May 21, 2024

The Woolly Mammoth: On the Trail of Genetic Secrets

Researchers compared the genomes of woolly mammoths from different eras with those of modern elephants to gain new insights into the genetics and evolutionary history of the Ice Age shaggy treks. Scientists report that the genetic clues reflect, among other things, how these special mammals evolved smaller ears, woolier fur, and more immunity over the course of their evolutionary history.

About 20,000 years ago, they roamed the cold steppes of the north in large herds: Woolly mammoths (Mammuthus primigenius) were our elephant cousins, adapted to the harsh conditions of the Ice Age. They separated from the other members of the giant group more than 700,000 years ago and have produced special properties. Much is known about the appearance and biology of these animals from samples found in permafrost, and scientists have already been able to obtain and analyze the genetic remains of some mammoths. But there are still some unanswered questions about the characteristics and evolutionary history of the Ice Age symbolic animals.

Shaggy giants symbol

“We wanted to know what makes mammoths such a woolly giant,” says first author David Díez-del-Molino of the Center for Paleontology in Stockholm. “The woolly mammoth has some very distinctive morphological features, like its thick fur and small ears, but there are also many other adaptations that are not obvious because they happen at the molecular level,” says Díez-del-Molino. In order to identify the genetic factors that played a special role in the woolly mammoth, special patterns had to be observed, the researchers explain: genes that have undergone a vigorous growth process show a relatively large number of mutations. To track them down, the team compared the genomes of 23 woolly mammoths discovered in Siberia with 28 genomes of contemporary Asian and African elephants.

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While previous studies have looked at the genomes of only one or two woolly mammoths, this is the first comparison of a large number of mammoth genomes, the researchers note. Sixteen of the genome has not been previously sequenced. However, the genome of the 23rd woolly mammoth was the centerpiece of the study: it came from a very early representative of the species: the animal called “Chukochya” that lived about 700,000 years ago. “Using the Chukochya genome, we were able to identify a set of genes that evolved as a species during the life span of the woolly mammoth,” says senior author Love Dalén of the Center for Paleogenetics.

Evolution mirrors ancient DNA

As the researchers report, their genetic analyzes revealed that many of the genes that show great adaptations in the woolly mammoth are related to life in cold environments. Interestingly, similar genetic traits also existed in unrelated modern Arctic mammals: “We found some genetic adaptations related to lipid metabolism and lipid storage that are also present in other Arctic species such as reindeer and polar bears, which means there are likely to be Parallel evolution of these genes in cold-adapted mammals,” says Diez del Molino.

As far as the changes in the woolly mammoth over its evolutionary history are concerned, it becomes clear that the early “Chukochya” 700,000-year-old specimen was in principle already equipped with the typical characteristics of the species. The systems may have already existed in the steppe mammoths, from which the woolly mammoth had separated earlier. However, genetic evolution in the descendants of Chukuchia went further than this, as evidenced by genetic comparisons. This is particularly reflected in the genetic basis for ear and fur development: “The first woolly mammoths were not fully developed yet,” Dalén says. “They probably had larger ears, and their wool was different—perhaps less insulating and fluffy than that of later woolly mammoths.”

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The researchers report that there is also genetic evidence regarding the evolution of the immune system: so later woolly mammoths showed many mutations in their genetic traits that correlate with immune cell properties that had not yet occurred in their ancestors. The researchers believe this may lead to improved resistance to the specific viral pathogens that eventually infect the proboscis.

The team now wants to look into the mammoth’s genes for traces of their characteristics and history. According to them, one aspect is that they have only examined woolly mammoths from Siberia so far. But the animals were also walking across North America. However, these representatives could have been special: “The North American woolly mammoth could also have carried genes from the non-woolly mammoth. So we have to take it into account if we want to include these animals in our studies in the future,” says Dalen. .

Source: Cell Press, article: Current Biology, doi: 10.1016/j.cub.2023.03.084