America is the last continent that humans settled. But when the first ancestors of the Native Americans arrived there is highly controversial. Archaeological finds in a cave in Mexico are now fueling the discussion. Because researchers have discovered hundreds of stone blades, animal bones and plant remains there that are over 30,000 years old. This suggests that people were present in this region some 10,000 years earlier than previously thought. You must have immigrated to America before the peak of the last ice age. The stone tools also have a design that is unlike any other documented so far on the continent.
The first people to set foot on the American continent came from Asia, as DNA comparisons show. At that time, these first immigrants probably moved across the Bering Strait to the new continent. Because during the last ice age, a 1,600 km wide and almost 5,000 km long land bridge connected Asia and North America. However, when this first settlement of the New World took place is still puzzling – and hotly debated. For a long time, the hunters of the Clovis culture, who left traces in many places in North America around 13,000 years ago, were considered the origin of all indigenous people of this continent. According to this theory, their immigration only became possible when an ice-free corridor opened between the eastern Laurentide ice sheet and the Cordillera ice sheet located in western North America. Only this passage cleared the way for the Clovis hunters to colonize the continent – so this long dominant view.
Find in a mountain cave in Mexico
But since then, archaeologists have discovered traces of human presence in many places in North and South America, some of which are several thousand years older than the Clovis culture. These include a 14,500-year-old mammoth slaughterhouse in Florida, but also relics from the southern tip of South America that are up to 18,000 years old. In view of the enormous distance of these settlement sites from the probable place of arrival of the first “ancient Americans”, this has long raised doubts about the Clovis hunters as first arrivals – and also the timing of their arrival. Accordingly, the first people should have come to America much earlier, possibly even at the height of the last ice age or shortly afterwards. Because the path through the ice-free corridor was still closed at the time, these first arrivals had to migrate south along the Pacific coast instead. Despite the finds of pre-Clovis relics, this theory of earlier arrival remained controversial.
Now a discovery in the highlands of Mexico provides new evidence of a far earlier settlement of America by humans. They tracked down Ciprian Ardelean from the Autonomous University of Zacatecas and his colleagues during excavations of the Chiquihuite cave lying on the mountain slope at 2,740 meters above sea level. The archeologists had already discovered the first signs of an early presence of humans during a test excavation there in 2012. In 2016 and 2017, they therefore carried out an extensive excavation. In several layers of the cave floor, the researchers came across animal bones and plant remains as well as stone tools that were man-made. In order to determine the age of these finds, the researchers performed radiocarbon dating for 59 samples and also dated samples of rock from the found layers using the optically stimulated luminescence.
More than 30,000 years old
The dates indicated that the oldest finds in this cave could have been around 30,000 years old. “According to our results, the find layer C begins at 33,150 to 31,400 years – and thus before the last glacial maximum,” report Ardelean and his team. According to this, people must have been present in America before the peak of the last ice age and have reached Mexico. However, it remains open who these people were. Because the scientists have not succeeded in isolating the DNA of the former cave dwellers. The design of the stone tools, however, indicates that it could have been a culture of its own, as yet unknown. Because they differ significantly from those previously known from America, as the archaeologists explain.
The stone tools include variously shaped blades, tips and wedges, which have been manufactured in some complex ways. Most of these tools also do not consist of the rough, gray limestone lying around everywhere, but of greenish and blackish colored, particularly dense and even variants of this rock. These occurred only sporadically in the vicinity of the cave and must therefore have been specifically searched for. “The systematic geological selectivity that emerges in the manufacture of these tools speaks for a conscious choice and for a deep knowledge of the stone raw materials available,” said Ardelean and his colleagues. Combined with the special design, this collection of finds represents a stone culture that is unique to any one previously known from America.
According to the researchers, their findings thus provide further evidence of the early presence of humans on this continent and at the same time illustrate the cultural diversity that has existed from the very beginning. Ruth Gruhn of the University of Alberta sees it similarly. In an accompanying comment, she writes: “This Mexican site is now being joined by around half a dozen other documented archaeological sites that suggest evidence of human settlement 30,000 to 20,000 years ago.” It was thus clear that the theory of Clovis culture as The starting point of all early cultures on this continent is out of date. “It is clear that people were present in North America long before the development of Clovis technology,” said Gruhn. But who these people were, when and where they set foot on the continent and how they moved on from there is still a mystery.
Source: Ciprian Ardelean (Universidad Autónoma de Zacatecas, Mexico) et al., Nature, doi: 10.1038 / s41586-020-2509-0