Earth and Planetary Science Letters 258 (2007) 283–292 www.elsevier.com/locate/epsl H4 abrupt event and late Neanderthal presence in Iberia ⁎ Pierre Sepulchre a, , Gilles Ramstein a, Masa Kageyama a, Marian Vanhaeren b, Gerhard Krinner c, María-Fernanda Sánchez-Goñi d, Francesco d'Errico e,f a Laboratoire des Sciences du Climat et de l'Environnement/IPSL, UMR CNRS-CEA-UVSQ 1572, CE Saclay, L'Orme des Merisiers Bât. 701, 91191 Gif sur Yvette Cedex, France b Ethnologie Préhistorique, UMR 7041 CNRS-ArScAn, 92023 Nanterre, France c Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS-UJF Grenoble, BP 96, F-38402, Saint Martin d'Hères, France d Ecole Pratique des Hautes Etudes, Département de Géologie et Océanographie, UMR 5805 CNRS-EPOC, Université Bordeaux1, 33405 Talence, France e Institut de Préhistoire et de Géologie du Quaternaire, UMR 5199 CNRS-PACEA, Université Bordeaux1, 33405 Talence, France f Department of Anthropology, George Washington University, 2110 G Street, NW Washington, DC 20052, United States Received 15 November 2006; received in revised form 23 March 2007; accepted 23 March 2007 Available online 31 March 2007 Editor: M.L. Delaney Abstract Heinrich event 4 (H4) is well documented in the North Atlantic Ocean and the adjacent continents as a cooling event 39,000 yr before present (BP). To quantify the impact of this event with respect to climate and vegetation over the Iberian Peninsula, we perform numerical experiments using a high-resolution general circulation model forced by sea surface temperatures before and during H4. Our model simulates an expansion of aridity over the peninsula during H4, a desertification of the south, and a replacement of arboreal by herbaceous plants in the north, all of which are in agreement with contemporaneous pollen sequences from marine cores located off the Iberian Peninsula. Our simulations demonstrate that the H4 marine event imprinted drastic changes over Southern Iberia, which would not have favoured its occupation by Anatomically Modern Humans, therefore providing a plausible explanation for the delayed extinction of Neanderthals in this region inferred from the archaeological record. © 2007 Elsevier B.V. All rights reserved. Keywords: Neanderthals; paleoclimate; Heinrich; abrupt event; Quaternary; Aurignacian; Mousterian 1. Introduction Several hypotheses based on ecological factors have been put forward to explain the apparent late survival of The dynamics of the colonisation of Europe by Neanderthal populations in the southern and western Anatomically Modern Humans (AMH) and Neanderthal regions of the Iberian Peninsula. The first of these extinction are the subjects of lively debate [1–6]. hypotheses suggests that AMH populations bearing an Climatic variability has been repeatedly invoked as a Aurignacian technology may not have expanded south potential cause for such crucial population events [2], of the Ebro River during Interstadial 9 which occurred occurring at ca. 41–32 cal ky BP (37–29 14C ky BP) [7]. just prior to Heinrich Event 4 [8–10] (H4, 39,000 calendar yr BP) [11]. This lack of expansion to the south ⁎ Corresponding author. Tel.: +33 1 69 08 65 49; fax: +33 1 1 69 08 77 16. may have been due to the fact that the regions to the E-mail address: [email protected] (P. Sepulchre). south were significantly more wooded [12] and thus less 0012-821X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2007.03.041 284 P. Sepulchre et al. / Earth and Planetary Science Letters 258 (2007) 283–292 favourable since large mammals, on which their subsis- duration of the meltwater injection in the North Atlantic tence systems were focused, preferred open landscapes. corresponding to this event has been recently updated to According to this hypothesis, AMH populations would 250±150 yr [20]. The duration of the cooling due to this have moved southwards only when the cold conditions perturbation is longer, as the thermohaline circulation associated with H4 allowed for the southern expansion needs another 400 yr to adjust and restart after the end of of the prey species that formed the basis of their the meltwater pulse. In terms of continental response, subsistence systems. Other authors [13] have proposed considering these ranges and regarding vegetation dy- that the climatic changes of the Oxygen Isotope Stage 3 namics, it seems that the H4 could have perturbed the (OIS 3, between ca. 60 and 25 ky BP) could have fatally biosphere for at least one millennium (see discussion). perturbed the Neanderthal seasonal activity cycle even Previous modelling studies [3] have been conducted on before the arrival of modern competitors in these south- the OIS 3 palaeoclimatic [21] and palaeovegetation [22] ern regions. A third scenario [2], based on comparisons variations, but have not specifically focused on the of archaeological and pollen data, suggests that the late impact of an abrupt cold climatic shift on neighbouring survival of Neanderthals