Rethinking Anthropological Perspectives on Migration

13. Continuity and Change in AnthropologicalPerspectives on Migration: Insights from Molecular Anthropology

13 Continuity and Change in Anthropological Perspectives on Migration Insights from Molecular Anthropology Deborah A. Bolnick Historically, anthropological discussions of migration have focused on migration as both a source and form of major change. The term “migration” has been used most frequently to refer to mass population movements over large distances and across sociocultural boundaries (Cabana 2002; Clark 2001). In most cases, it is assumed that these movements involve well-defined groups with distinct cultural and biological traits (Burmeister 2000). This characterization of migration suggests that immigrants to a new area will be clearly identifiable as foreigners, and Andresen has argued that “to demonstrate migration it is necessary to discover . . . a foreign group in the suspected immigration area” (2000:554). Many anthropologists also associate migration with population replacement, as in Rouse’s description of migration as when “the people of one area expands into another area, replacing the latter’s population ” (1986:13). These formulations of migration clearly emphasize the association between migration and change: migrants experience change when they move from one physical and social environment to another and they produce change in the geographic region where they eventually settle. As Cabana (this volume; 2002) argues, this conceptualization of migration (i.e., migration as a source and form of change) reflects the role that it has traditionally played in studies of human prehistory. In archaeological research, migration has generally been considered in the context of material culture change, as an explanation for discontinuities in the archaeological record. Similarly, in studies of prehistoric skeletal remains, physical anthropologists have often proposed migrations to account for changes in skeletal morphology over time. Migration hypotheses of this sort were especially popular among the culture historians and racial typologists of the early twentieth century (for example, see Childe 1925; Hooton 1930; and Parker 1916), but they have also 264 Deborah A. Bolnick played a role in more recent studies. Thus, while other sources of change certainly exist (e.g., cultural diffusion, in situ development, genetic drift, natural selection), migration has frequently served as a ready explanation for cultural and biological change in studies of human prehistory. In this chapter, I consider the study of migration in molecular anthropology in light of these broader traditions. I examine how molecular anthropologists investigate migration, and I draw upon examples from genetic studies of Native Americans to illustrate the benefits and limitations of such research. I discuss two case studies in detail to show how molecular anthropology can yield important insights about both the process and impact of migration. Migration Studies in Molecular Anthropology Anthropologists have traditionally approached the study of prehistoric migration by examining archaeological remains, skeletal traits, linguistic patterns, and ethnographic evidence. Over the past few decades, the development of new techniques in molecular biology has made it possible to investigate past migrations using genetic data. Molecular anthropologists focus on the genetic correlates of migration, which exist because migrants alter the genetic makeup of the population at their destination when they settle and reproduce. In other words, the movement of people is accompanied by the movement of genes (known as gene flow), and this gene flow has a significant impact on the patterns of genetic variation among human populations. Those patterns comprise another important source of information about past population movements. Genetic studies are also useful because they can help circumvent some of the problems that commonly arise in other anthropological studies. For example , many bioarchaeological studies focus on skeletal morphology, but skeletal traits are influenced by both genetic and environmental factors, making it difficult to determine the precise causes of morphological trait variation. In contrast, noncoding genetic loci are not directly influenced by environmental factors. Studies of these loci can therefore help separate the biological effects of migration from patterns produced by life history, environmental adaptation , and cultural practice (all of which may be confounded in studies of skeletal morphology). Similarly, it can sometimes be difficult to pinpoint the causes of cultural or linguistic patterns. When genetic data are considered in conjunction with cultural, linguistic, and archaeological evidence, it becomes easier to distinguish the effects of migration from the effects of trade, cultural diffusion, linguistic borrowing, and in situ innovation. Molecular anthropologists rarely provide an explicit definition for “migration ” in their studies, but the term is commonly used to refer to any type Continuity and Change in Anthropological Perspectives on Migration 265 of movement that leads to gene flow. This definition comes from...