By Will Dunham
WASHINGTON (Reuters) - Woolly mammoths spent their lives enduring extreme Arctic conditions including frigid temperatures, an arid environment and the relentless cycle of dark winters and bright summers.
An exhaustive genetic analysis of these bygone Ice Age giants and their living cousins, Asian and African elephants, has revealed a slew of genetic adaptations that enabled woolly mammoths to thrive for eons in such adverse circumstances.
The study, published on Thursday in the journal Cell Reports, compared the genomes of two mammoths whose remains were found in permafrost in northeastern Siberia, one 18,500 years old and the other 60,000 years old, with genomes of three Asian elephants and one African elephant.
Mammoths possessed genetic changes associated with skin and hair development, fat biology, insulin biology and temperature tolerance that differentiated them from the elephants, University of Chicago geneticist Vincent Lynch said.
"We think that these changes make sense in mammoths because we know that mammoths evolved long, thick hair, large fat deposits and lived in really cold places," Lynch said. "Insulin signaling is important for fat biology because insulin regulates how much sugar in the blood is converted to energy and fat."
The researchers also "resurrected" the mammoth version of a gene called TRPV3. When transplanted into human cells, it produced a protein less responsive to heat than its elephant versions, indicating it helped make mammoths less sensitive to cold.
Woolly mammoths, a bit larger than modern elephants, dwelled in the steppes of northern Asia, Europe and North America. The last mammoth disappeared roughly 4,000 years ago. Whether their extinction resulted from a warming climate or human hunting remains hotly debated.
The researchers acknowledged their genome sequencing could make it easier to bring back the mammoth via cloning much like the movie dinosaurs of "Jurassic World."
"If you want to build a woolly mammoth, we're showing some places to start. But that had nothing to do with why we studied mammoths," Penn State University biologist Webb Miller said.
"I don't know why people are interested in cloning mammoths. It would be much easier, and perhaps more useful, to clone Franklin Roosevelt," Miller added.
Lynch said it seems inevitable someone will clone a mammoth.
"While I think it will soon be technically possible to resurrect a mammoth, it is not something that we should do. Modern humans are not responsible for the extinction of mammoths, so we owe no debt to nature," Lynch added.
(Reporting by Will Dunham; Editing by Sandra Maler)