Faecal biomarker and archaeobotanical analyses of sediments from a public latrine shed new light on ruralisation in Sagalassos, Turkey

A public latrine in the ‘Imperial Baths’ of Sagalassos was transformed into a dump site in the early Byzantine period. Several layers of urban waste, including ceramics, bones, glass and perhaps excrements were deposited on the floor. Faecal biomarker analyses and archaeobotanical analyses were conducted to reconstruct the history of the room. 5β-stanols of human origin, such as coprostanol, were found in the sewage channels together with mineralised plant remains, indicating a human faecal context. The botanical remains are furthermore representative of the Roman diet of the Sagalassians. Soil layers, deposited on top of the latrine floor and dating to the early Byzantine period, contained herbivore derived 5β-stanols, such as 5β-stigmastanol and epi-5β-stigmastanol. Additionally, a clear predominance of epi-5β-stanols over 5β-stanols showed that the animal dung has been subject to composting. In this period, the former latrine was clearly used as a manure production site which is further confirmed by stratigraphic evidence of large amounts of urban waste artefacts, which were commonly collected together with manure before application on the fields. The results of the present study support the theory that off-site potsherd scattering can be used as a proxy for manuring events. Additionally, the data show key evidence for vertical migration of 5β-stanols and presumably also for the leaching of bile acids.