A international team led by study co-author Jesus Jorda, of the Spanish National University in Madrid, challenges the hypothesis that Neanderthals persisted in southern Iberia and were contemporary with modern humans who had just arrived. 
     According to new radiocarbon dating the Neanderthals died out around 45,000 years ago - 10,000 years earlier than has previously been proposed. A precise chronology is crucial to understanding what factors played a role in the Neanderthals' demise and the degree to which Neanderthals and humans interacted and possibly interbred.
     The researchers applied a new dating technique to bone samples taken from sites in southern Iberia, including two previously considered to have been the last refuges of the Iberian Neanderthals. To rule out possible intrusions by carnivores which might contaminate the samples, they selected mammal bones bearing clear signs of human manipulation such as cut marks, and marks of hammering or intentional breakage. 
     Jorda points out that more work will need to be done and more sites and samples will need to be examined before a truly strong case can be made for abandoning the coexistence theory, but if confirmed through additional research the new hypothesis has enormous implications for theories regarding the reason for Neanderthal extinction.
     The new research supports the view of archaeologist Olaf Joris of the Romano-Germanic Central Museum in Mainz, Germany, who concludes that the most-recent Neanderthals probably lived around 42,000 years ago.
     Other archaeologists are not convinced. Paul Pettitt, an archaeologist at Durham University in England, says "We shouldn't get too carried away over results that amount to a few radiocarbon dates from two sites." Joao Zilhao, of the University of Barcelona, notes that part of one cave where Neanderthals most recently lived has not been re-examined.

Edited from ScienceNews, Popular Archaeology (4 February 2013)