New research led by a University of Wyoming archaeologist near an ancient encampment in South America challenges a relatively new but widely accepted theory that the people who made and used Clovis points in North America were not the first inhabitants of the Americas south of the continental ice sheets.

Conducted by UW Professor Todd Surovell and colleagues from Chile, Austria and the U.S. Geological Survey, the new study finds that the famous Monte Verde archaeological site in southern Chile is only 4,200-8,200 years old, not 14,500 years old as posited by researchers who worked on the site from the 1970s through the 1990s.

Surovell developed the new study along with Claudio Latorre, of Pontificia Universidad Católica, of Santiago, Chile. The two worked on the project closely for four years with César Méndez and Juan-Luis García, also of Pontificia Universidad Católica.

The researchers’ findings appear today in Science, one of the world’s top academic journals. The paper is the latest development in the debate over the peopling of the Americas, in which many now doubt the long-held consensus that the first Americans were hunter-gatherers who entered North America from Asia via the Beringia land bridge up to 14,200 years ago — and then dispersed southward between two large glaciers that then covered much of the continent.

“Because of a validation of the Monte Verde site by outside experts 29 years ago, our understanding of the date of human arrival to the Americas was fundamentally changed,” Surovell says. “We now correct the record and show that the site is much younger than initially believed. With colonization of the Americas no longer anchored by Monte Verde, our revised chronology supports a more recent date of human arrival to the Americas.”

While not all archaeologists accept the conclusion that the Monte Verde site is 14,500 years old — almost 1,500 years older than firmly dated encampments of so-called Clovis people in North America, and 500 years older than the earliest confirmed human sites in Alaska — the previously purported Monte Verde findings have gained wide acceptance. In fact, world history textbooks were rewritten to account for the early evidence at this Chilean site.

To account for the early age and location of Monte Verde deep in the Southern Hemisphere, many now believe that the first Americans must have skirted the North American ice sheets along the Pacific Coast and continued to migrate along a coastal corridor all the way to South America.

“Monte Verde is best known as the site that broke the Clovis barrier, after a site visit in 1997 by external scholars who confirmed the archaeological nature and age of the site,” Surovell says. “Findings from Monte Verde were so important that they were viewed as paradigm changing, effectively rewriting the history of the last instances in which humans colonized previously uninhabited continental land masses.”

The Monte Verde site is situated on the banks of Chinchihuapi Creek, a tributary of the Maullín River located 36 miles from the Pacific Ocean. The new study led by Surovell and Latorre is the first investigation of the site, independent of the original researchers, in the nearly 50 years since its discovery.

The study involved sampling and dating nine alluvial deposits along the banks of Chinchihuapi Creek. Essentially, the researchers found that the dating of materials found at Monte Verde to 14,500 years ago can be explained by erosion or “redeposition” along the creek. Deposits along the creek are replete with Ice Age wood that became incorporated into younger archaeological deposits. This explains how a site that is younger than 9,000 years old can produce radiocarbon dates from more than 14,000 years ago. Much like directly dating the stone from which an artifact is made does not tell you the date of manufacture of a tool, dating wood at Monte Verde does not date the occupation of the site.

The researchers also identified 11,000-year-old volcanic ash, a regional stratigraphic marker, that is older than the human occupation at Monte Verde. If human presence at Monte Verde dates to 14,500 years ago, this ash should occur above the occupation layer. It does not.

In fact, Surovell and colleagues argue that the surface on which the Monte Verde materials came to rest did not exist 14,500 years ago — rather, it formed sometime after 8,600 years ago. That essentially eliminates Monte Verde as a pillar of the theory of the coastal colonization of the Americas, they say.

“The acceptance of the pre-Clovis age of Monte Verde led some to reject migration through the ice-free corridor as a possible route of initial entry, and a coastal route … has been suggested as more likely,” the researchers concluded. “Although our findings do not preclude the possibility of earlier dates of initial entry to the Americas, they do support an initial interior migration into continental North America as a viable colonization hypothesis.”

The new study builds on a previous analysis led by Surovell that suggested that misinterpretation of archaeological evidence at certain sites in North and South America might be responsible for theories that humans arrived long before 13,000-14,200 years ago. That analysis found that, while stratigraphic integrity of early archaeological sites in Alaska is high — producing strong evidence in support of unambiguous human occupation — the sites in more southern locations pointing to possible earlier human occupation show signs of artifact mixing among multiple time periods.

Other co-authors of the study are Christopher Luthgens, of Austria’s BOKU University, and Jay Thompson, of the U.S. Geological Survey.