Experts have responded sharply to a controversial study published earlier this year that sought to challenge the dating of archaeological features at Chile’s famous Monte Verde site.
Excavations that began at Monte Verde decades ago, led by archaeologist Tom Dillehay, established evidence of a human presence at the site as early as 14,500 years ago. The discovery was significant, as it marked the first unequivocal evidence of human presence in the Americas that predates the cultural manifestation known as Clovis, which had long been assumed to be the earliest human presence in the New World.
Those findings, supported by ongoing investigations Dillehay and his colleagues have conducted over the last several decades at Monte Verde, were challenged in March in a study led by archaeologist Todd Surovell, Ph.D., who, along with his colleagues, argued that a fresh analysis of features located near the Monte Verde site suggested it could be younger than previous estimates by as much as several thousand years.
Now Dillehay, who is currently the Rebecca Webb Wilson University Distinguished Professor of Anthropology, Religion, and Culture at Vanderbilt University, and more than two dozen other experts in the archaeology of the early Americas have responded in a series of eLetters published in Science, which argue that Surovell and his colleagues’ findings are not strongly supported by existing evidence.
Pre-Clovis in Southern Chile
Following its discovery in 1976 and Dillehay’s subsequent excavations, Monte Verde has long been considered a cornerstone of early American archaeology. With its array of well-preserved artifacts that include stone tools, as well as wooden structures, botanical remains, and even a human footprint, radiocarbon dating has periodically been undertaken at the site, which consistently places its occupation at an estimated 14,500 years ago.
At the time these discoveries were made, Monte Verde became one of the earliest securely dated human settlements in the Americas. Not only that, it became one of the first major challenges to the then-dominant “Clovis First” paradigm, which insisted that evidence showed the earliest arrivals in North America occurred no earlier than around 13,000 years ago.
Experts Challenge New Dates for Monte Verde
In March, University of Wyoming archaeologist Todd Surovell presented new geological data, along with the identification of a volcanic ash layer known as the Lepué Tephra, in a paper that argued Monte Verde may instead date to between 4,200 and 8,200 years ago—thousands of years later than widely accepted estimates.
Now, in a series of three scientific commentaries published in Science this month, Dillehay and colleagues, which includes leading experts like Michael Waters of Texas A&M University, David Meltzer of Southern Methodist University, Dr. Jim Adovasio, and more than two-dozen others, provide a sharp critique of the methods and conclusions presented in Surovell’s paper.
Fundamentally, the letters describe the original analysis as containing “substantive errors and misrepresentations,” and argue that its claims are “categorically false.”
Central to the dispute is the interpretation of what is called the Lepué Tephra layer. Surovell and his team argued that this volcanic deposit, dating to around 11,000 years ago, lay beneath the archaeological remains. Stratigraphically, this suggests the tephra layer is older than the archaeological features at the site, and therefore that any human presence at Monte Verde must have occurred more recently.
However, Dillehay and his co-authors contend that no such tephra layer exists beneath the Monte Verde II site’s archaeological features, and that the samples used in the study were taken from unrelated geological deposits outside the main excavation area.
“Surovell et al. did not undertake excavations within the original site location,” Dillehay and 20 co-authors of one of the recent eLetters write, adding that “hence they were unable to study its stratigraphy, in situ artifact patterning, and associated archaeological features.” Dillehay and his co-authors further argue that the Surovell-led reinvestigation “is derived from cherry-picked exposures within the drainage, specifically along creek margins exhibiting complex, discontinuous, and heterogeneous stratigraphy generated by variable depositional regimes and post-depositional erosion.”
Noting the complexities that are often associated with the geology of wetlands and stream beds like the environment where Monte Verde exists, “such contexts are not stratigraphically equivalent to the primary archaeological sequence documented at [Monte Verde],” the letter’s authors state. “The result of their study was a biased sampling strategy based on limited geochronological data designed to generate a composite chronostratigraphic schema rather than systematic resampling of intact archaeological deposits from MV-II or the natural stratigraphical equivalents,” the authors write.
Based on this, Dillehay and his co-authors write that the Surovell study’s reassessment of dates at Monte Verde is invalid, given that it does not directly apply to the original site’s cultural components. Instead, they add, the recent Surovell paper “advances an indirect and misunderstood geomorphic and chronostratigraphic perspective.”
In a statement provided to The Debrief, Dillehay said that the arguments presented by Surovell and his colleagues are “driven 100% by ideological bias.”
“Surovell and his team have spent their career defending the Clovis First Theory,” Dillehay told The Debrief, noting past articles that include a 2022 study that made similar challenges regarding pre-Clovis sites in North America.
