Washington: An international study has questioned a theory, which held 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.
The hypothesis has been widely accepted by the scientific community during the last twenty years.
"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," said Jesus F. Jorda, researcher of the Department of Prehistory and Archaeology of the Spanish National Distance Education University (UNED) and co-author of the study.
The scientific team, with researchers from Oxford University (United Kingdom), Australia National University, UNED (Madrid), University of La Laguna (Tenerife), Archaeological Museum of Lucena (Cordoba), 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.
New analyses were applied to bone remains found in the archaeological deposits in association with Middle Paleolithic stone artifacts. Bones bearing clear signs of human manipulation (cut marks, marks of percussion or intentional breakage) were selected in order to rule out possible intrusions by carnivores.
Despite the fact that samples were collected from numerous sites in southern Iberia, it was only possible to date those of Jarama VI and Zafarraya, as the remaining samples did not contain enough collagen to be dated.
In view of the new data according to Jorda "prehistory books would need revision", especially as new results become available.
"Although it is still controversial to change the theory in force, the new concept, which presents new data indicating that Neanderthals and H. sapiens did not co-exist in Iberia, is becoming accepted," he added.
The study was published in Proceedings of the National Academy of Sciences (PNAS).