Paleoecological patterns at the Hadar hominin site, Afar Regional State, Ethiopia.
ABSTRACT Reconstructing paleoecological patterns associated with hominin taxa, such as Australopithecus afarensis, is important for understanding possible evolutionary mechanisms involved in extinction and speciation events. It is critical to identify local, regional, or pan-African causal factors because patterns at these different levels may affect separate populations of the same species of hominin in unique ways. Habitat reconstructions of 12 submembers of the Hadar and Busidima formations (approximately 3.8-2.35 Ma) are presented here along with faunal differences in these submembers through time. Habitats with medium density tree and bush cover dominated the landscape through much of the earlier time period in the Hadar Formation. The lowermost Sidi Hakoma Member is the most closed habitat. The Denen Dora Member shows the influence of frequent floodplain edaphic grasslands with high abundances of reducin bovids. There is an influx of ungulates in the Kada Hadar Member (approximately 3.2--approximately 2.96 Ma) that indicates a more arid habitat populated by mammals that were recovered from earlier deposits further south in Ethiopia and Kenya. In the younger deposits from the Busidima Formation at Hadar, the landscape was open wooded grassland with some floodplain environments. The fossil assemblages from the Busidima Formation show a substantial species turnover. Although high numbers of A. afarensis specimens are associated with the lower Sidi Hakoma Member, they clearly inhabited a variety of habitats throughout the entire Hadar Formation. Australopithecus afarensis from Laetoli through Hadar times appears to have been a eurytopic species.
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ABSTRACT: The fossiliferous late Early Pleistocene deposits of the Buia Basin (dated to c. 1Ma) at the Danakil depression, contain three different suid species (Kolpochoerus olduvaiensis, Kolpochoerus majus, and Metridiochoerus modestus).These suid taxa are morphologically evolved and are found in association with a diverse large vertebrate faunal assemblage, including the genus Homoand a rich accumulation of Acheulean tools. The anatomic, biometric,morphometric and dental microwear analyses, showsignificant data of dietary traits, habitat and evolutionary changes. In suids, despite their omnivorous diets, microwear study can play a significant role in understanding dietary habits. The results of our study show morphological distinction between the three suid species. Conversely, the microwear patterns recorded on the dental surfaces show overlapping of ecological niches among the species. We believe that their opportunistic feeding and rapid reproduction process might have sustained their survival within the mosaic environments of the Buia Basin in competition with other faunas (other ungulates, carnivores and monkeys) and hominins.Palaeogeography Palaeoclimatology Palaeoecology 04/2015; 431:26-42. DOI:10.1016/j.palaeo.2015.04.020 · 2.75 Impact Factor
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ABSTRACT: The Upper Laetolil Beds of Laetoli, Tanzania (∼3.6–3.85 Ma) has yielded a large and varied faunal assemblage, including specimens of Australopithecus afarensis. In contrast with contemporaneous eastern African A. afarensis sites in Kenya and Ethiopia, there is no indication of permanent rivers or other large bodies of water at the site, and the apparently drier environment supported a quite different faunal and floral community as reconstructed from the fossil record. Therefore, a deeper understanding of the paleoecology at Laetoli can be illuminating for questions of habitat access and use by A. afarensis, as well as its behavioral flexibility. This paper reviews the substantial body of evidence accumulated that allows for a detailed reconstruction of the Pliocene paleoenvironment of Laetoli. A synthesis of the different lines of evidence suggests that the Upper Laetolil Beds was a mosaic of grassland–shrubland–woodland habitats with extensive woody vegetation in the form of shrubs, thickets and bush, as well as a significant presence of dense woodland habitats along seasonal river courses and around permanent springs. The vegetation during the Pliocene at Laetoli was likely impacted by the strongly seasonal availability of water and the volcanic ash falls that periodically blanketed the area. A comparison with the paleoenvironments of other A. afarensis sites and a review of its inferred dietary behavior suggest that A. afarensis was an ecological generalist that was able to consume a wide variety of dietary resources in mosaic habitats, although their differential abundances at different sites may be indicative of specific ecological requirements that impact their success in particular environments.Journal of African Earth Sciences 10/2014; DOI:10.1016/j.jafrearsci.2014.09.019 · 1.38 Impact Factor
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ABSTRACT: The mandibular third premolar (P3) of Australopithecus afarensis is notable for extensive morphological variability (e.g., metaconid presence/absence, closure of the anterior fovea, root number) and temporal trends in crown length and shape change over its 700 Ka time range. Hominins preceding A. afarensis have unicuspid, mesiodistally elongated P3s with smaller talonids, and subsequent australopiths have bicuspid, more symmetrically-shaped P3 crowns with expanded talonids. For these features, A. afarensis is intermediate and, thus, evinces the incipient stages of P3 molarization. Here, we examine A. afarensis P3 Phase II microwear and compare it with that of Australopithecus africanus and Cercocebus atys, an extant hard-object specialist, to assess whether the role of the P3 in food processing changed over time in A. afarensis. Premolar Phase II microwear textures are also compared with those of the molars to look for evidence of functional differentiation along the tooth row (i.e., that foods with different mechanical properties were processed by separate regions of the postcanine battery). Microwear textures were also examined along the mesial protoconid crest, the site of occlusion with the maxillary canine, of the A. afarensis P3 and compared with the same region in Pan troglodytes to determine whether microwear can be useful for identifying changes in the occlusal relationship between the P3 and maxillary canine in early Australopithecus. Finally, temporal trends in P3 Phase II and mesial microwear are considered. Results indicate that 1) both the P3 and molar Phase II facets of A. afarensis have less complex microwear textures than in A. africanus or C. atys; 2) A. afarensis P3 and molar Phase II textures differ, though not to the extent seen in taxa that eat hard and tough items; 3) microwear along the A. afarensis mesial protoconid crest is clearly distinct from that of the P. troglodytes, indicating that there is no honing equivalent in A. afarensis; and 4) there is little evidence of change over time in A. afarensis P3 microwear on either the mesial or Phase II facet. In sum, these results provide no evidence that A. afarensis routinely loaded either its premolars or molars to process hard objects or that A. afarensis P3 function changed over time.Journal of Human Evolution 07/2013; 65(3). DOI:10.1016/j.jhevol.2013.06.001 · 3.87 Impact Factor