In what an expert called “a real freak of preservation”, British archaeologists unearthed a decapitated skull dating back 2,000 years, which carried an unusually well-preserved shriveled remnant of a human brain. Some reports suggest that it is the oldest brain ever discovered in Britain, though researchers have not made any such claim.

According to a University of York statement, inside the skull, the scientists found “a yellow substance which scans showed to be shrunken, but brain-shaped.” Richard Hall, a director of York Archaeological Trust, said the skull was found in a muddy pit, unearthed during excavations, on the site of the University of York’s campus expansion at Heslington East.

It was Trust dig team member, Rachel Cubitt, who reached in for the skull, and while cleaning its outer surface, “she felt something move inside the cranium. Peering through the base of the skull, she spotted an unusual yellow substance.” Later, scans at York Hospital confirmed the presence of brain tissue.

Sonia O’Connor, research fellow in archaeological sciences at the University of Bradford, said: “The survival of brain remains where no other soft tissues are preserved is extremely rare. This brain is particularly exciting because it is very well preserved, even though it is the oldest recorded find of this type in the U.K., and one of the earliest worldwide.”

Hall said it was a mystery why the skull was buried separately from its body, suggesting human sacrifice and ritual burial as possible explanations. Moreover, there is no clue as to how the brain remained preserved for so long, though the tissue had apparently contracted over the years.