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CERHAS rendering of Serpent Mound

Sometimes it seems like everything about Serpent Mound is shrouded in mystery — or at least controversy.

Just about everyone agrees that the mound does, indeed, represent a gigantic serpent, but beyond that the answers to even basic questions, such as who built it, still are being debated.

At the Midwest Archaeological Conference held last month in Columbus, Bill Romain presented a paper entitled “Serpent Mound Project Results 2013.” His co-authors included William Monaghan (Indiana University), Jarrod Burks (Ohio Valley Archaeology, Inc.), Michael Zaleha (Wittenburg University), Karen Leone (Gray and Pape, Inc.), Tim Schilling (Midwest Archaeological Center), Al Tonetti (ASC Group), Matthew Purtill (Gray and Pape, Inc.) and Edward Herrmann (Indiana University).

The results presented by Bill were not limited to a discussion of the Serpent’s age, but since that’s the only aspect of his team’s work that I disagree with that’s the focus of my November column in the Columbus Dispatch and this blog post.

Bill has been arguing for years that the Serpent was built by the Hopewell culture. I have argued that it makes much more sense as a Fort Ancient culture effigy mound.


View of the initial 1991 excavation into a previously disturbed portion of Serpent Mound interpreted as one of Putnam’s trenches. From left to right, DeeAnne Wymer, Terry Cameron, Brad Lepper, Robert Fletcher.

In 1991, I worked with a team of amateur and professional archaeologists that recovered bits of charcoal from the Serpent. The charcoal produced two radiocarbon dates both around A.D. 1120. This roughly corresponds to the age of the vast majority of other effigy mounds in eastern North America, including Ohio’s other effigy mound — Licking County’s so-called Alligator. Also, the art of this period throughout eastern North America is rich in serpent symbolism. So, even without the radiocarbon dates, Serpent Mound fits rather comfortably into the context of what was happening throughout eastern North America at about this same time.

I think it’s fair to say that, over the last two decades, this interpretation has become accepted by most North American archaeologists — but all scientific knowledge is provisional and subject to rejection or revision in the light of new data or better arguments.

In his presentation, Bill stated five principal reasons for thinking the Serpent was built by the Adena culture, circa 600 B.C. to A.D. 100:

1. As part of his team’s 2011 investigation, they recovered several bits of charcoal from soil cores, which produced radiocarbon ages that average around 300 B.C.

2. Serpent iconography is present in Adena and Hopewell art.

3. His team recovered no Fort Ancient artifacts in their soil cores.

4. He expressed the opinion that the radiocarbon dates obtained for the Serpent in 1991 do not relate to the original construction of the mound, because they came from near the surface and were either in a disturbed context or relate to a re-furbishing of the mound in Fort Ancient times.

5. The design of the mound appears to incorporate “Adena and Hopewell metrics.”

I’m not convinced by Bill’s arguments and here’s why:

1. The charcoal was not found in a secure context. The fragments Romain’s team recovered from soil cores may be from the Adena occupation that Putnam discovered at the site. The Fort Ancient builders of Serpent Mound may have dug into the buried remains of Adena cooking fires while excavating for the earth used to build the mound and then accidentally incorporated some of that charcoal into the mound.

2. Serpent imagery is virtually absent in Adena art. The only example Romain mentioned in his presentation was the vaguely serpentine pattern on the loin cloth of the man on the Adena Pipe. There are serpents in Hopewell art, but just about every other animal that lived in Ohio also is represented. Serpents appear to have been regarded by the Hopewell as, at best, just one among many potential spirit guardians.


Sandstone palette engraved with two intertwined serpent monsters from a Mississippian mound in the state of Mississippi. Ohio Historical Society collections.

In contrast, serpents are a hugely important component of Mississippian symbolism. Especially important examples include rattlesnake palettes, rattlesnake engravings on shell gorgets, and the amazing Birger figurine.

Of course the Fort Ancient is not, strictly speaking, a Mississippian culture, but these people did live in a Mississippian world and to a greater or lesser extent they were active participants in that world and would have shared much of its cosmology.

3. It is unusual to recover artifacts in soil cores generally and anyway, Putnam didn’t report finding any artifacts at all in his excavation of the Serpent. Romain did not say whether his team recovered any Adena or Hopewell artifacts in their cores, but if he had I think he would have mentioned it.

4. The soil samples we recovered in 1991 and from which we obtained the charcoal that gave us the Fort Ancient dates were by no means from near the surface. Moreover, in our excavation profile we observed no evidence of any re-furbishing of the mound other than than Putnam’s restorations in the 1880s. There was a distinct boundary between the intact mound deposits and the material added by Putnam, so we’re reasonably sure our samples came from deep within the original mound.

