Mammoths and North American horses vanished later than previously thought: researchers

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Mammoths may not have disappeared until about 6,000 years ago — more recently than previously thought — as did the wild horses that grazing the North American plains, according to new findings from McMaster University.

A team of scientists in Hamilton as well as the University of Alberta, the Yukon government and the American Museum of Natural History used ancient DNA in soil samples from the Klondike region in central Yukon to study 30,000 years of natural history.

Postdoctoral fellow Tyler Murchie said: “Only by collecting small patches of dirt – in this case between about 0.5 and 1 gram, which is very little sediment – we can reconstruct the entire ecosystem with the variety of animals that once were in the area. “. at McMaster University and lead author on the paper.

The team was particularly interested in the Pleistocene and Holocene transition, an unstable period about 11,000 to 14,000 years ago when large animals such as mammoths, felines and toothed cats all disappeared.

they paper, published in nature connections, He found that mammoths and North American horses were in sharp decline before the Pleistocene and Holocene, but did not disappear for 13,000 years as bone records indicate. Instead, DNA evidence shows it was still around 6000 years ago.

This places the disappearance of the mammoths in the Yukon into the current geological age, the Holocene, which began about 11,000 years ago. By the time the mammoths disappeared from the region, human civilizations were emerging all over the world and the first cities were developing.

Pictured, Tyler Murchie said new methods of studying ancient DNA could eventually solve long-standing questions about humans’ role in the disappearance of animals like mammoths and wild Yukon horses. (Georgia Church)

DNA is best preserved in permafrost, Murchi said, because it is cold and has very little decomposition from liquid water, oxygen or the sun. Using DNA enrichment technology developed at McMaster, scientists extracted DNA preserved in the soil to discover when species appeared and disappeared from the area.

“They’re kind of locked in place until someone comes along and is able to get those fragments back,” Murchi said.

During the studied period, the Yukon’s environment transitioned from the rich grasslands known as the Mammoth Step to the dense boreal forests that exist today. One theory, Murchi said, is that with the large grazing animals gone, they can no longer keep plant life in check.

“Part of this theory is that most of the northern hemisphere was similar to the modern African savannah,” he said. “But when a lot of these big animals started to disappear, those kinds of ecological networks started to break down.”

Murchi added that it could be early evidence of humans’ impact on ecosystems. He said scientists still disagree on whether humans, rising temperatures or a combination of the two caused the extinction of large animals like mammoths.

Because ancient DNA is better preserved in cold conditions, permafrost in areas like the Yukon is ideal for soil samples. (Tyler Murchie)

He said that rebuilding ancient ecosystems could help get to the heart of this question and other discussions that have raged among scientists “at least 270 years”.

Study co-author Ross McPhee of the American Museum of Natural History. He said the study provides further evidence that the horse is native to North America.

“Although mammoths are gone forever, horses are no longer,” he said. “The horse that lived in the Yukon 5,000 years ago is directly related to the types of horses we have today.”

There may be a time limit for the search. Permafrost is It is melting fast in the Arctic As the Earth warms, creating a sense of urgency to collect DNA samples that can reveal the Earth’s natural history.

“If we don’t collect the samples, and then they just melt and decompose, we lose all the life history data that’s been preserved all this time.”

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