Fossiliferous karat deposits of Atapuerca. First 20 years of research.

The conception of a multidisciplinary research project on the ancient occup ants of Spain and Europe, and the ecological contexts of their evolution de rived in 1976 from the incidental find of 16 human fossils in a deep pit, S H, well into the 'Cueva Mayor' of Sierra de Atapuerca (Ibeas de Juarros, Bu rgos, Spain), and after visiting several outcrops of deep, well stratified karst deposits in an abandoned railway cut, not far. The human fossils from SH were assigned to the European group of pre-neandertalians (Aguirre et a l. 1976; Aguirre & de Lumley, 1977), and classified as Home sapiens heidelb ergensis (Aguirre & Rosas, 1985). A 'mosaic' evolution was then recognized on the morphological traits of human mandibles in Middle Pleistocene, also an African origin of the pre-neandertalians, and the ancestorship of the la tter relate to neandertalians. Different approaches led by 1987 to estimate the age of SH hominines c. 300/320 Ka. BP. Paleopathological and taphonomi cal studies allowed inferring good health overall; cultural factors were su ggested for several common deficiencies. In 1990 the SH site was finally cl eaned and human bones in situ exposed after removing more than 6 Tm of a ma ss of accumulated stones, mud and bone fragments removed by searchers of be ar teeth. All that overburden washed and shifted yielded thousands of bear fossils and more then 250 human pieces of a MNI = 11. Excavation of untouch ed deposit between 1990 and 1999 produced more than 2 400 human fossils bel onging to a MNI = 27. Studies of paleodemography are published, based on th e assumption that the corpses were deposited as death occurred along time a nd as a behavioural pattern; present author thinks that the simultaneous de ath of a group taking refuge in a cave under heavy rain, and land-slide fol lowing, is more consistent with observed evidences. Two sites on the railway cut were sampled: the Gran Dolina (TD), 18.5 m dee p, and Galeria (TG) with a connected vertical shaft (TN) in the 'Complejo T res Simas', yielding abundant microvertebrate fossils and continuous or dis continuous pollen record. Extension excavation started in both TD and TG si tes over c. 24 m(2) in each met successive horizons with mammal assemblages known in European sites of the upper third of Middle Pleistocene and evide nces of human occupation. Basal beds of TD also were excavated in a talus: these yielded a paleofauna known as Upper Bhiharian, or Early Cromerian. Th e extreme ages obtained for TD are c. 900 and c. 150 Ka. Lithic assemblages , analysed from the operational viewpoint, belong to Mode 1 in TD6, to a pa rticularly evolved Mode 2 in TG, to early Mode 3 in upper TD beds. Microwea r traces were studied on rodent and amphibian fossils to identify consumers , and on tools in search of traces of use. Differences were found in meat c onsumption and on use and permanence in various cavities. A slit open cut i n TD started in 1992 yielded fossil humans with abundant lithic and faunal context in upper Bed TD6 well below the B/M magnetic reversal. Presently de bated interpretations are indicated, and future potentials suggested. (C) 2 001 Editions scientifiques et medicales Elsevier SAS.