Humans arrived in Americas 30,000 years ago, Mexican cave excavation suggests

A discovery made by archaeologists inside a cave in central Mexico suggests that humans lived in the Americas more than 30,000 years ago as opposed to earlier claims of 15,000-16,000 years. The controversial study published in the journal Nature on July 22 suggests that humans arrived in Americas 15,000 years earlier than previously thought and the claim is based on excavation of Chiquihuite Cave in Mexico where archaeologists have discovered 2,000 stone tools, 239 of which were embedded in layers of gravel that have been carbon-dated to between 25,000 and 32,000 years old.

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However, the study has been dubbed controversial because some researchers suggest that stone artefacts discovered in the cave could have been probably produced by natural geological processes rather than by people. Until now, people have believed that humans began migrating to the Americas about 15,000 years ago, which is based on evidence and artefacts found at sites including the 14,000-year-old Monte Verde II in Chile.

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The latest study that claims humans may have occupied the Americas 30,000 years ago began in 2012 and was led by Ciprian Ardelean of the Autonomous University of Zacatecas. According to Ardelean, the site was visited only occasionally, perhaps used as a refuge every few decades, particularly during severe winters. At the height of the last ice age 26,000 years ago, North America would have been a dangerous place to live, Ardelean said adding that there must have been horrible storms, hail, snow in the region at that time. 

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'Notoriously troublesome' 

Francois Lanoe, an archaeologist, and anthropologist at the University of Arizona in Tucson said that even though the team makes a good case of ancient human occupation in Americas the data from caves are 'notoriously troublesome' to interpret. "Stone tools might have been shifted into deeper layers by geological or biological activity — perhaps moved by burrowing animals — making them seem older than they really are," he said. Some controversial studies have earlier claimed that humans reached the Americas 1,00,000 years earlier than previously thought. 

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