Was a comet responsible for the decline of the Hopewell?

Written by Andrew Sawyer, Education Outreach Specialist

On February 1, 2022 Scientific Reports published a report titled The Hopewell airburst event, 1699–1567 years ago (252–383 CE)[1]. In this report, the authors claim to have found evidence of a cosmic airburst event that took place in the Ohio River Valley between about 1,639 and 1,770 years ago. This kind of event occurs when a comet or meteorite explodes high in the Earth’s atmosphere creating an “airburst” that produces immense heat and shockwaves along with a shower of micrometeorites that fall to the ground. The authors believe this was a catastrophic event that may have led to the decline of what archaeologists refer to as the Hopewell culture. The lead author of this report is Ken Tankersly, an associate professor of Anthropology at the University of Cincinnati. There are instances of these types of events from the recent past. For example, in 1908, a major event of this type flattened eight hundred square miles of remote forest in Siberia.[2]

The Hopewell period, as defined by archaeologists, lasted from approximately 100 BCE (2,100 years ago) to about 500 CE (1,500 years ago). Features that are considered characteristic of the Hopewell, including the construction of large earthworks, have been found throughout much of what is now the eastern U.S.

Hopewell earthworks include large-scale geometric earthworks (Image 1) as well as hilltop enclosures (Image 2) that follow the natural contours of the landscape. Archaeologists have interpreted these as social or ceremonial centers. Geometric shapes incorporated into the earthworks include circles, squares, octagons, and other distinctive forms. Based on archaeological investigations, the Hopewell appear to have relied on a subsistence strategy that combined the hunting and gathering of wild food sources with the cultivation of domesticated crops of what is known as the Eastern Agricultural Complex (EAC). The EAC included squash, sunflowers, and plants many Americans might consider weeds today like goosefoot, maygrass, and knotweed.

The authors claim they have found evidence of this airburst event on burned surfaces at multiple Hopewell era sites (Image 3). Lead author Tankersly is quoted in a EurekaAlert.com news release: “These micrometeorites have a chemical fingerprint. Cosmic events like asteroids and comet airbursts leave behind high quantities of a rare element known as platinum,” Tankersley said. “The problem is platinum also occurs in volcanic eruptions. So we also look for another rare element found in nonterrestrial events such as meteorite impact craters — iridium. And we found a spike in both, iridium and platinum.”[3]

Map showing the distribution of Hopewell sites throughout the Ohio River Valley
Image 3: Image 1 from Tankersley et. al. showing the distribution of Hopewell sites discussed in the report.[1]

According to the report, “the Turner site was at or near the epicenter of the airburst.” From this epicenter the authors estimate that the primary impact area may have been as large at 500km2. They also claim that there is a corresponding decrease in anomalous platinum readings as the sites get farther away from the supposed epicenter. They conclude that the total area affected may have included an area of 14,900 km2 in the Ohio River Valley.

The authors suggest that memories of this, and possibly other, airburst events may be found in the traditional stories of the Tribal Nations who lived in the Ohio Valley region. Tankersly continues in the press release suggesting that “The Miami tell of a horned serpent that flew across the sky and dropped rocks onto the land before plummeting into the river. When you see a comet going through the air, it would look like a large snake,… The Shawnee refer to a ‘sky panther’ that had the power to tear down forest. The Ottawa talk of a day when the sun fell from the sky. And when a comet hits the thermosphere, it would have exploded like a nuclear bomb.”[3]

In reference to the horned serpent story that the authors claim to be a Myaamia story, George Ironstrack, the Assistant Director of the Myaamia Center, points out that “while we have many lenipinšia stories, we do not have one that talks about lenipinšia dropping rocks on the land as they pass overhead.”[4] He also noted that none of the authors of this report consulted with anyone from the Miami Tribe of Oklahoma or the Myaamia Center  during or since the preparation of this report to confirm the accuracy of the stories they cite. This leaves us to wonder if the authors consulted with representatives of other tribes whose stories they quote.

The authors believe a cosmic event could have damaged the crops that the Hopewell were relying on for their survival. Interestingly, University of Cincinnati biology professor David Lentz, one of the co-authors, is quoted in the News Release from the university suggesting that “It looks like this event was very injurious to agriculture. People didn’t have good ways to store corn for a long period of time. Losing a crop or two would have caused widespread suffering… When your corn crop fails, you can usually rely on a tree crop. But if they’re all destroyed, it would have been incredibly disruptive.”[3]  What makes this statement so interesting is that no confirmed macrobotanical remains of maize have been recovered from Hopewell or other Eastern Woodland sites of this era.[5] With no confirmed kernels or other identifiable remains of maize found in any of these sites, and no other evidence that maize made up a significant, or even an insignificant, part of their diet, it is not clear why any of the authors would refer to potential damage to corn crops from such an event impacting Hopewell food supplies.

