Not only superior means of transport by land or sea, but posses sion of more deadly weapons or improved implements for daily needs have given their owners decisive superiority when coming in contact with worse equipped peoples. These advantages have been potent factors in producing changes of population.
It is probable that a migration induced by an attraction is much rarer than one produced by an expulsion. The simplest cases of migration by attraction are those of peoples living on poor steppes or plateaux adjoining cultivated land or rich valleys. Agricultural peoples, as a rule, are averse to and ill-prepared for war and the more prosperous their circumstances the more they are likely to be enervated by their very civilization. They are thus liable at all times to be attacked by neighbouring brigands, who in some cases retire to their barren homes with their booty, but in others remain among the conquered people, and, assimilating with them, in due course become more civilized, and in their turn are subject to invasions from their barbarian kinsmen of the borders. The walled towns of ancient Greece in the centre of valleys opening out to the sea point to danger from the brigands of the moun tains and possibly also from pirates from the sea. The inhabitants of the rich plains of Assam have always been subject to raids and settlements by the hill tribes. The earliest records of the Nearer East show (and this has continued to the present day) that the pastoral peoples have preyed upon the agriculturalists and have frequently colonized considerable areas.
Hunger and loot are not the only impulses towards migration. The restless disposition of the "winners of the West" of North America was not due to an inability to maintain an existence in the eastern States nor to an expectation of speedy riches. A craving for land is only a partial explanation ; sentiment and a reaction against even the slightest of social restraints had a good deal to do with it, as it had for the trekking of the Boers. Gold rushes are different, as wealth may thus be speedily gained by rapid exploitation.
Migrations have taken place to gain freedom from social, political or religious bondage, like the exodus of the Hebrew bond men from Egypt, the voyage of the "Mayflower" or the migration of the Flemings and Huguenots into Britain. Religious enthusi asm may stimulate race expansion and lead to shiftings of popu lations as seen in the histories of Buddhism, Christianity and Islam. The partnerships of the crescent and the sword, of the cross and the gold of El Dorado, have been based upon a double enthusiasm which has led to migrations.
The movements of peoples which are sufficiently dramatic for the ordinary historian to record are often of less importance than the quiet, steady drift of a population from one area into another, as, for example, the emigration from Europe to America in modern times. Movements may result in a noticeable or even fatal depletion of a country, and the parent country may remain desolate or may be filled up in course of time by an alien people as in the case of eastern Germany and the Slays in the 4th and 5th centuries A.D.
An excellent example of the migration of cultures is given by Prof. V. Gordon Childe in his paper on "The Danube thorough fare and the beginnings of civilization in Europe" (Antiquity, i. p. 79, 1927), in which he traces the spread of culture along the deposits of loess in the Danubian region. The evidence seems to point to the fact that the majority at least of the people were long established in this region before the little settlements of Aegean fishers became outposts of Troadic commerce and led to the opening up of mines of cinnabar, gold, copper and tin. Childe says : "The discovery and original exploitation of the Bohemian tin deposits and hence the inauguration of a bronze industry in Central Europe was due to explorers coming up the Danube from the south-east. Now the first dated bronze objects found in a definite context in Britain come from the graves of the so-called Beaker Folk, who reached these islands from Central Europe. It therefore seems likely that we owe our first metallurgy in the long run to those explorers from Troy whose tracks we have been following up the Danube. So not only was that river one of the routes by which a so-called `neolithic' culture reached north western Europe, it was also a channel in the diffusion of the arts of metallurgy northward and westward from the Ancient East." In his Dawn of European Civilization (1925) Prof. Childe traces in detail the growth and spread of culture up to the Middle Bronze age. His view is that the cultures of the collectors and hunters and fishers of epipalaeolithic times do not in any real sense constitute points of transition from the palaeolithic to the neolithic culture, but that the latter gradually spread westwards. "Peasants with stone hoes and axes opened up its valleys to culti vation; hunters and herdsmen blazed the trail through its prim aeval forests ; mariners in dug-out canoes sailed the seas to the isles of the West ; prospectors with picks of horn and flint revealed the treasures of the earth and crossed mountain passes in search of merchandise. These explorers were the forerunners of Greeks and Phoenicians; the paths they discovered have been followed by Roman roads and modern railways" (p. 14). He regards the Occident as "indebted to the Orient for the rudiments of the arts and crafts that initiated man's emancipation from bondage to his environment and for the foundation of those spiritual ties that co-ordinate human endeavours. But the peoples of the West were not slavish imitators; they adapted the gifts of the East and united the contributions made by Africa and Asia into a new and organic whole capable of developing on its own original lines" (p. 13).