Issue Date: June 18, 2012
Neanderthals May Have Been Cave Artists
Scientists spelunking in 11 Spanish caves have used an uncommon radioactive-decay method to date Paleolithic wall art, showing that some of the paintings may have been made by either Neanderthals or the earliest humans in Europe (Science, DOI: 10.1126/science.1219957). The dating method uses mass spectrometry to measure trace levels of uranium and thorium found in thin crusts of calcite that build up on the cave art, explains Alistair W. G. Pike, a radioisotope specialist at the University of Bristol, in England, who led the study. The water that deposited this calcite contained trace amounts of dissolved uranium but no thorium. Thus, any thorium present in the calcite is the result of uranium’s radioactive decay into thorium. By comparing ratios of thorium and uranium in calcite crusts on the art, the team was able to establish minimum ages for some 50 Spanish cave paintings. In three cases, the art was dated to between 35,600 and 40,800 years ago. Neanderthals were present in Europe during this era, and modern humans likely appeared there around 41,000 to 42,000 years ago, says João Zilhão, a Neanderthal expert at the University of Barcelona who was involved in the study.
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