In this month’s ‘Science Notes’, we dive into the world of palaeoparasitology, and examine what the study of faecal matter can tell us about human health and behaviour in the past. While we may not like to acknowledge it, humans play host to a large number of parasites. Which parasites affect us and how they influence our health, however, can vary wildly based on our diet, living conditions, and other environmental factors.
Palaeoparasitology is not a new discipline, but it has grown considerably in recent years, particularly as more and more institutes and centres focusing on the archaeological sciences have been created. As such, we are starting to build up an idea of the evolution and spread of parasites across Europe, particularly during the Neolithic and medieval periods. Data from other periods are still sorely lacking, but a new study has examined the presence of parasites from the Bronze Age site of Must Farm, adding vital information on the evolution of human–parasite interactions throughout prehistory.
Must Farm is an amazingly preserved roundhouse settlement in the Cambridgeshire fens, excavated by Cambridge Archaeological Unit, that appears to have been destroyed by fire almost as quickly as it was built (see CA 312 and 319). Its complete destruction and subsequent burial under marshy conditions helped preserve it almost perfectly, and, during the excavation of the site between 2015 and 2016, some amazing examples of day-to-day life on the fen were recovered, including 15 examples of coprolites (or faeces) from both humans and canines.
All of these samples have now been analysed at the Ancient Parasites Laboratory at the University of Cambridge, along with sediment samples from ten different locations around the settlement in order to see what parasites may have been naturally present in the environment. By making each sample into a liquid suspension and then passing it through increasingly smaller sieves, the Cambridge team was able to isolate a wide range of eggs from parasitic worms, or helminths. These were then examined under a microscope in order to identify which species they came from.
Four different taxa of eggs were observed in the sediment samples: fish tapeworm (Diphyllobothrium sp.), whipworm (Trichuris sp.), Capillaria sp., and giant kidney worm (Dioctophyme renale). These same helminth species were also present in the coprolites, in even higher concentrations, but the coprolites contained another type of helminth egg that was not present in the sediment samples: Echinostoma sp., a genus of trematode that can infect the gastrointestinal tract of humans and other animals, causing a disease known as echinostomiasis.
Fish tapeworm, giant kidney worm, and echinostoma infections are commonly caused by consuming raw or undercooked fish. The presence of all three of these parasites would suggest a general level of contamination in the settlement area, and it is easy to see how this might have happened, as the settlement was built over a very slowmoving channel. With the inhabitants disposing of their waste in the very water from which they got their food, and without enough water flow to clear the waste from the immediate area, a feedback loop of contamination was created.
The whipworm eggs, however, may have had a slightly different origin. The size and shape of these eggs suggest that they are likely to all be examples of pig whipworm (T. suis), and not human whipworm (T. trichiura). This would indicate a case of ‘false parasitism’, as the humans and dogs from which the coprolites came were not the immediate hosts. Instead, their faeces probably acquired whipworm eggs when the eggs passed through their digestive tracts having been consumed with the intestines of infected domesticated pigs or wild boars. Indeed, the butchered bones of both pigs and boars were present around the site. A similar cause may also be hypothesised for the Capillaria eggs. While the exact subspecies of this helminth could not be identified, C. aerophilia appears to flourish in aquatic environments.
In comparing the parasitic make-up of Must Farm with that of the only other Bronze Age site in Britain to have been thoroughly investigated for the presence of parasites, we can clearly see how behaviour and environmental conditions affect parasite presence. At Brean Down, a coastal farming site in southern England, roundworm – a soil-transmitted helminth – was a commonly identified parasite; indeed, roundworm has been found to be common in many British and European sites stretching from the Neolithic through to the medieval period. The fact that it was not found at Must Farm is notable, and suggests that while the environment and diet of its inhabitants made them more vulnerable to aquatic parasites, at the same time it protected them from infections that require dry land to complete their life cycle.
The paper highlighting these results can be read for free at https://doi.org/10.1017/S0031182019001021.