Mammoths and other large Ice Age animals such as the woolly rhinoceros survived longer than scientists thought, coexisting for tens of thousands of years with humans before disappearing forever. This conclusion was made possible after the results of an ambitious research project, which for ten years analyzed the DNA of hundreds of soil samples found throughout the Arctic.
Scientists involved in the project collected 535 samples of permafrost and sediments from frozen lakes in 73 extremely cold locations where the mammoth genetic materials were found in Siberia, Alaska, Canada and Scandinavian countries.
DNA analysis showed that mammoths lived in mainland Siberia 3,900 years ago — after the great Pyramid of Giza in Egypt was built and the megaliths of Sotenehenge were erected. Most mammoths had died about 10,000 years ago, except for a very small population that survived on remote islands throughout Siberia.
Woolly rhinos, on the other hand, according to the researchers, still lived in the Arctic region for 9,800 years. Previous studies have shown that they had gone extinct about 14,000 years ago. However, the species actually went into extinction after the last areas of the Mammoth Steppe, an ecosystem unique in the Arctic, which no longer exists today, gave way to peat bogs, as the climate became wetter and warmer.
“The authors present several dates for mammoths, woolly rhinos, horses, and steppe bison, which are also substantially younger than the fossil record indicates, which constitutes a stronger case for late survival in the Arctic than was previously held. ,” said Tori Herridge, an evolutionary biologist and mammoth expert at the Natural History Museum in London.
“I’m very excited to see how this work will develop, and what new data might emerge to support or refute it. I’m sure it will undergo a thorough examination,” continued Herridge, who was not involved in the research.
Most of the DNA is taken from bones or teeth (the oldest DNA ever sequenced was from the tooth of a mammoth and was over 1 million years old). The use of new techniques allows the genetic material preserved in the soil to be analyzed, sequenced and dated.
All animals, including humans, constantly lose genetic material when they urinate, defecate, bleed, lose hair and dead skin cells. This genetic material penetrates the soil, where it can remain for tens, hundreds or thousands of years, when they are in the right conditions, such as in frozen soil.
“An animal scatters millions of DNA segments continuously throughout its life in its droppings, urine, skin cells and hair, as it wandered across the geographic range, but left only one skeleton after its death, which gives a lower probability for be preserved, recovered and dated,” said one of the study’s authors, Yucheng Wang, a research associate at the Department of Zoology at Cambridge University in England.
“By sequencing just a few of these DNA molecules preserved in the environment, we can identify their existence and scope. So it’s not surprising that sedimentary DNA could produce a more accurate later extinction estimate,” he continued.
Known as environmental DNA or eDNA, the technique was used by archaeologists to shed light on older humans. The same method was used during the pandemic to test city sewage in Covid-19 detection and tracking.
The study published in the journal Nature also detailed the Arctic ecosystem over the last 50,000 years. The environment in which the mammoths lived, known as Mammoth Steppe, was cold, dry and in a complex region, with distinct communities of vegetation composed of grasses (a grass-like plant), flowering plants and shrubs. As part of the research, the team sequenced the DNA of 1,500 arctic plants for the first time.
Large grazing animals such as the mammoth, which have gone extinct, have been the subject of debate for more than a hundred years, Wang said. There are two main theories: Mammoths were hunted to death centuries after their first contact with humans, or they weren’t able to adapt quickly enough to climate change at the end of the Ice Age. Wang also cites that his research supports the theory that climate change, 12,000 years ago, played an important role.
The long overlap between humans and mammoths in the Arctic region, along with a detailed understanding of the ecosystem and its rapid change, are reinforcements against the argument that humans were primarily responsible for the mammoth extinction, explains Wang.
“When the weather got wetter and the ice started to melt, it led to the formation of lakes, rivers and swamps. The ecosystem has changed and the vegetation biomass has decreased, and possibly has not been able to support the mammoth herds,” Wang argued.
“We showed that climate change, specifically precipitation, directly drove the change in vegetation – humans had no impact on them based on our models,” he concludes.
Tori Herridge of the Natural History Museum in London says more research needs to be done on the human presence in the Mammoth Steppe, if any human interference in the disappearance of the mammoths is ruled out.
In the models used in the article, according to Herridge, the researchers use the scarce presence of human remains in the archaeological record, and the existence of a climate suitable for humanity as a proxy, not as a DNA. More accurate data is needed to understand if and when humans and mammoths actually met in these regions.
“Environmental DNA studies like this have a lot of potential to directly test the presence of humans in the Arctic, just as they have done here with mammoths – that’s the kind of high-resolution data we need to unravel the true dynamics of mammoth extinction “, she said.
“Data overlay alone won’t solve this, as it’s not the last mammoth that matters. It’s finding out what made the number of mammoths drop so much that they were reduced to just a few isolated and vulnerable populations,” he concluded.
(This text has been translated. Read the original in English here)
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