Dillehay also noted what he and his colleagues deem to be errors and other inaccuracies in the Surovell paper.
“After all of our studies, we can confirm even more strongly what we knew before, the study was carried out with predetermined conclusions, it is full of errors and misrepresentations,” Dillehay told The Debrief.
Based on the problems he and his colleagues have found with the materials described in the Surovell study, Dillehay added that “we now even question whether many of the samples they took for study were legitimate,” concluding that the findings, as presented, were “a poor and sloppy study that involved observations from 50-400 meters away in distance,” rather than in near proximity to the Monte Verde site.
Complex Geology and Other Issues
Several of the new criticisms focus on the suggestion that older materials at the site—such as charcoal, wood, and bone fragments—may have been transported and redeposited by water, artificially inflating the site’s apparent age. However, a major focus of the expert critiques concerns the Surovell team’s knowledge of the often-complex geology at such sites.
Speaking with The Debrief in March, Dr. Michael Waters, a Texas A&M University Distinguished Professor and a principal co-author of one of the recent eLetters, characterized the Surovell study as “a working hypothesis that is poorly supported by the data.”
Specifically, Waters notes the presence of paleosols—a variety of ancient soils that geologists use as important records of past climates and ecosystems—which appear to have gone unacknowledged in the recent Surovell study.
“Obviously, whoever did the geology knew nothing about buried soils,” Waters told The Debrief in March. “You just look at the pictures, and I can see paleosols in their sections, which they don’t even describe.”
In their paper, Waters also said Surovell and his authors report that portions of Terrace 3 at the location they investigated were “both an erosional terrace and a depositional terrace.”
“That’s not possible in geology,” Waters told The Debrief. “It’s either one or the other, and they’re formed by different processes. They’re still fluvial processes, but they’re formed differently.”
“This is the Achilles heel,” Waters told The Debrief, adding that the Surovell paper’s authors “obviously don’t understand geology, or they would have realized that this is a dagger in their own arguments.”
“I think independent evaluation is good,” Waters conceded, adding that fresh analysis of existing sites is often “what keeps people honest.
“If somebody overlooks something, or there’s new technology available, you should apply it to a site,” Waters told The Debrief.
The Question of Genetics
Going beyond the geological debate, researchers also cite genetic evidence that aligns with the site’s older age. Studies of ancient DNA suggest that the ancestors of Native Americans had already diversified into distinct lineages by at least 15,700 years ago, supporting the presence of humans in the Americas well before the traditionally accepted appearance of the Clovis culture.
“Importantly, their conclusion that ‘a Holocene age for Monte Verde leaves open the possibility of later initial colonization,’ fails to consider multiple lines of genetic evidence – uniparental and genomic – from present-day and ancient individuals that independently support a pre-Clovis occupation of the Americas,” the authors of one of the eLetters focusing on the genetics of the debate write. “As early as 1993, and quite separately from Monte Verde, mitochondrial DNA (mtDNA) based estimates placed the initial peopling between 21 ka and 14 ka years ago.”
Additionally, the letter’s authors further note that “the single early study to reference Monte Verde suggested that genetics could serve to check the archaeology, not vice versa.”
However, for Dr. Surovell and his team, their findings were presented entirely with the expectation that they would receive some pushback.
In an email to The Debrief in March, Surovell wrote that he and his colleagues’ study “reports our interpretation of the age and formation of the site based on existing data and the new data we collected.”
“We welcome legitimate scientific debate and additional study,” Surovell told The Debrief, though he added, “I have little interest in engaging in debates concerning politics or arguments from authority.”
Overall, the recent fracas over Monte Verde only underscores the controversial nature of the ongoing debate over the now widely accepted idea of an earlier-than-Clovis human presence in the Americas. Since the late 20th century, a growing number of archaeological sites have reinforced the idea of earlier migrations into the Americas, with Monte Verde being among the most prominent examples.
In concluding one of the three eLetters, the authors charge that the accumulation of data supporting a pre-Clovis presence in the Americas is fundamentally overlooked by Surovell and his colleagues.
“The conclusions drawn by Surovell et al. disregard not only the Monte Verde II evidence, but also decades of research in diverse disciplines,” the authors write.
“Their lack of engagement with the full range of site data, selective use of the broader literature and overstated conclusions do not advance scientific discussion nor the field of first Americans studies,” the letter’s authors conclude.
Surovell and his colleagues’ recent Science study, and the recent eLetter rebuttals, can be found here.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.