Although we have plenty of fantastic artefacts on show in our attractions, there are also many fascinating objects which are too fragile to be on public display.

In Archaeology it is very rare to find any soft tissue remains: no skin, no flesh, no hair and definitely no brains. However, in 2009, the archaeologists from York Archaeological Trust (YAT) found something very surprising at a site in Heslington, York.

During the excavation of an Iron Age landscape at University of York, a skull, with the jaw and two vertebrae still attached was discovered face down in a pit, without any evidence of what had happened to the rest of its body. At first it looked like a normal skull.

It was not until Rachel Cubitt, from the Finds Department, was cleaning the skull and turned it over that she realised there was something loose inside.

“I peered though the hole at the base of the skull to investigate and to my surprise saw a quantity of bright yellow spongy material. It was unlike anything I had seen before.”

Sonia O’Connor, from Archaeological Sciences, University of Bradford, was able to confirm that this was brain. With the help of York Hospital’s Mortuary they were able to remove the top of the skull in order to get their first look at this astonishingly well-preserved human brain.

Since the discovery, a team of 34 specialists have been working on this brain to study and conserve it as much as possible. By radiocarbon dating a sample of jaw bone, it was determined that this person probably lived in the 6th Century BC, which makes this brain about 2,600 years old.

By looking at the teeth and the shape of the skull it is likely this person was a man between 26 and 45 years old. An examination of the vertebrae in the neck tells us that he was first hit hard on the neck, and then the neck was severed with a small sharp knife, for reasons we can only guess.

Preservation

No one quite understands how this strange preservation may have happened. We are all aware of cases where human bodies have been preserved in some way, but we normally have a good idea of how this worked.

Normally, in order for things to rot, they must have water, oxygen, and be at a temperature where the bacteria and rotting processes can be active. When one or more of these factors is missing, then preservation can occur.

Dry preservation

This is how your dried pasta works, as it has no moisture therefore does not have active bacteria.

Egyptian Mummies are a very famous example of this. During mummification most of the internal organs are removed, and the mummies are dried out by being covered and stuffed with salt for forty days. After that the body is stuffed with dry things like sawdust and linen. This complicated process leads to this type of dry preservation.

Cold preservation

This is how food in your freezer works. The temperature in your freezer is too cold for active bacteria, so your food does not rot.

This is how ice-men or frozen animals are preserved, like Otzi the Iceman.

Anoxic (oxygen-free) preservation

This is how your tinned food work: there is no oxygen inside the tins, so the food inside does not rot away.

This is also how bog bodies are preserved, like the Lindow Man. As there was so little oxygen in the soil, the skin and flesh of this man were preserved for about 2000 years.

What about the Heslington Brain?

In the case of the Heslington Brain, the outside of the head has rotted as normal, but the inside is preserved.

After a lot of research the evidence suggests that the head was cut from the body very quickly after the person was killed. It was then immediately buried in a pit in wet, clay-rich ground, providing a sealed, oxygen-free burial environment.

Over time the skin, hair and flesh of the skull did undergo chemical breakdown and gradually disappear, but the fats and proteins of the brain tissue linked together to form a mass of large complex molecules. This resulted in the brain shrinking, but it also preserved its shape and many microscopic features only found in brain tissue.

As there was no new oxygen in the brain, and no movement, it was protected and preserved.

We do not understand everything yet and the research continues. Perhaps the state of health of the person before death was also a factor that helped lead to its preservation? Who knows what more we will discover in the future?

YAT has lots of ways to get involved in Archaeology in York, check out our Archaeology Live website for a chance to get your own hands muddy!

For families and children, come and get a hands on experience of what archaeology is all about here at DIG.