The intrusive nature of the Châtelperronian in the Iberian Peninsula

RESEARCH ARTICLE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula Joseba Rios-GaraizarID 1,2 *, Eneko Iriarte 3 , Lee J. Arnold 4 , Laura Sa ´nchez-Romero 5 , Ana B. Marı ´n-Arroyo 6,7 , Aixa San Emeterio 2 , Asier Go ´mez-Olivencia 8,9,10 , Carflos Pe ´rezGarrido 11 , Martina DemuroID 4 , Isidoro Campaña 12 , Laurence Bourguignon 13 , Alfonso Benito-Calvo 2 , Marı ´a J. Iriarte 14,15 , Arantza Aranburu 8 , Amaia Arranz-Otaegi 16,17 , Diego Garate 18 , Marı ´a Silva-GagoID 2 , Christelle Lahaye 19 , Illuminada Ortega 20† 1Arkeologi Museoa, Bilbao, Spain, 2Centro Nacional de Investigacio ´n sobre la Evolucio ´n Humana (CENIEH), Burgos, Spain, 3Laboratorio de Evolucio ´n Humana, Dpto. Historia, Geografı ´a y Comunicacio ´n, Universidad de Burgos, Burgos, Spain, 4School of Physical Sciences, Environment Institute, and Institute for Photonics and Advanced Sensing (IPAS), University of Adelaide, Adelaide, SA, Australia, 5Human Evolution Research Center, University of California, Berkeley, CA, United States of America, 6Grupo de I+D+i EVOADAPTA (Evolucio ´n Humana y Adaptaciones Econo ´micas y Ecolo ´gicas durante la Prehistoria), Dpto. Ciencias Histo ´ricas, Universidad de Cantabria, Santander, Spain, 7Department of Archaeology, University of Cambridge, Cambridge, United Kingdom, 8Dept. Geologı ´a, Facultad de Ciencia y Tecnologı ´a, Universidad del Paı ´s Vasco-Euskal Herriko Unibertsitatea (UPV/EHU), Leioa, Spain, 9Centro UCM-ISCIII de Investigacio ´n Sobre Evolucio ´n y Comportamiento Humanos, Madrid, Spain, 10 Sociedad de Ciencias Aranzadi, Donostia-San Sebastia ´n, Spain, 11 Departamento de Mineralogı ´a y Petrologı ´a, Facultad de Ciencias Geolo ´gicas, Universidad Complutense de Madrid, Madrid, Spain, 12 Departamento de Ecologı ´a y Geologı ´a, Facultad de Ciencias, Universidad de Ma ´laga, Ma ´laga, Spain, 13 Inrap/AnTet Arscan UMR7041, Lotissement Actipolis Impasse sur rue Dionysos, Villeneuve-les-Be ´ziers France, 14 Geography, Prehistory and Archaeology Department, University of the Basque Country Vitoria-Gasteiz, Spain, 15 Basque Foundation for Science (IKERBASQUE), Bilbao, Spain, 16 Mu ´seum National d’Histoire Naturelle, UMR 7209, Arche ´ozoologie, Arche ´obotanique: Societe ´s, Pratiques et Environments (AASPE), Paris, France, 17 Dept. of Cross Cultural and Regional Studies, University of Copenhagen, Copenhagen, Denmark, 18 Instituto Internacional de Investigaciones Prehisto ´ricas de Cantabria (IIIPC, Gobierno de Cantabria, Universidad de Cantabria, Santander), Santander, Spain, 19 Professeure–Ge ´ochronologie, Universite ´ Bordeaux Montaigne, IRAMAT-CRP2A UMR 5060, Pessac, France, 20 Institut National de Recherches Archeologiques Preventives (INRAP), Paris, France † Deceased. *[email protected] Abstract Multiple factors have been proposed to explain the disappearance of Neandertals between ca. 50 and 40 kyr BP. Central to these discussions has been the identification of new techno-cultural complexes that overlap with the period of Neandertal demise in Europe. One such complex is the Cha ˆtelperronian, which extends from the Paris Basin to the Northern Iberian Peninsula between 43,760–39,220 BP. In this study we present the first open-air Cha ˆtelperronian site in the Northern Iberian Peninsula, Aranbaltza II. The technological features of its stone tool assemblage show no links with previous Middle Paleolithic technology in the region, and chronological modeling reveals a gap between the latest Middle Paleolithic and the Cha ˆtelperronian in this area. We interpret this as evidence of local Neandertal extinction and replacement by other Neandertal groups coming from southern France, illustrating how local extinction episodes could have played a role in the process of disappearance of Neandertals. PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 1 / 18 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Rios-Garaizar J, Iriarte E, Arnold LJ, Sa ´nchez-Romero L, Marı ´n-Arroyo AB, San Emeterio A, et al. (2022) The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula. PLoS ONE 17(3): e0265219. https://doi.org/10.1371/ journal.pone.0265219 Editor: Michael