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Alexandra Morton-Hayward, a funeral director turned academic, became interested in brains – and especially the way they break down – during her previous job.
‘I have worked with the dead for years. My own experience is that the brain liquefies quite quickly (post-mortem),” she said. “So it was a real shock when I came across a (scientific) article that referred to a 2,500-year-old brain.”
Morton-Hayward, a forensic anthropologist studying for a PhD at the University of Oxford, has found that brains, although not as often found intact as bones, are surprisingly well preserved in the archaeological record.
To understand why, the anthropologist has compiled a unique archive of information on 4,405 brains unearthed by archaeologists. Brains have emerged from northern European peat bogs, Andean mountain peaks, shipwrecks, desert graves and Victorian almshouses. The earliest specimens discovered were 12,000 years old.
Morton-Hayward mainly tries to understand how these brains survive the test of time, in which at least four preservation mechanisms play a role.
However, the database will also open up whole new areas of research, says Martin Wirenfeldt Nielsen, a senior physician and pathologist at South Denmark University Hospital, who was not involved in the study. He is also responsible for the medical brain collection at the University of Southern Denmark.
“This database will allow scientists to study brain tissue from ancient times and determine whether diseases we know today were also present many years ago in civilizations that were completely different from the one we live in today,” Wirenfeldt Nielsen said via e-mail.
“Examining tissue from brains that have not been exposed to the environment and stimuli in modern society could help us understand whether some of the brain diseases we see today could be at least partly caused by the way we now to live.”
A collection of old brains
Morton-Hayward searched scientific literature dating back three centuries and interviewed historians and archaeologists to catalog the brain. However, not all corresponding physical copies are still available for research.
The oldest were two 12,000-year-old brains, reported from a site in Russia in the 1920s, which researchers described as having been found with woolly mammoth teeth, Morton-Hayward said.. It’s not clear what happened to the brain, she added.
Morton-Hayward works in a laboratory in Oxford, England, where she has helped build a collection of 570 old brains. They are stored in refrigerators in takeaway style jars and plastic containers as they have secure lids. The oldest specimen in the lab is an 8,000-year-old Stone Age brain in Sweden, which was mounted on a spike before being buried in a lake bed.
Morton-Hayward and her colleagues identified four ways in which the brain, typically discolored and shrunken, was preserved – factors that were often related to the climate or environment in which they were found. The results were published on March 19 in the journal Proceedings of the Royal Society B Biological Sciences.
Dry, warm conditions dehydrate the brain in a way that mimics that the deliberate embalming of mummies, while in acidic peat bogs the body was essentially tanned like leather. In cold places the brains were frozen, while in some cases the fats in the brain were converted into ‘grave wax’, a process known as saponification.
However, in approximately 1,328 cases, the brain survived without other soft tissues, raising questions about why this organ can survive while others decompose. Interestingly, many of the oldest brains have been preserved in this unknown way, Morton-Hayward said.
“We have identified this fifth mechanism, this unknown mechanism that we hypothesize could be a form of molecular cross-linking, possibly promoted by the presence of metals such as iron,” she said, referring to the possibility of proteins and lipids fusing in the brain in the presence of elements such as iron or copper, which preserve the brain.
The researchers do not believe that the protective shell of the skull is responsible for preserving the brain in the absence of other soft tissue, because, according to the study, preserved brains have been found in skulls damaged by trauma or the fossilization process.
“Central nervous system tissue is extremely fragile and delicate, and discovering that brain tissue has been preserved for so many years is extraordinary,” said Wirenfeldt Nielsen.
Secrets waiting to be spilled?
It’s possible that ancient DNA and proteins could be plucked from the brain, spreading secrets about the people they once belonged to. If the material is successfully recovered, it could potentially reveal things that molecular information from bones and teeth cannot, Morton-Hayward said.
“The brain is the most metabolically active organ in the human body. It is 2% of our body weight, but uses 20% of our energy because we are constantly doing things. It is an incredibly complex organ and therefore it has a very unusual biomolecular composition. So the kind of wealth of information is just that much greater to begin with,” she said.
“Ancient DNA could very well be preserved in these brains because of the way that, at least, brains of the unknown type appear to be preserved,” she added. ‘They condense and shrink and expel the water. And that is forming a kind of closed system that could theoretically protect high-quality, high-yield DNA.”
Many of the people the brain belonged to had exciting stories that deserve more attention, Morton-Hayward said. One of the brains she documented belonged to a Polish saint. Another was the victim of an Inca sacrifice. As a former funeral director, she says she never forgets the people behind the body parts.
“I am so grateful for this experience,” she said. “The most important thing is never to lose sight of the fact that these monsters are human beings.”
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