New evidence shifts the timeline back for human arrival in the Americas

Ancient artifacts found at an archaeological site in Argentina suggest that humans occupied South America earlier than previously thought.

Sample of the lithic artifacts found in the levels associated with extinct fauna 
[Credit: Politis et al (2016)]

Approximately 13,000 years ago, a prehistoric group of hunter-gathers known as the Clovis people lived in Northern America. Previous research suggests that the Clovis culture was one of the earliest cultures in the Americas. However, more recent research from the Pampas region of Argentina supports the hypothesis that early Homo sapiens arrived in the Americas earlier than the Clovis hunters did.

The evidence for earlier human arrival in the Americas comes from a rich archaeological site in southeastern South America called Arroyo Seco 2. A group of scientists led by Gustavo Politis from CONICET and the Universidad Nacional del Centro de la Provincia de Buenos Aires present the research in a new PLOS ONE study.

Radius bone of Equus neogeus, an extinct American horse, dated to roughly 14,000 years ago. Here you can see 
three views with location of impact from tools. A detailed view of notches and flake-scars; dotted lines
 illustrate the maximum depth and breadth of notches and flake-scars [Credit: Politis et al (2016)]

At Arroyo Seco 2, the researchers excavated ancient tools, bone remains from a variety of extinct species, and broken animal bones containing fractures caused by human tools. They used radiocarbon dating to determine the age of the mammal bones and analyzed the specimens under a microscope.

The analysis revealed the presence of limb bones from extinct mammals at the site, which may indicate human activities of transporting and depositing animal carcasses for consumption at a temporary camp. The bones of some mammal species were concentrated in a specific part of the site, which could indicate designated areas for butchering activities. Microscopic examination also revealed that some bones contained fractures most likely caused by stone tools. The remains were dated between 14,064 and 13,068 years ago, and the authors hypothesize that Arroyo Seco 2 may have been occupied by humans during that time.

The evidence for earlier human arrival in the Americas comes from a rich archaeological site
in southeastern South America called Arroyo Seco 2 [Credit: Politis et al (2016)]

This timeline, along with evidence from other South American sites, indicates that humans may have arrived in southern South America prior to the Clovis people inhabiting the Americas, but after the onset of the Last Glacial Maximum, the last glacial period, which took place 19,000 to 20,000 years ago.

While the characteristics of some of these archaeological materials could be explained without human intervention, the combination of evidence strongly suggests human involvement. Humans' arrival in southern South America 14,000 years ago may represent the last step in the expansion of Homo sapiens throughout the world and the final continental colonization.

Source: PLOS [September 29, 2016]