Woolly mammoths and humans have coexisted in North America for much longer than experts realized
Woolly mammoths may have survived in North America thousands of years longer than scientists previously thought, vials of Alaskan permafrost reveal.
Hairy beasts may have persisted in what is now Yukon, Canada, until about 5,000 years ago – 5,000 years longer than experts previously estimated, according to a new study. This conclusion comes from mammoth extracts DNA that were found in vials of frozen dirt that had been stored and forgotten in a lab freezer for a decade.
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“Organisms are constantly shedding cells throughout their lives,” said study lead author Tyler Murchie, postdoctoral researcher in the Department of Anthropology at McMaster University in Ontario. For example, he explained that a person loses around 40,000 skin cells per hour, on average, which means that we are constantly ejecting pieces of our DNA into our environment.
This is also true for other forms of life; non-human animals, plants, fungi and microbes constantly leave microscopic traces of breadcrumbs everywhere. However, most of this genetic detritus does not linger in the environment. Soon after being thrown away, the vast majority of pieces of DNA are eaten by microbes, Murchie said. The fraction of lost DNA that remains can bind to a small piece of mineral sediment and be preserved. While only a tiny fraction of what was initially lost remains centuries later, it can nonetheless provide a window into a vanished world teeming with strange creatures.
“In a tiny patch of dirt,” Murchie told Live Science, “there is DNA from entire ecosystems.”
Murchie analyzed soil samples taken from the permafrost in central Yukon. Many samples dated from the Pleistocene-Holocene transition (14,000-11,000 years ago), a period marked by rapidly changing climatic conditions in which many large mammals – such as saber-toothed, mammoths and mastodons – has disappeared from the fossil record.
The DNA fragments in Murchie’s samples were small – often no more than 50 letters, or base pairs. However, on average, he was able to isolate around 2 million DNA fragments per sample. By analyzing DNA from soil samples of known ages, he indirectly observed the evolution of ancient ecosystems during this turbulent period.
The main advantage of studying ancient DNA is that researchers can observe organisms that tended not to fossilize well. “An animal has only one body,” Murchie said, and the chances of it fossilizing are not that great. On top of that, you have to find it. But this same animal has consistently ejected countless amounts of DNA into the environment throughout its life.
Soil samples – which cover a period ranging from 30,000 to 5,000 years – revealed that mammoths and horses likely persisted in this arctic environment much longer than previously thought. Mammoths and horses were in sharp decline during the Pleistocene-Holocene transition, DNA data suggests, but they did not disappear suddenly due to climate change or overhunting.
An earlier study, published in October in the journal Nature, suggested that some mammoths survived on isolated islands far from human contact until 4,000 years ago. However, the new study is the first to determine that small populations of mammoths coexisted with humans on the North American continent until the Holocene, just 5,000 years ago.
. The megafauna extinctions of this era have been largely attributed to one of two explanations: human paleo-hunters or climate catastrophe, said lead author Hendrik Poinar, evolutionary geneticist and director of the McMaster Ancient DNA Center.
However, the new study “changes the focus of this two-part debate that has tormented [paleontology] for so long, ”Poinar said.
The team’s research provides evidence that the extinction of North American megafauna is much more nuanced, he said. There is no doubt that the animals were under pressure from human hunters and a rapidly changing climate. The question is, “how many were hunted and whether or not that was really the tipping point,” Poinar told Live Science.
Analyzing ancient DNA from dirt has the potential to tell us a lot about ancient life; Poinar and Murchie said arctic permafrost is ideal for these types of ancient DNA studies because freezing preserves ancient DNA very well. But that might not be possible forever: As the ice in the Arctic melts due to the rapidly rising temperature, “we’re going to lose a lot of this life history data,” Murchie said. . “It’s just gonna drop before anyone has a chance to study it.”
This study was published on December 8 in the journal Nature Communication.
Originally posted on Live Science.