The Evolution of Ethnolinguistic Diversity

Humans divide themselves up into groups based on a shared cultural identity and common descent. Culturally inherited differences in dress, language, and institutions are often used as symbolic markers of the boundaries of these ethnic groups. Relatively little is known about the function of such ethnic groups, and why ethnic diversity is high in some regions yet lower in others. In this paper, we demonstrate how investigating the spatial distribution of ethnolinguistic groups can reveal the factors that affect the origin and maintenance of human ethnic group diversity. Here we describe the use of a Geographic Information System to construct a large database that integrates information about languages with a number of environmental, ecological, and ethnographic variables. Using these data on the spatial distribution of ethnolinguistic groups, we employ a hierarchical linear modeling approach to test a variety of hypotheses concerning the function of such groups. Despite revealing intriguing spatial patterns such as the latitudinal gradient in ethnolinguistic diversity, previous analyses suggested that the direct effects of environmental variables on the distribution of ethnolinguistic groups were in fact quite small. Here we show that the strength of the relationship between ethnolinguistic area and environmental variables is stronger in societies whose primary mode of subsistence is foraging. We then go on to demonstrate this same finding using the estimated native distributions of ethnolinguistic group in the Americas and Australia. In particular, Net Primary Productivity is shown to be a good predictor of the area covered by ethnolinguistic groups in foragers but not in agriculturalists. This provides support for the idea that the factors affecting ethnic diversity have changed in a systematic way with changes in subsistence strategies and social organization. We highlight future avenues for spatially explicit investigations of the evolution of ethnic diversity, and suggest that the evolutionary ecological approach adopted here may provide important insights into processes affecting ethnic diversity in the modern world.