Curiosity Leads Researchers to Identify A New Mystifying Quality of the Brain
Unlike the rest of our soft tissue, brains can survive for at least 12,000 years
Hiya
Scientists can learn a lot from studying the skeletal remains unearthed from archeological sites, including (but not limited to) the age of the person when they died, their sex, their health, their potential social status, and even some injuries they obtained when alive, even when those injuries occurred and how they healed.
But unless a body is intentionally preserved through mummification, for instance, then the skeleton is the only part of the body scientists usually have to learn from. Unlike bone, our soft tissue decomposes relatively quickly, and it was long thought the brain was one of the first organs to break down.
The idea that a brain could be naturally preserved for thousands of years was once laughable. However, following a curiosity, Oxford researchers have shown that brain preservation is more common than experts assumed.
The Curiosity
Alexandra Morton-Hayward, a postgraduate researcher at the University of Oxford and forensic anthropologist, told NPR’s Scott Simon in an interview that she worked as an undertaker and embalmer studying human remains to tell stories of the dead, but was also curious about decomposition on a scientific level.
Morton-Hayward said that of all our soft tissue, the brain is known in the forensic field as “one of the first organs to decompose after death.” Despite this, she says, scientists have found ancient preserved brains labeled as unique one-of-a-kinds.
Depending on the size, natural environment a body is in, and whether the body was embalmed, it can take anywhere between days to years for the soft tissue of a corpse to decompose.
It’s rare to find soft tissue preservation beyond a decade or so unless it’s deliberate, such as during embalming or freezing. Yet, Morton-Hayward’s curiosity deepened as she came across a growing pile of reports mentioning preserved brains, and she started to wonder just how rare such a finding actually is.
So, she and her colleagues began compiling archaeological research spanning 400 years that mentioned naturally preserved brains — and found over 4,400.
The Collection
Morton-Hayward and her colleagues at the University of Oxford located over 200 sources, written in over ten languages, reporting over 4,400 preserved brains from archeological dig sites on every continent except Antarctica. Their resulting study was published in the Proceedings of the Royal Society B on March 20, 2024.
Some of the preserved brains they found date back to the mid-17th century, but the oldest brains in their collection are 12,000 years old — as in the last Ice Age, around the time our species transitioned from hunting and gathering to farming. They came from nearly all over the globe, including a lakebed of Stone Age Sweden, the summit of Andean volcanoes during the peak of the Incan Empire, and the depths of an ancient Iranian salt mine from 500 BC.
The individuals the brains belonged to were as diverse as their locations and included people from Korean and Egyptian royalty, Arctic explorers, Danish monks, and war victims. In the interview with Simon, Morton-Hayward said:
“We have 80 criminals who were thrown into a well in the Middle Ages, for example. So it's a real cross section of society.”
You're not alone if you’re curious about what these ancient brains look like. Simon was too, and he asked her, “What does a preserved brain look like?” To which she answered:
Oh, they're fantastic - so invariably shrunken, usually to around a fifth of their volume in life. So they look kind of like a large walnut. They sit perfectly in the palm of your hand.
But here’s an image anyway:
The researchers sorted the thousands of brains into five categories based on the processes that prevented them from decaying. In a news release by the University of Oxford, the study’s co-author Erin Saupe, a palaeobiologist and professor in Oxford’s Department of Earth Sciences, said:
“This record of ancient brains highlights the array of environments in which they can be preserved from the high arctic to arid deserts.”
Four categories were specific. The first two are pretty self-explanatory: Some brains were dried out or dehydrated, while others were frozen. The third category belongs to the brains that underwent tanning, a chemical process used to treat leather but that occurs naturally in environments like bogs — known as bog bodies. The fourth category is saponification, a natural process that turns some fats into a relatively stable, soapy substance known as grave wax, which Morton-Hayward said “smells absolutely terrible.”
However, almost a third of the preserved brains didn’t belong to any of those four categories.
The Mysterious Fifth Group
This last group of preserved brains doesn’t indicate any particular reason for the brain to survive when the rest of the body’s soft tissue did not, making the fifth category a mystery.
The researchers analyzed past and present weather conditions linked to the timeframes of the remains to see whether the climate may have preserved the brains. Still, ultimately, they hypothesize that some unknown mechanism prevented the organ from decaying.
Whatever this unknown mechanism is, it appears to preserve brains for significantly longer than the other four categories. The oldest brains the researchers identified are in the fifth mystery group. Some are over 12,000 years old and belonged to people alive during the agricultural revolution when our species transitioned from hunting and gathering to farming.
However, it also remains unknown how this mysterious mechanism preserves brains, and only brains, for thousands of years. Morton-Hayward explained to Carolyn Wilke of Science News that after analyzing studies on preserved soft tissues from dinosaurs and other ancient animals, she and her team hypothesize the mysterious mechanism that involves the brain’s chemistry during life may also preserve it in death.
More specifically, the team thinks there may be some natural mechanisms, such as molecular crosslinking and metal complexation — when proteins and lipids fuse in the presence of elements like copper or iron to form stable molecules — that could “feasibly” preserve nervous tissues over time.
More research is needed, but Morton-Hayward is already working on it.
Future Research
In the news release, Morton-Hayward discusses how it’s commonly assumed in the forensic field that the brain is one of the first organs to decompose after death. Yet her research offers evidence that specific environments and biochemical circumstances preserve the brain. She explains:
“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.”
In the interview with NPR’s Simon, Morton-Hayward explains what researchers hope to learn from these ancient brains.
“There's a lot of work in paleopathology looking at ancient proteins as markers of nutritional status - the richness or poorness of one's diet. We can look at metabolic disorders, even the possibility of looking at neurological disorders in these particular brain remains. But we can study all sorts of things from past pandemics to whether an individual might have had a bit of a dodgy ticker.”
The human brain remains one of, if not the most mysterious organ we have. Perhaps learning more about the preserved brains and the people they belonged to will shed some light on some mysteries.
Perspective Shift
Morton-Hayward had a curiosity, and because she followed it, a long-held scientific assumption about the brain being one of the first organs to decompose was overturned, opening the door to new ways for us to learn about our past. I wonder how many more preserved brains will be identified thanks to Morton-Hayward’s research, and I’m excited about what scientists will learn from them.
I’m curious why, out of all of our soft tissue, the brain is what somehow survives, especially regarding the mysterious fifth category. I’m not a chemist or a scientist, for that matter, but Morton-Hayward’s hypotheses about a chemical reaction in the brain make sense to me.
Though, I wonder if the brain’s location in our body has anything to do with it. After all, the brain is the only organ completely encased in bone. So, perhaps the skull plays a part, too. I guess we’ll have to wait to find out.
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Interesting and surprising.