D. Petraglia, Max Planck Institute for the Science of Human History, GERMANY Received: October 5, 2021 Accepted: February 25, 2022 Published: March 30, 2022 Copyright: ©2022 Rios-Garaizar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: Research at Aranbaltza site has been funded by Diputacio ´n Foral de Bizkaia (2013-2020), Gobierno Vasco-Eusko Jaurlaritza (2014-2015), Harpea Kultur Elkartea (2013-2017), Edestiaurre Arkeologi Elkartea (2018). OSL dating research conducted by M.D. and L.J.A. was partly supported by Australian Research Council Future Fellowship grant FT200100816. AGO was supported by 1. Introduction The disappearance of Neandertal populations remains a complex, ongoing debate, with multiple factors purported to have affected survivorship between ca. 50 and 40 kyr BP, including endogenous causes, climate change and the arrival of Homo sapiens in Eastern Europe [1–5]. In the midst of this extinction process, several new techno-cultural complexes appeared in Europe, some of them introduced by Homo sapiens, while others were developed by Neandertal populations. One of these complexes is the Cha ˆtelperronian, which is found from the Paris Basin to the Northern Iberian Peninsula. The origins of the Cha ˆtelperronian remain widely debated. Some argue that it originated in Western Europe as an evolution of Middle Paleolithic technology [6,7], possibly under the influence of the growing population of Homo sapiens in Eastern and Central Europe [5,8,9], while others continue to doubt the links between the Cha ˆtelperronian and Neandertals, and thus propose that this technocomplex could have been made by Homo sapiens populations [10,11]. However, recent technical developments have significantly advanced these discussions by presenting paleoproteomic evidence for Neandertal authorship of the Cha ˆtelperronian at Arcy-sur-Cure [12]. The fact that the only human remains directly dated within the Cha ˆtelperronian age range in Western Europe have Neandertal affinities [13–15] further strengthens this link. In this study we present a new and significant Cha ˆtelperronian site, Aranbaltza II, located in the southernmost area of distribution for this complex. A detailed technological analysis of the lithic assemblage shows that there is no technological link with previous Middle Paleolithic technology in the Northern Iberian Peninsula. This, coupled with evidence of a chronological gap between the latest Middle Paleolithic (MP) and the Cha ˆtelperronian (CP) locally [16], suggests that Neandertal groups with MP technology had abandoned the region before the Neandertal groups with CP technology, likely coming from Aquitaine, crossed the Pyrenees and expanded through the Cantabrian Region. This illustrates how episodes of local extinction and population replacement could have played a role in the process of Neandertal disappearance. 2. Results 2.1 The site of Aranbaltza II The site of Aranbaltza (Northern Iberian Peninsula) is located in the Basque coastal region, in a short valley close to the current coastline (800 m NW) (Figs 1and 2). During Marine Isotope Stage (MIS) 3, sea level was 60–70 m lower than today, with the coastline ca. 4 km further offshore according to recently obtained bathymetric surveys [17]. The site is located in an old sand quarry complex (Ollagorta-Aranbaltza) that exploited Pleistocene fluvial sand deposits overlaying Upper Cretaceous bedrock (marine marls and limestone alternating with intercalated volcanic layers) (Section SI-3 in S1 File). It was discovered in 1957 by A. Aguirre, and in 1959 J.M. Barandiaran opened several test pits, finding a sandy level (C) containing Cha ˆtelperronian material [18] (Section SI-1 in S1 File). In 2012 a large Cha ˆtelperronian collection from the Aranbaltza II disturbed sediments was studied [19] (Section SI-5 in S1 File). The latest excavation project, which started in 2013, has since revealed a complex of archaeological sites (Aranbaltza I, II and III) with occupations ranging from Middle Paleolithic to recent prehistoric times (Fig 2) [20]. Between 2013 and 2016, the Aranbaltza II site was excavated in three different areas (ca. 18 m 2 ) (Area 1, 2 and 3) (Section SI-2 in S1 File) (Fig 3). All necessary permits were obtained for the excavation and study of materials. The archaeological collection of Aranbaltza II US4b is currently held at the Archaeologi Museoa in Bilbao (Basque Country, Spain). PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 2 / 18 Ramo ´n y Cajal fellowship (RYC-2017-22558). