Act II of the Middle Pleistocene: Human-occupied Europe
The Epivillafranchian and the transition from the Lower to the Middle Pleistocene are periods inhabited by the first Europeans: `Homo antecessor´. However, the second half of the Middle Pleistocene, between 500,000 and 130,000 years ago, witnessed the first great hominin expansion in Europe, that of the Neandertal lineage: `Homo heidelbergensis´ and posteriorly `Homo neanderthalensis´. Alongside these humans, a faunal community reflects the different ecosystems of this period, and several species that appear at this moment represent the precursors of extant taxa, while other species are displaced or disappear forever. Among the former, the lions stand out, and as mentioned previously, they appear on the European continent some 600,000 years ago, based on the remains recovered from Isernia la Pineta (Italy), with an intense geographic expansion since 400,000 years ago. This social felid, with a larger body size than its extant relatives, is present at the Sima de los Huesos, together with almost thirty `Homo heidelbergensis´ individuals, with an antiquity of nearly 500,000 years ago, and a little later at the Trinchera Galeria, where it is the most abundant carnivore, as well in the upper levels (TD10-11) from Gran Dolina.
The second half of the Middle Pleistocene is also characterized by the appearance of “true wolves”, whose earliest representatives are located in deposits between 400,000-200,000 years old in Europe, including Ambrona (Soria), Lunel-Viel (France), or Heppenloch (Germany). This period is also well-represented at the Sierra de Atapuerca in the upper levels (TD10-11) from Gran Dolina and the deposits at Trinchera Galeria. At the latter site, a small nearly complete mandible of this first `Canis lupus´ was recovered with a wolf-like morphology that makes it an ideal candidate for the first Iberian wolf. The transition from the Epivillafranchian and Cromerian wolf, `Canis mosbachensis´, to the first true wolves (`Canis lupus´), occurred close to the Holsteinian interglacial period (between marine isotopic stages 9 and 11) about 400,000 years ago. These “true” wolves are smaller than modern wolves and coexisted with the red dog (`Cuon alpinus´) during a period of time preserved in the Trinchera Galeria deposits. Remains of `Cuon´ are more abundant here, with five individuals of the same or similar size, compared to only a single wolf recovered to date. These two species of social canids presumably competed with each other, but the capacity of the ecosystem to sustain both taxa is unclear. Neither of these predators seem to have entered a decline, although towards the Upper Pleistocene `Cuon´ is displaced to the east, limiting its current range to present-day Asia. Furthermore, among extant representatives, body size has increased in wolves, but decreased in `Cuon´.
The modern “common” fox (`Vulpes vulpes´) is a species that is barely known until the second half of the Middle Pleistocene and is well represented for the first time in Atapuerca at the Sima de los Huesos around 500,000 years ago, persisting until the present day with little change in size.
The faunal association for this period is defined in Atapuerca by the following taxa: cave lion (`Panthera leo fossilis´), Iberian lynx (`Lynx pardinus spelaeus´), wildcat (`Felis silvestris´), cave bear (`Ursus deningeri-spelaeus´), red dog (`Cuon alpinus´), lion (`Panthera leo´), common fox (`Vulpes vulpes´), badger (`Meles meles´), weasel (`Mustela nivalis´), tahr (`Hemitragus bonnali´), horse (`Equus caballus´), Bos/Bison, `Stephanorhinus cf. hemitoechus´, wild hog (`Sus scrofa´), fallow deer (`Dama dama clactoniana´), red deer (`Cervus elaphus cf. priscus´), and several voles `Arvicola cf. sapidus´, `Pliomys lenki´, `Microtus agrestis´, `Microtus arvalis´, `Iberomys brecciensis´, and `Terricola atapuerquensis´. The bottom of level TD10 is one of few localities together with Mauer, Mosbach, Westbury, and Vertészöllös, where lions and saber-toothed tigers coexisted during the second half of the Cromerian period.
Rodents at the Trinchera Galeria complex are limited to two lithological units rich in fossils: Lower Unit II (GII), and Upper Unit III (GIII), which are characteristic of the Middle Pleistocene. Remains are scarce or absent at the lower portion of GII. The temporal difference between Units GII and GIII was likely not great since the rodent assemblage is quite similar on both Units. The presence/absence ofsSome taxa should be attributed to ecological and/or taphonomic reasons, rather than representing true appearance or disappearance by migration or immigration. Several kinds of voles appear, including: `Arvicola aff. A. sapidus´, `Microtus jansoni´, `Microtus arvalis´, `Terricola atapuerquensis´, `Iberomys brecciensis´, `Pliomys lenki´, `Allocricetus correzensis´, `Apodemus sp.´, `Eliomys quercinus´, `Marmota sp.´, `Hystrix (Acanthion) vinogradovi´. The presence of porcupines, together with other Mediterranean taxa like `Iberomys brecciensis´ and `Arvicola aff. A. sapidus´, could indicate a warm and humid climate during the period of time when sediments at units GII and GIII at Trinchera Galeria were deposited.