The Chances of Soft Tissue Preservation in the Geological Record
The chances of soft tissue preservation in the geological record are quite slim, unless efforts are made to halt the decay process artificially, such as through embalming or freezing. Among these, the survival of whole organs is an exceptionally rare occurrence. However, a recent study led by University of Oxford postgraduate researcher Alexandra Morton-Hayward has challenged the long-held belief that brain preservation in archaeological records is a one-of-a-kind phenomenon.
Comprehensive Database of Preserved Human Brains
The research team, which included scholars from the Department of Earth Sciences, Oxford, compiled a comprehensive database of preserved human brains and discovered that nervous tissues are more abundant than previously thought. This is aided by certain conditions that inhibit decay. The global archive, which includes data from over two hundred sources in more than ten languages, is the most extensive and complete study of archaeological literature to date, with over 4,000 preserved human brains - more than 20 times the number previously compiled.
Preserved Human Brains from Six Continents
Published in the Proceedings of the Royal Society B, the study reveals that over 4,000 preserved human brains have been found in six continents, dating back to over 12,000 years. These brains have been discovered in various settings, from the shores of a lake in Stone Age Sweden, to an Iranian salt mine dating back to 500 BC, and even the peak of Andean volcanoes during the Incan Empire.
Diverse Backgrounds of Preserved Human Brains
These brains, which appear shrunken and discolored, belonged to individuals from diverse backgrounds, including Egyptian and Korean royalty, British and Danish monks, Arctic explorers, and victims of war. According to co-author Professor Erin Saupe, the Department of Earth Sciences, University of Oxford, the diverse locations in which these ancient brains have been found highlight their potential for preservation, from the high Arctic to arid deserts.
Potential for Preservation of Soft Tissues
The researchers also analyzed historic climate data from each region to understand the environmental conditions that lead to preservation of soft tissues. Interestingly, over 1,300 of the preserved human brains in the database were the only soft tissues that were found, raising questions about why the brain can remain intact when other organs decay. These brains are also the oldest in the archive, with some dating back to the last Ice Age. However, the mechanism behind their preservation remains unknown, although the researchers suggest that molecular crosslinking and metal complexation may be responsible for preserving nervous tissues over such long periods.
The Existence of a Vast Archive
Lead author Alexandra Morton-Hayward explains that while it is well-known that the brain decomposes quickly after death, the existence of this vast archive proves that there are specific circumstances in which it can survive. The researchers hope to explore the unique biomolecules preserved in these ancient brains to gain insights into our ancestors' lives and deaths, as well as the evolution of human cognition and behavior.
Valuable Insights for Bioarchaeologists
Co-author Dr Ross Anderson adds that the discovery of preserved soft tissues is a significant breakthrough for bioarchaeologists, as they provide a wealth of information about our past that cannot be obtained from hard tissues alone. With less than 1% of preserved brains analyzed for ancient biomolecules, the untapped archive of 4,400 human brains described in this study could provide valuable insights into ancient health, disease, and the evolution of our species.