Insights on the paleoepidemiology of ancient tuberculosis from the structural analysis of postcranial remains from the Ligurian Neolithic (northwestern Italy)

The aim of this research is to gain insights on the progression timeline of osteoarticular tuberculosis (TB)in people from the Neolithic period by using skeletal traits that are independent of the bony lesions.The body proportions and postcranial mechanical strength of bones from two individuals from Liguria innorthwestern Italy (Arene Candide 5, adolescent, and Arma dell’Aquila 1, adult), were compared with therest of the Ligurian Neolithic skeletal series (45 individuals). If TB led to wasting of the skeleton and lack ofnormal function that endured for years, as often happens today, a clear signature of postcranial gracilityand disruption of development should be apparent. Conversely, rapid progress of the disease wouldleave little systemic macroscopic change in the skeleton, except for the bony lesions directly caused bythe TB pathogen, suggesting a different level of bacterial virulence in the past. The extreme biomechanicalgracility observed in the lower limb of Arene Candide 5 suggests a period of compromised diaphysealperiosteal apposition during ontogeny due to metabolic disturbances likely linked to TB. Results suggestthat, in Neolithic Liguria, TB in humans saw a slow, chronic progression, which is characteristic of diseaseswith long histories of host-pathogen co-evolution.