Susanna Sabin

How long has tuberculosis been an infectious disease in humans? Today, tuberculosis is one of the most deadly, omnipresent pathogens in the world, but its role in human history remains unclear. Our idea of when it emerged in human populations is caught between two hypotheses: a) that tuberculosis emerged during the Neolithic demographic transition as part of a large epidemiological trend in which virulent infectious diseases began to thrive in dense, sedentary populations, or b) that tuberculosis infected humans before the advent of agriculture, pre-dating the Neolithic transition, and potentially having a significant evolutionary impact on Homo sapiens. Sequencing ancient genomes of the Mycobacterium tuberculosis complex (MTBC), the group of bacteria that cause the disease, can provide the data necessary to test these hypotheses. Ancient genomes can act as calibration points for molecular dating techniques. The value of this calibration was seen in recent years as the first ancient tuberculosis genomes were published, suggesting the MTBC was considerably younger than indicated by prior estimates based on modern genetic data. However, given the different mutation rates between lineages within the MTBC, further calibration of this molecular clock is required. This project will scour diverse and under-utlilized sources of tuberculosis DNA, such as ancient wild pinnipeds from natural and archaeological contexts, ancient European humans, and modern non-human primates, in order to generate multiple, high-quality genomes that can act as calibration points across time, space, and host. This calibration will allow us to understand human history through the lens of an ancient pathogen, by clarifying how ancient it truly is.