Remerciez-le!

Remerciez @Admin pour avoir partagé cet document gratuitement, de la manière la plus simple, en partageant sur les réseaux sociaux.

C. R. Palevol 16 (2017) 140–154 Contents lists available at ScienceDirect Compt

C. R. Palevol 16 (2017) 140–154 Contents lists available at ScienceDirect Comptes Rendus Palevol w ww.s ciencedirect.com Human Palaeontology and Prehistory The paleoanthropology of Hadar, Ethiopia Paléoanthropologie d’Hadar, Éthiopie Donald Johanson School of Human Evolution and Social Change, Institute of Human Origins, Arizona State University, PO Box 874101 Social Sciences Rm. 103, Tempe, AZ 85287-4101, USA a r t i c l e i n f o Article history: Received 25 October 2016 Accepted after revision 26 October 2016 Available online 29 December 2016 Presented by Marcel Otte Keywords: Hadar Formation Afar depression Ethiopia Australopithecus Homo Palaeoanthropology a b s t r a c t Field research at the fossil-bearing deposits in the Afar Depression began in the 1970s. Prior to this, hominin fossils older than 3.0 Mya consisted of only a handful of frag- ments. During Phase I, the International Afar Research Expedition to Hadar, Ethiopia collected some 240 fossil hominins from Hadar over a time range of 3.0–3.4 Mya. Along with hominin fossils from Laetoli, they were deemed a new species, Australopithecus afarensis. This taxon was posited as the last common ancestor to robust Australopithe- cus and the Homo lineage in eastern Africa. Phase II research under the Hadar Research Project has added strength to the Phase I results, including the ﬁrst association of a Homo fossil with stone tools at 2.4 Mya. This presentation is a cursory synopsis of the impor- tance and implications of the hominin fossils recovered at Hadar during over the last 34 years. © 2016 Published by Elsevier Masson SAS on behalf of Acad´ emie des sciences. Mots clés : Formation d’Hadar Dépression d’Afar Éthiopie Australopithecus Homo Paléoanthropologie r é s u m é Les recherches de terrain sur les dépôts fossilifères de la dépression de l’Afar ont commencé dans les années 1970. Avant cela, les fossiles d’homininés vieux de plus de 3,0 Ma consistaient seulement en une poignée de fragments. Durant la phase I, l’International Afar Research Expedition à Hadar, en Éthiopie, a récolté quelque 240 homininés fossiles, sur un intervalle de temps de 3 à 3,4 Ma. Outre les fossiles d’homininés de Laetoli, une nou- velle espèce a été mise en évidence, Australopithecus afarensis. Ce taxon a été considéré comme le dernier ancêtre commun à la lignée d’Australopithecus et d’Homo en Afrique ori- entale. La phase II de recherche dans le cadre du projet de recherche Hadar a permis de renforcer les résultats de la phase I, en incluant la première association d’Homo fossile à des outils de pierre à 2,4 Ma. Cette présentation est un bref synopsis quant à l’importance et aux implications des fossiles d’homininés collectés à Hadar au cours des 34 dernières années. © 2016 Publi´ e par Elsevier Masson SAS au nom de Acad´ emie des sciences. E-mail address: johanson.iho@ASU.edu http://dx.doi.org/10.1016/j.crpv.2016.10.005 1631-0683/© 2016 Published by Elsevier Masson SAS on behalf of Acad´ emie des sciences. D. Johanson / C. R. Palevol 16 (2017) 140–154 141 1. Introduction Following 34 years of paleoanthropological ﬁeld research in South Africa inspired by the 1925 announce- ment of the Taung Baby, attention shifted to Africa’s Great Rift Valley in 1959. This was the result of the July 17, 1959 recovery of the “Zinj” skull at Olduvai Gorge (now referred to as Oldupai Gorge) on the eastern edge of Tanzania’s Serengeti Plain (Leakey, 1959). The late Mary Leakey’s Olduvai ﬁnd led to discoveries of fossil hominin remains in the lower Omo Valley, Lake Rudolf (now Lake Turkana), Peninj, Kanapoi, and Lothagam, where all localities were closely associated with the Great Rift Valley. In contrast to the South African sites, such as Swartkrans, Sterkfontein, Kromdraai, and Taung, the Rift Valley sites offered an enhanced data set for understanding human origins. The East African sites provided volcanic materials amenable to precise argon radiometric dating for fossil and archaeological ﬁnds. Additionally, the secure geological contexts from which these ﬁnds derived allowed associa- tions of hominin and non-hominin faunal remains, stone artefacts, as well as precising the depositional circum- stances that preserved these ﬁnds. During the 1960s, the transdisciplinary research strat- egy of paleoanthropology – knitting together expertise in the biological, geological and anthropological sci- ences – was articulated primarily by research teams in the circum-Turkana basin in Ethiopia and Kenya, as well as Oldvuai Gorge, Tanzania. With this successful and broad reaching approach to understanding human evolution, it was fortuitous that Maurice Taieb brought attention to unexplored and highly promising fossils