in Southern Iberia is the continental areas. Kageyama et al. [23] investigated the consequence of the expansion of semi-desert environ- impact of H1 over western Europe in terms of temper- ments over this region due to the climatic conditions ature and water cycle, but the interest of H4 is that this associated with H4, which limited the advance of AMH climate shift may have occurred contemporaneously groups, dependant on large ungulate species, into with important changes in human populations. Yet no regions south of the Ebro. Such a scenario would have spatial reconstruction of the H4 impact on Iberian delayed the replacement and eventual extinction of vegetation is available. Well-dated indications of envi- Neanderthals. The aim of this paper is to use appropriate ronmental changes are recorded in pollen-rich marine models to evaluate these hypotheses in terms of climatic cores located off the Iberian peninsula [24,25] and allow and vegetation changes associated with H4. for comparisons with our model outputs. Here we The small number of human remains associated with present two simulations made with a Global Circulation archaeological material dated to this period represents a Model (GCM) quantifying the climatic and vegetation major problem for testing hypotheses regarding the response before (BH4) and during (DH4) Heinrich 4 nature, extent, and chronology of relationships between event. AMH and Neanderthals. It is generally acknowledged, however, that the Aurignacian culture is a reliable proxy 2. Methods for the dispersal of AMH, that these new populations arrived in regions north to the Iberian Peninsula between To quantify climate changes produced by H4 over 42 and 41 ky cal BP (37–36 14CkyBP)[6,7], and that this region, we use the atmospheric general circulation their colonisation of southwestern Iberia occurred much model (AGCM) called LMDz developed at Laboratoire later, at around 35,200 cal BP (33 14CkyBP)[14].We de Météorologie Dynamique [26] with a high regional argue that the impact of H4, which is centered around ca. resolution over western Europe, providing a 60 km 39 ky BP, and its imprint on vegetation for a period of resolution over Iberia. The Dynamic Global Vegetation more than 1000 yr, played an important role in this Model (DGVM) ORCHIDEE [27] is forced by climate process. This phenomenon may explain, in part, the delay variables produced by LMDz in order to quantify the in Modern Humans progression southward and the longer spatial distribution of vegetation changes on the Iberian survival of Neanderthal populations in the south of Iberia. peninsula. In order to evaluate the environmental impact Data from deep-sea sediments [8], continental se- of the H4 event over Iberia, we run two numerical quences [15] and polar ice cores [9] show that, during experiments with the AGCM. The first experiment OIS 3, several abrupt climatic shifts occurred over the (BH4 for “Before H4”) aims at estimating the climate Atlantic Ocean and Europe. High levels of lithic ice- just before H4. It is constrained with appropriate 39 ky rafted debris (IRD) and low foraminiferal concentrations cal BP orbital parameters [28] and CO2 concentration define several Heinrich events of massive iceberg dis- set at 209 ppmv (partial pressure in parts per million, charges in the North Atlantic Ocean [10,16,17]. Among from the Vostok ice core [29]). Since no global dataset them, H4 was associated with strong decreases in North describing the SSTs before the H4 exists, the SSTs used Atlantic Sea Surface Temperatures (SSTs) [18]. Its exact for this first simulation are those given by the CLIMAP date is still a matter of debate (e.g. see Bard et al. [11] [30] Last Glacial Maximum global reconstructions. and Shackleton et al. [19]) but Roche et al. [20] suggest Similarly, no global ice-sheet reconstruction is available 38.9 and 39.3 ky BP as the most plausible dates. The for this period, but the sea-level drop at that time is P. Sepulchre et al. / Earth and Planetary Science Letters 258 (2007) 283–292 285 estimated to be 60 m lower than present [31]. We have nique applied to planktonic foraminifera assemblages therefore chosen to use the 14 ky BP ice-sheets recon- [18]. These authors reconstruct SSTs at several points in struction from Peltier [32] (ICE4G) which corresponds the North Atlantic Ocean. Error bars associated with to the same sea-level drop, and which is the closest these reconstructions are rather weak compared to the reconstruction to the ice sheets which existed before and anomaly. We use these reconstructions to create zonal during H4. This reconstruction is consistent to what temperature anomalies that we apply to the CLIMAP other authors used for the same period [33]. Thus our SST dataset (Fig. 1). LGM SSTs are reduced by 4 °C first experiment is a “glacial” state, with appropriate between 40°N and 50°N, 3 °C between 50 and 54°N, boundary conditions representing the pre-H4 conditions.