The Fossils of Castor Fiber from the Middle Pleistocene Site of Gruta Da Aroeira (Portugal) and Human-Beaver Interaction
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CUENCA-BESCOS Quaternaire, 32, (1), 2021, p. 1-10 1 THE FOSSILS OF CASTOR FIBER FROM THE MIDDLE PLEISTOCENE SITE OF GRUTA DA AROEIRA (PORTUGAL) AND HUMAN-BEAVER INTERACTION ■ Gloria CUENCA-BESCÓS1, Montserrat SANZ2,3, Joan DAURA2,3 & João ZILHÃO3,4,5 ABSTRACT Here we analyze the fossil remains of Castor fiber from the Middle Pleistocene site of Gruta da Aroeira, in the Almonda karst system, Tagus basin (Torres Novas, Portugal) and discuss the archaeological implications of the presence of beavers in the region. The Almonda karst system has been the backdrop for human evolution in Portugal, because there are different localities, of different ages, from the Middle Pleistocene to the Holocene, with fossil remains of hominins as well as faunal and archaeological remains. Beaver fossils have been found in the archaeological deposits of at least three cavities of the karst system: the Gruta da Aroeira, the Gruta da Oliveira and the Galeria da Cisterna. Here, for the first time, we describe the fossils ofCastor fiber from Gruta da Aroeira. The beavers from Aroeira are remarkable because they are the westernmost fossil record of Castor fiber in Europe dated to Marine Isotope Stage (MIS) 11, around 420 ka. The aim of the present article is twofold, firstly to study the fossils of beavers from the Aroeira locality, and secondly to discuss the palaeoecological and palaeoenvironmental implications of the presence of this rodent in the Almonda karst sites. This allows us to discuss the hominin-beaver interactions. Keywords: fossil beavers, skull, mandible, teeth, archaeology, human-beaver interactions, Portugal RÉSUMÉ LES FOSSILES DE CASTOR FIBER DE GRUTA DA AROEIRA (PORTUGAL) ET L’INTÉRACTION ENTRE HUMAINS ET CASTORS Ici, nous analysons les fossiles de Castor fiber du site Pléistocène moyen de Gruta da Aroeira, dans le système karstique de Almonda, bassin du Tage (Torres Novas, Portugal), et les implications archéologiques de la présence de castors dans la région. Le karst d'Almonda est un cadre de référence pour l’étude de l'évolution humaine dans la partie occidentale de l'Europe, du Pléistocène moyen à l'Holocène, avec aussi bien des restes d’hominidés fossiles, que de faunes et de vestiges archéologiques. Des fossiles de castors ont été trouvés dans les gisements archéologiques d'au moins trois cavités du système karstique : la Gruta da Aroeira, la Gruta da Oliveira et la Galeria da Cisterna. Ici, pour la première fois, nous décrivons les fossiles de Castor fiber de Gruta da Aroeira. Les castors d'Aroeira sont remarquables car ils sont la trace fossile la plus occidentale de Castor fiber en Europe; ils sont datés du Stade Isotopique Marin (MIS) 11, autour de 420 ka. Le but de cet article est double, d'une part de présenter l'évolution des castors à travers les fossiles d'Aroeira, et d'autre part de discuter des implications paléoécologiques et paléoenvironnementales de la présence de ce rongeur dans le karst d’Almonda. Cela nous permet de discuter des possibles interactions entre humains et castors. Mots-clés : castors fossiles, archéologie, interactions humains-castors, Portugal 1 - INTRODUCTION Europe: the extinct Trogontherium (Fostowicz-Frelik, 2008) and the current genus Castor (Barisone et al., 2006). The Eurasian beaver, the species Castor fiber, is a The single extant genus, Castor, comprehends two large and semiaquatic rodent with a sparse fossil record. species, the eurasiatic beaver, Castor fiber and the Since the emergence of the family Castoridae, during American beaver, Castor canadiensis. Fossils of the genus the Eocene, beavers were tiny to giant, and semiaquatic Castor are present in Eurasia since the late Miocene, ca. or burrowing rodents (Crusafont et al., 1948; Freye 10 Ma (Aldana Carrasco, 1992; Hugueney, 1999). 1978; Aldana Carrasco, 1992; Hugueney & Escuillie The first record of beavers in the Iberian Peninsula 1996; Meentemeyer et al., 1998; Hugueney, 1999). The occurs in Spain, in the late Pliocene fluvio-lacutrine family Castoridae was diverse during the Tertiary, but in layers of the Granada basin (García-Alix et al., 2007), the Quaternary only two genera of beavers survived in while the first fossil representatives of the species 1 Aragosaurus-IUCA, Department of Earth Sciences, University of Zaragoza, calle Pedro Cerbuna, 12, ES-50009, Zaragoza. Email: [email protected] 2 Grup de Recerca del Quaternari (GRQ-SERP), Dept. d'Història i Arqueologia, Universitat de Barcelona, Carrer Montalegre, 6, ES-08001, Barcelona. 3 Centro de Arqueologia da Universidade de Lisboa (UNIARQ), Faculdade de Letras de Lisboa, Universidade de Lisboa, Alameda da Universidade, PT-1600-214, Lisboa. 4 Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, ES-08010 Barcelona. 