of its genetic material remained surprisingly intact, allowing researchers to reconstruct its genetic code in remarkable detail. To do so, they used a novel technique known as “PaleoHi-C,” which helped them map sections of DNA and reassemble the genome in its original, three-dimensional configuration. In this case, studying the mammoth’s ancient DNA was like reading “an ordered stack [of pages] with dog-eared corners,” writes Scientific American’s Saima S. Iqbal.

By seeing the structure of the genome, scientists can “figure out which genes were active in that particular animal at the moment that it died and which genes were repressed,” says study co-author Marc A. Marti-Renom, a researcher at the National Center for Genomic Analysis in Barcelona, to the Washington Post’s Lizette Ortega.

Researchers compared the mammoth’s DNA to the genome of modern Asian elephants. They found plenty of similarities—for instance, that both animals had 28 pairs of chromosomes—but also some important distinctions. Roughly 4.1 percent of the two species’ skin genes were different, including one relating to hair growth, reports the New York Times’ Siobhan Roberts.

Their analysis showed that the gene responsible for hair growth was more active in the mammoth than in today’s elephants, which helps explain why modern pachyderms are bald while their ancient ancestors had luscious locks. They also pinpointed the genes responsible for the mammoth’s cold tolerance.

The team was curious to know whether the mammoth’s impeccably preserved DNA was a fluke—and whether their “PaleoHi-C” method would work on other specimens. So, they conducted a series of laboratory experiments with beef liver. They dehydrated some samples using both heat and freeze-drying, but kept others fresh and left them out at room temperature.

After three days, the fresh beef’s DNA had disintegrated into a mishmash of fragments. But the DNA in the dehydrated samples still had its three-dimensional structure a year later.

They even tried destroying the dehydrated DNA—using some pretty creative methods, like running over it with a car and firing a shotgun at it. But, still, it persisted.

Their hearty samples suggest the same method might be applied to other ancient creatures, even the remains of mummified humans, given the right preservation conditions.

“This new work opens up major new possibilities of exploring the biology of extinct species,” says Adrian Lister, a paleontologist at the Natural History Museum in London who was not involved with the research, to the Guardian’s Ian Sample. “This exceptional preservation might be found in fossils much older … back to 2 million years ago, opening the possibility to investigate the biology of much older extinct species and their relationship to and differences from living relatives.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.