Woolly mammoths: Some animals lived on the island 6,000 years longer – why they died out so far – Knowledge

Just 4,000 years ago, mammoths were still roaming the tundra of Wrangel Island in northern Siberia, shoveling snow with their massive, upturned tusks so they could eat the grass beneath. Why the prehistoric elephants went extinct remains a mystery to this day, and a team led by Swedish geneticist Marianne Dehasek is now at least one step closer to solving the mystery.

In a post just published in the scientific journal cell It has appeared, Researchers refute the theory that woolly mammoths on the island were no longer able to survive due to the harmful effects of inbreeding. “It was probably a random event that wiped them out,” Love Dalén, of the Centre for Palaeogenetics in Stockholm, said in a news release about the study. “If this event had not happened, mammoths would still be around today.”

In the last cold period, animals have become widespread, which are ideally adapted to low temperatures due, among other things, to their thick fur. Then, about 10,000 years ago, some woolly mammoths became isolated on Wrangel Island when sea levels rose and cut off the area from the mainland.

According to the current study, there were no more than eight mammoths separated from their mainland counterparts. Even then, the creatures seemed doomed to extinction because eight individuals are not enough to establish a new, stable population. By analyzing DNA from fossil remains, Marianne Dehascq’s team was able to show that the island’s mammoth population increased to 200 to 300 individuals within 20 generations. Ultimately, the animals outlived their mainland counterparts. But why did they finally go extinct about 4,000 years ago?

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“We can now safely rule out the idea that the population was simply too small, and that they were doomed to extinction for genetic reasons,” says Love-Dahlin.

For their study, the researchers analyzed the genomes of 21 woolly mammoths that lived at different times. Fourteen of the animals came from Wrangel Island. Seven of them lived on the mainland before the island was isolated. They were therefore ancestors of the island mammoths. In all, the DNA samples examined covered the last 50,000 years that mammoths have been on Earth, the researchers wrote in their paper. cell.

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According to their results, the island's mammoths were less genetically different from each other than those on the mainland. This low genetic diversity is a sign of inbreeding. This is due to the fact that related animals, which have a similar genetic makeup, have interbred with each other.

Over time, these effects of inbreeding can reduce the overall survival rate of a population because deleterious mutations gradually accumulate and lead to disease. A well-known example of this in humans is the increased incidence of hemophilia in European noble families.

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According to the study authors, this could not have been the reason for the extinction of the mammoths on Wrangel Island. According to their results, inbreeding mutations accumulated very slowly in the animals' genomes. And harmful mutations did not really take hold: “If an individual had a very harmful mutation, it would not have been able to survive,” says Dehasek. These animals die before they could reproduce and therefore do not pass on the harmful genes. “That is why such mutations gradually disappeared from the population again.” So paleontologists assume that the last mammoth population on Wrangel Island did not shrink slowly, but remained stable at 200 to 300 animals until the end.

Researchers can't pinpoint why the woolly mammoths on Wrangel Island went extinct about 6,000 years after their mainland counterparts. For once, though, humans don't seem to be to blame. They didn't set foot on the island until about 400 years after the last mammoths died out.