The Danube River’s right flanks in eastern Slavonia and western Srijem are covered by loess terraces 10 to 15 km wide. These allowed easy travel, and hosted permanent settlements for the first Neolithic agriculturalists in Europe (the Starčevo Culture), who in 6200 B.C. started to expand from the Anatolian Plateau, as well as for Indo-European peoples coming to Central and Western Europe from the southern Ural Mountains and northern Black Sea steppes.
Loess terraces do not hold water well, and so swamps and forests are not found on them. Only seasonal grasses grow, forming a steppe ideal for movement of livestock and peoples with their newly invented four-wheeled carts (the oldest known examples in the world). Beyond the terraces to the west, a thick band of oak forests covers the ill-drained clay soils of the broad swampy basins of the Sava and rivers of Slavonia, blocking communication westward. Possibilities for cultivation and herding are minimal. We find prehistoric settlements only on slightly more passable spots between edges of mountains and the rivers.
There are numerous open questions concerning the rapid movements of these agricultural peoples to the west; archaeologists and linguists are joining forces to resolve them.
The Vučedol people manifest a close connection between Indo-Europeans (the Baden culture – 3500 BC) and the older inhabitants from the Sopot and Vinča cultures.
Loess is a porous sedimentary rock appearing in the Pleistocene period. It came from pale yellow silt, dust, and very fine sand deposits, which the wind carried over great distances. It covers about 4% of the Earth’s land surface and 7% of Europe. Loess soil is unusually fertile and is the most productive sort for agriculture, particularly for cultivating annual crops, so that this came to be the most thickly settled area on Earth.