The transformations that took place in the prehistoric societies in the Northern Balkans around 5500 BC have long been discussed in the literature and are widely accepted as a “division point” between the Early and Late Neolithic. The most striking change is disappearance of the painted pottery decoration and the fast spread of black burnished ware. Some changes in flint production and figurines’ iconography have also been pointed out.

Extensive research in the last 15 years in the Upper Thracian Plain region (the Maritsa River valley in Southern Bulgaria) provides grounds for new insight into the complex transformations that occurred around 5500 BC. Several Late Neolithic sites have been excavated on a large scale during rescue projects enforced by road construction activities and many more were registered during field surveys. The number of Late Neolithic sites known so far largely exceeds the Early Neolithic ones and new trends in settlement structure and social organization are visible. While life on the place of the Early Neolithic settlements continued in a similar way, resulting in the formation of the so-called tell-sites, new type of sites appeared and quickly spread as well. These were large-scale scattered sites, often consisting of (or including) dug-in features, interpreted in some cases as dug-in houses while in others as ritual pit complexes. Their distribution is also connected to a shift in animal husbandry practices and the predominant role of cattle over sheep and goat.

The presentation aims at discussing the transformations in lifestyle in the mid 5^th millennium BC in the Upper Thracian Plain, their relation to the demographic expansion attested and the possible reasons for them, as well as the interaction between the Early Neolithic population and the probable newcomers that led to the formation of the Late Neolithic culture in the region.