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. 2.2 Stratigraphy The 2 m sedimentary sequence excavated at Aranbaltza II contains a succession of aggradational, erosive and paleosoil formation events. The Cha ˆtelperronian occupation is included in a sedimentary unit (US4) formed from three different sand accumulation intervals (US4a, b and c subunits) related to enhanced flood activity in the nearby river channel (Fig 4). The sands from US4b have an intense orange hue and mineralized bioturbations typical of Fe and Al illuviation in podzols. 2.3 Chronology Single-grain optically stimulated luminescence (OSL) dating undertaken on Unit 4c indicates that a series of aggradation events and paleosol development phases took place between late marine isotope stage (MIS) 5 and early MIS 3 (78.1 ±5.8 ka to 58.2 ±4.6 ka; Section SI-9 in S1 File) prior to the Cha ˆtelperronian occupation of Aranbaltza II. Several OSL ages obtained for US4b and US4c provide bracketing (indirect) age constraint for the US4b layer, with sample AAM13-10 providing the closest and most secure estimate for the timing of the Cha ˆtelperronian occupation 43.5 ±2.9 ka (1σ) (Section SI-9 in S1 File). 2.4 Lithic assemblage The archaeological assemblage is composed exclusively of lithic artifacts, which are found in a minimally disturbed accumulation (Section SI-4 in S1 File). We have analyzed a well-preserved Fig 1. Distribution map of the so-called transitional technocomplexes. CP: Cha ˆtelperronian; LRJ: LincombianRanisian-Jerzmanowician; ULU: Uluzzian. Base cartographic data obtained from the European Environment Agency (free of use, downloadable at https://www.eea.europa.eu/ds_resolveuid/070F2DAD-1AED-4B9B-950F0047E5ADDF35. Rivers and bathimetry obtained from Natural Earth (free for use). DEM built up with QGIS 2.18. Infographics made with Inkscape. https://doi.org/10.1371/journal.pone.0265219.g001 PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 3 / 18 assemblage of 5686 lithic remains, including all the lithic remains bigger than 1 mm (Fig 5), primarily made from local flint (Flysch flint), but also small quantities made from non-local flint, including the Salies-de-Be ´arn flint variety (SW France, >150 km away) (Section SI-6 and S25 Fig in S1 File). Other materials appear in very low proportions, including 30 small lumps of ochre (S34 Fig in S1 File). A large part of the assemblage (60.4%) is composed of natural blocks, chunks, thermal flakes and chips under 10 mm size, reflecting intensive block testing, core flaking and tool production. The cortical flakes and blades generated in the initial stages of core configuration are particularly abundant (S5 Table in S1 File). Cores appear in relatively Fig 2. Aranbaltza location maps. A) Digital Elevation Model showing the position of Aranbaltza site; B) Excavation plan, with the area of the excavated Cha ˆtelperronian deposits in red. Base cartographic data obtained from National Geographic Institute of Spain (IGN) under the Creative Commons License CC-BY 4.0. DEM built up with ArcGis 10.3. Infographics made with Inkscape. https://doi.org/10.1371/journal.pone.0265219.g002 PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 4 / 18 low numbers, which is similar to other open-air Cha ˆtelperronian sites (Grigoletto et al., 2008). Most of the cores have been exploited to produce bladelets (n = 10) and blades (n = 7), but there are also some non-standardized “expedient” flake cores (n = 4) and some core roughouts (n = 6), tested blocks (n = 3) and exhausted cores (n = 1). Among the blade cores, 4 are typical [21–24] bidirectional ones with two, opposed flaking surfaces that are not strictly parallel (bipolaire de ´cale ´), which were used for the production of pointed asymmetrical blades (Fig 5: 29; S26 Fig in S1 File: 1). The unidirectional cores have typical [25,26] quadrangular crossFig 3. Excavation map and