Migration means a change of abode or a removal from one country to an other country or place. Also migration is defined here a movement of population involving a change of permanent residence of substantial duration. Such migrations may be divided as under :-
(1) PREHISTORIC MIGRATIONS: By about 300,000 BP (Before the
present) Homo bad spread over most of Africa and into Southern, Western and Central Europe. Southern Asia: Central China, and Indonesia. Australia was reached about 32,000 BP and the Americas about 10-45,000 BP, Via Beringia. Patterns of early human occupancy were severely restricted by climatic conditions. Regions of initial habitation were at relatively low latitudes in Africa, Southern Europe and Asia. Major migrations to the North became possible only as tile climate moderated from the bitter cold of the ice age, and the technologies of fire use and clothing developed.
(2) ANCIENT MIGRATIONS : Though many migrations throughout history have been forced by conquest or slavery, such movements of people have nevertheless had the effect of changing the population geography of regions. The Romans, for example, imported slaves from Africa. As many as 600,000 of the people of Rome may have been “foreign” slaves, Invasions from central Asia into neighboring areas also redistributed population to some extent Vandals, Goths and Huns invaded the Roman Empire. for example, and the Mongols invaded the China and Asia Minor (Turkey).
(3) MODERN MIGRATIONS: Mostly modern migrations consist of the two main types, international migration and internal migration, the later involving no crossing of international boundaries