Climatic Adaptation and Postcranial Metric Variation in Precontact North America

The purpose of this dissertation is to investigate patterns of variation in the postcranial skeleton of prehistoric American populations as they are related to variation in climate. Two ecogeographical rules proposed by Karl Bergmann (1847) and Joel Allen (1877) describe expected patterns of variation with widespread, warm-blooded species. Modern humans in the Old World largely conform to this pattern (Holliday 1997a). This study seeks to explore if the same patterns are present in the New World.

Skeletal material from 25 North American bioarchaeological collections was used in this analysis. A series of 29 measurements of the postcranial skeleton were collected from 854 individuals. These measurements were analyzed with respect to site-specific temperature and precipitation data using univariate and multiple regression analysis, analysis of size and shape using “Mosimann” type shape variables (Darroch and Mosimann 1985), and canonical correlation analysis.

The results of this study show that there is a significant relationship between climate and postcranial variation in this sample, particularly in measurements of long bone length and epiphyseal size. Radius and tibia length appear to be the most highly correlated with climate variables, as would be expected if thermoregulation is a significant biological stress (Holliday 1999).

Comparison between this sample and data collected from Old World samples suggest that adaptation to climate has occurred in North America, but not to the same degree as is seen in the Old World. This suggests that the relatively recent peopling of the Americas, as well as other factors such possible long-distance migrations, have influenced the potential effects of adaptation to climate.