Actualistic research into dynamic impact and its implications for understanding differential bone fragmentation and survivorship

The relationship between bone mineral density and archaeological bone survivorship has played a critical role in zooarchaeological and taphonomic studies in recent decades. Numerous studies have suggested that higher-density skeletal element portions survive more frequently than lower-density element portions when archaeological assemblages are affected by some taphonomic processes. Interpretations of density mediated destruction have become commonplace in the archaeological literature, and are often used to explain the absence of certain bone elements and element parts in zooarchaeological assemblages. This study explores the effects of rockfall on bovid elements in varied environmental conditions and the differential survivorship of their element parts, and has implications for understanding the taphonomic processes through which bones are subjected to dynamic loading. Actualistic rockfall experiments conducted on twelve samples of frozen, fresh, and semi-dried bovid bones reveal that the generally low-density epiphyseal ends of bone elements resist fracture and analytical deletion with more frequency than the higher-density diaphyses. This evidence suggests that bone density does not correlate with likelihood of breakage or effective archaeological “destruction” when rockfall and other processes that result in dynamic impact are in action. While this research does not question the relationship between bone mineral density and the likelihood for archaeological survivorship as the result of some taphonomic processes, it presents one specific set of taphonomic processes that result in the differential survivorship of low density bone elements parts and the fragmentation and destruction of higher density element parts. This research presents evidence that shows that dynamic impact is a process capable of fragmenting and sometimes destroying high-density elements while low-density elements survive.