Early Chiquihuite Cave 'artifacts' likely natural in origin

Dr. David Kilby

In the summer of 2020, researchers working at Chiquihuite Cave in Zacatecas, Mexico, announced in the journal Nature they had discovered evidence of human occupation of the area more than 30,000 years ago—far earlier than the timeframes broadly accepted by the archaeological community.

Now, new analysis conducted in part by David Kilby, a professor in the Department of Anthropology at Texas State University, casts doubt on those findings. The research team, led by Jim Chatters, principal investigator of Proyecto Arqueológico Subacuático Hoyo Negro, and Ben Potter, professor in the Arctic Studies Center, Liaocheng University, China, publish their report, "Evaluating Claims of Early Human Occupation at Chiquihuite Cave, Mexico," in the journal Paleoamerica (www.tandfonline.com/doi/full/10.1080/20555563.2021.1940441).

The previous research at Chiquihuite Cave identified the site as having been inhabited by humans as early as 33,000 years ago. If true, this would place occupation of the site 17,000 or more years earlier than the oldest unequivocal early sites in the Americas. The Chatters team suggests that this would mean humans were present in northern Mexico at a time prior to the initial divergence of ancestral Native Americans and East Asians, which occurred in eastern Asia. Because of that, the hypothetical inhabitants of Chiquihuite Cave would represent a human population of the Western Hemisphere which has remained undetected in any genetic study, and which contributed no genes to the ancestral Native Americans who began migrating throughout the Americas after 16,000 years ago.

The new analysis also finds that the Chiquihuite Cave authors failed to adequately consider the possibility that the objects were the result of natural processes. Chatters' research team examined the likelihood that the purported stone artifacts had been created either by humans or through natural environmental processes. The new analysis determined that the Chiquihuite Cave assemblage is most likely composed of geofacts, that is, limestone pieces broken through natural processes that have the appearance of being man-made. Relevant data included fracture mechanics, where the stone pieces more closely match geofact expectations and the geochemical analyses which failed to distinguish purported artifacts from naturally occurring rocks.

Without additional, compelling evidence to the contrary, the Chatters team concluded that Chiquihuite Cave does not represent very early human occupations in the Americas and does not support the idea of human arrival before the last glacial maximum.