I’ll focus on the first two parts of the question, both dealing with human migration. The past and the present are profoundly shaped by human migration. Migration is defined as “the movement of groups and individuals from one place to another.” Examining the social consequences of human migration is a bit tricky to answer briefly, as it can depend what time period/geographic area you are referring to, but I can go over some general outcomes:
- Changes to population
- Populations can rise and fall based on migration patterns.
- Demographic changes to a geographic area can be permanent. For example, many people currently living in Latin America are descendants of African slaves, which has permanently changed the genetic makeup of these areas.
- Spread of culture
- When people move, they take their culture with them. The spread of foods, language, customs, knowledge, traditions, music, and artwork are all part of this transfer. It’s hard to underestimate the social impact of human migration over the course of history.
- One example of how entrenched this cultural exchange can become is spaghetti. While the pasta has become an icon of Italian cuisine, its origins are traced back to Asia.
- Another example of this is how, through the slave trade, religious beliefs, musical rhythms and language structures were spread from Africa to the Caribbean.
- Spread of disease
- Major historical events have been impacted by the spread of disease through migration. When European settlers arrived in North and South America, the diseases they brought with them decimated local populations, who had no immunity. This allowed Europeans to expand across an emptier and more weakly defended territory. Another major example would be the Black Plague of the Middle Ages, which spread from Asia to Europe via trading ships. The Black Plague was a powerful force in European history, undermining the Catholic Church and the feudal system.
When people move to new environments, they are also changed. Human beings have been able to inhabit the extremes of earth’s climate by adapting to the specific challenges they face. This includes genetic changes, such as building immunity to diseases of a certain region. An example would be some immunity to malaria among Central Africans. People also adapt by adjusting their cultural practices with technology. For example, “snow goggles” used by the Inuit in the Arctic protected their eyes from the sun being reflected by the snow.