The print, which is already 15,600 years old, predates the earliest known evidence of human presence in South America by 1,000 years.
Karen Moreno/PLOS OneEach row corresponds to a tracer, and each column shows the sediment content in the dry, wet, and saturated state, respectively.
Over the course of nine experiments, Moreno determined how much weight a given imprint could have left in the types of sediment it was found in.
She eventually figured out that the pressure that created the right footprint could have been that of a barefoot adult male weighing 155 pounds.
Added to this is the reasonable assertion that no animal could have left a print so similar to a human one. Moreno also expressed her doubts about the hypothesis that this form could have arisen completely by chance.
Eventually, a clever paleontologist assigned the print to Hominipes modernus, a term used for prints that could belong to both modern humans and their closest ancestors.
While some may remain unmoved by Moreno's well-founded claims (after all, evidence of human activity dating back 15,500 years has been found in Texas), it is nonetheless the oldest human footprint ever found in the South.
Sourse: www.allthatsinteresting.com
