Marks found on the 21,000-year-old bones of a giant, armadillo-like animal in Argentina may be the oldest evidence of humans in southern South America.
If confirmed through additional excavation and research, the findings could push back the date humans were known to be living in the area by about five millennia, to the end of the last glacial period. That would predate the currently accepted arrival of humans on either American continent by at least 1000 years, says at the Pasteur Institute in Paris, France.
鈥淗umans could have been present in South America much earlier than we thought and even earlier than what is assumed of the entry of people in North America,鈥� he says.
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快猫短视频s generally believe that people migrated across the Bering Strait from Asia into North America between 15,000 and 20,000 years ago and then spread down into Central and South America, says Rascovan. However, the proposed dates have stirred significant controversy among experts since the mid-19th century.
Recently, the apparent discoveries of and jewellery made of giant sloth bones in Brazil from up to 27,000 years ago have made researchers question whether humans reached the Americas much earlier, he says.
Further south in the 鈥渃one鈥� that includes southern Chile and Argentina, the oldest butchered bones generally date to about 16,000 years ago, says at the National University of La Plata, Argentina. A few other studies suggesting humans were eating animals in the region more than 16,000 years ago have among the scientific community.
New discoveries from a construction site along the Reconquista river in greater Buenos Aires appear to support the idea that humans appeared there earlier, says Delgado. Surveyors uncovered multiple hip and tail bones and shell parts of what was once a 1.5-metre-long mammal called a glyptodont, which resembled an armadillo, in this case from the genus Neosclerocalyptus.
Its bones and shells were marked by 32 straight cuts that looked like they had been made by stone tools, given the inner stripes within the grooves and their V-shaped form. Radiocarbon dating placed the specimen in the last glacial maximum, as late as 21,000 years ago.
Delgado, Rascovan and their colleagues scanned a selection of cut marks and created 3D models for closer analysis. The angles of the entry point of the grooves and the depth of the cuts reflect a pattern that is consistent with butchering of fresh bone, they say.
The bones showed no signs of scrapes from the teeth of carnivores or scavengers. The team鈥檚 investigation of the sediment around the bones and shell suggests that the animal parts were buried quickly in partially wet climate conditions like those of the region 21,000 years ago.
The findings are 鈥渁n extraordinary claim鈥� given the currently accepted archaeological evidence about human presence in South America, says at the University of Alaska Fairbanks. But the study lacks critical data like detailed maps of the site and sediment layers, he says. 鈥淭here remains room for ambiguity.鈥�
鈥淎 red flag is the total absence of any associated human-made artefacts with these [bones],鈥� says Potter, adding that the marks might be due to carnivore activity or trampling. 鈥淪tone tools and debris are ubiquitous in actual human processing sites.鈥�
Such evidence may appear as the excavation continues, says Rascovan.
In the meantime, though, Delgado says his team feels confident about the findings since the marks strongly fit with scientific models of cuts made by human tools and patterns that would be followed during butchering.
The discovery could support the hypothesis that humans contributed to the extinction of many of the continent鈥檚 large mammals by the end of the last glacial period, he says.
PLoS One
