The Greenwood Democrat has been contacted several times about the destruction of mounds that are located in fields along hwy. 10 East. The callers usually complain that the mounds were created by Indians as burial sites and that construction is destroying a piece of history.
The mounds are a bit of a mystery, even among archaeologists, however the one thing that they do seem to agree on is that the earthen structures are not man made.
Commonly known as mima mounds, prairie mounds or prairie pimples, are a naturally occurring phenomenon that can be found all across the United States and on every continent except Antarctica.
“They are definitely natural,” said Tim Mulvihill, Station Archaeologist with the Arkansas Archeological Survey with the University of Arkansas Fort Smith. “We have dug into prairie mounds when we are asked to see if something is constructed by humans and we don’t find human artifacts in the mounds. Usually you can see basket loading in mound like you would see in Spiro or the Cavanaugh Mound in Fort Smith where you can see where they brought up basket loads of fill and piled them up in an actual construction method. Prairie mounds have more of a natural stratigraphic profile.”
A study by George W. Cox of San Diego State University in 1987 attributed the mounds to pocket gophers, a burrowing rodent that weigh less than a quarter of a pound. Cox proposed that the animal pushed soil uphill to create the mounds. He tested his theory by placing iron cap nuts in active pocket tunnels at the edges of mounds and observing their movement uphill using metal detectors. Cox concluded that, “Rodents are the builders of Mima mounds, the largest most widespread landscape features produced by an mammal other than man.”
Cox states that a gopher could move anywhere from one to ten tons of soil in a year and could potentially create a mound, such as those found in San Diego, in as little as 110 years.
In 2014 an article by Jane Palmer for BBC.com a computer model was created that seemed to prove Cox’s theory at least as far as the west coast of the United States is concerned, but states that factors such as plant life, erosion and termites could play a role.
The biggest obstacle in determining the cause of the mounds is time. "One of the challenges with mima mounds is that, in many cases they are actually very old, and that makes it very difficult to work out what might have been going on," said Michael Cramer, a biologist at the University of Cape Town in South Africa. “Scientists estimate that some of the mounds could be as much as 30,000 years old with an undisputed slow growth rate that presents a challenge for traditional field experiments.”
So while theories abound about the origin of the mounds, more than 30 if you dig deep enough, one thing seems certain; humans were not involved.
“That is not to say that humans have not used them in the past to camp on,” said Mulvihill. “But they don’t seem to be a hotspot for human activity.”