itself influenced by the Mesopotamian Uruk culture, had notable social effects on the Proto-Indo-European way of life. Meanwhile, the Khvalynsk-influenced cultures that had emerged in the Danube-Donets region after the first migration gave way to the Cernavodă (4000–3200), Usatovo (3500–2500), Mikhaylovka (3600–3000) and Kemi Oba (3700—2200) cultures, from west to east respectively. Yamnaya period (3300–2600) The Yamnaya horizon, associated with the Late Proto-Indo-European language (following both the Anatolian and Tocharian splits), originated in the Don-Volga region before spreading westwards after 3300 BCE, establishing a cultural horizon founded on kurgan funerals that stretched over a vast steppic area between the Dnieper and Volga rivers. It was initially a herding-based society, with limited crop cultivation in the eastern part of the steppes, while the Dnieper-Donets region was more influenced by the agricultural Tripolye culture. Paleolinguistics likewise postulates Proto-Indo-European speakers as a semi-nomadic and pastoral population with subsidiary agriculture. Bronze was introduced to the Pontic-Caspian steppes during this period. Following the Yamnaya expansion, long-distance trade in metals and other valuables, such as salt in the hinterlands, probably brought prestige and power to Proto-Indo-European societies. However, the native tradition of pottery making was weakly developed. The Yamnaya funeral sacrifice of wagons, carts, sheep, cattle, and horse was likely related to a cult of ancestors requiring specific rituals and prayers, a connection between language and cult that introduced the Late Proto-Indo-European language to new speakers. Yamnaya chiefdoms had institutionalized differences in prestige and power, and their society was organized along patron-client reciprocity, a mutual exchange of gifts and favors between their patrons, the gods, and human clients. The average life expectancy was fairly high, with many individuals living to 50–60 years old. The language itself appeared as a dialect continuum during this period, meaning that neighbouring dialects differed only slightly between each other, whereas distant language varieties were probably no longer mutually intelligible due to accumulated divergences over space and time. As the steppe became dryer and colder between 3500 and 3000, herds needed to be moved more frequently in order to feed them sufficiently. Yamnaya distinctive identity was thus founded on mobile pastoralism, permitted by two earlier innovations: the introduction of the wheeled wagon and the domestication of the horse. Yamnaya herders likely watched over their cattle and raided on horseback, while they drove wagons for the bulk transport of water or food. Light-framework dwellings could be easily assembled and disassembled to be transported