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Written by Andrew Sawyer, Education Outreach Specialist

In February of last year we posted a skeptical review of a Scientific Reports article authored by University of Cincinnati anthropology professor Kenneth Tankersley and colleagues claiming that a catastrophic cosmic event took place over what is now southern Ohio between about 1,639 and 1,770 years ago that lead to the collapse of what archaeologists identify as the Hopewell culture. The Hopewell occupation of what is now southern Ohio is best known for the construction of monumental earthworks built between about 100 BCE and 400 CE. These authors claimed to have identified burned surfaces at many of these sites that they proposed were the result of an airburst event caused by a comet fragment entering the earth’s atmosphere and exploding. Carl Sagan is often quoted as saying “extraordinary claims require extraordinary evidence.” While events similar to what these authors claim to have happened have indeed been documented, the evidence presented by these authors was neither convincing nor extraordinary.

The initial release of the article garnered a lot of attention. Not only was the story published by a reputable science journal, Scientific Reports, but national news outlets including the Washington Post and publications geared towards readers interested in science and nature, like Smithsonian Magazine, yes that Smithsonian, shared the story online with no critical review or evaluation of the claims of the authors.

Despite what seemed like a lot of positive popular press at first, several researchers quickly began to express concerns about many of the claims the authors were making. Many noted that Hopewell cultural practices continued for at least another hundred years (until about 500 CE or 1,500 years ago) following the latest proposed date (383 CE) for this alleged airburst event, contradicting any arguments for a quick decline.

Discrepancies were also noted in the types of contexts that the dated samples were collected from and the descriptions Tankersley et al. gave for those contexts. The University of Cincinnati team described many of the dated samples as coming from catastrophically burned structures. Other researchers pointed out that many of those samples actually came from prepared surfaces where fires had been intentionally lit, as opposed to features that burned due to some sort of cosmic explosion. Other critiques focused on the alleged cometary origin of the material analyzed and whether or not there was any actual evidence of an airburst happening at all around that time. As a result of some of these critiques, Tankersley and his collaborators subsequently suggested that an asteroid was the more likely source of their hypothesized airburst event as opposed to their original claim of a comet, though they held firm in their stance that some sort of airburst event happened at this time.

The most exhaustive response to the claim that a cosmic airburst wreaked havoc on the Hopewell culture was recently published online by Scientific Reports.  Lead author Dr. Kevin C. Nolan from Ball State University and this group of researchers, which included Miami Tribe citizen Dr. Tim McCoy, the Curator of Meteorites at the Smithsonian National Museum of Natural History, critically examined the airburst claim on multiple fronts. Some of these concerns were initially shared at the Ohio Archaeological Council’s Spring 2022 meeting soon after the initial report was first published. You can view the presentation on their YouTube channel.

As in some of the earlier critiques, Nolan et al. point out that what Tankersley et al. claimed to be habitation areas catastrophically burned by a cosmic explosion were actually ceremonial basins, burned floors within mounds, or other prepared and intentionally burned features that are well documented in Hopewell sites. They suggest that this is just one of many misinterpretations and mischaracterizations of what was uncovered at these sites that were manipulated to allow the airburst proponents to arrive at their conclusion.

Some of the sharpest criticism comes when Nolan et al. suggest that the UC team confuse the deposits from one part of a site that Tankersley himself excavated with an entirely different and unrelated part of that site. In this example they look at the reports from Tankersley’s field work at what is known as the Jennison-Guard site in Lawrenceburg, Indiana.^[1] The report published in 2021 describes one of the areas that Tankersley excavated as a location where “No artifacts were recovered.” The report, however, goes on to suggest that traces of Iridium and Platinum, elements they claim originate from the cosmic event, along with charred material identified in that area which they describe as “Pre-habitation” are somehow related to Hopewell artifacts found 10 meters away in an entirely unrelated excavation unit. This seems like a pretty big leap in logic to create a relationship between things that just isn’t there. For Nolan et al. this not only led them to question the UC team’s methodology and interpretations, but also raised serious concerns about the integrity of their work.

Nolan et al. also challenge both the cometary and the cosmic origin of the elements that the UC team suggests came from an extraterrestrial source. Nolan and colleagues agree with an earlier response to the airburst hypothesis suggesting that those elements could not have originated from a comet. Based on the analysis of meteorite fragments positively identified from other Hopewell sites, however, they also point out that if the material Tankersley et al. analyzed were of meteoric origin they should expect to find notable levels of magnesium and nickel. The lack of those elements in the material analyzed by the airburst proponents suggests to Nolan et al. that those samples originated in the local soils as opposed to coming from space.

Ultimately Nolan et al. suggested that this airburst theory is just another in a series of recent reports attempting to attribute the decline of past cultures to “cosmic catastrophism.” These types of explanations ascribe the collapse of past civilizations, both real (in this case Hopewell) and mythical (i.e. Atlantis), to cosmic events of extraterrestrial origin. Speculation along these lines seem to have become somewhat trendy lately with folks who eschew some traditional scientific methods and evidentiary requirements coming up with theories that are commonly associated with pseudoscience, and lack the rigor of serious scientific inquiry.

This recent response to the hypothesis that a cosmic “airburst” precipitated the decline of Hopewell cultural practices, along with other responses and comments over the last year or so, raised serious concerns about the methodologies employed to reach this conclusion and the interpretation of the available evidence. This post shares just some of the concerns that Nolan and his colleagues pointed out, their full response is available through Scientific Reports. Due to the detailed concerns “raised by Nolan et al. about errors in methodology, analyses, and interpretation of the data in the Article, indicating that the study does not provide data to support the claims of an airburst event or that such an event led to the decline of the Hopewell culture” the editors of Scientific Reports officially retracted Tankersley et al.’s original article indicating that they “no longer have confidence that the conclusions presented are adequately supported.”

For more see:

• Did A Comet Really Wipe Out A Native American Culture 1,500 Years Ago?
  https://www.iflscience.com/did-a-comet-really-wipe-out-a-native-american-culture-1500-years-ago-70244?fbclid=IwAR2wnfdMulzmElHTzQWn-GrZaoOg0UOuBNtZbHhDtxzswgCMy7KY0tZXmVA
• Comet Catastrophe Debunked: Archaeologists Refute Claims That a Comet Destroyed Hopewell Culture
  https://scitechdaily.com/comet-catastrophe-debunked-archaeologists-refute-claims-that-a-comet-destroyed-hopewell-culture/?expand_article=1&fbclid=IwAR2kq4BxRdPJK1G_ZtYEd51ZDkddlDojipg5o1IqCjEqeoRBKroEVr3TmFc
• A sensational theory about a civilization-ending comet in ancient Ohio has been retracted.
  https://bigthink.com/the-past/ancient-ohio-comet-airburst-retracted-hopewell/?fbclid=IwAR1LyKPeazAdirxuL0iuVuzU4_w8faYGbpQsSvUNIctODV9MZixHa7IACjs 

References: 

[1] Tankersley, K. B. 2019 & 2020 Investigations at the Jennison-Guard Site (12D246): Evidence of an Ancient Comet Airburst Event, Lawrenceburg Township, Dearborn County (Department of Anthropology University of Cincinnati, 2021).