Soft tissues preserved in the geological record, let alone entire organs, are rare finds for palaeobiologists. But new research suggests that preserved human brains are more common in the archaeological record than previously thought.
A team led by researchers at the Oxford University has compiled a new archive of more than 4,000 preserved human brains from more than 200 sources – in the most complete study of the archaeological literature to date.
“In the forensic field, it’s well-known that the brain is one of the first organs to decompose after death – yet this huge archive clearly demonstrates that there are certain circumstances in which it survives,” says palaeobiologist Dr Alexandra Morton-Hayward, lead author of the study published Proceedings of the Royal Society B.
They found that the brains, which were up to 12,000 years old and sourced from all continents except Antarctica, were assisted by conditions that prevent decay.
Co-author, Professor Erin Saupe from the Department of Earth Sciences at Oxford adds:“This record of ancient brains highlights the array of environments in which they can be preserved, from the high arctic to arid deserts.”
Analysis of historic climate data revealed patterns in the environmental conditions associated with different modes of preservation through time – including dehydration, freezing, saponification (the transformation of fats to ‘grave wax’) and tanning (usually with peat, to form ‘bog bodies’).
Interestingly, more than 1,300 of the human brains in this study were the only soft tissues preserved in the whole body. This raises questions about why the brain can remain while other organs decompose.
“Whether those circumstances are environmental, or related to the brain’s unique biochemistry, is the focus of our ongoing and future work,” says Morton-Hayword.
“We’re finding amazing numbers and types of ancient biomolecules preserved in these archaeological brains, and it’s exciting to explore all that they can tell us about life and death in our ancestors.”
