The Persistence of the Mind: How the Brain Can Outlast the Body

It has become fairly cliched to say that time heals all wounds – attesting to the power of forgetfulness when it comes to tragedy. For better or worse, the passing days and years erode trauma done both to the mind and the physical landscape of the world – turning battles and tragedies into distant memories. There are, all too often, times in which the memories long outlast the places we’ve been. The human brain, it turns out, can be surprisingly resistant to the ravages of time – preserving itself even beyond the needs of the body it leads.

This year, a new study made a catalog of human brains that had been excavated and placed on the archaeological record across the globe and found a rather surprising aspect of the brain’s ability to last even beyond the life of its owner. Even after the body’s soft connective tissue – flesh and blood, has long dissipated, the brain manages to keep itself intact somehow.

Alexandra Morton-Hayward of the University of Oxford is a molecular taphonomist, that is, she’s versed in the study of how plants and animals deteriorate as they break down and enter the fossil record. Leading a team of scientists, her team identified more than 4,400 specimens of preserved human brains, some of them dating as far back as 12,000 years ago. The study’s results are a divergence from previous evidence suggesting that our brains are among the first of our organs to decompose after we die.

This latest discovery, according to the experts, could provide a comprehensive archive that will help further advance the knowledge we have of our own evolutionary history, and the array of diseases that have plagued us through time.

“In the forensic field, it’s well-known that the brain is one of the first organs to decompose after death – yet this huge archive clearly demonstrates that there are certain circumstances in which it survives,” says Morton-Hayward.

“Whether those circumstances are environmental, or related to the brain’s unique biochemistry, is the focus of our ongoing and future work. We’re finding amazing numbers and types of ancient biomolecules preserved in these archaeological brains, and it’s exciting to explore all that they can tell us about life and death in our ancestors.”

The archaeological preservation of soft connective tissue when a dead body is left exposed to the elements (and not artificially preserved in ways like embalming or freezing), remains a rare event. When conducting studies of anatomical decay, the brain is demonstrably one of the first organs to atrophy in the process of decomposition.

Consequently, it is believed that the preservation of a human brain in these bodies where everything else but the bones has fully decayed was an incredibly rare phenomenon – an almost one of a kind event that one would even go so far as to call a miracle. Morton-Hayward and her team of researchers wanted to learn how rare these instances really are, so they embarked on what became an all out global search for fully preserved human brains.

Their work encompassed a careful perusal of all the published scientific literature they were able to dig up, along with crossing disciplines to reach out to various historians around the globe. They ultimately gathered a grand total of 4,405 preserved human brains from 213 different sources that reported accounts from every single continent in the world with the sole exception of Antarctica, with records that dated as far back as the middle of the 17th century to the present day.

The brains they studied had come from a large variety of environments. One of them was a mass grave of the 1930s Spanish Civil War, where there were brains were preserved despite devastating gunshot wounds that felled the soldiers; or the sandy deserts of Ancient Egypt, whose arid terrain preserved much of our current knowledge of the former Roman Empire; those in South America who had likely been the victims of a ritual Incan sacrifice performed at the dormant volcano Llullaillaco some time around 1450 CE; the 220 BCE Tollund Man, discovered mummified in a peat bog; and the bank of a lake in Stone Age Sweden.

The environmental conditions under which these brains were uncovered were then correlated with the pathways that they brought about natural preservation. These include methods like dehydration, freezing, tanning (a process that occurs in peat bogs), as well as saponification, in which fats coagulate to produce a wax-like mould around the preserved body.

And then there was something else too that caught the attention of the research team. Out of the 4,405 brains, a staggeringly high number – 1,308 of them, nearly one third of the total sample – were in fact the only structure composed of soft tissue that survived out of what were otherwise remains reduced to bare bone. Bear in mind that these samples were in fact among the oldest brains in their collection as well, hearkening to ages as far back as 12,000 years ago.

The methods of preservation for each of these brains was not something that could simply be attributed to the conditions of natural preservation. The samples were in fact, discovered in locations as diverse as shallow or mass graves, in tombs, from shipwrecks, among burial mounds, and even in a few cases, decapitated heads – either summary execution or in battle. This, the researchers suggest, indicates that there could be a kind of soft tissue preservation mechanism that is specific only to our central nervous system.

What exactly that mechanism may look like continues to be a giant enigma to researchers, but the team does suspect that key to understanding it is a type of interaction between the basic molecules of the brain crossing with something already hovering in the external environment. For example, various proteins, lipids, or sugars within the brain could bond and develop stable polymerized macromolecules when in the presence of certain types of metals, possibly copper, which has an abundance throughout the brain.

The researchers hope to further investigate this intriguing phenomenon in greater depth so they can better determine the sequence of reactions that make it possible. What remains, however, the research itself has opened up a whole host of questions building onto what we already know.

“The archive compiled here represents the first step toward a comprehensive, systematic investigation of ancient brains beyond approximately 12,000 years before the present, and is essential to maximizing the molecular and morphological information they yield as the most metabolically active organ in the body, and among the most commonly preserved soft tissues,” the authors conclude in the paper summarizing their findings.

How different were brains that endured the Ice Age from ours – is our initial concern, but what different aspects of that time period shaped us into who we are today? The answer lies in how much we’re able to recreate conditions of that bygone age as we come to understand them.

“Ancient brains may provide new and unique paleobiological insights, helping us to better understand the history of major neurological disorders, ancient cognition and behavior, and the evolution of nervous tissues and their functions.”

Their latest research has been published by the journal Proceedings of the Royal Society B: Biological Sciences.

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