The Neanderthal Occupations at Veldwezelt-Hezerwater (Belgium) and the Challenge of the Eemian Forest in Northwest Europe

The loess-paleosol sequences in the provinces of Belgian and Dutch Limburg (Northeastern Belgium and Southern Netherlands, respectively) reveal a continuous record of paleo-climatic variations during the late Middle and Upper Pleistocene. These abrupt impacts of climate change will alter the intricate ecological balances that let specific plants and animals grow and thrive and must have deeply altered the nature of the successive ecosystems. The climatic challenges Neanderthals had to face, as new ecological communities formed, must have been colossal. The data from Veldwezelt-Hezerwater show that the Neanderthals in Northwest Europe preferred interstadial, open mosaic or even steppe-like environments (e.g., the ‘Mammoth Steppe’). When there was a major change in their preferred habitat, Neanderthals could either move and track their favored habitat or they could adapt to the new situation. Otherwise, they would become extinct locally. One of the strategies with which Neanderthals responded to rapid changes in habitat was the adaptation of their stone tool kits. The observed variation in the frequency and diversity of lithic tool types derived from presumed environmental factors was clearly separated in space and time. The study of the loess-paleosol sequences at Kesselt-Op-de-Schans (Belgium), Maastricht-Belvédère (The Netherlands) and Veldwezelt-Hezerwater (Belgium) yielded at least 17 different Middle Paleolithic levels. The lithic assemblages of most of these archaeological levels are mainly characterized by Levallois technology and Mousterian tools. So-called ‘Quina tools’ were only excavated in the early Middle Weichselian horizons (first half of Marine Isotope Stage [MIS] 3) at Veldwezelt-Hezerwater. Crude laminar lithic assemblages were found in horizons dating most probably to MIS 6.01 at Veldwezelt-Hezerwater. Neanderthals were also moderately specialized to hunt large, cold environment animals. However, being specialized became a problem when changes in climate passed certain limits and when some of those cold environment animals went extinct. The data from the loess-paleosol sequences at Veldwezelt-Hezerwater show that not only cold, glacial and stadial ‘harsh’ environments—but also wet, full interglacial ‘climax’ environments—were extremely stressful for Neanderthals. Notwithstanding these observations, some researchers still make the assertion that Neanderthals did, for instance, occupy the Eemian climax forests, but at the same time fail to explain why the Neanderthal signal during the Eemian is so weak. It is known that climate in Northwest Europe is strongly affected by sea-air exchanges of heat and moisture. The raised temperature and increased evaporation and precipitation allowed the rapid expansion of moisture-requiring vegetation. The ‘oceanic effect’ in Northwest Europe during the Eemian interglacial period must have led to dense climax forests that were largely uninhabitable for Neanderthals. On the other hand, the extreme cold climatic conditions in Northwest Europe during glacial periods must have affected the distribution and viability of the Neanderthal populations as well. In Northwest Europe, the weakness or total absence of the Neanderthal signal in the archaeological record during certain time periods can neither be explained by research bias nor by taphonomic issues. The data suggest that during extreme cold and dry, and during extreme warm and wet periods of time, the Neanderthals in Northwest Europe went through a deep demographic crisis. We further argue that (1) during the climatic optimum of the Eemian (MIS 5e), (2) during the cold second half of MIS 4, and (3) during the cool and unstable second half of MIS 3, the Neanderthal population in Northwest Europe must have collapsed. In conclusion, supportive evidence was found for the presumption that three major population bottlenecks hit the Neanderthal population in Northwest Europe during the Eemian interglacial (around 125 thousand years ago (‘ka’)), during the cold second half of MIS 4 (around 68 ka), and finally during the second half of the Middle Weichselian (around 47 ka). These population bottlenecks severely reduced their numbers, leaving Northwest Europe largely empty of Neanderthals.