The human brain, the most delicate and sensitive organ in our body, protected by a thick skull and robust vertebrae, seems to be able to defy time and decomposition more than any other tissue. This is what emerges from a study by the University of Oxford (I link it here), which has cataloged over 4.400 naturally preserved human brains. Some even date back 12.000 years.
This astonishing archaeological collection includes brains of all sorts. Inca sacrificial victims. Prehistoric men. North Pole Explorers. They all open up new perspectives on the resilience of this extraordinary organ.
Brains, brains everywhere
The preservation of human soft tissues, including the brain, is often due to well-understood processes such as dehydration, freezing, and tanning, resulting from human actions or natural factors. It is not unusual for brains to survive along with other internal organs in cases where the soft tissues are well preserved. Researchers have found brains in the dried remains of desert burials, in frozen bodies from mountain passes, and in tanned bodies from peat bogs.
However, researchers have also identified brains preserved without other soft tissue, such as those found alongside ancient bones in a swampy pond. Some of these brains have been discovered in sunken shipwrecks, floating alongside the bones.
How do they keep themselves like this?
Until this study, there had been no significant effort to systematically study preserved brains to understand why they last longer than other soft tissues. To challenge the notion that brain preservation is uncommon, the scientists involved in this research created an archive of preserved human brains from archaeological sites.
They conducted statistical analyzes to determine their prevalence, how they persist and the diversity of their conservation conditions. They also examined the nature of preserved nerve tissues and mapped their distribution across the globe and over time. Finally, they explored how studying preserved human brains can improve our understanding of ancient diseases and genetics.
a mine of information
Comparing where brains are found and historical climate data provides clues to factors that prevent brain decay. Over a third of the samples remained intact due to dehydration, while others were preserved through freezing or tanning. The conditions? They vary widely, from dry and brittle to soft and tofu-like in texture.
Curiously, about a quarter of the brains were discovered in bodies devoid of any other preserved soft tissue. No skin, kidneys or muscles, but the brain in the skull does.
In these cases, says the forensic anthropologist Alexandra Morton-Hayward, known processes that preserve all tissue types cannot explain why these brains endure.
Brains, a mystery to be revealed
The exact reason why these brains remain preserved while other soft tissues deteriorate remains a mystery. But it may have to do with the brain's unique chemical makeup.
The brain has a 1:1 ratio of protein to lipid, which is different from other soft tissues that contain more carbohydrates and have different protein-lipid ratios. This specific ratio could be crucial, especially when metals like iron come into play, potentially making proteins and lipids bind together and last longer. Many of these preserved brains (no coincidence) contain iron oxide, also known as rust.
The mechanisms are similar to those we see in neurodegenerative diseases, such as dementia. So if we can understand what happens to brains after death, we may also be able to shed light on what happens in brain aging during life
Alexandra Morton-Hayward
The research team is currently employing new techniques to delve deeper into the molecular interactions that facilitate brain preservation. Preserved nervous tissue could offer an unprecedented opportunity to study diseases in ancient humans, and understand their evolution.
