A Freeze-Dried Woolly Mammoth Yields 52,000-Year-Old Chromosomes

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DNA extracted from a woolly mammoth excavated in 2018 was so well preserved that scientists have, for the first time, constructed a three-dimensional genome from ancient genetic material.

That information, from an animal that died in Siberia about 52,000 years ago, allows better comparisons between extinct mammoths and contemporary elephants, according to a report in Cell.

Freeze-Dried Woolly Mammoth

A team of 56 scientists from four organizations collaborated to find the fossil, excavate it, then analyze what co-author Erez Lieberman Aiden described as “ancient beef jerky,” during a virtual news conference.

Aiden, the director of the Center for Genome Architecture at Baylor College of Medicine, said the researchers tested dozens of samples over five years before hitting the fossil jackpot in Siberia.

They had sought to perform 3D sequencing — a relatively new technique — on an ancient fossil. But they needed the perfect sample. The researchers tested dozens of samples over the course of five years before landing on an unusually well-preserved woolly mammoth that was excavated in northeastern Siberia in 2018.

That sample, unlike others, had not frozen and thawed repeatedly. That meant that the DNA — including the physical structures of the chromosomes — remained intact. To preserve the fossil and its genetic materials, they had to essentially power wash around the frozen creature to create a cavern.

Read More: Can Scientists Revive Ancient Frozen Animals?

Ancient Genetics

Once cleared, the team noticed intact hair. Later, under a microscope, they could detect hair follicles. As they zoomed in further, they could see complete cells. Even closer in, they could visualize intact chromosomes and physical clues showing what genes were turned on or off.

“That’s where we really started getting excited,” Aiden said. “We were in the presence of a new kind of fossil.”

Typically, when DNA can be recovered from an ancient specimen it tends to be in tiny, disjointed fragments. Scientists can sometimes piece them together, but there tends to be holes.

Read More: Million-Year-Old DNA Yields Mammoth Surprises

Woolly Mammoths vs. Elephants

In this case, the chromosomes and DNA were in such good shape, it was relatively easy to compare the mammoth’s genetic architecture to that of a contemporary elephant’s. There are some obvious similarities.

Both animals have 28 pairs of chromosomes. The majority of the genes each contain are similar. The exceptions — perhaps not surprisingly — had to do with hair follicle length and adaptations to the cold.

The researchers are optimistic that the 3D sequencing technique could be applied to other ancient specimens, like Egyptian mummies. It may also work on newer, better-preserved fossils.

Read More: Will Woolly Mammoths Ever Make a Comeback?

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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.

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