Ancient parasite analysis: Exploring infectious diseases in past societies

Parasites are the causative agents of infectious diseases that have affected humans throughout our evolution. Some appear to have been ubiquitous in past societies around the globe, but others were only viable in distinct regions where the conditions suited their complex life cycles. This review considers how we can recover and identify ancient parasites, before interrogating the literature to explore some of the ways this evidence can help us to better understand past societies. Variability in sanitation infrastructure, diet, cooking methods, lifestyle, behaviour and environment all affected the kinds of parasites that could infect past people, and determined how common infection was. The health consequences of parasite infection in different past communities are considered, as we think about the many ways health can be impaired by such infections. Where a good number of studies have focussed on one geographic region, variation in the apparent endemic range of certain parasite species allows an assessment of the relationship between humans and the surrounding environment. When parasites are found outside of their usual range this can be used as a marker of long distance travel and migrations. As the body of evidence for parasites in past populations expands, so do the ways we can use this information in an innovative manner to better understand those who lived in the past.