Meanwhile, the Danubian Lengyel culture absorbs its northern neighbours in the Czech Republic and Poland for some centuries, only to recede in the second half of the period. In Bulgaria and Wallachia (southern Romania), the culture of Boian-Marica evolvef into a monarchy with a clearly-royal cemetery near the coast of the Black Sea. The model seems to have been copied later in the Tiszan region with the culture of Bodrogkeresztur. Labour specialisation, economic stratification and possibly the risk of invasion may have been the reasons behind that development. The influx of early Troy (Troy I) was clear in both the expansion of metallurgy and social organization.