A fresh look at a jawbone unearthed in southern England 85 years ago reveals its original owner to be the oldest known modern human in northwestern Europe, according to a new study.
The new dating, if correct, would tilt a long-simmering debate in favour of those who say anatomically modern man lived alongside Neanderthals for thousands of years before the enigmatic hominid disappeared.
It would also help explain the existence of tools and artefacts, discovered nearby, from the so-called Aurignacian period dating back nearly 45,000 years.
The upper jaw fragment containing three teeth, excavated from a cave called Kent’s Cavern, is 44,000 to 41,500 years old, according to the new calculation, published in Nature.
For decades, scientists thought the fossil was no more than 35,000 years old.
But researchers scrapped the estimate after discovering traces of glue, used to conserve the jaw after discovery, on the sample. They believe the glue badly skewed the dating.
“We knew we were going to have to do additional testing to re-date the bone,” explained Beth Shapiro, a professor at Penn State University and a co-author of the study.
The problem was how, because the area, left uncontaminated by the glue was too small to carry out radiocarbon dating.
Prof. Shapiro’s team went about the problem sideways, or rather from the top and the bottom: They found samples of animal bones in layers of earth both above and below the level where the jaw bone had been found.
Working with wolf, deer, cave bear and woolly rhinoceros bones ranging in age from 50,000 to 26,000 years old, the scientists used a statistical modelling technique to reassess the jawbone.
“The new dating evidence allows us, for the first time, to pinpoint the real age of this key specimen,” said Tom Higham, deputy head of Oxford University’s radiocarbon accelerator unit and a co-author of the study.
“We believe this piece of jawbone is the earliest direct evidence we have of modern humans in northwestern Europe.”
To verify that, the anatomical fragment did not, in fact, belong to a Neanderthal. The researchers used a virtual 3-D model based on a CT scan, comparing the internal and external shapes of the teeth between the two hominid species.
All but three of 16 criteria they found, corresponded to the dentition of Homo sapiens sapiens, as anatomically modern man is known.
The remaining three smacked of Neanderthal, but the scientists chalked that up to either an inadequate sampling of early human teeth, shared dental features or possibly a bit of inter-species hanky-panky.
In another study published in Nature, Stefano Benazzi of the University of Vienna and colleagues reanalysed two molars attributed since their discovery in southern Italy in 1964 to Neanderthal pedigree.
New radiocarbon dating of the teeth show that they belonged to modern humans, while personal ornaments from the same site suggest the molars are 45,000 to 43,000 years old.
Neanderthals lived in parts of Europe, Central Asia and the Middle East for up to 300,000 years but appear to have vanished some 40,000 years ago. Gibraltar was their last known bastion.
Why they died out is a matter of sharp debate.
A recent study by French researchers suggested that modern humans gleaned a competitive immune advantage through inter-breeding.
Earlier theories hypothesise that these upright but stooped cavemen were crowded out by modern humans, and that their demise may have been hastened by a series of harsh winters.