Humans settled in the Americas much earlier than previously thought, according to new finds from Mexico.
They suggest people were living there 33,000 years ago, twice the widely accepted age for the earliest settlement of the Americas.
The results are based on work at Chiquihuite Cave, a high-altitude rock shelter in central Mexico.
Archaeologists found thousands of stone tools suggesting the cave was used by people for at least 20,000 years.
During the second half of the 20th Century, a consensus emerged among North American archaeologists the Clovis people had been the first to reach the Americas, about 11,500 years ago.
The Clovis were thought to have crossed a land bridge linking Siberia to Alaska during the last ice age.
This land bridge subsequently disappeared underwater as the ice melted.
And these big-game hunters were thought to have contributed to the extinction of the megafauna – large mammals such as mammoth, mastodon and various species of bear that roamed the region until the end of the last ice age.
As the “Clovis First” idea took hold, reports of earlier human settlement were dismissed as unreliable and archaeologists stopped looking for signs of earlier occupation.
But in the 1970s, this orthodoxy started to break down.
In the 1980s, solid evidence for a 14,500-year-old human presence at Monte Verde, Chile, emerged.
And since the 2000s, other pre-Clovis sites have become widely accepted – including the 15,500-year-old Buttermilk Creek site in central Texas.
Now, Ciprian Ardelean, from