were introduced around 4700 BCE from the Danube valley to the Volga-Ural steppes where the Early Khvalynsk culture (4900–3900) had emerged, associated by Anthony with the Early Proto-Indo-European language. Cattle and sheep were more important in ritual sacrifices than in diet, suggesting that a new set of cults and rituals had spread eastward across the Pontic-Caspian steppes, with domesticated animals at the root of the Proto-Indo-European conception of the universe. Anthony attributes the first and progressive domestication of horses, from taming to actually working with the animal, to this period. Between 4500 and 4200, copper, exotic ornamental shells and polished stone maces were exchanged across the Pontic–Caspian steppes from Varna, in the eastern Balkans, to Khvalynsk, near the Volga river. Around 4500, a minority of richly decorated single graves, partly enriched by imported copper items, began to appear in the steppes, contrasting with the remaining outfitted graves. The Anatolian distinctive sub-family may have emerged from a first wave of Indo-European migration into southeastern Europe around 4200–4000, coinciding with the Suvorovo–to–Cernavoda I migration, in the context of a progression of the Khvalynsk culture westwards towards the Danube area, from which had also emerged the Novodanilovka (4400–3800) and Late Sredny Stog (4000–3500) cultures. Recent genetic studies have shown that males of the Khvalynsk culture belonged to the Western Steppe Herder (WSH) cluster, which is a mixture of Eastern Hunter-Gatherer (EHG) and Caucasus Hunter-Gatherer (CHG) ancestry. This admixture appears to have happened on the eastern Pontic–Caspian steppe starting around 5,000 BC. Late Khvalynsk/Repin (3900–3300) Steppe economies underwent a revolutionary change between 4200 and 3300 BCE, in a shift from a partial reliance on herding, when domesticated animals were probably used principally as a ritual currency for public sacrifices, to a later regular dietary dependence on cattle, and either sheep or goat meat and dairy products. The Late Khvalynsk and Repin cultures (3900–3300), associated with the classic (post-Anatolian) Proto-Indo-European language, showed the first traces of cereal cultivation after 4000, in the context of a slow and partial diffusion of farming from the western parts of the steppes to the east. Around 3700–3300, a second migration wave of proto-Tocharian speakers towards South Siberia led to the emergence of the Afanasievo culture (3300–2500). The spoke-less wheeled wagon was introduced to the Pontic-Caspian steppe around 3500 from the neighbouring North Caucasian Maykop culture (3700–3000), with which Proto-Indo-Europeans traded wool and horses. Interactions with the hierarchical Maykop culture,