Prehistoric teeth unearthed at a site in Jersey reveal signs of interbreeding between Neanderthals and our own species, scientists say.
UK experts re-studied 13 teeth found between 1910 and 1911 at La Cotte de St Brelade in the island's south-west.
They were long regarded as being typical Neanderthal specimens, but the reassessment also uncovered features characteristic of modern human teeth.
The teeth may represent some of the last known Neanderthal remains.
As such, they might even yield clues to what caused the disappearance of our close evolutionary cousins.
The Neanderthals evolved around 400,000 years ago and inhabited a large area from western Europe to Siberia.
They were typically shorter and stockier than modern humans, with a thick ridge of bone overhanging the eyes.
They finally disappeared around 40,000 years ago, just as anatomically modern humans (Homo sapiens), a newly arrived species from Africa, was settling in Europe.
However, the two types of human may have overlapped for at least 5,000 years.
The teeth were discovered on a small granite ledge at the cave site.
They were previously thought to belong to a single Neanderthal individual. However, the new research found they were from at least two adults.
The researchers used computed tomography (CT) scans of the teeth to study them at a level of detail that wasn't available to researchers in the past.
While all the specimens have some Neanderthal characteristics, some aspects of their shape are more typical of teeth from modern humans.
This suggests these were traits that were prevalent in their population.
Research leader Prof Chris Stringer, from London's Natural History Museum, said: "Given that modern humans overlapped with Neanderthals in some parts of Europe after 45,000 years ago, the unusual features of these La Cotte individuals suggest that they could have had a dual Neanderthal-modern human ancestry."
At the time these individuals were alive, the climate in this part of the world was colder than it is today and the sea level was tens of metres lower.
Co-author Dr Matt Pope, from the Institute of Archaeology at University College London (UCL), said the area would have been "fantastic for hunting", because of its "dead-end valleys and blind gulleys".
"Caves of that scale and size are extremely rare in that landscape," he said, adding: "It seems to be embedded in their routines, coming back to that place for tens of thousands of years."
In fact, there is a record of occupation at the La Cotte site going back to 250,000 years ago.
The human teeth are thought to be around 48,000 years old, close to the presumed Neanderthal extinction date of 40,000 years ago.
So, rather than going extinct in the traditional sense, were Neanderthal groups simply absorbed into incoming modern human populations?
"This now needs to be a scenario that's seriously considered, alongside others, and it's going to emerge as we get more understanding of the process of genetic admixture," Dr Pope told BBC News.
"But certainly, that word 'extinct' now starts to lose its meaning where you can see multiple episodes of admixture and the retention of a significant proportion of Neanderthal DNA in humans beyond sub-Saharan Africa."
Neanderthals contributed 2-3% of the genomes - the genetic instruction booklet for making a person - of people with ancestry from outside Africa.
"This idea of a hybrid population could be tested by the recovery of ancient DNA from the teeth, something that is now under investigation," said Prof Stringer.
The study has been published in the Journal of Human Evolution.