Estimates of the age of the earthwork are now radically revised as the result of a new radiocarbon analysis, suggesting that the mound is about 1,400 years older than conventionally thought. The new date of construction is estimated at approximately 321 BCE, one year after the death of Aristotle in Greece.
Signs and other interpretive material have been made obsolete virtually overnight, along with ideas about the indigenous culture responsible for the astounding artwork. A paper by an eight-member team led by archaeologist William Romain has been published in the Journal of Archaeological Science with a free-access summary available on Romain’s website.
The new data alters thinking about three things: the culture responsible for the mound; the Native groups that are direct descendants of those builders; and the purpose and iconography of the work. Dispatching other theories about Serpent Mound’s origin, Romain’s summary concludes: “Both the consensus of opinion and radiocarbon evidence suggest an Adena construction.”
Traditionally, Serpent Mound was attributed to the Adena Culture or Civilization, based on an adjacent conical Adena burial mound, and the similarity of style of the effigy with many other Adena earthworks of the Ohio Valley. Just 30 miles southeast of Serpent Mound were the Portsmouth Works, with only a few surviving remnants, interpreted by the pioneering archaeoastronomer Stansbury Hagar as representing the effigy of a rattlesnake 50 times larger than Serpent Mound, both with species identification features indicative of the timber rattlesnake.
However, an investigation in the 1990s found two charcoal samples in Serpent Mound that dated to the later time of about 1070 CE. Site managers then attributed construction to the Late Woodland “Fort Ancient Culture,” even though the so-called “Fort Ancient Culture” has been disassociated from the Fort Ancient earthwork in Warren County, Ohio, and is not known to have built large earthworks. Indeed it has been misnamed a “culture” and is now understood more as an interaction phenomenon involving multiple ethnolinguistic groups that came together in the Ohio Valley in the Late Woodland Period, between 500 CE and 1200 CE.
“Fort Ancient Culture” is neither a fort, nor ancient, nor a culture. Yet it has been identified as the author of Serpent Mound, except in those circles where the mound has been attributed to giants or space aliens or giant space aliens.
The “Fort Ancient” designation has been problematic, because as an unreal entity, the so-called culture has no clear descendants. Adena, on the contrary, is strongly identified from archaeology, genetics, and historical linguistics as Algonquian, its descendants being the Anishinaabeg, the Miami-Illinois, the Shawnee, the Kickapoo, the Meskwaki, and the Asakiwaki.
The new investigation by Romain and others found much older charcoal samples in less-damaged sections of the mound. The investigators conjecture that the mound was originally built between 381 BCE and 44 BCE, with a mean date of 321 BCE. They explain the more recent charcoal found in the 1990s as likely the result of a “repair” effort by Indians around 1070 CE, when the mound would already have been suffering from natural degradation. Late Woodland Period graves at the site suggest the earthwork continued to serve a mortuary function, and that this was the principal nature of the site, directing spirits of the dead from burial mounds and subsurface graves northward, not a place to conduct large ceremonial gatherings as has been suggested by tourism/promotion interests.
Without Serpent Mound as a “ceremonial center” at its geographic core, the notion of a “Fort Ancient Culture” has literally been gutted.
That the new date adds a very sophisticated earthwork to the corpus of the Adena, whom some had considered “primitive,” lends new weight to reconsideration of the non-distinction between “Adena” and “Hopewell” and the need for a general revision of the naming conventions for prehistoric cultures of the Ohio Valley. A simplified revised chronology would see the Adena Civilization leading straight to the historic Central Algonquian tribes in the heartland of the Ohio Valley.
The new study comes just as Serpent Mound is being advanced for addition to the UNESCO World Heritage List, a nomination that will have to be rethought as a result of the new date and its implications. Members of the Central Algonquian tribes now have scientific claim to be considered the heirs of Serpent Mound, raising questions about the structure of site management, now conducted by the Ohio History Connection and Arc of Appalachia Preserve System.
What is certain is that ancient Ohioans were not only building extremely sophisticated geometric works that rivalled or surpassed those of contemporary classical Greece, but they were also repairing or renovating them over millennia.