Woolly mammoths’ distinctive traits, including smaller ears, large fat deposits and fluffy coats, became more pronounced over 700,000 years as they adapted to the harsh climate of the Siberian steppes, a study suggests.
Researchers compared the genomes of 23 Siberian woolly mammoths with 28 modern-day elephants and found that many of the woolly mammoth’s traits were already genetically encoded in the earliest animals. However, as they evolved, their bodies adapted to their environment, enabling them to retain more heat.
The study’s senior author, Love Dalén, professor of evolutionary genomics at the Centre for Palaeogenetics in Stockholm, said: “The very earliest woolly mammoths possibly had larger ears, and their wool was different – perhaps less insulating and fluffy compared to later woolly mammoths.”
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He said that using a 700,000-year-old genome, belonging to a woolly mammoth named Chukochya, and comparing it with 22 relatively modern woolly mammoths, which lived within the past 100,000 years, had enabled researchers to identify how mammoths’ genes evolved during the species’ lifespan.
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“This allows us to study evolution in real time, and we can say these specific mutations are unique to woolly mammoths,” he said.
The researchers found that many genes that were adaptive for woolly mammoths were related to living in cold environments, and some of them were shared by unrelated modern-day Arctic mammals such as reindeer and polar bears.The lead author David Díez-del-Molino, also of the Centre for Palaeogenetics, said: “We wanted to know what makes a mammoth a woolly mammoth. Woolly mammoths have some very characteristic morphological features, like their thick fur and small ears, that you obviously expect based on what frozen specimens look like, but there are also many other adaptations like fat metabolism and cold perception that are not so evident because they’re at the molecular level.”
The study, published in Current Biology, drew on 16 genomes that had previously not been sequenced. It revealed a gene with several mutations that might have been responsible for the animal’s small ears.
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The 700,000-year-old Chukochya genome shared approximately 91.7 per cent of the mutations that caused changes in the more modern woolly mammoths. This suggests that many defining traits were probably already present when the woolly mammoth first diverged from its ancestor, the steppe mammoth.
The researchers said their work had entailed a number of practical challenges.
Dalén said: “Apart from the field work, where we have to battle both polar bears and mosquitoes, another aspect that makes this much more difficult is that you have to work in an ancient DNA laboratory. And that means that you have to dress up in this full-body suit with a hood and face mask and visor and double gloves, so doing the lab work is rather uncomfortable.”