The Neolithic was a critical turning point in the evolution of human societies that fell in the time of the Holocene climatic optimum. The principal changes ushered in through the Neolithic included the development of agriculture and pastoralism, the emergence of sedentary lifeways, and highly structured societies with large-scale communication systems which included exchange networks for the transfer of objects, animals, people, ideas and know-how. This relatively stable way of life, sustained economic growth, and the complexity developed by societies reshaped forever human vision and the conceptualisation and re-organization of the world; these changes have led some authors to characterize the Neolithic as an era of ‘living well together’. Unfortunately, the interest of the researchers for the end of this ‘glorious’ stage in the human history is obviously much lower, and lacks the appropriate depth of large-scale treatment. Under these circumstances, the outstanding challenge of the DOMINO-CLIMATE project is to track the decline of the Neolithic in the East-Central and South-Eastern European region between 4550-(3600) 3250 cal. BC from multiple perspectives, such as palaeo-environmental change, climate fluctuations, subsistence economy, socio-economic collapse and ‘foodscape’ markers.

According to current terminology, the 5th millennium BC represents the last stage of the Neolithic, known as the Late Neolithic, Copper Age, Eneolithic or Chalcolithic (Late or Final NC). In the study region (Fig. 1), the early and middle 5th millennium BC was the most flourishing development period for the NC, known as the ‘golden 5th millennium’ due to the substantial progress made by human communities at multiple levels. About 4550-4200-4000 cal BC, the first signs of decline became visible, with the burning and/or abandonment of hundreds (>600) of tell settlements apparently in the same centuries in the East Balkans (BG-RO, SRB-HU). In very few cases, the burnt houses contained human skeletons, suggesting the massacre of the inhabitants (Hotnitsa, Yunasite). Sometimes, tell residents seem to have dispersed into smaller villages and farmsteads (e.g. Jilava, Ujvár, Vinča-Belo Brdo, Vésztő-Bikeri) or retreated into hilly areas (Brătești, Teiu). In Serbia and Hungary several newly founded sites were traced without a considerable time gap, while in Bulgaria a clear discontinuity is seen after the 4200 cal BC abandonment of tells. In Romania, these archaeological findings correspond with the penetration of new populations from the North Pontic steppe (NPS) (Cernavodă I - Pevets / C.I-P), which had a different lifestyle, economy, and material culture. Based on these facts, some archaeologists have considered that the NC ended in the Balkans by the end of the 5th millennium BC, and it was caused by the steppe migration, marked by violent conflict and the disappearance of the old populations. Further west, in the Carpathian Basin, steppe migration cannot be detected, instead the gradual southward movement of a technologically more developed group, the Tiszapolgár and Bodrogkeresztúr group and dispersed, fortified small farmsteads are present. On the other hand, the NPS area (the forest-steppes of the Southern Bug and Dnieper interfluve) also presents the markers of significant changes in human lifestyle between 4000-3500 BC. In the Western part of the Cucuteni-Trypillia (C-T) civilization (phases B2 and C1), similar developments and old traditions were maintained, while, in the Eastern area of C-T culture mega-sites occupying hundreds of hectares emerged in the Southern Bug - Dnieper Interfluve. However, around 3400 cal BC, the mega-sites disappear, and small hamlets spread all over the C-T area. About 4100-3900 cal BC a similar change was noted in NW BG / SW RO, where the Kodžadermen–Gumelniţa–Karanovo (KGK) culture shows a significant change in the topographic characteristics and the density of the settlements. However, after 3900 BC, an extensive barrow construction phenomenon started in the North-West Pontic region, which also had previously spread into the Balkan area. There are three broad explanations for the decline of NCs in the study region: (1) population movements, (2) environmental fluctuations, and (3) internal social changes.

The principal marker of the first explanation is the appearance of barrow burials in the study area, and several archeogenetical studies attest to the early, sporadic intrusions of human groups from the NPS around 4500-4000 BC. In terms of the second explanation of environmental fluctuations, the onset of cooler summers and increasing wetness that characterise the mid-5th millennium BC were likely also important. It is obvious from the studies of past vegetation that the natural biomes of both the vast Pontic and Pannonian steppes and the forests of the low and mid mountains (the Carpathians and Balkan Mountains) underwent rapid changes between 4600 and 4200 BC, with a ~1.7oC decrease in July mean temperatures in the Southern Carpathians at the same time. The long-term general trend in increased available moisture and summer cooling facilitated the expansion of forest steppe in the NPS, a biome shift towards warm temperate forest steppe with the expansion of hornbeam and withdrawal of spruce in both Transylvania and the Pannonian steppe. At this time, traditional crop cultivation was increasingly complemented with hunting and animal husbandry of large-bodied animals, as is shown by discoveries from the last phases of some tell settlements from RO (Vitanesti) and HU  This period was, however; also beset with short-lived arid events, most conspicuously in the eastern steppe zone around 4200 BC when the local population moved North and West. However, no such marked arid events are obvious in Transylvania and the Danube Plain. Other records suggest that the rapid changing of environmental conditions probably led to a crisis in agriculture and the disintegration of tells at the end of 5th millennium BC against the background of solar activity oscillations. It is widely known that the coastal areas and riverine floodplains were the preferred site locations and the most densely populated areas of the NC, but now, in the lower Danube valley and other rivers from the study region, floods occurred more frequently and affected the crops both by local intensified erosion and rapid sediment overburden. Recent studies on Lower Danube floodplain and delta show extraordinary rapid sedimentation in response to both precipitation increase and to early Holocene sea-level rise including melt water pulses, which significantly affected the low-lying coast positions and the lower reaches of the tributaries.

There were a few concrete attempts to connect the NC collapse with climatic change. These demonstrated that the 4.2-3 kyr cal BC rapid climate change event (RCC) visible in the Greenland GISP d18O (proxy for North Atlantic air/ocean temperature) and potassium (K+; proxy for the strength of the Northern Hemispheric winds, intensification of the Siberian High) records can likely be invoked in the explanation of the NC collapse together with the above-mentioned insolation driven longer term climate changes. The GISP2 record shows elevated potassium concentrations between 4.2-3 kyr cal BC indicative of a colder/dryer period in Northern Asia that led into intensified dust flux to Greenland. Paleoclimate and paleoenvironmental research in the region demonstrated a notable impact coincident with this Holocene RCC anomaly upon the terrestrial and aquatic environments. A short-lived cooling at 4200 cal BC and 3.4 cal BC was demonstrated by several studies in Hungary and Romania, but similar paleoclimate studies are not yet known in Serbia and Bulgaria.

The third explanation of internal social change concerns the inability of communities with ever increasing social and material complexity to find ways to manage internal change. One key variable here is the consolidation of copper and gold metallurgy in ways that challenged the traditional, egalitarian social structure of the earlier Neolithic, leading to tensions between traditionalists and wealth accumulators. The loss of other key exotic materials may also have threatened the stability of these communities when exchange networks were interrupted.

Figure 1. Location of the archeoloical sites, lowland and alpine lakes studies in scope of the DOMINO-CLIMATE project. For site names see the Study site section