Statistical methods for bioarchaeology: applications of age-adjustment and logistic regression to comparisons of skeletal populations with differing age-structures

Previous studies of patterns of osteoarthritis involvement in prehistoric skeletal populations have been used to suggest differences in lifestyle or subsistence patterns. In spite of the intriguing nature of such studies, inadequate controls for the potential confounding effects of age have made results less secure than they appear. While researchers remain unable to control for the inherent limitations imposed by preservation bias, meaningful advancement could be made in the analysis of these data. Here we propose two methods from epidemiology that would allow more robust comparisons between populations with differing age-structures: age-adjustment and logistic regression. We apply these two methods to previously published data from prehistoric populations of the American Great Basin. In doing so, we are able to discern sex differences in risk for osteoarthritis at the shoulder (beta = −1.82, SE = 0.74, OR = 0.16, 95% CI = 0.04–0.69, p = 0.013), elbow (beta = −2.07, SE = 0.82, OR = 0.13, 95% CI = 0.03–0.63, p = 0.011), and in the foot (beta = −3.11, SE = 1.57, OR = 0.04, 95% CI = 0.00–0.97, p = 0.048), that were not noted in previous analyses of these data. These findings suggest that greater clarity of results and more precise comparisons of risk may be achieved by using these methods. We conclude that further application of these methods to bioarchaeological studies would potentially improve what can be said about prehistoric health patterns and lifeways.     

Review

Bininj Gun‐wok: a pan‐dialectal grammar of Mayali, Kunwinjku and Kune. By Nicholas Evans. Canberra: Pacific Linguistics. 2003. 2 volumes. Pp: xxix + 357, xxii + 389. Price: A$159.50 (for both volumes)     

Landcare: Policy,Practice and Partnerships

Landcare is a response to the land degradation crisis facing Australia and is both a community process and a government policy. ‘Landcare’ is a contested term with different meanings being placed on it by individuals and groups from different places with different levels of power and local knowledge. A key concept of Landcare is forming partnerships, which are also seen in very different terms by various Landcare stakeholders. Landcare places great value on local environmental knowledge and senses of place. The achievements of Landcare in facilitating cultural change are assessed and the factors identified that will determine whether Landcare can be ‘scaled up’ to address wider issues of ecological sustainability.     

The Sheep Project (1): determining skeletal growth,timing of epiphyseal fusion and morphometric variation in unimproved Shetland sheep of known age,sex, castration status and nutrition

The Sheep Project was designed to investigate the effects of castration, breeding age and nutritional plane on bone growth, epiphyseal fusion, tooth eruption and tooth wear in sheep. The project investigates a population of 356 unimproved Shetland sheep skeletons evenly distributed between females bred at different ages, males and castrates, raised on either high or low nutritional planes. This first instalment focuses on two aspects of our larger study, namely bone growth and epiphyseal fusion as affected by sex, castration and nutrition. Nutrition, sex and castration are shown to influence bone growth in ways that are often element-dependant and not consistent through time. We demonstrate that metric variability (variance) is strongest in males, with little difference between females and castrates, and that, in our sample, nutrition has little influence on variance in any sex cohort. Of importance to the development of models of past animal management this study demonstrates that the standard epiphyseal fusion ranges used by zooarchaeologists are too narrow in most instances and do not account for the large variation between sexes or the lesser variation between planes of nutrition. We recommend methods for recognizing castration and the presence of more than one sheep breed, or type, within the zooarchaeological record.