Archaeologists rewrote the history books when people first arrived on the Americas, shifting the date of the first migration 15,000 years in the past.
Excavations in a cave in Mexico called Chiquihuite revealed archaeological evidence of human occupation going back as far as 27,000 years.
However, computer analysis continues to push this date back. The study says people first lived in the cave about 33,000 years ago.
This contradicts the widespread belief that people only reached North America about 16,000 years ago.
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Archaeologists have rewritten the history books for the arrival of people to the American continent and set the initial migration of current estimates at 15,000
During a ten-year investigation period, nearly 2,000 stone tools were found in the Mexican cave, the age of which was calculated using a radiocarbon analysis
Stone tool below the LGM (Last Glacial Maximum) layer in the Mexican cave. It shows that people lived in the cave about 27,000 years ago
State of the world 33,000 years ago
Planet Earth looked very different 33,000 years ago than people were in the middle of world domination.
Homo sapiens had already surpassed the Neanderthals in Eurasia and forced our sister species to extinction after migrating from Africa via the Levant.
We had gradually spread to Europe and Asia and expanded the human range, and Southeast Asia, Indonesia and Australia had been colonized some 20,000 years ago.
Previous studies have shown that the rugged wilderness of Northeast Asia remained unexplored until about 35,000 years ago and is in line with the latest findings.
The previous estimate of when people first entered America was about 16,000 years ago when the Caribbean islands were conquered 8,000 years ago.
The date of America was long since it was believed that the Bering Strait bridge was not blocked by glaciers during the Ice Age.
Scientists agree that people have most likely migrated from Asia to America via a land bridge over the Bering Strait, which is now under water and forms the sea between Alaska and Russia.
However, during the ice age, which started about 33,000 years ago and lasted until about 16,000 years ago, this route was blocked by glaciers.
It was formerly believed that people went to America for the first time after the ice age, when the glaciers melted, and most of the archaeological evidence previously discovered supports this theory.
The Chiquihuite Cave, however, indicates that humans have been on the continent for millennia.
The researchers suggest two possible explanations for how people first colonized North America over 30,000 years ago.
First, people from Northeast Asia may have crossed the land bridge on Beringstrasse before the Ice Age when there was a gap between the Laurentide ice sheet and the Cordilleran ice sheet.
Alternatively, they could have followed the Pacific coast from Asia until they had bypassed the glaciers.
Today Nature publishes two studies, one detailing the Chiquihuite site and another statistically analyzing 42 archaeological sites in America.
"It is generally believed that the first Americans arrived on the continent 16,000 to 13,000 years ago," said lead author of the statistical model study, Dr. Lorena Becerra-Valdivia.
"Our results show evidence of people some 15,000 years ago."
During a ten-year investigation period, nearly 2,000 stone tools were found in the Mexican cave, the age of which was calculated using a radiocarbon analysis.
Homo sapiens was responsible for the extinction of the Neanderthals
A supercomputer may have finally ended the debate over what caused the Neanderthals to die out.
Mathematicians used the enormous computing power of the IBS supercomputer Aleph to simulate what happened all over Eurasia around 40,000 years ago.
It turned out that the most likely explanation for the Neanderthal extinction was that Homo sapiens, who immigrated to Europe at the time of the Neanderthal extinction, were better hunters and outdid them for food.
Humans and Neanderthals are known to have overlapped and even mated, but Homo sapiens' superior brain power eventually wiped out their distant cousins.
Experts have long argued over whether it was turbulent climate patterns, competition for food with Homo sapiens or the crossing with this new species that ultimately led to the death of the Neanderthals.
"Using archaeological evidence and Bayesian age modeling – a powerful tool that incorporates data and archaeological evidence through statistics – we can estimate that people arrived in the Chiquihuite cave 33-31,000 years ago," says Dr . Becerra-Valdivia.
"These results help us understand the initial human occupation of America in more detail than ever before."
