“An archive of ancient human brains.”

Science Daily has research from University of Oxford archaeologists that is potentially upending a long-standing belief about digging up our long-ago ancestors. After looking through records in 10 different languages, they’ve determined that it’s far more common than you’d think for human brains and nerves to be preserved along with skin and bone:

A new study conducted by researchers at the University of Oxford, led by postgraduate researcher Alexandra Morton-Hayward (Department of Earth Sciences, Oxford), has challenged previously held views that brain preservation in the archaeological record is extremely rare. The team compiled a new archive of preserved human brains, which highlighted that nervous tissues actually persist in much greater abundances than traditionally thought, assisted by conditions that prevent decay. This global archive, drawing on source material in more than ten languages, represents the largest, most complete study of the archaeological literature to-date, and exceeds 20-fold the number of brains previously compiled.

This work, published today in the Proceedings of the Royal Society B, brings together the records of more than 4,000 preserved human brains from over two hundred sources, across six continents (excluding Antarctica). Many of these brains were up to 12,000 years old, and found in records dating back to the mid-17th century. Scouring the literature and canvassing historians worldwide, this concerted search revealed a bewildering array of archaeological sites yielding ancient human brains, including the shores of a lakebed in Stone Age Sweden, the depths of an Iranian salt mine around 500 BC, and the summit of Andean volcanoes at the height of the Incan Empire.

These shrunken, discoloured tissues were found preserved in all manner of individuals: from Egyptian and Korean royalty, through British and Danish monks, to Arctic explorers and victims of war.

Over 1,300 of the human brains were the only soft tissues preserved, prompting questions as to why the brain may persist when other organs perish. Interestingly, these brains also represent the oldest in the archive, with several dating to the last Ice Age. The mechanism of preservation for these oldest brains remains unknown; however, the research team suggest that molecular crosslinking and metal complexation — proteins and lipids fusing in the presence of elements like iron or copper — are feasible mechanisms by which nervous tissues might be preserved over long timescales.

Alexandra Morton-Hayward, lead author of the study, said “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. Whether those circumstances are environmental, or related to the brain’s unique biochemistry, is the focus of our ongoing and future work. 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.”

You can read more of the brain research here, in Proceedings of the Royal Society B.