Changing environments during the Middle-Upper Palaeolithic transition in the eastern Cantabrian Region (Spain): direct evidence from stable isotope studies on ungulate bones

www.nature.com/scientificreports OPEN Received: 12 June 2018 Accepted: 10 September 2018 Published: xx xx xxxx Changing environments during the Middle-Upper Palaeolithic transition in the eastern Cantabrian Region (Spain): direct evidence from stable isotope studies on ungulate bones Jennifer R. Jones 1,2, Michael P. Richards 3, Lawrence G. Straus4, Hazel Reade5, Jesús Altuna6, Koro Mariezkurrena6 & Ana B. Marín-Arroyo 1,7 Environmental change has been proposed as a factor that contributed to the extinction of the Neanderthals in Europe during MIS3. Currently, the different local environmental conditions experienced at the time when Anatomically Modern Humans (AMH) met Neanderthals are not well known. In the Western Pyrenees, particularly, in the eastern end of the Cantabrian coast of the Iberian Peninsula, extensive evidence of Neanderthal and subsequent AMH activity exists, making it an ideal area in which to explore the palaeoenvironments experienced and resources exploited by both human species during the Middle to Upper Palaeolithic transition. Red deer and horse were analysed using bone collagen stable isotope analysis to reconstruct environmental conditions across the transition. A shift in the ecological niche of horses after the Mousterian demonstrates a change in environment, towards more open vegetation, linked to wider climatic change. In the Mousterian, Aurignacian and Gravettian, high inter-individual nitrogen ranges were observed in both herbivores. This could indicate that these individuals were procured from areas isotopically different in nitrogen. Differences in sulphur values between sites suggest some variability in the hunting locations exploited, reflecting the human use of different parts of the landscape. An alternative and complementary explanation proposed is that there were climatic fluctuations within the time of formation of these archaeological levels, as observed in pollen, marine and ice cores. Marine Isotope stage 3 (MIS3) (60-25ka BP) was a period of instability with rapid and acute climatic changes1,2. Mid-late MIS3 was the time of the Middle-Upper Palaeolithic transition (c.45-25ka BP) (MP-UP), when late Neanderthal populations became extinct and were replaced by Anatomically Modern Humans (AMH). Neanderthal extinction is now known to have been relatively rapid, following a regional pattern, rather than a uniform pan-European one3. Climate cannot be claimed as a homogeneous, monolithic driver for their extinction in a single event across the continent as previously proposed by some4–7. How climate was expressed locally within the continental scale of Europe is not well understood, with climatic proxies identified from caves such as 1 Instituto Internacional de Investigaciones Prehistóricas de Cantabria, (Universidad de Cantabria, Santander, Gobierno de Cantabria), Santander, 39005, Spain. 2Department of Archaeology, School of Geosciences, University of Aberdeen, Aberdeen, AB24 3FX, Scotland, UK. 3Simon Fraser University, Department of Archaeology, Burnaby, V5A 1S6, B.C, Canada. 4University of New Mexico, Anthropology Department, MSC01 1040, Albuquerque, NM, 87131, USA. 5UCL Institute of Archaeology, 31-34 Gordon Square, London, WC1H 0PY UK, UK. 6Centro de Conservación e Investigación de los Materiales Arqueológicos y Paleontológicos de Gipuzkoa, Paseo Zarategi, 84-88, Donostia/ San Sebastián, 20015, Spain. 7Leverhulme Centre for Evolutionary Studies, Department of Archaeology and Anthropology. University of Cambridge, Cambridge, CB2 1QH, United Kingdom. Correspondence and requests for materials should be addressed to A.B.M.-A. (email: ) SCIentIfIC REPOrtS | (2018) 8:14842 | DOI:10.1038/s41598-018-32493-0 1 www.nature.com/scientificreports/ Figure 1. Map of the eastern Cantabrian region, northern Spain, showing the locations of the Bizkaia and Gipuzkoa sites studied. In Bizkaia: Axlor and Bolinkoba. In Gipuzkoa: Lezetxiki, Labeko Koba, Ekain, Amalda and Aitzbitarte III. pollen, charcoal and plant remains, as well as microstratigraphies for this period all being relatively scarce, and although useful as environmental indicators8, they can be subject to taphonomic and diagenetic alterations9,10. There is a lack of radiometric chronologies for environmental and archaeological records independent of ice11 and marine cores12,13, which are not directly related to the localised conditions experienced at the archaeological sites. New methods have been recently proposed with great promise to overpass these limitations for a continental scale such as tephrochronology14 or atmospheric circulation modelling15, but they have some limitations and higher levels of precision are required. Since the early 2000s, δ13C and δ15N analyses have been used to reconstruct animal palaeoecology and past environments16. Bone collagen δ13C and δ15N analysis within animal bones derive directly from diet consumed17, representing long-term feeding behaviour, informing on average environmental conditions throughout the period of bone growth18,19. Collagen δ34S analysis can be used as a locational tool, with values directly linked to local geology and soil type, proximity to the sea and rainfall20. These techniques have successfully been applied to European Palaeolithic environmental reconstructions directly related with human occupations to unravel the ecological conditions those populations confronted16,21–30. An ideal location to apply this methodology to reconstruct the conditions faced by late Neanderthals and early AMH during MIS3 is the Cantabrian region in the Atlantic zone of northern Spain, which contains a high density of Middle and early Upper Palaeolithic sites31. The Cantabrian geographical region is formed by the Autonomous Communities of Asturias in the west, Cantabria in the centre and the Basque Country in the east. In this paper, we focus on the latter sector which is encompassed by the modern-day provinces of Gizpukoa, Bizkaia and Alava (Fig. 1). Gipuzkoa and Bizkaia are ecologically distinct from the western sectors of the Cantabrian region and are characterised by deep, steep-sided closed in mountains that often drop directly to the ocean. The Cantabrian Cordillera mountain range, relatively low in the Basque sector, separates the Atlantic coastal region from the Mediterranean-draining Ebro basin32. A recent chronological review of dates for MP-UP transitional sites undertaken using ultrafiltration radiocarbon method has provided a high-precision sequence of events for the timing of both human species’ activities in the region3,33–36. Therefore, it is now possible to obtain an accurate, independently dated environmental record in those archaeological sites by undertaking stable isotope analysis of ungulate bones exhibiting evidence of human manipulation (i.e. cut marks and fresh fractures) during the Mousterian, Châtelperronian, Aurignacian and Gravettian periods. The results can be integrated with the available sedimentology, palynolo (...truncated)