ﬁelds in Ethiopia (Fig. 1). During the course of his late 1960s geological ﬁeldwork in Ethiopia’s Afar sedimentary basin (the Afar Region), the northeast- ern extension of the Great Rift Valley, Taieb encountered hitherto unknown Plio/Pleistocene sedimentary deposits rich in well-preserved and diverse mammalian fossils. The Afar sedimentary basin, sometimes referred to as the Afar Triangle, comprises a vast area constrained to the west by the Western Ethiopian Escarpment, to the southeast by the Somalian Escarpment and to the northeast by the Danikil Horst. In early 1972, Taieb organized a small exploratory reconnaissance to the Afar Region to evaluate the poten- tial of there for more extensive paleoanthropological ﬁeld investigation. Following six weeks of survey, he formed the International Afar Research Expedition (IARE), a multi- national, transdisciplinary team dedicated to exploring in greater depth these geological exposures with the goal of recovering fossil hominins (Taieb et al., 1972). In 1973, ﬁeld exploration focused on the site Hadar, (11◦06′ N, 40◦35′ E), where deep, fossil rich sedimentary exposures were situated just north of the Awash River (Fig. 2). A fossil knee joint estimated based on biostratig- raphy to be in excess of three million years (now dated to 3.4 Mya) constituted the ﬁrst fossil hominin to be found in the Afar Triangle (Fig. 3). The knee, and associated prox- imal femoral elements from Afar Localities 128 and 129 (A.L. 128 and A.L. 129), provided indisputable evidence for human bipedalism (Johanson and Coppens, 1976). Subsequent IARE missions to Hadar were rewarded with a richness of fossil hominins. Particularly notewor- thy was the 1974 discovery of partial skeleton, A.L. 288-1 (Fig. 4), and the 1975 recovery of over 200 hominin bones at A.L. 333. Dubbed the “First Family,” they were undoubt- edly the casualties of a catastrophic event. These two discoveries, dating to 3.2 Mya, proved invaluable for under- standing anatomical and developmental variation in the Hadar hominins. Beginning in 1981, a moratorium on ﬁeld research was imposed by the Ethiopian Government due to the insta- bilities resulting from the coup d’état by the Marxist Derg and the overthrow of Emperor Haile-Selassie. This inter- ruption of ﬁeld research at Hadar lasted until 1990, as Fig. 1. Overview of Hadar deposits looking south. Fig. 1. Vue générale des dépôts d’Hadar, en regardant vers le sud. 142 D. Johanson / C. R. Palevol 16 (2017) 140–154 Fig. 2. Map of Hadar (Kimbel and Delezene, 2009). Fig. 2. Carte d’Hadar (Kimbel et Delezene, 2009). which time the Hadar Research Project (HRP) coordinated by the Institute of Human Origins re-initiated exploration that continues to this day. 2. Hadar chronology, geology and paleoenvironment The Hadar Formation (Fig. 5), as deﬁned by Taieb et al. (1972) consists primarily of ﬂuvio-lacustrine related mud- stones, siltstones, ﬁne-grained sandstones and volcanic tuffs. The 150-meter thick formation is divided into four members: the Basal Member, the Sidi Hakoma Member, the Denan Dora Member and the Kada Hadar Member. Three tuffs, the Sidi Hakoma Tuff (SHT), the Triple Tuff (TT) and the Kada Hadar Tuff (KHT) separate the four members. Reed (2008) identiﬁes ﬂuctuating paleoenvironments over the 400,000 years of time in the Hadar Formation. Habitat reconstructions were based on careful analysis of the faunal remains within the Hadar Formation. The Sidi Hakoma Member was characterized by a more closed habi- tat with high rainfall and low seasonality. The overlying Denan Dora Member was an edaphic grassland habitat. Finally, the Kada Hadar Member was even a more open and arid habitat as seen in the high abundance of antilopins; open area bovids. Australopithecus afarensis was a eury- otropic species found throughout the Hadar Formation, able to tolerate a wide range of habitats. The Hadar Formation is separated from the overlying Busidima Formation just above the 2.95 Mya Bouroukie Tuff-2 (BKT-2) by a geological unconformity. Reed (2008) notes that above this datum, in signiﬁcantly younger deposits, is a recognizable faunal turnover. She interprets this change as a response to a wooded grassland habitat with ﬂoodplain environments. Notable is the absence of A. afarensis in the Busidima Formation, but a 2.4 Mya max- illa assigned to Homo (Kimbel et al., 1996, 1997) was found in the Makaamitalu Basin. Fossil pollen recovered from the Hadar Formation (Bonneﬁlle et al., 2004) conﬁrmed a forested habitat in the Sidi Hakoma Member. Pollen from the Denen Dora Mem- ber reﬂects a drier habitat in contrast to the Kada Hadar Member, which was more wooded and humid. Further evidence from studies of paleosols and car- bon and oxygen isotopes of mollusks (Hailemichael, 2000; Hailemichael et al., 2002) agrees with the habitat recon- structions reported by uploads/Science et Technologie/ the-paleanthropology-of-hadar-ethiopia-pdf.pdf