A group of British researchers analyzed archaeological finds of preserved human brains and compiled an archive of more than four thousand samples. The authors also proposed a mechanism that ensures long-term preservation of nerve tissue.

Soft tissues, such as muscles or internal organs, are much worse preserved in the geological record than bones. Usually the decomposition process is stopped by anthropogenic preservation – mummification, embalming, freezing. In the natural environment, this happens very rarely: such “time capsules” can be called, for example, swamps, where the corpses of mammoths and people who lived more than four thousand years ago were discovered. And in the Alps they found the frozen mummy of a Bronze Age Tyrolean iceman.

It is believed that the human brain is among the first internal organs to decompose after death. For this reason, findings in preserved human brain samples are called unique or very rare. However, a group of experts from Oxford University (Great Britain) rejects this opinion. Scientists have amassed an archive of more than four thousand human brain remains, many of which are at least 12,000 years old. An article describing the examples was published in the magazine Proceedings of the Royal Society B.

The authors searched the literature to find evidence of preserved human nerve tissue, analyzing the general characteristics of the remains and the environment in which the deposits were found. They then linked the findings to specific points on the map, examining paleoclimatic conditions and different types of security.

A total of 4,405 human brain samples have been found all over the world (mostly in Europe) except Antarctica. Researchers have identified five types of preservation: dehydration, freezing, saponification and tanning (in an acidic environment). The fifth type, as the authors of the article note, is not codified in the scientific literature; They called it “the unknown.”

Almost a third of the ruins belong to this type of preservation; such mummified remains have been found in sunken ships, tombs, wooden and lead coffins, and even severed heads. Interestingly, almost all of the brain samples preserved in some unknown way are the only soft tissue remaining from ancient humans. This correlates with the overall incidence of preserved soft tissue births. In the period from the Mesolithic Age (about 9000 BC) to the 20th century, muscles and intestines were found 43 times, and the brain was found much more frequently, 3862 times.

The largest share of all nerve tissue remains analyzed was dehydrated, with 1,667 samples. However, the mechanism of protection is still unknown. A strong skull can protect its contents from complete decay, but brain remains have also been found in the fragmented skulls of hunter-gatherers.

The authors of the paper suggested that protein and lipid compounds with metals found in the brain, such as copper or iron, can form strong molecular bonds under certain conditions. Such complex compounds form minerals and stabilize nervous tissue for a long time.

“The question of whether these conditions are environmental or related to the brain’s unique biochemistry is the focus of our current and future work. “We are finding an incredible number and type of preserved ancient biomolecules in these archaeological brains and what they tell us about the life and death of our ancestors,” said study author Alexandra L. Morton-Havor. “It’s exciting to hear what they have to say,” he said.