When people move, it is usually for a reason and although the reason might seem to the individual or family to be highly personal, like seeking a new life or going away to school, it is almost inevitable that the movement and the reason for the movement are shared with hundreds or thousands or even millions of other individuals and families in similar circumstances. If you know when someone disappeared from a certain location, it is likely that historic population movements will give you clue as to where they might have ended up.
Even if a movement seems counter to the prevailing population, there is likely a reason shared by many other people at the same time.
My early contact with the issues and problems of population movements came in graduate school where I worked on a National Science Foundation Grant to describe the origins of the Uto-Aztecan languages (also called the Piaute-Shoshone expansion). If you want to see the product, you could look at:
The modern approach would rely more on DNA and less on language, but the investigators are looking for the same thing. But language and genetics are not the same thing. Populations that are racially diverse can all speak the same language like those in the U.S. or racially homogeneous peoples may speak different languages. Language migration patterns may show a more culturally uniform migration than simply looking at DNA samples. Then again, neither language or DNA are likely to shed any light on how my ancestors arrived in the desert Southwest. My own family, even family members I remember knowing, were part of the great western migration in the United States and the Mormon settlement of the Inter-mountain West. My great-grandparents arrived by wagon in Arizona beginning in 1876.A Lexicostatistic Study of Shoshoni DialectsAnthropological Linguistics
Vol. 13, No. 4 (Apr., 1971), pp. 142-164
Fortunately, many historical population movements are documented. But how many, even more advanced, researchers are aware of population movements. There are some major population movements that are well known such as the western movement of settlers in the U.S. but nearly every part of the United States and almost every other country in the world has some history of population movement. Finding information about these important aspects of ancestral history is as simple as making a Google search. But, mind you, it will take days and weeks and months to read even the barest outlines of the history of migrations.
Whether your family came from Scandinavia, the British Isles, Europe, Africa, Asia or the Pacific, you can trace population movements and explain when and how families came to another country or part of the same country.
In the U.S. I consider one of the basic references to understanding the original settlement of the area now in the United States to be the book:
Fischer, David Hackett. Albion's Seed: Four British Folkways in America. New York: Oxford University Press, 1989.
I have read few books that give a more graphic and concise explanation for early European populations movements in America.
Here are a number of websites to get you started is searching and learning about the movement of people across the world:
- Wikipedia:Human migration (look especially for reference sources)
- Pew Social and Demographic Trends; Maps, U.S. Migration Flows
- Great Migration of Puritans from England to New England (1620–1643)
- Great Serb Migrations from the Ottoman Empire to the Habsburg Monarchy (1690 and 1737)
- Great Migration of Canada, increased migration to Canada, (approximately 1815–1850)
- Great Transatlantic migrations, a voluntary mass migration of Europeans to the Americas (1836–1916), including over 30 million Europeans who migrated to the United States
- Great Migration, resulting from the 1947 Partition of British India
- African American "Great Migrations":
- The original Great Migration from the southern United States to the northern United States (1910–1930)
- The Second Great Migration from the southern United States to the northern and western United States (1941–1970)
- The New Great Migration, reverse migration from the North, Midwest and the West to the southern United States (1965–present)
- The Great Migration of 1843, the first large group of settlers to travel via the Oregon Trail to the Oregon Country