Photograph of the 1991 excavation into Serpent Mound compared to our stratigraphic profile. The darker layer at the top (including both strata I & II) is earth added by Putnam when he restored the mound. The light colored layer (including both strata III & IV) is the remnant of the original mound. The profile shows the locations of the two soil samples, 4A and 5A, from which we recovered charcoal. Both samples produced dates of around AD 1120. Modified from Figures 9 and 10 in Fletcher et al. 1996.

Photograph of the 1991 excavation into Serpent Mound compared to our stratigraphic profile. The darker layer at the top (including both strata I & II) is earth added by Putnam when he restored the mound. The light colored layer (including both strata III & IV) is the remnant of the original mound. The profile shows the locations of the two soil samples, 4A and 5A, from which we recovered charcoal. Both samples produced dates of around AD 1120. Modified from Figures 9 and 10 in Fletcher et al. 1996.

5. The alleged use of “Adena and Hopewell metrics” by the builders of Serpent Mound is an interesting, but controversial claim. Even if true, it would only demonstrate that the mound was built during or after the Adena and Hopewell eras. The modern foot appears to have been adopted in Europe in the early 12th century A.D. and structures incorporating this “Norman metric” are still being designed and built today.

So, who built Serpent Mound? We still don’t know for sure. Given our inability so far to recover and date charcoal clearly related to the construction of the mound, future investigations may attempt to resolve the controversy by using new dating techniques, such as Optically Stimulated Luminescence, to provide a definitive answer. Until that happens, I think the existing data point to the Fort Ancient culture as the most likely builders of the Great Serpent. If it’s an Adena mound it’s a wildly precocious anomaly, whereas if it’s a Fort Ancient mound, it is still an anomaly, but it’s not unprecedented — it fits within a broad, regional tradition of effigy mound building that includes Alligator Mound and the Kern stone serpent effigies located in the Little Miami Valley.

Timeline showing the overlap of radiocarbon dates for Serpent Mound, Alligator Mound and the hundreds of effigy mounds in the upper Midwest. The specific cultural connections between the Ohio mounds and those of Wisconsin and Iowa are not strong, but the people in Ohio could not have been entirely unaware of the revolution in mound-building taking place in the upper Mississippi valley. Graphic from Lepper 2001.

Timeline showing the overlap of radiocarbon dates for Serpent Mound, Alligator Mound and the hundreds of effigy mounds in the upper Midwest. The specific cultural connections between the Ohio mounds and those of Wisconsin and Iowa are not strong, but the people in Ohio could not have been entirely unaware of the revolution in mound-building taking place in the upper Mississippi valley. Graphic from Lepper 2001.

I look forward to reading the final report of the investigations by Romain’s team, which undoubtedly will include more data and a fuller presentation of their interpretations. Even if I end up still disagreeing with their assessment of the age of the Serpent, I am sure I will learn a lot that I didn’t know before about this amazing mound.

For further reading

Burks, Jarrod
2012 Ohio’s Great Serpent Mound surveyed. ISAP News 32, pp. 6-7.

Fletcher, Robert, Terry Cameron, Bradley T. Lepper, Dee Anne Wymer, and William Pickard
1996 Serpent Mound: a Fort Ancient icon? Midcontinental Journal of Archaeology 21:105-143.

Lepper, Bradley T.
1998 Great Serpent. Timeline 15(5):30-45.

2001 Ohio’s Alligator. Timeline 18(2):18-25.

Lepper, Bradley T. and Tod A. Frolking
2003 Alligator Mound: geoarchaeological and iconographical interpretations of a Late Prehistoric effigy mound in central Ohio, USA. Cambridge Archaeological Journal 13(2):147-167.

Romain, William F.
2000 The Serpent Mound. In Mysteries of the Hopewell: astronomers, geometers, and magicians of the eastern Woodlands, pp. 233-253. University of Akron Press.

Weintraub, Daniel and Kevin R. Schwarz
2013 Long shadows over the valley: findings from ASC Group’s excavations at Serpent Mound State Memorial. Current Research in Ohio Archaeology 2013.

Brad Lepper

Comments (14)

  1. Stefan Radivoyevitch

    The mound that you see before you was made by the Putnam people of 1890. Originally it was probably a poduct of Southeastern Ceremonial Complex. Stylistically it doesn’t fit within the context of the rigid geometries of the Adena Hopewell. Like confusing Picasso (cubism) with van Gogh. Two entirely different birds.
    (- from the perspective of a layman)

    • Stefan Radivoyevitch

      The oval and back-wing projections, when taken together, reminds me a lot of the v-shaped Forked Eye motif of the S.C.C..It is the only theory that can account for both features.