sections. A) Detailed map of the excavated Cha ˆtelperronian deposits with the position of the sedimentological cores and the coordinated archaeological remains; B) North and east section of Area 3 excavation with the projected position of the archaeological materials and the positions of the pollen samples and the dated OSL samples. https://doi.org/10.1371/journal.pone.0265219.g003 Fig 4. Stratigraphic section between Area 1 and 3 (section C) and synthetic stratigraphic section with the position of the dated OSL samples Stratigraphy. A detail photograph of the sequence in corner C/D is presented in S6 Fig in S1 File. https://doi.org/10.1371/journal.pone.0265219.g004 PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 5 / 18 sections for the production of asymmetrical blades (S26 Fig in S1 File: 2). All the bladelet cores are unidirectional: five of them are nucleiform burins (Fig 5: 23; S28 Fig in S1 File: a; S29 Fig in S1 File: 1–2), and the other five have been made on blocks (S28 Fig in S1 File: b, c; S29 Fig in S1 File: 3, 4 and 6). These cores have produced narrow (ca. 4 mm) bladelets and are similar to the bladelet production described in Quinc¸ay (Fig 2: 24–28; S28 Fig in S1 File: 1–19) [26]. Blanks are dominated by narrow (6.4–13.5 mm width) and wide (>13.6 mm) blades and Fig 5. Cha ˆtelperronian lithic assemblage. Aranbaltza II, US4b (Cha ˆtelperronian) archaeological materials. 1) Complete thin Cha ˆtelperronian point; 2–4) Proximal fragments of thin Cha ˆtelperronian points; 5) Thick Cha ˆtelperronian point, with the point made in the proximal part; 6) Distal fragment of wide Cha ˆtelperronian point; 7–10) Distal fragments of Cha ˆtelperronian points: #9 exhibits axial diagnostic impact fracture; 11–13) proximal fragments of backed blades, possible Cha ˆtelperronian points; 14) Distal fragment of backed blade; 15,16,20) Fragments of marginally backed blades; 17–19) Distal fragments of marginally backed points; 21–22) Marginally backed points; 23) Nucleiform burin; 24–28) Backed bladelets; 29) Bidirectional blade core for the production of pointed blades; 30– 31) Unidirectional crested blades; 32) Endscraper on natural fragment; 33) Endscraper on blade; 34–35) Blades; 36) Overshot blade dragging an opposed platform; 37) Platform rejuvenation flake. Figure made by Aixa San Emeterio and Joseba Rios-Garaizar. https://doi.org/10.1371/journal.pone.0265219.g005 PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 6 / 18 bladelets (<6.4 mm width) (S30 Fig and S6 Table in S1 File). Bladelets show great morphological variability, which is also reflected in the variability in terms of productivity and morphology of bladelet cores. Flakes are abundant: they have been mostly obtained from unidirectional elongated flake cores, from non-standardized “expedient” flake cores, or as part of blade core preparation and maintenance. Typical Levallois, Discoid or Quina flakes are all absent from the assemblage. There are 117 retouched tools, all but one made on Flysch flint (S7 Table in S1 File). Among them, we found typical marginally backed blades (n = 26) [22,24,25,27] including total, partial, pointed and inversely retouched blades (Fig 2: 15–20; Fig 6: 14–21); typical Cha ˆtelperronian points (n = 10) (Fig 5: 1–10; Fig 6: 1–7, 10–12), some of them broken during the fabrication process [28]; blade fragments with curved backs (n = 8) which are very likely proximal fragments of Cha ˆtelperronian points (Fig 5: 11–13; Fig 6: 8–9); and typical wide endscrapers (n = 2) (Fig 5: 32). Among the retouched bladelets, as identified at other Cha ˆtelperronian sites like Quinc¸ay [26], there is a single typical Dufour (Fig 6: 24), five backed, five marginally backed, two partially retouched and one truncated bladelet (Fig 5: 24–28; Fig 6: 22–27). Other tools such as retouched blades, burins, borers, truncations, notches, denticulates, sidescrapers, splintered pieces, marginally backed flakes and retouched flakes represent almost half of the retouched toolkit at the site (Fig 5: 33; S32 Fig in S1 File), but these are not very standardized and probably represent opportunistic and non-specific tool making and use at the site. 3. Discussion The technological and typological