Remote islands aside, Argentina's “Southern Cone” was probably one of the last places on Earth to be occupied by humans. A study of bones deposited at the archaeological dig site Arroyo Seco 2 makes the case that humans reached the area at least 14,000 years ago, substantially earlier than previously suspected. Such an arrival would easily predate the Clovis culture, once thought to have been responsible for taking humans to the extremities of the Americas.
The Arroyo Seco 2 site (not to be confused with the city Arroyo Seco further north) contains a rich store of mammal bones from late in the last Ice Age. Dr Gustavo Politis of the National University of Central Buenos Aires claims to have found evidence that many of these bones were brought there by humans and butchered using stone tools.
The bones have been dated to between 13,000 and 14,000 years ago, an unexpectedly early time for humans to have arrived so far south.
In PLOS One, Politis presents a detailed study of the Arroyo Seco 2 site. He records dozens of bones from extinct Ice Age mammals, along with an even larger number of what he calls “lithic artifacts”, primarily stones that appear to have been shaped into tools.
A leg bone from an extinct South American horse from three angles (A). A detailed view of notches and flake-scars that are thought to have been made by stone tools, rather than teeth; the dotted lines illustrate the maximum depth and breadth of notches and flake-scars. Politis et al/PLOS ONE
Politis admits there are non-human explanations for the older discoveries – some of the animals may just have died at this location, and stones may have been shaped more recently or broken by other forces. However, the sheer volume of material, most of it concentrated at depths between 0.4 and 1.1 meters (1.3 and 3.6 feet), suggests human involvement.
The fact that people were at Arroyo Seco 2 is less important than when they got there. Precise dating of specimens such as these can be difficult, and when Politis had different laboratories date the same specimens, he got estimates that varied by up to 5,000 years – a huge difference on this sort of timescale. Much of the variation comes from the way the labs treat the bones prior to analysis. To reduce the uncertainty, Politis had eight laboratories around the world working on 14 specimens. He concludes that the “earliest human signal” was 14,064 years ago and occupation of the site continued sporadically for a thousand years.
Anthropologists agree that humans reached the Americas by crossing what is now the Bering Strait towards the end of the last Ice Age, and dispersed through North and South America from there. However, much debate continues on the timing and origins of the great migrations that brought people to parts of the continents for the first time.
Most early human remains in the Americas come from the Clovis culture, who probably arrived 13,000 years ago and represent the ancestors of almost all living Native Americans. For a long time, the dominant theory held that most of the Americas were first conquered by Clovis people. However, in recent years this has been challenged with discoveries of what appear to be pre-Clovis settlements in many parts of the continents, and Politis considers his discovery powerful evidence that South America was inhabited long before the arrival of the Clovis peoples.
Map showing Arroyo Sec 2's location, with a photograph of the dig site.Politis et al/PLOS ONE