Multi-isotopic tracking (δ13C, δ15N, δ34S) of ancient trophic webs around the time of Neandertal replacement by anatomically modern humans in North-Western Europe

Abstract

The study investigated ecological aspects of the mammoth steppe ecosystem in NW Europe with a special focus on the role of late Neandertals and early modern humans through the analysis of stable isotopes in bone collagen (delta 13C, delta 15N and delta 34S). Around the time of Neandertal extinction and the arrival of modern humans a diverse community of large herbivorous and carnivorous mammal lived under cold, fluctuating environmental conditions in NW Europe. The study reconstructed the ecological robustness of this ancient ecosystem and its response to oscillating climatic conditions as well as in regard of the ecological participation of Neandertals and early modern humans. The trophic web, the niche partitioning, the ecological flexibility of single species, as well as the general buffer capacity of this biocenosis are objects of investigation. The Belgium site Troisième caverne of Goyet provided a broad set of directly dated late Neandertal and very early modern human skeletal remains associated with a considerably assemblage of Pleistocene faunal remains. The occurrence of late Neandertals and early modern human skeletal remains at the same place are unique circumstance and allowed a direct comparison of several ecological aspects during a time span with a special relevance for the human evolution. The site Ziegeleigrube Coenen is contemporaneous with the occurrence of late Neandertals and reflects the ecosystem during or shortly after a cold spell. Even during such phases the structure of the mammoth steppe ecosystem was intact and provided consequently an adequate basis for late Neandertal subsidence. In an ecological context the Neandertals were part of there are no indications for any stress on the structure of the ecosystem. Through the analysis ofdelta delta 13C and delta 15N isotopic ratios in bone collagen of faunal and hominid remains the trophic web was evaluated. Processing of the isotopic data 2 through several statistical approaches allowed a detailed reconstruction of ecological niche partitioning of late Neandertals and early modern humans. Both hominid species occupied the same distinct ecological niche in terms of diet with a clear preference for mammoth and reindeer. The investigation of the delta 34S composition in Pleistocene bone collagen is a relatively novel approach and provided insights into spatial hominid procurement. The Goyet Neandertals do not reflect the local fauna delta 34S congruously their main prey had an origin different from the neighborhood of the Belgium sites (Scladina, Spy and Goyet). In contrast the delta 34S signal of the Spy Neandertals and the Goyet ancient modern humans corresponds to the values obtained on the local fauna. Potentially different mobility strategies among Pleistocene hominids while exploring the same prey species is the drafted scenario. The site Lommersum reflects the ecosystem at an initial phase of occupation by modern humans in the area, when Neandertals became already extinct. At this time the regional mammoth population was declining, since the horses entered their niche in distinct region of Western Europe. This study hypothesized that increasing hunting pressure on mammoth by modern humans was the main reason for this, since so far no significant environmental changes on terrestrial ecosystems could be observed in NW Europe. This study indicates that no distinct ecological change happened through the time of the last Neandertals, even during colder phases of the OIS 3. Potential ecological reasons could not be served as arguments for Neandertal extinction in NW Europe. With the capture of the area by representants of the Aurignacian the mammoth steppe ecosystem started to show evidences for stress, in this case at least partly independently of environmental fluctuations.