Sima del Elefante is one of the excavation sites within the Archaeological Site of Atapuerca. Sierra de Atapuerca is located in the province of Burgos, in the Autonomous Community of Castilla y Leon, in the northern part of the Iberian Peninsula [8][3].  The caves of Sierra de Atapuerca contain a rich fossil record of Europe’s earliest humans, dating back to more than a million years. They represent an exceptional reserve of data that provides invaluable information about the appearance and the way of life of our remote distant ancestors [8].

The archaeological significance of Atapuerca was first recognized in the early 1900s, as an old railway trench revealed numerous fissures and caves in Cretaceous limestones on the slopes of the Sierra de Atapuerca [9]. Deep cuts were made through the karst geology, exposing rocks and sediments from Gran Dolina, Sima del Elefante, and Sima de los Huesos. The subsequent excavation in 1964, led by Francisco Jordá Cerdá yielded anthropogenic artefacts and human fossils spanning a wide time span. From 1978 to 1990, teams led by Emiliano Aguirre excavated further, and later by Eudald Carbonell, José Mara Bermudez de Castro, and Juan Luis Arsuaga [3]. Sima del Elefante was first excavated in 1992, but it was not until 1996 that it was systematically excavated [5][10].

Stratigraphy and Chronology

The Atapuerca karst system is divided into two subsystems with two current openings, namely Cueva Mayor and Cueva del Silo. Sima del Elefante site is a major cave infill located in the intermediate level of the Cueva Mayor - Cueva del Silo multi-level karst system and forms part of a now sealed palaeoentrance connected to Galería Baja, a passage that is located in the intermediate level of the karst system that leads to the interior of Cueva Mayor - Cueva del Silo [11][5][12][2]. 

The exposed section in Sima del Elefante has a stratigraphic succession with a thickness of 25 m and width of 15 m, divided into 16 lithostratigraphic units namely TE7 to TE21, from the bottom upwards [13][14][5][15][2]. The lower red units (TE7 to TE14) are dated to 1.13 ± 0.18 Ma (TE7) and 1.22 ± 0.16 Ma (TE9) via cosmogenic nuclides and are associated with a human mandible (Homo sp.), faunal fossils and Mode 1 Oldowan stone tools [4][16][15][2]. The middle section, which consists of units TE15 - TE17 is sterile but a palaeomagnetic reversal has been discovered at the top of units TE16/base and TE17 and has been interpreted as the Brunhes-Matuyama boundary [9], thus establishing a Brunhes Chron age (<780ka) for the overlying units (TE17-TE21). This chronology was confirmed by extended-range luminescence dating of quartz and K-feldspar, which produced ages of 864 ± 88 ka and 804 ± 47 ka for unit TE16 and 781 ± 63 ka and 724 ± ka for unit TE17 [17]. The paired luminescence ages for the upper occupation levels for the upper units (TE18 - TE19) agree and show that the host deposit accumulated 576 - 481 ka for the TE18 stratified scree layers and 266 - 237 ka for TE 19 [2]. 

Oldest Europeans

The Sima del Elefante site provides strong evidence of human settlement in the Iberian Peninsula over a million years ago [5]. It is especially known for the discovery of hominin fossils from the TE9 level. During the 2007 field season, ATE9-1, the mandible, and isolated permanent left lower second premolar (LP4) of an undetermined Homo was recovered from the excavation of square H-29 of the TE9C level. This mandible was the earliest hominin discovered in Europe at the time, dating to 1.2 to 1.3 Ma. It was tentatively assigned to Homo antecessor but identified palaeopathologies prevent a specific taxonomic assignment [17][1][4]. Also found in the TE9 level in 2008, is a proximal left-hand phalanx of an adult Homo sp. [6].

In July 2022, the Atapuerca team revealed that an even older fossil was discovered during excavations on June 30. The facial fragment or jaw bone was discovered in the TE7 level, 2 m below ATE9-1, indicating that it is older. It is currently estimated to be approximately 1.4 million years old. Geological samples are currently being taken to estimate the age of the fossil at the Geochronology laboratories of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) in Burgos, Spain. The samples will be dated using three methods: Electronic Spin Resonance (ESR), Paleomagnetism, and Cosmogenic Nuclides [7][18].

Stone Tools

Sima del Elefante has produced a number of lithic artefacts from its stratigraphic horizons. Early Pleistocene units TE9 - TE14 have produced a number of Mode 1 (Oldowan) tools dating from 0.78 to 1.77 Ma. Lithic tools from the lowest levels (TE9 through E14) are typically made of Cretaceous flint and some knapping on calcareous rocks is present.  These units’ flakes are mostly composed of micritic limestone [9]. Mode 1 lithic tools found in level TE9c (1.22 ± 0.16 Ma) were directly associated with a human mandible (ATE9-1) and a phalange, as well as faunal remains with anthropogenic processing marks [4][16].

Units TE15, TE16, and TE17 have yielded no lithic materials or vertebrate fossils to date. The Middle Pleistocene units of Sima del Elefante (TE18 and TE19) produced Mode 2 (Acheulean) and early Mode 3 lithic assemblages [4][14][5][9][2]. Units TE18 and TE19 have produced a smaller lithic assemblage (mostly from TE19) that is largely composed of knapping products, flake tools and hammerstones, and a few cores. The assemblage is composed of medium-to-large sized implements, as well as several large cutting tools (LCTs), displaying high morphological standardization and longitudinal or centripetal reduction sequences. Quartzite is the most common raw material used, followed by sandstone and Neogene chert [19].