Early contact during the 5th millenium in southeastern Europe
Archaeogenetic studies have described two major genetic turnover events in prehistoric western Eurasia: one associated with the spread of farming and a sedentary lifestyle starting ~7000-6000 BCE, and a second with the expansion of pastoralist groups from the Eurasian steppes starting ~3300 BCE. The period between these events saw new economies emerging on the basis of key innovations, including metallurgy, wheel and wagon, and horse domestication. However, what happened between the demise of the Copper Age settlements ~4250 BCE and the expansion of pastoralists remains poorly understood. To address this question, we analysed genome-wide data from 135 ancient individuals from the contact zone between southeastern Europe and the northwestern Black Sea region spanning this critical time period. While we observe genetic continuity between Neolithic and Copper Age groups from major sites in the same region, from ~4500 BCE on, groups from the northwestern Black Sea region carried varying amounts of mixed ancestries derived from Copper Age groups and those from the forest/steppe zone, indicating genetic and cultural contact over a period of ~1000 years earlier than anticipated. We propose that the transfer of critical innovations between farmers and transitional foragers/herders from different eco-geographic zones during this early contact was integral to the formation, rise and expansion of pastoralist groups ~3300 BCE.