Signs of human settlement in central Mexico have been found while archaeologists were excavating a cave in regional mountains. From their discovery, it is possible that the area was occupied over 30,000 years ago during the Middle Paleolithic Era.
In the cave, they've discovered hundreds of stone tools and were compared to the origins of data from other sites. Some archaeologists concluded that the discovery suggests the arrival of humans in North America 15,000 years earlier than previously recorded, causing controversy among several researchers. 'When I see claim being made that is so dramatic, then the evidence has to be there to substantiate the claim,' said Kurt Rademaker, an archaeologist at Michigan State University.
The new study published in the journal Nature seems to question the timing of the earliest human arrivals in North America. The paper provides 'new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research.'
Previously, it was theorized that people traveling to the Americas from East Asia began as early as 130,000 years ago. The Clovis First theory has been disputed despite archaeological evidence such as simple stone artifacts that skeptics say must be produced from natural geological processes rather than human design. The mainstream belief is that the Americas became inhabited at least 15,000 years ago based on artifacts and genetic evidence.
Stone Tools
Archaeologists from the Autonomous University of Zacatecas were excavating Chiquihuite Cave in the Astillero Mountains. In the cave, they found 1,900 stone tools. Two hundred thirty-nine tools were embedded in gravel that has been carbon-dated to be at least 25,000 years old.
Ciprian Ardelean, the team leader, believe that the cave might have been used as a refuge every few decades since there are only a few of the oldest tools. Describing the peak of the ice age, or the Last Glacial Maximum, about 26,000 years ago, he said, 'There must have been horrible storms, hail, snow.' Chiquihuite Cave was an ideal shelter during the harshest winters in North America and was well insulated too.
François Lanoë from the University of Arizona said that the study makes a good argument about the timing of early settlers in the Americas, but the evidence is difficult to interpret. The stone tools may have been moved by burrowing animals or altered by geological and biological activity through time, which could make the artifacts appear older than they actually are.
'If an artifact is a stone tool, you see numerous chips removed from the edge,' explained Rademaker. However, Ben Potter from Liaocheng University, China, saw no clear evidence from the images of the tools.
Ardelean described that some tools have possibly shifted into lower layers, while the oldest tools were found under an impenetrable layer of mud dating back to the last ice age. He also believes that some of the tools have markings suggesting they were made by novices who were learning to make them. He said, 'Somebody was teaching somebody else at this site.'
READ: Scientist Used 3D Facial Reconstruction to Reveal a Man's Face Who Lived 8,000 Years Ago
'Lost Group'
While the tools suggest human populations in central Mexico during the Last Glacial Maximum, there was no genetic evidence found in the cave. Furthermore, David Reich from Harvard Medical School said that 'there continues to be no convincing genetic evidence of a pre-15,000-years-ago human presence in the Americas.'
If there had been early settlers, it remains a mystery exactly when the first humans arrived in the Americas. Ardelean believes that the people who went to Chiquihuite Cave were a 'lost group' and are not part of the modern genetic pool simply because they did not survive.
READ MORE: Siberians and Native Americans Related? Recent Discovery Shows Oldest DNA Link
