Mammoth DNA found in sediment likely comes from animals long dead – ScienceDaily

The very extinction of the mammoth has fascinated paleontologists for generations, perhaps because their decline coincided with the arrival of humans in North and South America.

So it’s only natural to wonder if humans contributed to the extinction of these giant Ice Age beasts more than 10,000 years ago.

A University of Cincinnati paleontologist refutes the latest timeline published in the journal in 2021 Nature this suggested that mammoths met their end much sooner than we thought. An international team of researchers studied the environmental DNA of mammoth remains and more than 1,500 Arctic plants to conclude that a wetter climate was rapidly changing the landscape from tundra-grassland-steppe to forested wetlands that could not sustain many of these large grazing animals , which drove mammoths to extinction recently like 3,900 years ago.

But in a rebuttal paper in NatureUC College of Arts and Sciences assistant professor Joshua Miller and co-author Carl Simpson of the University of Colorado Boulder argue that the environmental DNA used to create their updated timeline is more complex than previously thought.

“The problem is, you have no idea how old this DNA is,” Miller said. “Sedimentary deposits are complex. Materials of different ages are routinely buried together.”

Researchers have many tools to date sedimentary deposits and the materials they contain. But not everything can be dated, Miller said.

“We can radiocarbon date all sorts of things: bones, teeth, charcoal, leaves. That is very meaningful. But currently we cannot independently date DNA found in sediments,” Miller said.

From recent discoveries like the baby mammoth found in Canada this year, we know that many Ice Age animals that died tens of thousands of years ago can become mummified in the dry, cold environment of the Arctic. Miller said the researchers couldn’t tell whether the environmental DNA preserved in the sediment was shed from a living or dead animal.

“DNA is constantly being shed by organisms,” Miller said. “In fact, the DNA continues to be excreted long after the animal has died. In places where decomposition is slow, this means that long-dead and even long-extinct species can continue to make their way into the surrounding sediments. In the Arctic and other cold weather conditions, it can take thousands of years for anything to decompose.”

The researchers say the slow decomposition of animals in arctic regions could explain why mammoth DNA emerges thousands of years later than the last mammoth fossil discovered. The paper notes that the mummified remains of elephant seals near Antarctica may be more than 5,000 years old.

Simpson said his work studying the marine environment of recently eroded slopes shows how difficult it is to date ancient specimens.

“Mussels can remain on the sea floor for thousands of years. If you see shells on the beach, some might be from animals that died recently, while others might be from shellfish that died millennia ago,” Simpson said. “This also happens in the vertebrate record.”

Miller said the question remains what, if any, human impact has been on the global decline and extinction of mammoths. Humans are known to use fire to transform landscapes in profound ways, Miller said. They also hunted mammoths and used their ivory tusks.

When did the last mammoths die? Scientists say most mammoths went extinct more than 10,000 years ago, but remnant populations lived on islands like Russia’s Wrangel Island until recently.

This coexistence with modern humans is one of the reasons mammoths capture our imaginations, researchers said.

“They are intriguingly similar to the animals that live among us today,” Miller said. “We can almost touch her. This is what makes mammoths so fascinating. For many people, they are the figureheads of the Ice Age megafauna.”

Simpson noted that mammoths once lived in the California Channel Islands near his childhood home. A pygmy mammoth weighing 2,000 pounds lived on the islands. Today, the island’s largest mammal is a small endemic fox.

“I think about how great it would have been to grow up with all these big animals,” Simpson said. “But I just missed her.”

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Materials provided by University of Cincinnati. Originally written by Michael Miller. Note: Content can be edited for style and length.

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