Preservation of brain material in the archaeological record: A case study in the New Zealand colonial context

The preservation of soft tissue in the archaeological record is a rare phenomenon, especially in temperate contexts. Despite this, brain material is sometimes preserved in temperate climates, even in the absence of other soft tissue survival. However, little has been published on such finds. Archaeologists understandably have minimal experience in handling soft tissue, which may lead to brain material being left under-studied, or potentially unrecognised in situ. As such, there is a need to improve awareness of the preservation of brain material to further its identification, recovery, and analysis in the archaeological record. This paper examines preserved brain material identified in 8 of 77 unmarked colonial burials dating from the mid-to late-nineteenth century in New Zealand. This New Zealand case study provides an opportunity to consider brain preservation in archaeological contexts, and a means to study both in-life health and burial environment conditions. The preserved brain material was analysed macroscopically and microscopically using histological techniques to assess whether in vivo structures were preserved or pathogens affecting the individuals' health could be identified. Analysis revealed that all preserved brains were diagenetically altered by the burial environment macroscopically in the form of shrinkage, fragmentation, colour change, and incorporation of exogenous microorganisms. Microscopically, neural structures were not observable in the tissue, however in five cases vasculature might be preserved. Preserved vasculature in archaeological contexts may prove useful in the investigation of bloodrelated disorders, such as sickle cell disease, aneurisms, and blood clotting. Spirochetes (bacteria responsible for multiple diseases in humans, including syphilis) were observed in one individual; however, this analysis could not determine if these were a species which would have caused pathology in life or a species endogenous to the soil and incorporated after death. Importantly, no correlation between macroscopic and microscopic preservation was apparent, serving as a cautionary tale for archaeologists who may wish to analyse brain material in the future - microscopic analysis is necessary to fully assess preservation.