5 Universitat de Barcelona, Department d’Història i Arqueologia, Facultat de Geografia i Història, c/Montalegre 6, ES-08001, Barcelona. Manuscrit reçu le 15/10/2020, accepté le 02/02/2021 2 Fig. 1: Localities from the Iberian Peninsula with beaver remains. Pleistocene localities: 1/ Gruta da Aroeira, 2/ Galeria da Cisterna, 3/ Gruta da Oliveira, 4/ Caldeirão, 5/ Arlanpe, 6/ Lezetxiki, 7/ Olazagutía, 8/ Zatoya, 9/ Els Muricecs, 10/ La Blanca, 11/ Valdegoba, 12/ Atapuerca (Sima del Elefante and Gran Dolina), 13/ Cueva Millán, 14/ Pinilla del Valle, 15/ Cueva de las Figuras, 16/ Cueva de los Casares, 17/ Áridos I, 18/ Bolomor, 19/ Cova Negra, 20/ Las Hienas. Holocene localities: 21/ Cuesta del Negro, 22/ Ronda, 23/ Alcaria de Arge, 24/ Vila Nova de São Pedro, 25/ Perales del Río, 26/ Sima del Ruidor, 27/ El Soto de Medinilla, 28/ Era Alta, 29/ Atapuerca (Portalón), 30/ Clunia, 31/ Ucero, 32/ La Peña, 33/ Bilbilis, 34/ Sant Pere de Gavà, 35/ Barranc Fondo. Map extracted from OpenStreetMap. Fig. 1 : Sites de la Péninsule Ibérique avec fossiles de castor. Sites pléistocènes : 1/ Gruta da Aroeira, 2/ Galeria da Cisterna, 3/ Gruta da Oliveira, 4/ Caldeirão, 5/ Arlanpe, 6/ Lezetxiki, 7/ Olazagutía, 8/ Zatoya, 9/ Els Muricecs, 10/ La Blanca, 11/ Valdegoba, 12/ Atapuerca (Sima del Elefante and Gran Dolina), 13/ Cueva Millán, 14/ Pinilla del Valle, 15/ Cueva de las Figuras, 16/ Cueva de los Casares, 17/ Áridos I, 18/ Bolomor, 19/ Cova Negra, 20/ Las Hienas. Sites holocènes : 21/ Cuesta del Negro, 22/ Ronda, 23/ Alcaria de Arge, 24/ Vila Nova de São Pedro, 25/ Perales del Río, 26/ Sima del Ruidor, 27/ El Soto de Medinilla, 28/ Era Alta, 29/ Atapuerca (Portalón), 30/ Clunia, 31/ Ucero, 32/ La Peña, 33/ Bilbilis, 34/ Sant Pere de Gavà, 35/ Barranc Fondo. Carte extraite de OpenStreetMap. Castor fiber appear in the Early Pleistocene levels of Portugal (fig. 2). It forms part of the Almonda karst the Atapuerca site complex: “Trinchera-TE; TD”, Sima system (fig. 2) (Zilhão et al., 1991, 1993; Daura et al., del Elefante (level TE9, 1.2 Ma) and Gran Dolina (TD4- 2017, 2018). Fieldwork was first conducted in an area TD6, 0.9-0.78 Ma) (Cuenca-Bescós et al., 1999, 2001, external to the site between 1997 and 2002, where 2017) (fig. 1). erosion had already exposed the sediments of the cave Here, we describe Castor fiber remains from Gruta (in the so-called Brecha das Lascas locus), and in the da Aroeira, one of the scarce contexts in the Iberian reopened cave entrance (Gruta da Aroeira). In the Peninsula containig Acheulean-bearing hominins (Daura published studies of these initial excavations, Gruta da et al., 2017, 2018; López-García et al., 2018; Sanz et al., Aroeira was designated as “Galerias Pesadas” (Marks 2018, 2020). The site has yelded a rich assemblage of et al., 2002a,b; Trinkaus et al., 2003). Archaeological beaver remains dated to MIS 11, the earliest evidence of excavations resumed in 2013 in a 6 m² area at the back the species in Portugal. The aim of this paper is to provide of the cave (squares H-J/6-8) (fig. 2), with the aim of the description of the beavers from Aroeira, and enable us reaching the base of the stratigraphic succession, assess to discuss the palaeoecological and palaeoenvironmental the depth of the archaeological sequence and determine implications in relation to the human presence. its chronological range. In this area, the stratigraphic succession spans a thickness of 4 m and comprises three major units. The uppermost one, Unit 1, is a brecciated 2 - SITE DESCRIPTION infill capped by flowstone. Unit 2 (fig. 2) is a 2.2 m-thick mud-supported breccia, rich in angular and sub- Gruta da Aroeira (39°30’20”N, 08°36’57”W) is a cave rounded clasts, corresponding to Acheulean layer X and located in the Central Limestone Massif of Estremadura capped by a second flowstone dated to 418 +37/- 27 ka (municipality of Torres Novas, Santarém), in central (2 σ). Layer X is divided into sub-layers X and Xb/c 3 Fig. 2: The site. (1-3) Geographical location of the Gruta da Aroeira site in the Central Limestone Massif of Estremadura (municipality of Torres Novas, Santarém), in central Portugal, Iberian Peninsula. The site is a cave forming part of the Almonda karst system, in the Tagus basin. Maps are extracted from OpenStreetMap. (4) The Almonda escarpment with the position of Aroeira and the other caves mentioned in the text (image from Pedro Souto). (5) Gruta da Aroeira plan and excavation grid. (6) Gruta da Aroeira stratigraphic profile. Layer X is divided into sub- layers X and Xb/c excavated between 1997-2002 and between 2013-2017. Fossils of beaver remains are signalled with the animal’s silhouette. Note the flowstone capping the deposit containing the beaver remains. Fig. 2 : Le site. (1-3) Situation géographique de la Gruta da Aroeira dans le massif calcaire central d'Estremadura (commune de Torres Novas, Santarém), au centre du Portugal, péninsule ibérique.