Scientists have uncovered human skulls that were used by ancient Britons as drinking cups in some kind of ritual.
The 14,700-year-old artefacts were discovered in Gough's Cave, Somerset, and have been analysed by experts from London's Natural History Museum.
Three skull-cups belonging to two adults and a young child have been identified among the human bones from the cave.
They are believed to be the oldest directly dated skull-cups and the only examples known from the British Isles.
The brain cases were fashioned in such a meticulous way that their use as bowls to hold liquid seems the only reasonable explanation, scientists said.
Gough's Cave is in the Cheddar Gorge, a deep limestone canyon on the southern edge of the Mendip Hills. In 1903 "Cheddar Man", the complete skeleton of a male dating to about 10,000 years ago, was found at the site.
Scientists said the evidence demonstrated that early Britons were skilled in post-mortem manipulation of human bodies. Results of the research suggest the processing of cadavers for the consumption of bone marrow, accompanied by meticulous shaping of cranial vaults.
The distribution of cut marks indicates that the skulls were scrupulously "cleaned" of any soft tissues, and subsequently modified by the removal of the facial region.
The vaults were also "retouched", possibly to make the broken edges more regular. This manipulation suggests the shaping of skulls to produce skull-cups
Lead author Silvia Bello, who is based in the Natural History Museum's department of palaeontology, said: "We suspected that these early humans were highly skilled at manipulating human bodies once they died, and our research reveals just what great anatomists they were.
"The cut marks and dents show how the heads were scrupulously cleaned of any soft tissues shortly after death.
"The skulls were then modified by removing the bones of the face and the base of the skull.
"Finally, these cranial vaults were meticulously shaped into cups by retouching the broken edges, possibly to make them more regular.
"All in all it was a very painstaking process given the tools available."
The team's findings have been published in PLoS One.
Although the team found evidence that some of the flesh and bone marrow from the skulls was eaten, they concluded that cannibalism was unlikely to have been the main purpose of the modifications.
They said that at sites where cannibalism has been found, skulls are broken into pieces and there is often damage at the top of the skull from an impact.
"At Gough's Cave, there was clear determination to preserve the cranial vault as complete as possible," Dr Bello said. "It is likely that this was part of some symbolic ritual and not mere necessity."
Professor Chris Stringer said the amount of effort that went into making the skull-cups suggested they served a special purpose.
He added: "We do not know the exact circumstances for Gough's.
"At one extreme, were these individuals killed, butchered and eaten, with the skull-cups just the end of this event?
"Or could these people have been part of a group who had died singly or together, and were eaten, perhaps in a crisis situation, with the skull-cups acting as a final tribute to the dead? We simply do not know."