Surprisingly Well-Preserved Human Brains Discovered at Archaeological Sites

Forensic anthropologist Alexandra Morton-Hayward discovered interesting information while conducting her early research. She stumbled upon a report detailing a 2,500-year-old brain that had been preserved in a detached skull. With each subsequent paper she found, more preserved brains were described. What initially seemed to be totally unique, she started noticing a pattern by the time she reached her 12th paper. So, she continued to investigate further.

Morton-Hayward from the University of Oxford, in collaboration with her team, found that brains naturally preserved are not so uncommon. They reported their findings on March 20 in the Proceedings of the Royal Society B. The team has developed a collection of approximately 4,400 human brains preserved in archaeological records, some of which are nearly 12,000 years old. This archive features brains from a multifarious mix, including North Pole explorers, Inca sacrificial victims, and Spanish Civil War soldiers.

However, because of the exceptional rarity associated with preserved brains, there has been a dearth of research on them. Morton-Hayward explains, “If they’re precious, one-of-a-kind materials, then you don’t want to analyze them or disturb them,” revealing that less than 1 percent of the archive has been analyzed.

By contrasting the place of discovery of these brains with chronicle climate models, certain trends emerge which could explain why these brains didn't decompose. More than a third of these samples were preserved due to dehydration, while others were either frozen or tanned. Depending on the environment, the texture of the brains varied - it could be anything from dry and brittle to squishy, like tofu.

Morton-Hayward notes a peculiar finding - about a quarter of these brains had no other surviving soft tissue in the body. These were devoid of organs like skin, kidneys, or muscles. “Just this shrunken perfect little brain rattling around in a skull,” she explains.

While it remains uncertain as to why brains continue to exist when other soft tissues decompose, the solution may be hidden in the brain's chemical composition. What sets it apart is the ratio of proteins to lipids, which is uniquely 1-to-1. Different soft tissues have more carbohydrates and also different protein to lipid ratios. This distinction in ratio might matter because when metals like iron join in, they can cause proteins and lipids to blend together and last longer.

Currently, the team is applying innovative techniques to further understand the molecular interactions that contribute to brain preservation.