Dating sites for scientists
Various geologic, atmospheric and solar processes can influence atmospheric carbon-14 levels.
Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.
Israel Hershkovitz of Tel Aviv University Sackler Faculty of Medicine’s department of anatomy and anthropology.
Hershkovitz led an international team of anthropologists that included Prof.
Marine records, such as corals, have been used to push farther back in time, but these are less robust because levels of carbon-14 in the atmosphere and the ocean are not identical and tend shift with changes in ocean circulation.
A jawbone with teeth recently discovered in Mount Carmel’s Misliya Cave dating back 177,000 to 194,000 years, proves Homo sapiens were present in the Levant at least 50,000 years earlier than previously believed, Israeli scientists announced on Thursday.
But there's long been a debate about whether were the only species capable of thinking this way and engaging in this sort of behavior. "According to our new data Neanderthals and modern humans shared symbolic thinking and must have been cognitively indistinguishable," Joao Zilhao, team member from the Catalan Institution for Research and Advanced Studies in Barcelona, said in a news release.
"On our search for the origins of language and advanced human cognition we must therefore look much farther back in time, more than half a million years ago, to the common ancestor of Neanderthals and modern humans." Questions about whether Neanderthals were cognitively on the same level as early modern humans will remain controversial.
The clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the 1960 Nobel Prize in Chemistry.
But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science.
As a rule, carbon dates are younger than calendar dates: a bone carbon-dated to 10,000 years is around 11,000 years old, and 20,000 carbon years roughly equates to 24,000 calendar years.