An apparent human footprint uncovered by archaeologists in Chile has been dated to 15,600 years old, placing it among the oldest prints ever found in the New World. It’s an intriguing discovery that suggests an early settlement of South America by humans, but not everyone is convinced by the new evidence.
The lone print was uncovered in 2011 at the Pilauco archaeological site in the Chilean city of Osorno. This site underwent excavations from 2007 to 2016, resulting in the discovery of various animal bones, plant matter, simple stone tools, and this apparent human footprint. The finding is particularly significant owing to the dearth of ancient footprints in the Americas, and because of a longstanding debate about the peopling of South America during the Late Pleistocene. The new research, led by paleontologist Karen Moreno and geologist Mario Pino from Austral University in Chile, was published last week in PLOS One.
Other significant footprints in the Americas include 14,600-year-old tracks at the nearby Monte Verde, and a pair of trackways in Mexico dating back to 10,700 years ago and 7,200 years ago. Last year, archaeologists uncovered 29 human footprints on the shoreline of Calvert Island in British Columbia, which were dated to 13,000 years ago. The prints at Monte Verde are the oldest evidence of a human presence in South America, though they remain controversial. That a human footprint may now have been found about 100 kilometers (60 miles) away at the Pilauco site, dating to roughly the same era as the Monte Verde tracks, bolsters the case that humans lived in South America at this time. But at 15,600 years old, it would represent the oldest print ever found in the Americas. That’s obviously a big deal.
For the analysis, Moreno and Pino radiocarbon dated organic plant materials found in the same the layer as the lone footprint. Measurements made by hand, a plaster reconstruction, and a series of x-ray images allowed the researchers to analyze the print in fine detail. They estimated that the print was made by a barefoot male weighing approximately 155 pounds (70 kilograms). Due to its dimensions, shape, and level of preservation, the footprint of Pilauco “corresponds to a right foot impression of an adult human,” and not some other animal, such as a ground sloth, the authors wrote in the new study.
As the new paper pointed out, the print was assigned to the ichnospecies Hominipes modernus (with ichnospecies describing a distinct trace fossil). The researchers believe the print to have been made by Homo sapiens, as no evidence has ever been found to suggest that a human species other than Homo sapiens ever made it to the Americas.
Moreno and Pino also conducted an experiment to test different scenarios of footprint formation. The team extracted soil samples from Pilauco, rehydrating the sediment with various amounts of water. Three people, all featuring body proportions consistent with the presumed original track maker, were recruited to walk across a test bed containing the soggy mixture. The “results demonstrate that a human agent could easily generate a footprint [shape] equivalent to the sedimentary structure when walking on a saturated substrate,” wrote the authors in the study.
That said, the researchers don’t understand why a single footprint was recovered, and not an entire trackway. They cited sediment mixing over time as a likely cause.
But Stuart Fiedel, an archaeologist with the consulting firm Louis Berger Group, interpreted the new research differently. Fiedel doesn’t believe that the footprints found at Monte Verde, nor the one found at Pilauco, are actual human footprints.
“If you compare both of these bean-shaped, filled depressions to actual ancient human footprints, you’ll notice that the outer edge of the real prints is always straight, and does not curve sharply inward from heel to toe, like the Monte Verde and Pilauco impressions,” Fiedel told Gizmodo. “This difference can be seen even in the experimentally produced prints shown in the article.”
What’s more, he said the authors seem to be interpreting the protrusion as the impression left behind by a big toe. But this “is not the normal morphology of human toes,” he said. Nor do the authors convincingly explain why there’s a lump in the middle of the “sole,” added Fiedel.
The apparent stone tools found near the prints, Fiedel argued, are not actually tools but “merely broken pebbles with no evidence of human manufacture of use.” The animal bones, he said, were inconsequential, as “clearly animal carcasses accumulated at this location” some 16,000 to 15,000 years ago.
Fiedel said he believes the print could have been made by a piece of decayed wood, and noted that there were pieces of wood of a similar size and shape to the print found nearby.
Nicholas Felstead from Swansea University said the new paper was interesting, telling Gizmodo that the “reliable radiocarbon dates obtained by the authors makes this discovery pretty compelling.” The work, he said, provides more evidence in support of the Pacific Coastal Migration Route. Indeed, there’s a big debate as to when humans first populated the Americas, with the two main theories being the Pacific Coastal Route hypothesis (also known as the Pre-Clovis theory) and the Clovis First hypothesis.
“Archaeologists on the Clovis First side believe the first humans, the Clovis people, arrived around 14,000 years ago in the far north when the ice sheets had retreated enough to allow passage from Alaska into the northern states of the USA,” Felstead, who’s not affiliated with the new study, wrote in an email to Gizmodo. “The primary support for this theory is that there is no solid evidence for pre-Clovis humans in the Americas. It became the standard model of how and when humans first arrived in the Americas.”
But as Felstead pointed out, other archaeologists believe that humans traveled down the Pacific coast of the Americas much earlier than 14,000 years ago and much faster. Monte Verde in Chile is probably the most famous site related to the Pacific Coastal Route, with footprints dating back to around 14,600 years ago—but these footprints are highly contentious in the debate, he said.
“These new footprints are significant as they provide further solid evidence of pre-Clovis humans in the Americas,” said Felstead. “If indeed human, these footprints provide compelling evidence in support of the Pacific Coastal Migration Route.”
Given the big claim being made by Moreno and Pino and the ambiguity of the both the lone print and the nature of the artifacts found at the site, it would be valuable to have a second research team examine the available evidence. Until then, the debate about when humans first settled South America will continue to rage on.