Professors likes Chantal Thomas of Cornell find the movement of large segments of the population from one country to another is far from being a modern-day phenomenon. The movement of prehistoric man from Africa to Eurasia and then on to other parts of the globe started a shift of population that would continue through the Roman and Norman conquests. Climatic changes, territorial expansion and shortages in the food supply were, and continue to be, some of the causes for population shifts.
Industrial development in the 18th and 19th centuries resulted in large population movements as workers in primarily agrarian regions left to seek jobs in urban areas and industrial centers.
Before enactment of the 13th amendment in 1865, the Atlantic slave trade prospered. Even a provision in the Constitution adopted in 1787 pointing toward the eventual abolishment of slavery did not initially curtail slavery. As a compromise to bridge the widening gap between abolitionists and those supporting a continuation of the Atlantic slave trade, Article One of the Constitution limited the right of Congress to restrict or take action to eliminate the importation of slaves into the country until 1808.
Countries throughout the world experienced labor migration in the 20th century. In the United States, an internal shift in population took place from rural areas of the South, where economic conditions offered workers few opportunities, to the factories and industries of cities in the Northeast, West and Midwest. Globally, nations such as Italy, China, Ireland and Norway experienced large shifts in population density in the early stages of the 20th century as workers left to seek employment opportunities elsewhere.
Armed Conflict and Natural Disasters
During war or armed conflict, people flee to escape the fighting, or they leave to escape persecution or reprisals. The post World War II European population migration included approximately 16 million German nationals ousted from countries in Eastern Europe. Members of Jewish communities who survived the Holocaust fled Europe and sought shelter and safety by settling in the United States and in the region that would later become the nation-state of Israel.
Hurricane Katrina hit U.S. coastal regions in Louisiana, Mississippi and other states leaving almost 1,800 people dead and millions more homeless or at least temporarily displaced. Drought in Ethiopia that began with the start of the 21st century continues to create food shortages for people. Natural disasters such as hurricanes, earthquakes and outbreaks of disease have led to internal and transnational migrations of segments of the global population.
The need for security and the exercise of national sovereignty are legitimate arguments favoring restrictions on the movement of people across national borders. However, the right of people to seek safety or to better themselves economically fuels the debate both for and against immigration law reform throughout the world.