Mammoths and other extinct Ice Age giants clung on longer than previously thought, DNA analysis suggests

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Scientists involved in the project collected 535 samples of permafrost and sediment from frozen lakes, often in extremely cold locations in Siberia, Alaska, Canada and Scandinavia, at 73 places where mammoth remains have been found.

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Analysis of the DNA contained in the soil showed that mammoths were living in mainland Siberia about 3,900 years ago – after the Great Pyramid of Giza in Egypt was built and the megaliths of Stonehenge.

Most woolly mammoths are believed to have died out around 10,000 years ago, except for a very small population that survived on remote islands off Siberia.

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Instead, the time of extinction came when the last region of the mammoth steppe – a unique ecosystem in the Arctic which does not exist today – as the climate became warmer and wetter, peatlands gave way.

“The authors present several dates for the mammoth, woolly rhino, horse and steppe bison that are much shorter than even the fossil record, which makes a stronger case for late survival in the Arctic than previously thought,” said Tory Herridge. said. Evolutionary biologist and giant specialist at the Natural History Museum in London.

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“I’m very excited to see how this work develops, and what new data can be generated to support or refute it. I’m sure it will come under intense scrutiny,” she said by email. Said through. Herridge was not involved in the research.

Most of the ancient DNA is usually taken from bones or teeth (oldest DNA Once the sequence was from a giant tooth and more than 1 million years old), but new techniques mean that genetic material preserved in soil can now be analyzed, dated and sequenced.

All animals, including humans, continually shed genetic material when they urinate, defecate and bleed, losing hair and sloughing off dead skin cells. This genetic material is absorbed into the soil, where it can remain for hundreds, if not thousands, of years when conditions are right – such as in frozen ground.

“An individual animal spreads DNA throughout its lifetime in its dung, urine, epidermal cells and hair, containing millions of DNA segments as it moves across its entire geographic range, but at its death only a skeleton is left , which is very unlikely to have been preserved, retrieved and dated,” said one of the study’s authors, Yucheng Wang, a research associate in the Department of Zoology at the University of Cambridge.

“By sequencing only a few of these DNA molecules conserved in the environment, we can identify its existence and extent. It is therefore not surprising that sedimentary DNA can predict later extinctions more accurately.”

Known as environmental or eDNA, this technique has been used by archaeologists to shed light on ancient humans, and the same method has also been used to test sewage of human populations during epidemics. To detect and track Covid-19.
Arctic Environment Today.

megafauna mystery

The study, published in the journal Nature, also describes the Arctic ecosystem in detail for the past 50,000 years. The environment in which the mammoths lived, known as the Mammoth Steppe, was cold, dry and regionally complex, with a distinct set of vegetation composed of grasses, sedges, flowering plants and shrubs. was community. As part of the research, the team sequenced the DNA of 1,500 Arctic plants for the first time.

Why giant, grazing animals such as the mammoth became extinct has been debated for more than 100 years, Wang said. There are two main theories: the mammoths were hunted within centuries of their first contact with humans, or they may not have adapted enough to the rapidly changing climate at the end of the Ice Age.

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Wang said his research supported the theory that climate change played a major role at the end of the last ice age 12,000 years ago.

The prolonged overlap between humans and mammoths in the Arctic region, along with a detailed understanding of the mammoth steppe ecosystem and how quickly it changed, strengthened the case against the idea that humans were the main drivers of the mammoth extinction, explained Wang. .

“When the climate became wetter and the snow began to melt, it led to the formation of lakes, rivers and swamps. The ecosystem changed and the biomass of the vegetation decreased and the herds of mammoths would not be able to sustain.” Wang said in a news release.

“We have shown that climate change, especially rainfall, directly induces changes in vegetation – based on our model humans had no effect on them.”

true mobility?

Herridge at the Natural History Museum said more work is needed on human presence in the mammoth steppe if any human role in the mammoth’s disappearance is to be ruled out.

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In the models used in this paper, he said, the researchers used the rare presence of human remains in the archaeological record and the existence of a climate suitable for mankind, not DNA, as a proxy. Much finer data is needed to understand whether and when humans and mammoths actually overlapped in these areas.

“Environmental DNA studies like these have great potential to directly test for the presence of humans in the Arctic through time, just as they’ve done for mammoths here — it’s the kind of high resolution data that we need to know.” We need to tease out the real dynamics of the extinction of the woolly mammoth,” she said.

“Overlap data alone won’t cut it, because it’s not the last giant that matters, it’s working out that the giant numbers have shrunk so much that they were reduced to just a few isolated and vulnerable populations.”

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Credit : www.cnn.com

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