      The mound is its own “artifact” that needs to be returned to the NA.

      (-my two cents worth anyhow)

  2. Richard Thomson

    Hello There,

    Wonderful debate you’ve got going on here Lepper. I hope all the best for your research.

    Entire books have been written on the contingent nature of the serpent mound; many have studied into its deepest roots and have ran along the controversial timelines, searching for significant relations and a sign to point our understanding of this massive snake effigy in a direction that tells its true story. What if we can find that true story subsequently after another archaeological investigation like the one done in 1991? I know extreme care is taken to leave things just as they were left, and when getting in and abrasively disturbing its original state, it ruins the soul purpose for preserving a site, but isn’t a story – the true story – really what we’re aiming to find when we study our past? And would it not be worth it if an excavation conjures up new premises of understanding, implicating mysteries, answering questions and ultimately putting a real story on the face of the mound to tell the tale of its creators for generations to come?

    Lepper, thank you for posting this. I would love to hear about any further understandings you may acquire on the serpent mound.

    Richard Thomson

  3. Brad, I find you arguments here extremely unpersuasive.

    You label Serpent Mound as “an effigy mound” which has some rigorous definition only in your own mind. Algonquian language employs geometric field terms, one of which is for serpentine form, so Serpent Mound could well be considered a geometric earthwork, and your chosen label for it is not especially relevant. You say there were only two effigy mounds in all of Ohio (which is false by any definition), and since the other one, some 80 miles away in Licking County, dates to around 1100 CE (by general agreement) you think Serpent Mound should be of that date, too. Why?

    You fail to note that the Portsmouth Works, only thirty miles from Serpent Mound, were built to represent a rattlesnake, as identified by Stansbury Hagar in 1933, in part on the basis of how the Shawnee of the area saw it. Portsmouth likely dates to the early Woodland Period — when Serpent Mound was also built. Circle-square earthworks of the Scioto Valley, which likely also begin in the early Woodland (Portsmouth being a prototype) likely represent the body patterning of the Timber Rattlesnake, and oral tradition of the area’s Algonquians referred to the builders of these works as “the Snake People.”

    Your contention that the “Adena” and “Hopewell” were such distinctive cultures that one may have venerated serpents while the other didn’t is untenable. There is no justification to even distinguish between so-called Adena and Hopewell as the civilization was continuous genetically, architecturally, and linguistically, a position strengthened by the new findings. We should dispense with the weirdly-derived “Hopewell,” and simply call it the Adena Civilization.

    Your point that there is little early serpent imagery neglects that we have little effigy art of any kind from the period that you narrowly defines as Adena, but you clearly ignore two kinds of art that we do have from that period — the Adena tablets which are consumed with complex serpent/bird images, and, again, the Portsmouth Works, which were a 10 mile-long rattlesnake.

    Serpent images from the late Woodland period are best understood as inheritances from the early and middle Woodland Period, obviously.

    You fudge the issue of where your 1991 samples came from by saying they came from “deep” in the mound, when you have often acknowledged that they came from the middle of the mound and not the base layers. That’s important because everyone acknowledges the mound may have been restored or supplemented around 1100 CE, when “intrusion” into prior mounds was common.

    You dismiss the apparent use of Adena standard metrics by an analogy to long use of the English foot without any evidence whatsoever that the “Fort Ancient Culture” — whatever that is supposed to be — actually did employ Adena metrics. Ohio Valley archaeologists now realize the concept of a “Fort Ancient Culture” is a false one (see Woodland Period Systematics in the Middle Ohio Valley) that now collapses without Serpent Mound as its central defining site. What happened during that period involved different groups, some native and some transient, with no real evidence of major earthwork construction near Adams County.

    Your conjecture that the newly analyzed charcoal may derive from old Adena “cooking fires” that mysteriously lasted hundreds of years on the surface is likewise entirely speculative.

    You’re on extremely weak ground here, especially since you so heavily invested in a late Woodland date before the new findings were in, even to the point of giving a public talk at Serpent Mound at which you dismissed the idea of a different date as practical nonsense.

    On the other hand, some of us were quite a bit more insightful. Before the new findings were announced, I estimated the date would be determined as 250 BCE, which was pretty close to the mark, and I had good reasons.

    You should be big enough to admit that you were mistaken. YOU may wish to continue to deny the identity of the builders of Serpent Mound, but WE know who built it, and that “we” is an awful lot of folks.