features of the Aranbaltza II US4b archaeological assemblage show direct parallels to other Cha ˆtelperronian open-air [22–24,29] and cave/rock-shelter sites [23,25,30,31]. Although knapping was the main activity at the site, other tasks were probably also performed alongside this, as happens at other Cha ˆtelperronian open-air sites [24,29,32]. The units below US4b are archaeologically sterile, precluding any possible admixture of the Cha ˆtelperronian assemblage with Middle Paleolithic materials, which are otherwise very abundant at Aranbaltza I and III [20,33]. Moreover, the lithic assemblage from Aranbaltza II US4b does not preserve any technological traits that would link it with the local or regional Middle Paleolithic. In particular, typical Middle Paleolithic tools (denticulates or sidescrapers on flakes) are rare, and the flakes at Aranbaltza II were obtained as a by-product of blade core configuration and maintenance, or as the result of non-systematic and rather opportunistic flake production. No typical Middle Paleolithic Levallois, Discoid or Quina products have been identified at Aranbaltza II US4b. Furthermore, blank production at Aranbaltza II is basically oriented towards the production of blades and bladelets, following the same production schemas seen at classic sites such as Roc de Combe, La Co ˆte and Quinc¸ay [21,26], Morin level 10 [34], and also evidenced in assemblages such as Labeko Koba [27], Ekain [35], and Cova Foradada [36]. Blade and bladelet production in the regional Middle Paleolithic are very rare, and never formed part of the structural productions for the Mousterian Neandertals [37–40]. Additionally, there are no MTA-B assemblages in the Cantabrian Region [41], while and backed tools associated with Mousterian assemblages, like the Abri Audi knifes, are very rare in the Northern Iberian Peninsula [33,42,43]. Elsewhere in the Northern Iberian Peninsula there are several Cha ˆtelperronian cave sites with small lithic assemblages [35] that have no technological links with the previous Late Middle Paleolithic [41,44], suggesting that the Cha ˆtelperronian was not derived from previous Iberian Peninsula Middle Paleolithic tradition as has been suggested for SW France [6]. There is, however, one exception to this trend, namely level 10 of Cueva Morı ´n, which is characterized by the use of different raw materials, including flint and coarse-grained quartzite, ophite and PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 7 / 18 sandstone, and by the combination of typical Middle Paleolithic (Discoid) and Cha ˆtelperronian production schemas [34,45]. Cueva Morı ´n level 10 is situated directly between the Late Middle Paleolithic (level 11) and Protoaurignacian (level 9). This assemblage has been interpreted as an admixture of Middle Paleolithic, Cha ˆtelperronian and Protoaurignacian materials [46,47], though other explanations have also been invoked, including the adaptation to raw material availability and techno-functional demands [45]. Whatever be the case, a part of this Fig 6. Cha ˆtelperronian retouched tools. Selected retouched tools from US4b. 1) Complete thin Cha ˆtelperronian point; 2) Thick Cha ˆtelperronian point, with the point made in the proximal part; 3) Distal fragment of wide Cha ˆtelperronian point; 4–7) Distal fragments of Cha ˆtelperronian points: #5 exhibits axial diagnostic impact fracture; 8–12) Proximal fragments of backed blades, possible Cha ˆtelperronian points; 10–12) Proximal fragments of Cha ˆtelperronian points; 13) Distal fragment of backed blade; 14–15) Marginally backed points; 16–18) Fragments of marginally backed blades; 19–21) Distal fragments of marginally backed points; 22–26) Backed bladelets: #24 presents typical Dufour ventral semi-abrupt retouch. Drawings made by Joseba Rios-Garaizar. https://doi.org/10.1371/journal.pone.0265219.g006 PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 8 / 18 collection, which is made basically of flint, represents a clear Cha ˆtelperronian assemblage with some features that are very similar to the ones observed at Aranbaltza II [34]. Additionally, a few sites have provided Cha ˆtelperronian points in Middle Paleolithic contexts, such as