A HUMAN brain found in Heslington may have been preserved for more than 2,000 years because it was encased in mud, archaeologists have said.

The ancient organ was discovered inside a decapitated skull at a dig on the site the new University of York buildings at Heslington East in 2008.

Tests showed the grisly remains dated back to the 6th Century BC, making them 2,600 years old.

Now archaeologists have said the fact the skull was buried in wet, clay-rich ground with no oxygen may explain why it was so well preserved, although the exact reason for its survival is unknown.

The York Archaeological Trust said it was "exceptionally rare" to find any soft tissue remains dating from so far back.

Since the discovery in 2008, a team of 34 specialists have been working on this brain to study and conserve it.

Tests show the skull likely belonged to a man aged between 26 and 45, who was hit hard on the neck before his head was removed from the body using a small, sharp knife and subjected to a quick burial - which may be another reason for its survival.

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, preservation can occur. Over time the skin, hair and flesh of the skull had rotted but no new oxygen in the brain and a lack of movement, may have protected and preserved it, the trust said.