    –Geoffrey Sea

    • Geoffrey,

      Thanks for sharing your insightfulness with readers of this blog.

      There is no point in my commenting upon your speculative interpretation of the Portsmouth Earthworks. You and Mr. Hagar certainly are entitled to your opinions.

      I do wish to address your serious accusation that I have somehow “fudged” the issue of where in the mound my team recovered the 1991 charcoal. In our published article (and in the images posted on this blog) you can see exactly from where we took the samples and it is quite clearly well below the sediment added by Putnam. And, in so far as there is any stratigraphy evident in the lower portion of the profile, the charcoal is from the “basal layer.”

      When I provide photographs and diagrams showing where we took the samples, I don’t see how you can accuse me of “fudging” anything.

      Finally, I have no emotional investment in the age of the Serpent. It may well prove to be an early Woodland effigy mound. If reliable radiometric dates are ever forthcoming to demonstrate such an antiquity, I will cheerfully present the results in another post here on this blog.


      • Brad,

        Well all interpretations of “effigies” are speculative aren’t they? Especially such labeling of “Alligator Mound” which isn’t an alligator (there’s nothing close to agreement on what it may be) and Serpent Mound which is no identifiable species of snake and could be a river emerging from a spring or a flock of birds.. And both of them are portrayed geometrically which could categorize them as geometric earthworks.

        On the contrary, as Hagar detailed in his well-referenced article that was a founding work in archaeoastronomy, the Portsmouth Works clearly represent a rattlesnake, with a four-ringed rattle identical to the way rattles were often portrayed in Native American art, and exactly analogous to the Pyramid of the Sun at Chichen Itza, which overtly represents the rattle of a rattlesnake, with snakes that travel up and down the pyramid corners at equinox. (Actually, Hagar was confused about which end was the rattle, but can be forgiven for that since both ends incorporate the number 4, a number associated anatomically with rattlesnakes.)

        Moreover, Hagar showed very convincingly that the Portsmouth Works formed a shadow-image of the arc of the sun, the sun’s path being represented throughout Woodland Indian (and Mayan) iconography as a serpent in the sky. So perhaps there is really only one effigy mound in Ohio — Portsmouth.

        As to the source of the 1991 samples, you have publicly acknowledged that the Serpent Mound results were not as robust as your results for “Alligator Mound,” because in the latter case you were able to find charcoal at the very base of the earthwork, unlike in the former case. My understanding was that this deficiency was the justification for the recent investigations headed by Romain. If the 1991 results had been robust, the recent investigation may not have been justified.

        That you now change your story is curious. I certainly hope that you will not stand in the way of changing the signs, displays, and other public information about Serpent Mound to reflect the new scientific consensus.

        • Geoffrey,

          I am not claiming that the 1991 radiocarbon dates proved anything — and I have not changed my story. Clearly, dating particulate charcoal that wasn’t recovered from a discrete feature won’t give you a definitive result. When we began our excavations in 1991 we expected to find the ash layer referred to by Putnam at the bottom of the mound. If we could obtain charcoal from such a layer, it would provide a reasonably definitive date for the construction of the mound. In the absence of such a layer, we did the next best thing. We took soil samples from the most intact portion of the mound to look for charcoal that could be dated. We realized at the time that whatever dates we got would have to be regarded as tentative, but we figured it was better than having nothing to show for our efforts.

          As I understand it, based on Romain’s presentation, the charcoal obtained by his team also did not come from a discrete feature. The samples consist of particulate charcoal from mound fill and from what Bill called disturbed A horizon. My point is that these dates are no better than the dates my team obtained in 1991. Neither set of dates is conclusive.

          Before rushing to re-write the textbooks and change the signage at the site based on these new but unimproved results, we should try other means of dating the mound more reliably, such as the OSL dating technique that I mentioned in my blog post.


          • I doubt any “textbooks” worth the name corroborate the 11th century date, which never represented any scientific consensus. It was the posting of the signs that do state that date as definitive that was the error.

            Why does Romain’s dating require “proof” (a nonexitent thing in science) but your 1991 dating seems to only have required that it was proffered by certain persons who had the authority to post signs?

            It is an elementary consideration that when charcoal from a given site that has admittedly undergone disruption shows two different periods of dates, the earlier date wins in terms of determining original construction. Indians of the Late Woodland Period were known to engage in “intrusive mound-building” at earlier sites, and this is the most likely explanation of the charcoal found in 1991.

            The attempt to date Serpent Mound by other means has already been accomplished. Serpent Mound is a geometric earthwork, with architectural and ethnographic features that identify it with the Adena Civilzation. This analysis informed Romain’s work — he said it was a Middle Woodland site before radiocarbon confirmed an earlier date. I said (before the latest results) that it appears to be an Early Woodland site, based on a number of considerations.

