Article

Paleoecological patterns at the Hadar hominin site, Afar Regional State, Ethiopia. Journal of Human Evolution, 54, 743-768

Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287-4101, USA.
Journal of Human Evolution (Impact Factor: 3.73). 07/2008; 54(6):743-68. DOI: 10.1016/j.jhevol.2007.08.013
Source: PubMed

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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    • "It also needs to be borne in mind that a dietary change towards stenotopy tends to be unusual among mammals (Price et al., 2012), even more so if A. bahrelghazali is derived from A. afarensis, either as a regional variant or through cladogenesis. A. afarensis was a eurytopic species that occupied different habitats (Reed, 2008; Kimbel and Delezene, 2009; Behrensmeyer and Reed, 2013) and successfully negotiated fluctuating environmental conditions during its lifetime (Bonnefille et al., 2004). It too incorporated C 4 foods into its diet (Wynn et al., 2013), althoughdon averagedconsiderably less so than A. bahrelghazali (Lee-Thorp et al., 2012). "
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    ABSTRACT: Australopithecus bahrelghazali, its origin and palaeobiology are not well understood. Reported from only one location some several thousand kilometres away from East African Pliocene hominin sites, it appears to have predominantly fed on C4 sources. Yet, it lacks the morphological adaptations of other primate C4 consumers like Paranthropus boisei and Theropithecus oswaldi. Furthermore, although considered to belong to Australopithecus afarensis by most researchers, A. bahrelghazali appears to differ from the former in a key aspect of its morphology: enamel thickness. To assess the phylogeny and palaeobiology of A. bahrelghazali, I first evaluate the dietary adaptations and energetics of A. bahrelghazali using empirical data of the feeding ecology of extant baboons, Papio cynocephalus. Information published on A. bahrelghazali morphology and habitat preference is used to select C4 foods with the appropriate mechanical properties and availability within the environment to create the models. By altering the feeding time on various food categories, I then test whether A. bahrelghazali could have subsisted on a C4 diet, thus accounting for the d13C composition of its dental tissue. The effects of body mass on the volume of food consumed are taken into account. The outcomes of these simulations indicate that A. bahrelghazali could have subsisted on a diet of predominantly sedges, albeit with limitations. At higher energy requirements, i.e., above 3.5 times the BMR, it would be difficult for a medium-sized primate to obtain sufficient energy from a sedge-based diet. This is apparently due to constraints on foraging/ feeding time, not because of the nutritional value of sedges per se. These results are discussed against the backdrop of A. bahrelghazali biogeography, palaeoenvironment, and phylogeny. The combined evidence makes it plausible to suggest that Northern Chad may have been a refugium for migrating mammals, including hominins, and throws new light on the deep history of A. bahrelghazali.
    Full-text · Article · Oct 2015 · Journal of Human Evolution
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    • "Detailed records of paleoenvironment, paleoclimate, and paleohabitats , as well as temporal changes in these conditions, are crucial to appreciate the role of environmental change in faunal and human evolution, diversification, extinction, and migration patterns (Dart, 1925; Vrba, 1985, 1988, 1995; Coppens, 1994; Spencer, 1996; Behrensmeyer et al., 1997; Reed, 1997; Potts, 1998; Bobe et al., 2002; Wynn, 2004; Alemseged et al., 2007; Kingston, 2007). The occurrence (e.g., Vrba, 1985) and abundance (e.g., Reed, 2008) of fossil mammalian taxa, particularly bovids, are often used as paleoecological and paleoenvironmental indicators (Harris, 1991; Vrba, 1995; Spencer, 1996; Bobe and Eck, 2001). Meanwhile, stable isotope analysis of mammalian tissues can be a quantitative indicator of an organism's diet and is an efficient tool in differentiating between grazing and browsing paleodiets (DeNiro and Epstein, 1978; Ambrose and DeNiro, 1986; Wang and Cerling, 1994; Koch, 1998; Kohn and Cerling, 2002). "
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    ABSTRACT: Preservation of the stable carbon isotopic composition of fossil tooth enamel enables us to estimate the relative proportion of C3 versus C4 vegetation in an animal's diet, which, combined with analysis of faunal abundance, may provide complementary methods of paleoenvironmental reconstruction. To this end, we analyzed stable carbon isotopic composition (δ(13)C values) of tooth enamel from four bovid tribes (Tragelaphini, Aepycerotini, Reduncini, and Alcelaphini) derived from six members of the Shungura Formation (Members B, C, D, F, G, and L; ages from ca. 2.90-1.05 Ma (millions of years ago) in the Lower Omo Valley of southwestern Ethiopia. The bovids show a wide range of δ(13)C values within taxa and stratigraphic members, as well as temporal changes in the feeding strategies of taxa analyzed throughout the middle to late Pliocene and early Pleistocene. Such variation suggests that the use of actualistic approaches for paleoenvironmental reconstruction may not always be warranted. Alcelaphini was the only taxon analyzed that retained a consistent dietary preference throughout the sequence, with entirely C4-dominated diets. Reduncini had a mixed C3/C4 to C4-dominated diet prior to 2.4 Ma, after which this taxon shifted to a largely C4-dominated diet. Aepycerotini generally showed a mixed C3/C4 diet, with a period of increased C4 diet from 2.5 to 2.3 Ma. Tragelaphini showed a range of mixed C3/C4 diets, with a median value that was briefly nearer the C4 end member from 2.9 to 2.4 Ma but was otherwise towards the C3 end member. These isotopic results, combined with relative abundance data for these bovids, imply that the environment of the Lower Omo Valley consisted of a mosaic of closed woodlands, with riverine forests and open grasslands. However, our data also signify that the overall environment gradually became more open, and that C4 grasses became more dominant. Finally, these results help document the range and extent of environments and potential diets that were available to the four hominin species encountered in the Shungura sequence. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · Sep 2015 · Journal of Human Evolution
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    • "Based on isotope data, trophic adaptations of suids have also been investigated (Harris and Cerling, 2002). However, some researchers argue that suids are unlikely to be grazers because of their bunodont dentition (Harris and Cerling, 2002; Janis et al., 2002) because they consume a variety of resources and their microwear in modern species remained complicated (Kingdon, 1979; Ward and Mainland, 1999; