Arguments for the identification of the Proto-Indo-Europeans as steppe nomads from the Pontic–Caspian region had already been made in the 19th century by German philologists Theodor Benfey and especially Otto Schrader. In his standard work about PIE and to a greater extent in a later abbreviated version, Karl Brugmann took the view that the urheimat could not be identified exactly at that time, but he tended toward Schrader's view. However, after Karl Penka's 1883 rejection of non-European origins, most scholars favoured a Northern European origin. The view of a Pontic origin was still strongly favoured, e.g., by the archaeologists V. Gordon Childe and Ernst Wahle. One of Wahle's students was Jonas Puzinas, who in turn was one of Gimbutas's teachers. Gimbutas, who acknowledges Schrader as a precursor, was able to marshal a wealth of archaeological evidence from the territory of the Soviet Union (and other countries then belonging to the eastern bloc) not readily available to scholars from western countries, enabling her to achieve a fuller picture of prehistoric Europe.
When it was first proposed in 1956, in The Prehistory of Eastern Europe, Part 1, Marija Gimbutas's contribution to the search for Indo-European origins was an interdisciplinary synthesis of archaeology and linguistics. The Kurgan model of Indo-European origins identifies the Pontic–Caspian steppe as the Proto-Indo-European (PIE) urheimat, and a variety of late PIE dialects are assumed to have been spoken across the region. According to this model, the Kurgan culture gradually expanded until it encompassed the entire Pontic–Caspian steppe, Kurgan IV being identified with the Yamna culture of around 3000 BC.
The mobility of the Kurgan culture facilitated its expansion over the entire region, and is attributed to the domestication of the horse and later the use of early chariots.[c] The first strong archaeological evidence for the domestication of the horse comes from the Sredny Stog culture north of the Azov Sea in Ukraine, and would correspond to an early PIE or pre-PIE nucleus of the 5th millennium BC.[c]
Subsequent expansion beyond the steppes led to hybrid, or in Gimbutas's terms "kurganized" cultures, such as the Globular Amphora culture to the west. From these kurganized cultures came the immigration of Proto-Greeks to the Balkans and the nomadic Indo-Iranian cultures to the east around 2500 BC.