Wyoming, US, A new analysis of archaeological sites in the Americas challenges relatively new theories that the earliest human inhabitants of North America arrived before the migration of people from Asia across the Bering Strait.

Conducted by University of Wyoming Professor Todd Surovell and colleagues from UW and five other institutions, the analysis suggests that misinterpretation of archaeological evidence at certain sites in North and South America might be responsible for theories that humans arrived long before 13,000-14,200 years ago.

The researchers' findings appear today in PLOS One, a journal published by the Public Library of Science. The paper is the latest development in the debate over the peopling of the Americas, in which some are now questioning the long-held consensus that the first Americans were hunter-gatherers who entered North America from Asia via the Beringia land bridge up to 14,200 years ago, and then dispersed southward between two large glaciers that then covered much of the continent.

The conclusions of Surovell and colleagues are based on an analysis of buried archaeological deposits, using a new statistic called the Apparent Stratigraphic Integrity Index they developed. While the stratigraphic integrity of early archaeological sites in Alaska is high the sites in more southern locations pointing to possible earlier human occupation show signs of artifact mixing among multiple time periods.

Specifically, the new analysis compared the stratigraphic integrity of three sites argued to contain evidence of earlier human occupation -- two in Texas and one in Idaho -- with the integrity of sites in Alaska, Wyoming and Pennsylvania. The three sites claimed to be older than 13,000 years ago all showed patterns of significant mixing, while the others did not.

The researchers were unable to obtain detailed information about some other sites in North and South America purported to contain evidence of human occupation before 13,000 years ago.

The paper doesn't completely rule out the possibility that humans colonized the Americas at an earlier date. "But if they did, they should have produced stratigraphically discrete occupation surfaces, some of which would be expected to have large numbers of artifacts, the Science Daily news reported.

Source: Oman News Agency