During researching ethnogenetic processes in Eurasia, it was noted that certain territories are characterized by their special, albeit few, linguistic features and cultural characteristics that continue to exist for a long time despite the changes in the ethnic composition of the population. This gives grounds to assume that the newcomers are amenable to the cultural influence of the previous population, perceiving the vocabulary, toponymy, technology, some customs, and elements of the rites that correspond for the new conditions of dwelling places. In other words, with such a superposition, the culture and language of the native population is a substrate that influences the further development of the culture and language of the new population of the territory. The degree of this influence depends on the ratio of the level of culture of old-timers and newcomers.
The found by the graphic-analytical method ethno-produsing areas, where at different times distinct dialects were formed from a paternal language, which later developed into independent languages, help to restore the superposition process. The ethno-producing areas are located in several places on the earth's surface, but the substrate phenomena are very well displayed in the Middle Dnieper basin, which were repeatedly populated by people of different linguistic affiliation. The study was conducted just here (see the map below).
Map of Ethno-producing areas in Eastern Europe illustrating alternation of substratum influences.
At different times parent languages were separated into dialects which later developed into individual languages in the same areas. Present-day names of people were given to their ancestors. The number of areas corresponds to such periods: 1. The uprising Indo-European languages 2. The uprising of Germanic and Iranian languages. 3. Formation of Slavic languages. 4. East Slavic tribes during Kiev Rus'.
While researching ethnogenetic processes in Eastern Europe, it was observed that certain areas are characterized by their special, though not numerous linguistic and cultural features that continue existing after superposition, ie layering of aliens speaking another language on remains of the local population, or at the conquest of its territory by people standing on a higher cultural level, but not necessarily more numerous. In any case, the aliens fell under the spiritual influence of the local community. They perceived existing place names, and the necessary vocabulary for new conditions and often also liked customs and rituals. Thus, the culture and language of the native population is the substrate, which affects the further development of the culture and language of the new population of the territory.
The substratum is most displayed in onomastics. A large number of Ukrainian toponyms that cannot be deciphered using the Slavic languages can be explained by means of Germanic, Iranian, Slavic, and Turkic. This topic is discussed in detail in the section Prehistoric Place Names of Eastern Europe. In general, the cultural substratum of Ukraine to a large extent contains traces left by the ancestors of the modern Chuvash, which were the Proto-Bulgarians, the later Scythians. Proto-Bulgarians as one of the Turkic tribes inhabited the forest-steppe part of Right-Bank Ukraine from Bronze Age to the arrival of Slavs there. As a result, the cultures of the Chuvash and Ukrainians correspond with folk songs, dances, embroidery, and crafts. However, they can be not only of substrate origin but also be evidence of cultural exchange. Ukrainian surnames of hypothetical Bulgarian origin suggest that the Proto-Bulgarians dwelled in close proximity with the Ukrainians for quite a long time, right up to historical times. Otherwise, we should have thought that some surnames appeared more than two thousand years ago. Obviously, the Bulgars were a part of the "black hoods", among which were the Turkic tribes of the Torqs, Berendeys, and Kovuys. Chronicles' evidence of them extends to the 13th century, then their remains, are obviously, scattered among the Ukrainian population. Under such circumstances, it is very difficult to separate substrate inheritance from later borrowings.
Exactly knowing that Ukrainian territory was inhabited by Bulgars in prehistoric times, you can carry out targeted searches for cultural and social relations between Ukrainians and Chuvashes. Such connections can be found in folk songs, dances, embroidery, and handicrafts. Discovered analogies can characterize not only the continuity and interaction of cultures but also estimate the time of occurrence and source of borrowing new beliefs, customs, and the timeframe for their existence.
Unlike a cultural substrate, the influence of a language substrate is less noticeable; it must be sought purposefully in the languages of those peoples whose ancestors inhabited ethno-producing areas. However, even without knowing about their existence, A. Meye found traces of the influence of the substrate on the language of newcomers in phonology thanks to the knowledge of many languages. He saw one of the reasons for its manifestation namely in phonetic correspondences in using inherited speech skills by the heirs of the native population. He asserted that they are not lost when mastering the new language and emphasized that the influence of the substrate primarily affects the pronunciation: "New sounds, as a rule, are not reproduced with absolute precision. " In addition, the names of plants, animals, and customs that do not have exact equivalents in their language penetrate the alien language (MEILLET A., 1954: 68).
However, the importance of language substratum was long contested by other linguists, including Julius Pokorny, since the influence of the language of the previous population on the language of aliens displayed often only in a few generations after the invasion or conquest that was seemed impossible. Later, agreeing with the phenomenon of the influence of the substrate, Pokorny explained this delay by the fact that the conquered people stayed on lower social levels until some time, and their language was neglected by the higher strata of society, most of whom were strangers. However, after the infiltration of the local population to invaders, the relation to their language was changing and began its influence despite it may lose some of its features. This, in particular, could explain the dismemberment of the Latin language under the influence of different substrates in Spain, France, and the Balkans (POKORNY JULIUS, 1968, 178-180). The influence of different Baltic substrates also explains the formation of separate Slavic languages on a common Proto-Slavic base.