Scientists are hoping to extract DNA from a piece of jawbone found in Devon thought to be from a Neanderthal man who roamed Britain 35,000 years ago.
The fragment was found in Torquay.(Image:Torquay Museum)
Experts plan to use an upper jaw tooth to establish whether the closest relative of modern humans lived on the British Isles later than thought.
The jaw fragment was found at Kents Cavern in Torquay in 1927 and was originally thought to be human.
But experts now think it could date back even further.
Professor Chris Stringer, research leader in human origins at the Natural History Museum, said it was a critical test that could have "historic" results.
Torquay Museum in Devon, which looks after the piece of jaw bone, has agreed in principle to the DNA test and carbon dating tests, he said.
The only late Neanderthal fossils on the British Isles were found on the Channel Islands around 1910.
MODERN HUMANS AND NEANDERTHALS
Neanderthals evolve about 250,000 years ago
Their range extends from Europe to Central Asia and the Middle East
Modern humans leave Africa about 60,000 years ago and arrive in Europe around 40,000 years ago
By 27,000 years ago, the Neanderthals are extinct
Possible reasons include climate change and competition with modern humans
However, Prof Stringer said the teeth discovered at the site date back to a time when the island was joined to France around 50,000 years ago.
His team has also found evidence which dates the arrival of primitive ancestors in Britain to 700,000 years ago, 200,000 years earlier than previous findings.
They found the archaeological evidence at Pakefield, near Lowestoft, Suffolk, and also plan to continue looking for more evidence in other areas.
Professor Chris Stringer, who is also director of the Ancient Human Occupation of Britain (AHOB) project, said: "Neanderthal DNA is very distinct and would show up clearly in tests.
"It is a critical test as this could be the first late Neanderthal fossil on mainland Britain.
"But it is also historic if there is modern human DNA as this would prove they were here earlier than previously thought.
"Neanderthals are so close to us in time, and a closely related species.
"We have lots of Neanderthal tools but no fossils. The team is excited about the tests but we need a bit of luck as the DNA may not have survived."
Bone spearheads date modern humans living in Britain to 31,000 years ago, 4,000 years later than the earliest finds of modern humans in Europe, he added. Prof Stringer said the roots, crown, size and shape of the tooth, which is thought to date back 35,000 years, would also be studied.