Many Hopewell researchers are contesting the conclusion that there is evidence that this type of event took place. They are especially skeptical that it could have impacted the Hopewell communities of the Ohio Valley enough to bring about their ultimate decline. While many acknowledge that an airburst event could have been responsible for the elevated levels of iridium and platinum and the presence of iron-rich microspherules, they do not believe that the evidence provided in this report proves that an airburst event of this type was the source.

Many also point out that artifacts made from meteoric iron have indeed been found on Hopewell sites, including the Turner Site. Chemical analysis, however,  shows that at least some of this material originated from what is known at the Brenham meteorite which fell in what is now Kansas about 20,000 years ago. The Hopewell are well known for their trade networks that stretched across what is now the United States and beyond, so this material certainly made its way into the Ohio Valley via trade.

The archeological evidence indicates that Hopewell cultural practices continued until about 500 CE (1,500 years ago). Any suggestion that an event such as this occurred as late as 383 CE, or earlier, and led to the decline of the Hopewell needs to account for the continuance of their practices for at least another 100 years.

Brad Lepper, Senior Archaeologist at the Ohio History Connection, is one of the many critics of this report. When asked to comment on the report he responded: “First of all, the burned layers that the group has studied are not the remains of domestic houses consumed by a sudden firestorm as the authors claim. For the most part, they are prepared basins or surfaces on which ceremonial fires were intentionally set. Also, there is no evidence whatsoever that all of the fires at these various sites were burning at the same instant in time in response to a single event. Radiocarbon dates for these Hopewell sites extend over nearly four hundred years. So there is no evidence for any sort of Pompeii-like event, but rather a series of ceremonies involving intentionally set fires that took place over an extended period of time.”[6]

Lepper’s comments indicate that along with concerns about the dates that the authors are proposing for this event, there is also no evidence that the sampled materials came from the types of features that the authors are suggesting. In his blog dedicated to debunking pseudoscience in archaeology, blogger Jason Colavito noted: “Regardless of the authors’ correctness on the source of the meteoric fragments, their conclusion cannot be correct because the Hopewell did not enter a terminal decline after their proposed impact date of c. 255-300 CE but flourished for another 200 years.”[7]

Researchers continue to investigate the Hopewell era in the Ohio Valley. The authors of this report claim that an airburst event happening as late as 383 CE may have helped lead to their eventual collapse. With Hopewell traditions continuing for at least another 100 years after the proposed date for this event, the conclusions in this report don’t correspond with the well-established timeline of Hopewell activity.


Below are some of the recent responses to this report. As additional reviews of the report are posted we plan to add them here, so please check for more.

[1] The Hopewell airburst event, 1699–1567 years ago (252–383 CE). Kenneth Barnett Tankersley, Stephen D. Meyers, Stephanie A. Meyers, James A. Jordan, Louis Herzner, David L. Lentz & Dylan Zedaker. https://www.nature.com/articles/s41598-022-05758-y 01 February 2022

[2] The Tunguska Impact–100 Years Later.  Editor: Dr. Tony Phillips, Credit: Science@NASA https://science.nasa.gov/science-news/science-at-nasa/2008/30jun_tunguska June 30, 2008

[3] Did comet’s fiery destruction lead to downfall of ancient Hopewell? University of Cincinnati. https://www.eurekalert.org/news-releases/942039 NEWS RELEASE 1-FEB-2022

[4] George Ironstrack, personal communication 2/10/2022

[5] New Dates and Carbon Isotope Assays of Purported Middle Woodland Maize from the Icehouse Bottom and Edwin Harness Sites. Mary L. Simon, Kandace D. Hollenbach and Brian G. Redmond. American Antiquity , Volume 86 , Issue 3, July 2021 , pp. 613 – 624 DOI: https://doi.org/10.1017/aaq.2020.117

[6] Brad Lepper, personal communication 2/9/2022

[7] Researchers Behind Ice Age Comet Claim Say a Comet Destroyed the Hopewell, Too. Jason Colavito. https://www.jasoncolavito.com/blog/researchers-behind-ice-age-comet-claim-say-a-comet-destroyed-the-hopewell-too 2/6/2022

Updated: February 28, 2022

One Comment Add yours

  1. stevehinds says:

    Interesting possibility – that is for publishing/

    On Tue, Feb 22, 2022 at 3:04 PM Aacimotaatiiyankwi wrote:

    > Myaamia Center Staff posted: ” Written by Andrew Sawyer, Education > Outreach Specialist On February 1, 2022 Scientific Reports published a > report titled The Hopewell airburst event, 1699–1567 years ago (252–383 > CE)[1]. In this report, the authors claim to have found evidence of ” >

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