Ah to be swallowed… the importance of the Dnieper-Donets Culture, Samara Culture & Khvalynsk Culture was that they would eventually be spit up...
The Dnieper-Donets Culture was a culture based on hunting and geathering, but eventually would come around to farming. This makes the Dnieper-Donets a culture that straddled the Mesolithic and Neolithic periods of European history. The Dnieper-Donets appares to be your average, run of the mill Meso-Neo transitional culture except for the fact of who they appear to have evolved into. The Dnieper-Donets appear to be a precursor to the later Yamna Culture, with the Yamna adopting a number of Dnieper-Donets traits. This puts the Dnieper-Donets culture as a centerpiece to the Kurgan Hypothesis of the Indo-European invasion and subsequent takeover of Europe. So, it’s possible that this incredibly primitive, even by Neolithic standards, culture is a precursor to most European language speakers and genetic frameworks.
The Samara Culture was a Russian contemporary of the Belorussian Dnieper-Donets Culture (Volga vs. Dnieper River basins) but had adopted the use of copper, making it a Chalcolithic culture. In addition to having the use of the handy metal copper, the Samara Culture was superior to their southeasterly neighbors in that they had domesticated horses. Other than that, the two cultures were very similar. Undoubtedly though the Samara Culture elite looked down on their stone age counterparts from their high standing as early metal tech adopters. But, their own self-righteousness was unimportant when the Yamna Culture came along to swallow them up. But, that act of swallowing ensured that the Samara Culture would go on to great things as the Indo-Europeans would emanate from this area to become masters of Europe (again, based on the Kurgan Hypothesis).
Lastly, the Khvalynsk Culture was another Russian Chalcolithic culture that served as a basis for the later and vastly more important Yamna Culture. In fancy terms the Khvalynsk is referred to as a proto-Kurgan culture, but that is simply jargon and antagonistic towards basic understanding of European prehistory. Basically whoever coined the phrase proto-Kurgan was looking to compensate for something when they were seeking approval from academic circles. But, like the Dnieper-Donets of Poland and Belarus and their Russian counterparts the Samara, the Khvalynsk would be swallowed deep by the Yamna Culture and eventually spit out all over Europe if Marija Gimbutas, the author of the Kurgan Hypothesis was right.