From Scientific American Today in Science
Original story By Colin Barras, Nature magazine


Miles from anywhere, Chiquihuite Cave in the mountains of central Mexico seems like an unlikely place for anyone to live. But stone objects recovered from deep inside the cave may tell another story. Archaeologists excavating a cave have unearthed evidence suggesting that humans arrived in North America at least 15,000 years earlier than thought. But, as you might expect, not everyone agrees.

The discovery, which includes hundreds of ancient stone tools, is backed up by a fresh statistical analysis that incorporates data from other sites. Data from caves are “notoriously troublesome” to interpret, says archaeologist François Lanoë from the University of Arizona in Tucson.

Whilst it is agreed that the first humans in the Americas came from East Asia, it is when they began to arrive that is hotly debated. Some researchers think that it could have been as early as 130,000 years ago, but most of the archaeological evidence supporting this theory is disputed. For instance, some of the stone artefacts are so simple that sceptics say they were probably produced by natural geological processes rather than by people. The mainstream view is that human occupation of the Americas began about 15,000 or 16,000 years ago, based on genetic evidence and artefacts found at sites including the 14,000- year-old Monte Verde II in Chile.

The latest discoveries, published on 22nd July 2020 in Nature, question that consensus. Since 2012, a team led by Ciprian Ardelean (who is Honorary University Fellow at the University of Exeter) at the Autonomous University of Zacatecas in Mexico has been excavating Chiquihuite Cave, which is 2,740 metres above sea level in the Astillero Mountains. The researchers found almost 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 – roughly twice as early as most current estimates for when the first humans arrived on the continent.

There are so few of these oldest tools that Ardelean thinks the site was visited only occasionally, perhaps used as a refuge every few decades, during particularly severe winters. At the height of the last ice age, 26,000 years ago, North America would have been a dangerous place to live.

The full story is here.

References: Ardelean, C. F. et al. Nature https://doi.org/10.1038/s41586-020-2509-0

By the way, there’s a great visual on the National Geographic website, here.

 

Martin Pollins
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