Ermitons, Reclau Viver or L’Arbreda [48], or in disturbed or unclear contexts, such as A Valiña, La Gu¨elga, El Pendo, Cueva Oscura, Santimamiñe, Mugarduia and Abauntz [49–55]. However, in terms of Cha ˆtelperronian occupation dynamics, these sites must be considered with caution. The settlement system during the Cha ˆtelperronian around the Bay of Biscay is characterized by (i) a combination of different site types, including open-air encampments situated near flint outcrops, which are basically oriented to the production of Cha ˆtelperronian points (like Aranbaltza II, Le Baste ´and Bidart); (ii) hunting camps with small assemblages and relatively abundant Cha ˆtelperronian points (like Labeko Koba, Ekain or Brassempouy); and (iii) less abundant, encampments in caves like Cueva Morı ´n. The identification of a Cha ˆtelperronian occupation at Aranbaltza II that basically functioned as a flint workshop changes the perception that the Cha ˆtelperronian presence in the Northern Iberian Peninsula was marginal [35]. The poor development of open-air Paleolithic archaeology in the Cantabrian Region, the geomorphological limitations for the preservation of such sites [56] and the fact that the Cha ˆtelperronian probably lasted only a few hundreds of years here, could explain the limited record and hence the low visibility of the Cha ˆtelperronian in this region. This settlement pattern has not been identified in the regional Late Middle Paleolithic: none of the Late Middle Paleolithic sites in the Northern Iberian Peninsula has been interpreted as hunting camps, and much of the open-air occupations near flint outcrops seem less focused on the production of specific lithic tools in comparison to Aranbaltza II, Le Baste ´or Bidart (see Le Prisse or Aranbaltza I and III as examples) [33,57]. The chronology of Cha ˆtelperronian occupations in the Northern Iberian Peninsula and the Western Pyrenees is primarily based on 14 C ages from Labeko Koba IXinf (S12 Table in S1 File), which place this occupation around 43,850–40,950 cal BP [58]. Unfortunately, all efforts to date Cueva Morı ´n level 10 have been fruitless, and the age obtained from Ekain level Xa, 34,350±550 BP (OxA-34930, 40,700–37,700 cal BP), is relatively young compared with Labeko Koba and the earliest Aurignacian for the region [16,58,59]. Three 14C ages obtained from charcoal samples from Cova Foradada level IV are statistically indistinguishable from each other and indicate a similarly young age range of 41,450–36,900 cal BP (S12 Table in S1 File) [36]. A significantly younger fourth age of 31,900±200 BP (36,750–35,750 cal BP) has also been obtained for Cova Foradada (Mediterranean margin of the Iberian Peninsula) level IV, though this is probably an artifact of the charcoal pre-treatment procedure [36]. The OSL age of Aranbaltza II US4b (~43.5 ±2.9 ka; 1σ), which is probably slightly older than the occupation itself, is systematically younger than the latest Middle Paleolithic in the region, dated to 48–45 kyr cal BP [16]. Comparison of the Aranbaltza II US4b OSL age with all reliable and stratigraphically well-constrained Cha ˆtelperronian AMS 14C, TL and OSL ages from France and Iberia shows a perfect fit with the time range of the Chatelperronian culture for southwest Europe, which our Bayesian model reveals as occurring between ca. 43,760–39,220 kyr (Fig 7; S14 Table in S1 File; Section SI-9 in S1 File). The original nature of the Cha ˆtelperronian assemblages from Aranbaltza II and Labeko Koba, together with the chronological gap between the latest Middle Paleolithic and the Cha ˆtelperronian in the region, and the absence of any link in lithic management and settlement strategies between the Cha ˆtelperronian and the regional Late Middle Paleolithic reveal that there is a discontinuity between the Middle Paleolithic and the Cha ˆtelperronian, and that the latter is intrusive in the Northern Iberian Peninsula (i.e., it originated elsewhere and was then introduced to the region). PLOS ONE The intrusive nature of the Cha ˆtelperronian in the Iberian Peninsula PLOS ONE | https://doi.org/10.1371/journal.pone.0265219 March 30, 2022 9 / 18 25. Connet N. 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