Prehistoric Human Brains Baffle Scientists
The most delicate organin the human body is the brain, which is why it’s protected by a thick-bonedskull. What’s baffling is that this squishy mass, out of all the organs, cansurvive the most time without decay.
Researchers havecataloged over 4,000 naturally preserved human brains, some as old as 12,000years. This archive includes Inca sacrificial victims, prehistoric people, andNorth Pole explorers. And yet, the discovery of a preserved brain is perceivedto be a very rare incident.
Human soft tissue,including the brain, can be preserved by some well-understood processes such asdehydration, freezing, and tanning. These methods can be the result of humanactions or natural factors. It’s not unusual for brains to survive when other internalorgans are well-preserved, such as in dried-out remains of desert burials,frozen bodies from mountain passes, and tanned bodies from bogs.
However, preservedbrains have been found without other soft tissues, such as floating alongsidebones in sunken shipwrecks, or sitting alongside ancient bones from a swampypond.
Until now, there hasbeen no systemic study to determine why brains last longer than other softtissues.
This new archiveallowed researchers to determine the prevalence of intact brains, to study howthey persisted, and the diversity of their preservation conditions. They alsomapped their distribution worldwide across time. Finally, the researchersstudied the brains to understand ancient diseases and genetics.
About a quarter of thebrains were discovered in bodies lacking any other preserved soft tissue. Knownprocesses that preserve all types of tissue can’t explain why these brainsendured.
The reason why thesebrains were preserved is a mystery, but it might be because of the brain’schemical composition. The brain has a 1-to-1 ratio of proteins to lipids, whileother soft tissues have different ratios. This ratio could mean that if metalslike iron are introduced, it could cause the proteins and lipids to bindtogether and last longer. Many preserved brains were found to contain ironoxide (rust).
The team is employingnew techniques to study the molecular interactions leading to the preservationof brains. The brains could also offer an opportunity to study neurologicaldiseases in ancient humans.
