Mandibular hypodontia and osteoarthritis in prehistoric bighorn sheep (Ovis canadensis) in eastern Washington State,USA

Mandibular hypodontia of the p2 was found to occur in 3 out of 21 individual prehistoric Rocky Mountain bighorn sheep (Ovis canadensis canadensis) from Moses Coulee Cave in eastern Washington State, similar to its frequency of occurrence in modern bighorn. There is no evidence of lumpy jaw (mandibular osteomyelitis) in the Moses Coulee Cave collection. Evidence from Moses Coulee Cave aligns with the hypothesis that low frequencies of hypodontia and lumpy jaw occur in healthy, evolutionarily old (maintenance) populations in order to maintain the occlusal area and thus maximise efficiency of food procurement and processing. Osteoarthritis was found to occur in 1 out of 70 individual Rocky Mountain bighorn sheep (Ovis canadensis canadensis) astragali in the Moses Coulee Cave collection. This prevalence is unsurprising given a population dominated by prime‐age individuals. Osteoarthritis was likely selected against given that individuals must be agile to effectively use rugged terrain to escape predation and as a general measure suggests a healthy population. Copyright © 2009 John Wiley & Sons, Ltd.