Tools found in Mexico evidence humans lived in region 15,000 years earlier than previously believed, scientists say.
Tools excavated from a cave in central Mexico are strong evidence that humans lived in North America at least 30,000 years ago, some 15,000 years earlier than previously thought, scientists have said.
Two studies published in the Nature journal on Wednesday said researchers had found artefacts, including some 1,900 stone tools, that showed human occupation of the high-altitude Chiquihuite Cave over a roughly 20,000-year period – spanning from 12,500 years ago to at least 31,000 years ago.
“Our results provide new evidence for the antiquity of humans in the Americas,” Ciprian Ardelean, an archaeologist at the Universidad Autonoma de Zacatecas and lead author of one of the studies, told the AFP news agency.
“There are only a few artefacts and a couple of dates from that range,” he said, referring to radiocarbon dating results putting the oldest samples at 33,000 to 31,000 years ago. “However, the presence is there.”
No traces of human bones or DNA were found at the site, but the study concluded that “it is likely that humans used this site on a relatively constant basis, perhaps in recurrent seasonal episodes part of larger migratory cycles”.
In the second study, evidence from 42 sites around North America indicated human presence dating to at least a time called the Last Glacial Maximum, when ice sheets blanketed much of the continent, about 26,000 to 19,000 years ago and immediately thereafter.
The research also implicated humans in the extinction of many large Ice Age mammals such as mammoths and camels.
Descubren evidencia humana de 30,000 años de antigüedad en la Cueva del Chiquihuite, Zacatecas.
— INAHmx (@INAHmx) July 22, 2020
Translation: [Researchers] discovered human evidence of 30,000 years old in the Chiquihuite Cave, Zacatecas, the National Institute of Anthropology and History in Mexico wrote on Twitter.
Until recently, the widely accepted storyline was that the first humans to set foot in the Americas crossed a land bridge from present-day Russia to Alaska some 13,500 years ago and moved south through a corridor between two massive ice sheets.
Archaeological evidence – including uniquely crafted spear points used to slay mammoths and other prehistoric megafauna – suggested this founding population, known as Clovis Culture, spread across North America, giving rise to distinct native American populations.
But the Clovis-first model has fallen apart over the last 20 years with the discovery of several ancient human settlements dating back 2,000 or 3,000 years before earlier.
The recent findings also suggest low numbers of people entered the continent earlier than previously understood – some perhaps by boat along a Pacific coastal route rather than crossing the land bridge – and some died out without leaving descendants.
Archaeological scientist Lorena Becerra-Valdivia of the University of Oxford in England and the University of New South Wales in Australia said the continent’s populations then expanded significantly beginning about 14,700 years ago.
“These are paradigm-shifting results that shape our understanding of the initial dispersal of modern humans into the Americas,” Becerra-Valdivia added.