Since the initial settlement of the continent went far back in time, the researchers also started to map the timeline of the first people in America.
Because despite the undeniable evidence in Mexico, most other prehistoric human sites in the adjacent United States are no more than 16,000 years old.
Professor Tom Higham from Oxford University, who was involved in the research, theorized that the "surprisingly early movement" took place across the oceans.
"The people who have traveled to these new countries must have used marine technology because the northern parts of North America were impenetrable until 13,000 years ago and were sealed off from East Eurasia by a massive ice sheet," he says.
This theory of coastal migration says that people have found their way along the Pacific coast from the Arctic Circle to today's Mexico.
They may have formed settlements along the sea that are under water due to the rising sea level after the glacial melt at the end of the last ice age.
This theory would explain why only a few of the known mainland settlement areas match Chiquihuite in old age.
Ruth Gruhn, emeritus professor of anthropology at the University of Alberta, who was not involved in the study, says that another option is land migration before the ice age brought an impenetrable ice wall between the continents.
While the researchers postulate how people have reached the Mexican cave, they believe that the site itself offers irrefutable evidence of human settlement.
The researchers used archaeological evidence (such as stone tools pictured) and Bayesian age modeling – a powerful tool that uses data and archaeological evidence through statistics – to estimate that humans were in the Chiquihuite cave 33-31,000 years ago arrived
The stone tool shown is located above the LGM layer (Last Glacial Maximum) within the stratigraphic component B. This special piece was made from a greenish-crystallized limestone
In the picture, archaeologists enter the Chiquihuite cave. Decades of excavation here has provided evidence that uprooted existing theories about human migration to America
In the picture, assistant professor Mikkel Winther Pedersen and his team members carefully show the different cultural layers in the cave that rewrite the history of human migration to America
15,000 year old mammoth cemetery in South America
During excavations, scientists in Mexico discovered a cemetery with almost 70 petrified mammoths to clear land for a new airport.
Breathtaking pictures from the website show the brilliant white skulls and tusks of the prehistoric giants.
The fossilized remains of the now extinct cousin of modern elephants were first discovered in 2019 and are now shown for the first time.
Ongoing work by anthropologists has shown that the mammoths were probably hunted by Neolithic people 15,000 years ago.
Last year, the same researchers announced the discovery of two man-made pits just 12 miles from the airport that may have been used to catch mammoths.
Dr. Ciprian Ardelean, who led the archaeological excavations, says: “The finds in the Chiquihuite cave are extremely exciting.
“Archeology is older than anything we've seen before, and the stone tools are of a type that is unique on the American continent.
“There are thousands of man-made stone artifacts embedded in layered sediment deposits that are now well dated.
"It is strange that the place was occupied so much earlier than others – it seems to us likely that the people in Chiquihuite represent a" failed colonization "that may not have left a genetically detectable legacy in today's First Americans."
While the attempt to colonize America initially failed, there was a population boom about 15,000 years ago.
At this point in history, people regularly appear in archaeological records in the United States, Canada, and Central and South America.
This also coincides with the reappearance of the land bridge in Beringstrasse when the ice age ended and the two ice sheets separated, which may have triggered a wave of mass migration from Asia.
At this point in history, people and their tools dominated the continent. 15,000 to 13,000 years ago, many large animals were threatened with extinction, including mammoths, old horses and camels.
Dr. Jean-Luc Schwenninger, senior co-author of the paper on the excavations, says the publication of the research is very satisfactory and will "question long-established views."
He says that formulating such a bold new theory requires "extra care, control, patience and persistence".
Professor Gruhn agrees that the results will ruffle feathers and spark a lively debate about when America was first reached by humans.
Professor Gruhn writes in an accompanying article on news and views, also published in Nature: will be very difficult to accept for most archaeologists who specialize in early America.
"This interpretation and careful examination of the location data will undoubtedly pose challenges."
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