The fundamental cause of linguistic change and hence of linguistic diversification is the minute deviations occurring in the transmission of language from one generation to another. But other factors contribute to the historical development of languages and determine the spread of a language family over the world’s surface. Population movements naturally play a large part, and movements of peoples in prehistoric times carried the Indo-European languages from a relatively restricted area into most of Europe and into northern India, Persia, and Armenia. The spread of the Indo-European languages resulted, in the main, from the imposition of the languages on the earlier populations of the territories occupied. In the historical period, within Indo-European, the same process can be seen at work in the Western Roman Empire. Latin superseded the earlier, largely Celtic languages of the Iberian Peninsula and of Gaul (France) not through population replacement (the number of Roman soldiers and settlers in the empire was never large) but through the abandonment of these languages by the inhabitants over the generations as they found in Latin the language of commerce, civilization, law, literature, and social prestige.

Conquest does not always lead to the supersession of a language. Greek survived centuries of Turkish rule and indeed remained a focus of national feeling, as has happened elsewhere in history. Much depends on the various circumstances and on the mutual attitudes of those involved; what must be kept quite clear is the difference between movements of peoples and the spread of languages.

Languages do not just spread and compete with each other for territorial use. They are in constant contact, and every language bears evidence of this throughout its history. Modern Greek is full of words of Turkish origin, despite efforts made at various times since independence to “purify” the language by official action. The Norman Conquest and a period in which French was the language of the ruling class in England effected great changes on English and contributed a very substantial number of French words to English vocabulary—hence the quantity of near synonymous pairs available today: begin, commence; end, finish; kingly, royal; fight, combat; and so on.

Tendencies against change

These historical processes take place without any direct volition on the part of speakers as regards the language itself. Latin was learned as part of personal advancement, not for its own sake. Loans were incorporated almost without their being noticed, along with the concomitant cultural changes and innovations. Deliberate action directly related to a language does occur. The creation of pidgins involves some degree of linguistic consciousness on the part of their first users. More deliberate, however, have been various attempts at preserving the purity of a language, at least for some uses, or at arresting the processes of change. The care bestowed on the preservation of the Sanskrit used in religious ritual in ancient India and efforts to free Modern Greek from much of its Turkish vocabulary have already been noticed. For a period, under Nazi rule, efforts were made to replace some foreign words in the German language by words of native origin, and there have been movements to replace later accretions in English by words derived from Old English forms. In the long run, such attempts never succeed in preventing or reversing change; at best they preserve collaterally supposedly purer forms and styles for certain purposes and in certain contexts.

With the picture painted above of the tendency for languages to fragment first into dialects and then into separate languages, it might be thought that dialects are relatively late in appearance in the history of a language family. This impression is reinforced by the fact that most nonstandard dialects are unrepresented as such in writing, and so comparatively little is known about dialectal differences within most languages as one goes back in time. In this respect the very detailed knowledge of the Ancient Greek dialect situation is quite untypical.

In fact, dialect divisions must have been a feature of linguistic communities as early as there is any knowledge of them. Dialect splitting is fostered by isolation and loss of contact between groups within a speech community, and the sparse populations of earlier days, often nomadic and spread over large areas relative to their numbers, will have encouraged this process. It is simply the case that all but literate dialects have been lost in the past, and an artificial homogeneity is attributed to most ancient languages and to the so-called reconstructed parent languages of families.

Present-day conditions tend toward the amalgamation of dialects and the disappearance of those spoken by relatively few people. Urbanization, mass travel, universal education, broadcasting, ease of communication, and social mobility are among the forces that foster rather large regional and social dialects, with special occupational types of language within them, in place of the small, strictly localized dialects of earlier times. This is one reason for the urgency with which dialect studies are being pursued in many Western industrialized countries, such as England and parts of the United States. If work is not done soon, many dialects may perish unrecorded.

For the same reasons, dialect divisions that earlier would have widened into distinct languages are now unlikely to do so. One may compare the emergence of the separate Romance languages from once unitary Latin with the splitting of South American Spanish and Portuguese into different dialects of those two languages. Those dialectal divisions are not now expected to widen beyond the range of intercomprehensibility. Those same conditions, together with the spread of literacy, are leading to the extinction of languages spoken by relatively small communities. Such is the fate of most of the North American Indian languages, and Irish, Welsh, Scots Gaelic, and Cornish may ultimately survive only as learned second languages, preserved as cultural focuses for their communities. But in situations like that, both past and present, the intervening period of extensive bilingualism and the concomitant use of two languages has its effect on the changes taking place in the dominant language, which is influenced by the phonetic and grammatical composition of the speakers’ former language. The closing decades of the 20th century also saw a new enthusiasm for the preservation of minority languages, illustrated by the formation of the European Bureau for Lesser-Used Languages in 1982 (although it ceased functioning in 2010).