The Monte Verde archaeological site in Chile, discovered in the 1970s, revolutionized the thinking about when humans entered the Americas, with scientists calculating decades ago that this former abode for ancient hunter-gatherers was about 14,500 years old. But a new study suggests it is much more recent than that.
Researchers said a fresh analysis of this Ice Age creek valley site found it dates to between 4,200 and 8,200 years ago. Such a date would make Monte Verde irrelevant to the longstanding scientific debate about when the initial peopling of the Western Hemisphere occurred.
"This finding suggests a later date of human arrival to the Americas than is widely believed," said University of Wyoming archaeologist Todd Surovell, lead author of the research published on Thursday in the journal Science.
The researchers used three scientific dating methods on material from in and around Monte Verde, located in southern Chile about 36 miles (58 km) from the Pacific coast.
"We sampled in the site area. We also sampled the same landforms upstream and downstream of the site," Reuters quoted Surovell as saying.
"These landforms are continuous throughout the valley, and our dating of them was consistent in all locations. We placed these into stratigraphic (soil and rock layers) context, and the dating errors of the previous investigators were immediately apparent," Surovell said.
Testing in 1997 concluded the site was 14,500 years old. That would make it more than 1,500 years older than the previous earliest-known human occupation sites south of the continental ice sheets that covered parts of North America at the time. Those sites were associated with North America's Clovis culture, known for distinctive stone tools and named for a locale in New Mexico.
Because Monte Verde was considered older and was thousands of miles south of the Clovis locations, scientists saw it as evidence that people must have been in the Americas much earlier than the Clovis sites had indicated.
Humans are thought to have crossed from Siberia into Alaska over an Ice Age land bridge, then later journeyed south.
The new research dated pieces of wood, sand deposited by the creek and a layer of ancient volcanic ash.
"The dating of the volcanic ash was especially important," Surovell said.
The ash was determined to have been deposited about 11,000 years ago. It was in a layer that was below the evidence of occupation, showing that the human presence must have come after that date, Surovell said.
Within the age range indicated by the new testing, Surovell said the Monte Verde human occupation most likely dates to 6,000 to 8,000 years ago.
Surovell said the site's older age was calculated using a technique called radiocarbon dating on wood recovered there. Surovell said while the wood indeed was 14,500 years old, it greatly predated the human occupation and was simply mixed among older material trapped in the banks of the creek.
"Imagine the stream undercutting the bank as it meanders in the valley. Materials in the bank then get transported and redeposited by the stream," Surovell said.
Vanderbilt University anthropologist Tom Dillehay, who has studied Monte Verde extensively since the 1970s, cited "many methodological and empirical errors" in the new study.
Its interpretation of the wood, Dillehay said, "disregards a vast body of well-dated cultural evidence associated with Monte Verde, including stone tools, wooden and bone artifacts, edible plant remains including seaweed and potatoes, hearths, human footprints, and animal meat and hide remains."
"These and other elements constitute a complex cultural context that has been extensively documented over five decades of interdisciplinary archaeological research," Dillehay said. "In turning to their data, it is a mixture of inventions and misunderstandings. They saw what they wanted to see, and came to the site with predetermined conclusions."
The timing of the peopling of the Americas remains contentious.
"Monte Verde is internationally recognized as one of the most significant archaeological sites on the American continent, having played a decisive role in replacing the longstanding 'Clovis First' paradigm," Dillehay said, a theory positing that the first inhabitants of the Americas arrived approximately 12,800 years ago.
Surovell said the new findings show Monte Verde postdates the Clovis sites.
"The Monte Verde site is still important for understanding the Holocene (geological epoch, beginning 11,700 years ago) human occupation of its region, but it no longer has much significance for understanding the initial peopling of the Americas," Surovell said.
