The extinct osteoarthritic lagomorphs (Prolagus sardus) from Sardinia (Italy) reveal further evidence of life history evolution in insular domains

The study of past pathologies by means of quantitative reports is an underexplored approach to deal with the biology and ecology of extinct taxa. In the present study, we assessed the prevalence rate of primary osteoarthritis in a large sample of Prolagus sardus (Mammalia, Lagomorpha) from Medusa Cave (also known as Grotta Dragonara, Sardinia, Italy; Late Pleistocene) to shed light on the evolutionary history of small mammals under isolation regimes. The hip and knee joints of 246 femora were examined grossly, microscopically, and using advanced radiology, recording essential biological features such as age or weight. We noted that 27.7% of skeletally mature sample had degenerative disorder of the joints, with higher frequency in adults (p-value < 0.05), regardless of their body mass (p-value > 0.05). Histologically, affected joints displayed changes in subchondral plate potentially reflecting adaptive modeling. Our analysis revealed ageing (the extended lifespan) as the main driver of this prevalence rate, whereas mechanical factors (caused by a particular lifestyle) were considered of significantly lesser importance. Our results provide additional empirical support to the analytical framework of life history theory from a new perspective, according to which, under low extrinsic mortality regimes, selection should favor slow-strategies (extended lifespan) in small-sized mammals.