            The new radiocarbon supports this analysis, while the 11th century date lacks any support.

          • Geoffrey, You’re entirely wrong about the interpretation of radiocarbon dates on particulate charcoal. Neither date “wins.” They’re both suspect. And actually it’s easier to account for older charcoal in a mound — especially when the earth used to build the mound can be expected to have come from deposits in which that older charcoal could have originated. It’s harder to account for “younger” charcoal in an old mound. The essential problem is that neither set of dates come from charcoal that can be reliably linked to the construction of the mound.

            No one ever said Romain’s dating required “proof.” The 1991 study was published in a peer-review journal, which doesn’t necessarily make it “true,” but it does mean it was reviewed and approved by other professionals. And no one ever said the 11th century date was “definitive.” All scientific knowledge is provisional and if better dating confirms the Adena date I’ll be happy to acknowledge it. If you actually read the 1991 report you will find that the conclusion that Serpent Mound is best understood as a Late Prehistoric earthwork is supported by much more than the radiocarbon dates.

            Finally, with regard to “textbooks” that accept the 11th century date, I am appending a few such titles that I have close at hand. You, of course, are free to conclude that they aren’t “worth the name.”

            Fagan, Brian
            2000 Ancient North America: the archaeology of a continent. Thames & Hudson, New York.

            King, J.C.H.
            1999 First peoples, first contacts: native peoples of North America. British Museum Press, London.

            Penney, David W.
            2004 North American Indian Art. Thames & Hudson, New York.

            Thomas, David Hurst
            2000 Exploring Native North America. Oxford University Press, New York.

          • But why do you assume I have not read your 1991 paper? Of course I have, and you and I have discussed the salient issues. That is how I know that your personal opinions about Serpent Mound being “Fort Ancient Culture” as you insist on calling that non-entity, are lacking support.

            It should be noted that those sources who mistakenly took your word for the Serpent Mound date are all more than a decade old as you list them, from the period before it was commonly understood that large-scale corn agricultural did not come to the Ohio Valley until sometime late in the Late Woodland period, that the designation “Fort Ancient Culture” is an unhelpful fiction (see Mainfort and Applegate’s volume at ), and that the principal earthworks of the Valley were funereal not “ceremonial” despite the ceremonial promotional campaign.

            Since the Mainfort-Applegate volume in 2006 and a number of genetic studies, there is a clearer understanding that Adena-Hopewell describe a unitary contiunuos civilzation (best called Adena), and that the Late Woodland Period in the region was one of multi-cultural interaction in the valley, not anything that can be described by any one “culture” name, nor involving large new earthwork ventures like Serpent Mound.

            The smoke has also cleared as to the staged progression of earthwork construction, with Serpent Mound functionally akin to other EARLY Woodland sites like Portsmouth and the Junction Group. An article of mine describing the archaeoastronomical significance of the Junction Group has just been published at Serpent Mound has a very similar functionality marking it as roughly contemporaneous, as will be made clear in forthcoming work.

            As to the two radiocarbon dates the actual logical conclusion is to accept the earlier date because the later one can be attributed to intrusive mound-building, which you seem to not want to acknowledge. Your proposal that older charcoal from “campfires” could have survived on the surface to be scooped up for the mound is weird — It might happen in the desert southwest, but you’d have an extremely hard time demonstrating that old charcoal survives more than a few seasons on the surface in water-logged Ohio.

            It is unfortunate, Brad, that you seem unable to detach your personal stake in the 1991 work from the need to objectively appraise new information. Given your strong avowed devotion to your own hypotheses, I trust you will be wise enough to recuse yourself from all decision-making on questions such as whether the signs or museum displays at Serpent Mound should be changed. That is a matter for parties without that kind of proprietary interest and for the tribes that represent descendants of the builders. By the way, the original “Adena” sign remains at the site, more accurate than ever.

  4. […] Who Built Serpent Mound? – dunno. […]

  5. […] Great Serpent Mound dates (probably) from the eleventh century, a period when people we call the Hopewell culture were building complex […]

    • Um, are you trying to get everything wrong? The newest radiocarbon dating for SM show that it was built between 400 BCE and 1 CE, during the Early Woodland Period. Neither this period nor the period of the 11th century are “Hopewell.” and “Hopewell” is an out-dated term. There were no “Hopewell” Indians.

  6. The Great.Serpent Mound was built by Lilith as a present to Lucifer
    For leading Adam and Eve I to sin.

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