Climate deteriorations and Neanderthal demise in interior Iberia

Abstract

Time and circumstances for the disappearance of Neanderthals and its relationship with the advent of Modern Humans are not yet sufficiently resolved, especially in case of the Iberian Peninsula. Reconstructing palaeoenvironmental conditions during the last glacial period is crucial to clarifying whether climate deteriorations or competition and contacts with Modern Humans played the pivotal role in driving Neanderthals to extinction. A high-resolution loess record from the Upper Tagus Basin in central Spain demonstrates that the Neanderthal abandonment of inner Iberian territories 42 kyr ago coincided with the evolvement of hostile environmental conditions, while archaeological evidence testifies that this desertion took place regardless of modern humans' activities. According to stratigraphic findings and stable isotope analyses, this period corresponded to the driest environmental conditions of the last glacial apart from an even drier period linked to Heinrich Stadial 3. Our results show that during Marine Isotope Stages (MIS) 4 and 2 climate deteriorations in interior Iberia temporally coincided with northern hemisphere cold periods (Heinrich stadials). Solely during the middle MIS 3, in a period surrounding 42 kyr ago, this relation seems not straightforward, which may demonstrate the complexity of terrestrial climate conditions during glacial periods.

Figure 1

Maps showing (A) the location of the Tagus loess record in central Spain and (B) the position of the loess sections mentioned in the text: 1 Section Paraíso; 2 Section Villarubia; 3 Section Fuentidueña; 4 Section A3. The map was generated using ArcGIS 10.2.2 (http://www.esri.com/software/arcgis).

Figure 2

Stratigraphic evidences and age model of the Tagus loess record. Treaded profile sections are shown, together with sampling positions and ages obtained. The classification into sediment units is based on the results presented in Fig. S6. The detailed expose of the OSL ages is to be found in SI Text 5.

Figure 3

Main loess deposition periods (indicated by vertical ochre bars) in the upper Tagus Basin from the past 120 kyrs compared with human occupation patterns of interior Iberia and other palaeo-climate indicators from marine and ice-core records. (a) Temporal placement of Upper Palaeolithic and Middle Palaeolithic occupations of interior Iberia are based on the results presented in SI Text 9. (b) Loess deposition rates were estimated based on the thickness of loess units and the mean of obtained OSL ages. (c) δ²H record on G. bulloides of core MD95-2040; δ²H values were calculated based on δ¹⁸O values using the global meteoric water line. (d) δ²H values of the n-alkane compounds n-C₂₉ (red) and n-C₃₁ (blue) from the loess section Paraíso. (e) δ¹³C values of the n-alkane compounds n-C₂₉ (red) and n-C₃₁ (blue) from the loess section Paraíso; the red dotted line marks the estimated limit for habitability of the interior of Iberia. (f) SST of marine drilling core MD95-2042 and SU81-18, and Heinrich Events detected in the same core. (g) Pollen percentage of Mediterranean forest from core MD95-2042 and SU81-18. (h) δ¹⁸O record of the NGRIP ice core with numbers referring to stadials. Timing of HS-1 to HS-6 (Heinrich stadials) is based on ref., and C-19 to C-24 (North Atlantic ice rafting events) on ref..