Noncommunicable human diseases (NCDs) exact devastating emotional, physical, and financial tolls on modern society. While ancient DNA research has shed some light on the evolutionary histories of infectious diseases, researchers have not yet been able to track the origin and emergence of NCDs. Understanding when and how these emerged and which dietary, environmental, and behavioral factors associate with them would prove immensely useful in developing ameliorative strategies for these conditions. Although NCDs cannot be directly traced archeologically due to the absence of distinctive pathological agents, many of these conditions are associated with specific, and often inflammation-associated, microbiome characteristics in modern populations. Due to the remarkable preservation of ancient human microbiomes in dental calculus, it may be possible to identify differential morbidity and mortality risks in ancient populations by analyzing these microbial profiles. Indeed, preliminary research into this area has already revealed the association of distinctive ancient microbial communities with skeletal health markers linked to systemic conditions. The goal of this proposed project is to expand upon this underlying work via three major aims: (1) identify and describe the associations between ancient oral microbial functions and ecologies with skeletal health indicators, (2) investigate whether differences in ancient oral microbiomes that are associated with disparate health outcomes are linked with dietary, environmental, or behavioral factors, and (3) evaluate whether the oral microbiome can be used as a tool for modeling NCD-associated frailty in ancient people. Aims 1 and 2 will be executed within a well-described archeological population (n = 127) from medieval and post-medieval London comprising 9 archeological sites, and aim 3 will utilize a more geographically-diverse ancient British population (n = 108) to evaluate frailty-associated models.