Migration, because it inherently links points of origin and destination through trajectories, draws attention to the connections that are central to understand­ing world history.

Studies of migration, especially in recent years, have been effective both in documenting the evolving patterns of human migration and in illustrating the accompanying historical connections.

The study of migration is especially helpful in advancing the understand­ing of communities. Language communities, ethnic communities, political communities, religious communities - all of these are best studied not simply as discrete social groupings with their own traditions, but as permeable groups that are linked to each other through the voluntary and involuntary movement of individuals and groups. A migration-oriented approach to communities draws attention to heterogeneity and processes of interaction within communities. Further, study of migration facilitates the understand­ing of the multiple levels and scales at which the human experience unfolds. Effective stories of migration range from the individual tales of merchants, warriors, students, and the enslaved - male and female - to the chronicles of ethnic groups on the move or in formation, and to narratives of the repopu­lation of whole continents. More generally, studies of migration illustrate several types of scale: in space, in time, in the specific populations migrating, and in the range of human affairs affected by migration.

The study of migration relies on a range of methodologies, and recent research is bringing advances in the articulation of these methods. Documen­tary research based on records of governments and business firms has provided much of the information on migration in recent times. Written narratives and oral traditions have provided further information on migrations, especially in times before the past five centuries. Archaeological research was long the core of research on migration for times before the written record began.

Studies of migration need not be limited to the movement of people: they can also trace movements of technology (from bows and arrows to tele­phones), of ideas (Buddhism, literacy), and of associated or commensal species (lice, dogs, and potatoes). Indeed, the relations of these different aspects of migration to each other form a growing portion of current studies in migration. The full range of these studies begins to make it possible to develop an assessment of the function of migration in human society. That is, at the most basic levels migration brings genetic diversity and allows exchange of innovations that have enabled humans to learn and spread in ways exceeding the range of any previous large animals. While migration- induced learning has brought dramatic and recurring change in human experience, migration also reveals a fundamental continuity in history. Social processes relying on cross-community migration have been at the core of the big changes from the early days of humanity, and give every indication of continuing in similar form far into the future.