The durability of the human brain can span millennia

Archaeologists, take note: unearthed human skulls may contain brains. New data shows that the human brain is Resistant to corrosion for at least 12,000 years.

When scientists discover an ancient preserved brain, they often call the find unique or one-of-a-kind, says Alexandra Morton-Hayward. As a forensic anthropologist, she studies human remains to tell the story of the dead. She works at the University of Oxford in the UK. But as she came across report after report of preserved brains, Morton-Hayward began to wonder just how rare such finds might be.

So she and her colleagues scoured four centuries of archaeological research for descriptions of naturally preserved brains, uncovering more than 4,400 brains from hundreds of excavation sites.

The researchers categorized the brains into five types based on how they were prevented from decaying: Some were frozen or dried, others were tanned, preserving the organs in the same way that leather is treated (this happens when the remains react with chemicals found in swamps), and still others were saponified.

This final natural process turns some of the fat into a fairly stable, soap-like substance called grave wax. “It’s really nasty,” Morton-Hayward says. “It smells really bad.”

Nearly a third of the brains did not fit into any of these four types. In these cases, only the brain remained, preserving the once-soft, fluffy body tissue. The team theorized that some unknown mechanism had protected the tissue from deterioration. The researchers also gathered past and present climate information to learn about conditions associated with the preservation of each type of brain.

The brains, preserved by an unknown process, tended to last much longer than other types of brains. The oldest was dated to 12,000 years ago. Most of these specimens came from moist environments, such as sunken ships, the bottoms of wells, and lake beds.

The study was published on March 20th. Proceedings of the Royal Society B.

Based on their study of the soft tissues of dinosaurs and other ancient creatures, the team hypothesized how a still-unknown mechanism might protect the brain. Morton-Hayward now thinks that the brain’s chemistry and how it worked during life might persist after death. Types of proteins and lipids in the brain might tend to bind together to form large, stable molecules.

Data Dive:

1. Which type of storage method takes up the most brain space?
2. Which process preserves the brain for the shortest period of time?
3. How does the number of brains in the “unknown” category change over time?
4. How does the change in the number of “unknown” brains over time compare to the number of frozen brains? How does it compare to the sun-dried brains?
5. Where do you think they found the frozen brains? What about the dehydrated brains?
6. What is another way to present this data?