Experts have long believed that the human brain is one of the first organs to rot and decay after we die, but new research suggests that’s not the case.
And in fact, it turns out that brains preserve quite well, according to a team of scientists at the University of Oxford – although they don’t know how long nearly a third of brains lasted that long than them.
Until now, whenever archaeologists discovered an ancient, well-preserved brain, it was considered some kind of oddity — or at least the product of intentional preservation efforts on the part of ancient people.
But the team behind a new study searched archaeological records of more than 4,000 human brains, many dating back 12,000 years or more, to determine the truth about brain decay.
This 1,000-year-old brain belonged to a person whose remains were discovered in the 10th-century Sint-Maartenskerk cemetery in Ypres, Belgium. The folds of the fabric are still soft and damp. They are colored orange with iron oxides
They concluded that the tissues that make up the brain are much more resistant to degradation than scientists previously thought.
Organizing the brains based on where they were found also revealed that local environmental conditions may lead to even better preservation.
Generally speaking, archaeologists find soft tissues like muscles and internal organs much less often than things like bones and skin.
They thought it was because skin could be preserved like leather and bones were hard.
Usually, decomposition is only slowed or stopped by processes such as mummification, embalming, or freezing.
Very rarely, these things can occur naturally, such as with human remains buried in dry, mineral-rich soil – or those preserved in peat bogs.
But for a long time, it was thought that the brain was one of the first things to decompose after death.
To disprove this, the team behind the new research searched the scientific literature for accounts of preserved tissue from the human nervous system.
With files in hand, they analyzed the chemical and physical characteristics of the remains in question and determined where they had been found.
This included not only where they were found on a map, but also the climatic conditions at the time the person died and chemical evidence regarding the preservation of their brain.
The study looked at 4,405 brain samples in total, found all over the world – mostly in Europe, none in Antarctica.
Among the samples, they identified five distinct types of preservation: saponification, freezing, tanning, dehydration, and a mysterious category simply labeled “unknown.”
Brains preserved by unknown processes account for nearly a third of recorded brains.
Specimens of this category have been found in sunken ships, in tombs, and in coffins made of wood and lead.
In these ancient human remains, the brain is often the only soft tissue discovered by archaeologists.
Alexandra Morton-Hayward, a forensic anthropologist and doctoral student at the University of Oxford, holds two halves of a 200-year-old brain, preserved in formalin.
This table shows the five main types of brain preservation: saponification, freezing, tanning, dehydration and “unknown”. The middle bars show that the further back in time we go, the less of each type of preservation we find.
Saponification is the same process that turns grease and lye into soap, and it can leave a brain with roughly the same consistency: from hard and crumbly to soft and mushy.
This type of preservation occurred when the chemical bonds of brain fats were broken and their components combined with metals like calcium, sodium or magnesium to produce a substance known as adipocere or “funeral wax”.
Most saponified brains are less than 200 years old.
Freezing is pretty self-explanatory and it tends to happen when someone dies in cold climates.
Because cells can break down after thawing and refreezing repeatedly – think spinach frozen after thawing – brain preserved by freezing is often difficult to study.
Tanning produces a “slightly supple, dark-colored mass,” much like another familiar tanning product: leather.
This brain belonged to a person buried in the First Baptist Church of Philadelphia, founded in 1698. More than 40 brains were exhumed from this cemetery and many of the brain owners had died from a devastating yellow fever epidemic in 1698. The end of the 18th century.
Brain fragments from a person buried in a Victorian cemetery around 200 years ago in Bristol, UK. No other soft tissue survived among the bones, which were excavated from the heavily waterlogged grave.
Tanning most often affected the brains of bodies preserved in peat, because environmental conditions prevented bacteria from destroying the tissue.
Dehydration, the most common type of preservation, accounted for 1,667 of the samples, or 38 percent.
The loss of water meant that these brains became quite fragile.
These brains came either from natural processes such as hot, dry climates or exposure to drafts, or from actual intentional mummification.
Notably, the “unknown” brains were found to be similar in terms of consistency and chemical composition.
This group included 1,308 brains, or almost a third.
In these samples, these were the only soft tissue remains with skeletons – and they were the oldest, some dating back 12,000 years.
But scientists still don’t know how this preservation method, which appears to be unique to the brain and no other body tissue, works.
These brains were not found in a specific environment, but rather in people buried in mass graves.
THE study was published in the journal Proceedings of the Royal Society B.