Serpent Mound arguably is the most recognizable icon of ancient America. Therefore, you might be surprised to learn that much about this mound is arguable, including its age.
Serpent Mound was long thought to be an Adena mound, dating to between 800 B.C. and A.D. 100, but opinions shifted in the 1990s when a team of archaeologists obtained radiocarbon dates on charcoal recovered from the mound.
The results seemed to indicate that the Great Serpent was built by the Fort Ancient culture around A.D. 1120. But a study presented at last month’s Midwest Archaeological Conference in Columbus suggests it might be an Adena mound after all.
Serpent Mound was excavated by Frederic Ward Putnam in the late 1800s. He didn’t find any artifacts in the serpent, but there were two other mounds nearby in which he found artifacts that belong to what we now identify as the Adena culture.
Putnam also found traces of an Adena village near the mound. This is why it was widely believed that Serpent Mound was an Adena effigy mound.
But Putnam also found traces of a large village of the Fort Ancient culture overlying the earlier Adena village, and another nearby mound contained Fort Ancient artifacts. If you date the mound based on the age of what else is in the vicinity, you could say it was built by either the Adena or the Fort Ancient.
In 1992, I worked with a team that reopened one of Putnam’s original excavation trenches and recovered the charcoal that produced the Fort Ancient dates. Unfortunately, the charcoal did not come from a discrete feature, such as a fire pit. Instead, it consisted of small flecks mixed into the body of the mound.
That means we’re not really sure what we dated. It could have been the remains of fires burning when the mound was being built. Or it could have been charcoal from Fort Ancient-era campfires that somehow worked its way into an older mound.
Last year, William Romain and a team of scientists from various universities and private archaeology firms went to Serpent Mound to conduct research aimed, in part, at obtaining better dates for the mound’s construction. They recovered numerous flecks of charcoal in soil cores from across the mound, including several of which yielded dates of between 400 and 80 B.C.
These results appear to indicate that the Adena culture built the mound as originally thought. However, these samples have the same issues as the charcoal recovered by the 1992 team. The charcoal could be from old Adena fire pits that were dug up and incorporated into the effigy by Fort Ancient or even later mound-builders.
Does knowing the age of Serpent Mound really matter? Absolutely. Without being able to place it in time and understand its historic context, this mound, however magnificent, is little more than a generic icon of Ohio’s ancient American Indian heritage.
For a variety of reasons, I’m still convinced that the Serpent Mound was built by the Fort Ancient culture. But the new dates make it clear that the debate is far from over.
