Human migration is the movement over long distances, movement from one country/region to another ) by people . Humans moved because of the changing climate and landscape and inadequate food supply. The first human movement was the movement of Homo erectus out of Africa across Eurasia about 1.75 million years ago.
Than industrialization encouraged migration wherever it appeared.
Wars also created migration. (The First and Second World Wars, and wars, genocides, and crises sparked by them, lead to migrations).