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.
Re-writing Prehistory books
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.
Cueva Antón (Murcia) is the only site that still provides recent dates in accordance with what has until now been postulated in relation to the persistence of the Neanderthals. However, neither the technological remains are clearly related to the Neanderthals nor are the dated charcoal samples perfectly associated with the lithics.
In view of the new data according to Jordá "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 adds.
Concerning the possible coincidence of both groups in the cantabrian area, the researcher is cautious. "Sites as La Güelga (Asturias) are being analyzed anew in order to determine if co-existence occurred. We must wait for the results to verify or not this hypothesis" he concludes.
Rachel E. Wood, Cecilio Barroso-Ruíz, Miguel Caparrós, Jesús F. Jordá Pardo, Bertila Galván Santos and Thomas F. G. Higham. "Radiocarbon dating casts doubt on the late chronology of the Middle to Upper Palaeolithic transition in southern Iberia", Proceedings of the National Academy of Sciences (PNAS). 04-02-2013. DOI: 10.1073/pnas.1207656110