The question of when humans first arrived in the New World in once of most significant unresolved debates within archaeology. The traditional view, known as the “Clovis First” model, held that the first people into arrived into what is now Canada and the “Lower 48” of the United States around 13,000 years ago. The ancestors of these Clovis people lived in Eastern Beringia (Alaska) around 14,000 years ago and then moved south when an ‘ice free corridor’ existed between the glacial ice sheets that covered most of Canada.

However, a number of archaeological sites in the New World have been proposed to be “pre-Clovis”, older than the 13,000 years, which would suggest humans entered the Americas earlier. Proposed pre-Clovis sites include the Gault Site in Texas and White Sands in New Mexico.

For decades, one of the most famous pre-Clovis sites was Monte Verde along Chinchihuapi Creek in Chile. The site contains the remain of a campsite dated back 14,800 years ago. In addition to artifacts like stone tools and rope - preserved in a peat bog - the site also held the remains of extinct Pleistocene animals like gompotheres (elephant relatives) and Paleolama (a relative of modern llamas). The site was considered to be so significant that it even became a UNESCO World Heritage site.

Yet, a new analysis of Monte Verde, published yesterday, March 19, in the journal Science suggests the original dating of the site is incorrect. The article, titled A mid-Holocene age for Monte Verde challenges the timeline of human colonization of South America, argues that local geologic factors account for the mistaken date and that the site is no older than 8,200 years. Todd Surovell, Ph.D., an anthropologist at the University of Wyoming, was the paper’s lead author.

The importance of reproducible results

Having results that can reproduced by others is a key component of the scientific method. You probably learned this in middle school science class. You mix together vinegar and baking soda and get a reaction. You lab partner can do the same thing to reproduce your experiment and see the same results.

For decades, Monte Verde seemed like something of an anomaly - not just because of the pre-Clovis dates for the site, but because it was in Chile, thousands of miles away from other pre-Clovis sites known from the United States.

Sacha Vignieri, editor for the article in Science, explained that Monte Verde “was mostly only studied by a single group, meaning that replication of the dating has been lacking.” Surovell and his co-authors claim that their study is “the first investigation of Monte Verde, independent of the original investigators, in the nearly 50 years since its discovery.”

Their sampling took place along Chinchihuapi Creek where the site is located and their results “fail to support the hypothesis” that Monte Verde dates back to the Late Pleistocene.

The importance of understanding local geology

The team’s reassessment of Monte Verde is based in re-examining the local geology. Surovell and his co-authors found that the cultural layer of Monte Verde said to be pre-Clovis - known as Monte Verde II - is above a layer of tephra (volcanic material). They identified the layer as belonging to the Lepué Tephra, which is dated by geologists as being 11,000 years old.

The team is correct in identifying the Lepué Tephra laying “stratigraphically underlying the archaeological component”, then Monte Verde II cannot be older than 11,000 years, making the pre-Clovis dates impossible. In fact, the team things the site is even younger.

While the radio-carbon dated wood and megafauna fossils found at Monte Verde may indeed date back to the Pleistocene, it appears that those items weren’t brought to the site by pre-Clovis hunters. Instead, the team believes these materials were washed in and deposited at the site as the result of erosion and glacial outwash after 8,600 years ago. The authors explained in the paper that:

When alluvial deposition resumed after ~8600 years B.P., Pleistocene wood, megafaunal remains, and other organic matter present in [the Salto Chico Formation] in the immediate site area were reworked by Chinchihuapi Creek into Middle Holocene alluvium […] Although the organic-rich deposits of the [Monte Verde II] component can produce Late Pleistocene radiocarbon ages, this material was redeposited after 8600 years B.P.

Digging deeper

If you’d like to dig deeper into this topic, I’d recommend checking out this video in which YouTuber and anthropologist David Ian Howe interviews Surovell about his findings at Monte Verde.