Percorrer por autor "Geraads, Denis"
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- Afar fossil shows broad distribution and versatility of paranthropusPublication . Alemseged, Zeresenay; Spoor, Fred; Reed, Denné; Barr, W. Andrew; Geraads, Denis; Wynn, Jonathan G.; Bobe, RenéThe Afar depression in northeastern Ethiopia contains a rich palaeontological and archaeological record, which documents 6 million years of human evolution. Abundant faunal evidence links evolutionary patterns with palaeoenvironmental change as a principal underlying force1 . Many of the earlier hominin taxa recognized today are found in the Afar, but Paranthropus has been conspicuously absent from the region. Here we report on the discovery, in the Mille-Logya research area, of a partial mandible that we attribute to Paranthropus, dated to between 2.5 and 2.9 million years ago and found in a well-understood chronological and faunal context. The find is among the oldest fossils attributable to Paranthropus and indicates that this genus, from its earliest known appearance, had a greater geographic distribution than previously documented2 . Often seen as a dietary specialist feeding on tough food, the range of diverse habitats with which eastern African Paranthropus can now be associated shows that this suggested adaptive niche did not restrict its ability to disperse as widely as species of Australopithecus and early Homo. The discovery of Paranthropus in the Afar emphasizes how little is known about hominin evolution in eastern Africa during the crucial period between 3 and 2.5 million years ago, when this genus and the Homo lineage presumably emerged.
- Faunal turnover at Mille-Logya (Plio-Pleistocene, Ethiopia) reflects in situ environmental change: implications for the origins of HomoPublication . Barr, W. Andrew; Geraads, Denis; Reed, Denne; Bobe, Rene; Wynn, Jonathan; Alemseged, ZeresenayThe lower Awash Valley of Ethiopia preserves a significant record of Australopithecus afarensis at Hadar and Dikika in addition to the earliest fossil yet attributed to Homo from Ledi-Geraru at 2.8 Ma. However, understanding the context of the extinction of A. afarensis and the origin of Homo is hampered by the limited preservation of sediments between 2.9 – 2.3 Ma in the region. The Mille-Logya Project (MLP) preserves fossiliferous sediments post-dating 2.9 Ma. Here we present a quantitative analysis of the MLP mammalian fauna and explore implications of MLP faunal change for the origin of Homo.
- Fossils from Mille-Logya, Afar, Ethiopia, elucidate the link between Pliocene environmental changes and Homo originsPublication . Alemseged, Zeresenay; Wynn, Jonathan G.; Geraads, Denis; Reed, Denne; Andrew Barr, W.; Bobe, Rene; McPherron, Shannon P.; Deino, Alan; Alene, Mulugeta; J. Sier, Mark; Roman, Diana; Mohan, JosephSeveral hypotheses posit a link between the origin of Homo and climatic and environmental shifts between 3 and 2.5 Ma. Here we report on new results that shed light on the interplay between tectonics, basin migration and faunal change on the one hand and the fate of Australopithecus afarensis and the evolution of Homo on the other. Fieldwork at the new Mille-Logya site in the Afar, Ethiopia, dated to between 2.914 and 2.443 Ma, provides geological evidence for the northeast migration of the Hadar Basin, extending the record of this lacustrine basin to Mille-Logya. We have identified three new fossiliferous units, suggesting in situ faunal change within this interval. While the fauna in the older unit is comparable to that at Hadar and Dikika, the younger units contain species that indicate more open conditions along with remains of Homo. This suggests that Homo either emerged from Australopithecus during this interval or dispersed into the region as part of a fauna adapted to more open habitats.
- The late pliocene to early pleistocene lomekwi faunas, west Turkana, Kenya: systematics, paleoecology, and biochronologyPublication . Geraads, Denis; Bobe, René; Ward, Carol V.; Plavcan, J. Michael; Manthi, Fredrick KyaloWe describe here the vertebrate fauna collected by the West Turkana Paleo Project at Lomekwi, a site best known for yielding the holotype of Kenyanthropus platyops and Lomekwian stone tools, and consisting of several collecting areas providing fossil samples ranging in age from about 3.6 to 2.2 Ma. Analysis of the newly recovered material, alongside a thorough revision of earlier collections, has led to the identification of 85 vertebrate taxa, which provide biochronological indications that help refine the site's chronology and shed light on the paleoenvironmental conditions prevailing during a critical period of early hominin diversification. The newly described fauna illustrates that during the time of Kenyanthropus, hominins shared their landscapes with a rich assemblage of vertebrates, including abundant megaherbivores, some 28 species of artiodactyls, diverse large and medium-size carnivores, and giant crocodiles as apex predators in the lakes and rivers of the Turkana region in the Pliocene. Among primates, the recurring association of Theropithecus with hominins is found at Lomekwi as it is elsewhere. Paleoenvironmental proxies from the Turkana region emphasize the complex and dynamic nature of the habitats that supported this rich biodiversity.