Monday, February 04, 2013

Did the Last Iberian Neandertals Die Out Before the Arrival of Modern Man?

The theory that the last Neanderthals –Homo neanderthalensis– persisted in southern Iberia at the same time that modern humans –Homo sapiens– advanced in the northern part of the peninsula, has been widely accepted by the scientific community during the last twenty years. An international study, in which researchers of the Spanish National Distance Education University (UNED) participate, questions this hypothesis.

"It is improbable that the last Neanderthals of central and southern Iberia would have persisted until such a late date, approximately 30,000 years ago, as we thought before the new dates appeared" assures Jesús F. Jordá, researcher of the Department of Prehistory and Archaeology of the UNED and co-author of the study published in Proceedings of the National Academy of Sciences (PNAS).

The scientific team, with researchers from Oxford University (United Kingdom), Australia National University, UNED (Madrid), University of La Laguna (Tenerife), Archaeological Museum of Lucena (Córdoba), and National Museum of National History (Paris), applied a new technique in order to repeat analyses at the sites of Jarama VI (Guadalajara) and Zafarraya (Malaga), considered up to now two of the last refuges of the Iberian Neanderthals.

To the usual radiocarbon dating method, the ultrafiltration protocol was added, which aims to purify the collagen of the bone samples from contaminants. The AMS dating technique was applied that requires minimum sample quantities.

The scientists, by applying this new method, assure that the neanderthal occupation of the sites did not last until as late as previously thought; instead it should be placed approximately 45,000 years ago.

"The problem with radiocarbon dating alone is that it does not provide reliable dates older than 50,000 years" explains Jordá. An additional problem is contamination; the older the samples are the more residues are accumulated. If contaminants are not removed the obtained dates are incorrect.

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