The mystery of brains preserved for millennia – 04/13/2024 – Science

The brain is perhaps the softest of the soft tissues in the human body and, therefore, it is an organ that tends to decompose quickly after death, transforming into a liquid that disappears, leaving only the skull.

Hence forensic anthropologist Alexandra Morton-Hayward’s fascination with uncovering thousands of cases of brains that have been preserved practically intact for hundreds of years, or even millennia, in some cases.

The professor in the Department of Geosciences at the University of Oxford, in the United Kingdom, led research to debunk the belief that perfectly preserved brains are an extremely strange archaeological discovery.

In fact, thanks to his study, it was possible to verify that nervous tissues persist in much greater abundance than previously assumed, aided by specific conditions that help prevent their putrefaction.

The study, published in the scientific journal of the Royal Society — one of the world’s leading scientific organizations — compiled a sample of more than 4,000 human brains that appear in more than 200 records, including some dating back to the mid-17th century.

Among them is a 12,000-year-old brain that turned up near some mammoth teeth in modern-day Russia.

In the records there are mentions of a wide variety of archaeological sites, such as the shores of a lake bed in Stone Age Sweden, the depths of an Iranian salt mine around 500 BC, and the summits of Andean volcanoes at their height. of the Inca Empire.

Morton-Hayward believes these ancient brains could be an important source of information about our past that has not yet been explored.

“In principle, we should find proteins and DNA in brains that are less degraded than those in bones. Once we have this material, we can learn a lot about our ancestors from it,” she explained in an interview with Science magazine.

Fifth conservation mechanism

Morton-Hayward first became interested in brain preservation while working at a funeral home.

“One of the things that intrigued me most was decomposition. Just as we are all different in life, we all decompose differently in death. And it seems like a lot depends on how you lived and what you died from,” he said.

Each of the recorded brains was compared with historical climate data from the same area, to explore trends in when and where they were found.

The analyzes revealed patterns in environmental conditions associated with different modes of preservation over time, including dehydration, freezing, saponification (transformation of fats into a type of soap-like substance known as “corpse wax”) and a tanning process.

But these known processes preserve all soft tissue, not just the brain. Therefore, they do not explain the 1,300 cases in which the brain is the only soft tissue that survives.

According to the researchers, this is due to what they classify as a fifth conservation mechanism.

“This unknown mechanism is completely different,” Morton-Hayward told the NewScientist portal.

“The key feature is that we only have the brain and bones left. There is no skin, no muscles, no viscera.”

The hypothesis is that, under certain circumstances, substances such as iron and copper can catalyze the formation of bonds between proteins and lipids, forming more stable molecules that resist degradation. And it is in the nature of the proteins and lipids found in the brain, or in their proportion, that the secret may lie.

“(Answering) whether these circumstances are environmental or related to the brain’s unique biochemistry is the focus of our current and future work,” Morton-Hayward said.

For the researcher, it is relevant that these mechanisms “are similar to those we see in neurodegenerative diseases, such as dementia”.

“So if we can figure out what’s happening to brains after death, we might be able to shed some light on what’s happening to brain aging in life as well,” he added.