Rohingya refugees walk along a road

Human migration sparked by wars, disasters, and now climate

Homo sapiens have been on the move from almost their beginnings. Climate-caused floods, drought, and water shortages will likely join the list of reasons to migrate.

Rohingyan refugees, forced to migrate to Bangladesh from Myanmar, walk in search of refugee camps.
Photograph by John Stanmeyer, Nat Geo Image Collection

Migration is defined as “movement from one country, place or locality to another.” Ever since the earliest humans began to spread from Africa, humans have been on the move. Even today, 3 percent of the world’s population—at least 258 million people—live outside of their country of origin. Whether voluntary or forced, migration has profoundly shaped our world.

The earliest migrants were ancient humans who originated on the African continent. Their spread to Eurasia and elsewhere remains a matter of significant scientific controversy. The earliest fossils of recognizable Homo sapiens were found in Ethiopia and are approximately 200,000 years old.

The “out of Africa” theory posits that around 60,000 years ago, Homo sapiens dispersed across Eurasia, where they met and

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