[3] They speak the East Slavic languages,[4] and formed the majority of the population of the medieval state Kievan Rus', which they claim as their cultural ancestor.

The few known facts come from archaeological digs, foreign travellers' accounts of the Rus' land, and linguistic comparative analyses of Slavic languages.

It lists twelve Slavic tribal unions which, by the 10th century, had settled in the later territory of the Kievan Rus between the Western Bug, the Dniepr and the Black Sea: the Polans, Drevlyans, Dregovichs, Radimichs, Vyatichs, Krivichs, Slovens, Dulebes (later known as Volhynians and Buzhans), White Croats, Severians, Ulichs, and Tivertsi.

In the first millennium AD, Slavic settlers are likely to have been in contact with other ethnic groups who moved across the Eastern European Plain during the Migration Period.

[citation needed] Another group of East Slavs moved to the northeast, where they encountered the Varangians of the Rus' Khaganate and established an important regional centre of Novgorod for protection.

This culture was strongly influenced by the autochthonous Finno-Ugric and Baltic peoples, from whom it adopted a specific burial rite and some features of ceramics, but in general, the way of life of the Eastern Slavs changed little.

[9] Among the East Slavs, fortified cities, apparently, first appeared among the Ilmen Slovenes in the 5th century (based on archaeological data in the town on Mayat river).

The first settlements near the Polans and Severians arose in the region of Kyiv and Chernigov already by the 7th–8th centuries,[10] which indicates at least a partial rejection of the previous strategy of scattered and secretive living among the forests.

A number of such settlements of the Prague-Korchak (Zimino, Lezhnitsa, Khotomel, Babka, Khilchitsy, Tusheml) and Penkovo (Selishte, Pastyrskoe) cultures existed in the 6th–7th centuries.

The center of the territory controlled by the dulebs (Zimino, Lezhnitsa) was in the basin of the Western Bug; the geographical center of the Penkovo culture falls on the Dnieper region, but the main fortress of the Antes (Selishte) was located in the western part of this area, near the borders of Byzantine Empire (in modern Moldova), on which they made military campaigns.

[13] The disintegration, or parcelling of the polity of Kievan Rus' in the 11th century resulted in considerable population shifts and a political, social, and economic regrouping.

[16][18] Genetic research has shown that the genomes of East Slavs are homogenous and contrary to popular belief, unaffected by Turkic or Mongol influences.