This is just a presentation, so it will be interesting to find an alternative source for it. Still, it seems to agree with other evidence about the hybrid origin of Bronze Age European steppe nomads. A detailed look at the evidence from the Balkans, north Pontic steppe, and the Caucasus (and perhaps also the trans-Caspian region) will determine on who went where and when.
Genetic Analysis of Ancient Human Remains from the Bronze Age Nomadic Steppe Cultures of Ukraine
Jeff Pashnick, Grand Valley State University
During the transition between the late Neolithic and the Early Bronze Age (EBA) proto-Indo-European languages began to spread from southeastern steppes (prairielands) westwards into Europe. Southern Ukraine (North Pontic Region, NPR) was the meeting place between the Old Europe and steppe nomadic cultures. Using mitochondrial DNA (mtDNA), we tested ancient human remains from the EBA cultures from the NPR to determine if there was genetic evidence for the mingling of these cultures. Our data shows mtDNA lineages (haplogroups) of nomadic pastoralists in the NPR to have mainly common haplogroups with European hunter-gatherer cultures, with an inclusion of haplogroups common to farming cultures of Europe. The similarities in the haplogroup composition between European Neolithic hunter-gatherers and the NPR steppe pastoralists suggests that they share a common genetic past, in part influenced by the neighboring farmers and in part stemming from the Mesolithic native European ancestry.