Moving from one area to another with the intent of living in the new area for life.
Fossil evidence indicates that Asia has been under human occupation for at least one million years and possibly longer. The first humans in Asia are believed to have descended from groups of the extinct species Homo Erectus that migrated to the continent from Africa. There is much debate as to whether modern Asian peoples evolved from these first inhabitants or represent the descendants of later migrations of anatomically modern peoples out of Africa. It is also not clear when and where the modern races emerged, but the continent is now populated by three major groups: the Asiatic geographic race, the largest and most widespread of the three, in North, Central, East, and Southeast Asia; the Indian geographic race, the next most populous group, in South Asia; and the European geographic race, in Southwest and West Asia. In addition, the Polynesian and Melanesian geographic races are represented on the far south-eastern island fringe of the continent, and there are now significant populations of European Russians living in Siberia and Central Asia.
The two primary prehistoric centres from which migrations of modern human populations over the continent took place were Southwest Asia and a region comprising the Mongolian plateaux and North China. From prehistoric to historic times, possibly beginning as early as 30,000 years ago, movements from Southwest Asia continued toward Europe and into Central Asia; significant movements into India also took place. The Greeks were one of the late Indo-European groups moving westward, about 2000 BC, as were the Aryans, who moved east to invade northern India from 1600 to 1500 BC. Asiatic migrational movements have always trended primarily toward Southeast Asia. Important Asiatic migrations, however, also occurred in a westward direction through Central Asia toward the European peninsula. Such movements must have begun as early as 10,000 years ago, but they continued into the early centuries AD as Mongols pushed Turkic peoples westward, setting off additional displacements of such peoples as the Finns and the Magyars. These westward Asiatic movements also produced, over a period of time, much mixing of early European and Asiatic peoples in Central and West Asia. Northern Eurasia continued to be inhabited chiefly by thinly distributed residual elements of very early eastern Asian peoples, although some fairly late northward movements of Turkic peoples did take place.
The original habitat of the Slavs was Asia, from which they migrated, in the 3rd or 2nd millennium BC to populate parts of eastern Europe. Subsequently, these European lands of the Slavs were crossed or settled by many peoples forced by economic conditions to migrate. In the middle of the first millennium BC, Celtic tribes settled along the upper Oder River, and Germanic tribes settled on the lower Vistula and lower Oder rivers, usually without displacing the Slavs there. Finally, the movement westward of the Germans in the 5th and 6th centuries AD started the great migration of the Slavs, who proceeded in the German wake westward into the country between the Oder and the Elbe-Saale line, southward into today's Bohemia, Moravia, Slovakia, Hungary, and the Balkans, and northward along the upper Dnieper River.
There were many small-stream migration movements away from the main trends, now mostly undetectable, which often complicated the ethnic pictures of particular regions. At least one prehistoric European movement penetrated East Asia and is represented today by the remnant indigenous inhabitants of Japan known as the Ainu. A counter-movement out of India by a nomadic ethnic stock about AD 1,000 contributed to the Gypsy strain now widespread in Europe.
Gypsies, "the children of the wind", were the last wave of the great Indo-European migration from central and north-western India. At the very beginning of the 11th century, India came under attack by the Muslim general Mahmud of Ghazni, who was trying to push Islam eastwards into India, which was mainly Hindu territory. The Indian rulers had been assembling troops to hold back the Muslim army for several centuries already, deliberately drawing their warriors from various populations who were not Aryan. The Aryans had moved into India many centuries before, and had pushed the original population down into the south, or else had absorbed them into the lowest strata of their own society, which began to separate into different social levels or castes, called varnas (colours) in Sanskrit. The Aryans regarded Aryan life as being more precious than non-Aryan life, and would not risk losing it in battle. So the troops that were assembled to fight the armies of Mahmud of Ghazni were all taken from non-Aryan populations, and made honorary members of the Kshattriya, or warrior caste, and allowed to wear their battle-dress and emblems. They were taken from many different ethnic groups who spoke many different languages and dialects. Some were Lohars and Gujjars, some were Tandas, some were Rajputs, non-Indian peoples who had come to live in India some centuries before, and some may also have been Siddhis, Africans from the East African coast who fought as mercenaries for both the Hindus and the Muslims. This composite army moved out of India through the mountain passes and west into Persia, battling with Muslim forces all along the eastern limit of Islam. While this is to an extent speculative, it is based upon sound linguistic and historical evidence, and provides the best-supported scenario to date. Because Islam was not only making inroads into India to the east, but was also being spread westwards into Europe, this conflict carried the Indian troops - the early Roma - further and further in that direction, until they eventually crossed over into south-eastern Europe about the year 1300. In Western Europe they appeared by the 15th century. By the second half of the 20th century, Gypsies had spread throughout North and South America and to Australia.
Migration is inherently natural and very important traditional activity of all cultures in the world. Notwithstanding, particular groups have differing tendencies to travel. Some people are traditionally sedentary and will better face their fate and keep their lands and houses, other are more free from property and ready to move wherever it seems appropriate.
Migrating is simply substituting one set of known social problems for a set of unknown problems. Migration removes the skills and cultural heritage that could contribute to improving a society.