In the summer of 2008, archaeologist Rachel Cubitt was in the middle of a routine cleanup procedure when she noticed something peculiar.
The oddity wasn’t the ancient, mud-caked human skull she held in her hands. (As an employee of the York Archaeological Trust, Cubitt considered such specimens par for the course.) Rather, it was what Cubitt noticed inside the grubby noggin that left her baffled. Enclosed within the cranium—dug up earlier that year near modern day York, England—was a loose, spongy lump that in a baffling twist of fate would turn out to be a shockingly well-preserved piece of a 2,600-year-old brain.
Over the following decade, analyses yielded more questions than answers about the ancient organ—now known as the Heslington brain—and the mysterious Iron Age man to whom it once belonged. But as Ashley Strickland reports for CNN, researchers may have finally solved one of the biggest mysteries of all: namely, how such delicate tissue survived so many centuries underground in its natural state.
Per a new study published in the Journal of the Royal Society Interface, the brain’s pristine preservation appears to boil down to a few architectural quirks. Two types of protein structures that helped maintain the organ’s integrity had clumped unusually tightly in the brain, the researchers found. These durable clusters then protected the rest of the tissue, a bit like clothes swaddling fragile electronics in a well-packed suitcase.
The findings make the Heslington brain even more of an anomaly. Under normal circumstances, death rapidly ushers in a period of tissue breakdown. Fatty, spongy organs such as the brain, which is about 75 percent water, are among the first to go. They usually disintegrate beyond salvage within the first few years of death, according to Gizmodo’s George Dvorsky.
“The preservation of human brain proteins at ambient temperature should not be possible for millennia,” write the researchers, led by Axel Petzold of University of London’s Queen Square Institute of Neurology, in the study.
The Heslington brain defied decomposition several millennia beyond its standard issue expiration date despite never being embalmed or otherwise treated before burial. What’s more, the organ flew solo: No other bits of soft tissue, like skin, managed to survive alongside it, suggesting that the brain’s resilience was at least partly internal, not merely a byproduct of the boggy earth that once entombed it.
To figure out how the organ accomplished this remarkable feat, Petzold and his colleagues spent a year with the Heslington brain, running a battery of tests aimed at determining how its internal structure changed over time. Remarkably, hundreds of proteins remained intact enough to be identified; some had even held their shape.
Some of the brain’s most critical protein structures—ropy fibers called neurofilaments and glial fibrillary acidic proteins that act as scaffolding—were still intact, holding the rest of the tissue together in a dense, ultra-compact state.
After death, enzymes produced by the body usually start to chew through the brain’s scaffolding, unraveling the organ’s infrastructure. Though the researchers still aren’t sure exactly what hit the pause button on this process, Vice’s Becky Ferreira reports that a natural chemical preservative may have leaked into the skull early on, halting decomposition.
Another less likely theory might involve a brain disease like Alzheimer’s, which tends to produce dense clumps of proteins in neural tissue, albeit of a slightly different sort, according to Rodrigo Pérez Ortega of Science magazine.
The nature of the man’s death and burial could have also played a role, says Petzold in a statement. The rest of his body is still missing, suggesting he was probably decapitated, perhaps after being bludgeoned or hanged in some kind of ritual. His head was then stuffed under cold, fine sediment mostly devoid of oxygen, bumping up the potential for preservation—something that was ultimately a boon for the brain, though perhaps less so for its ill-fated owner.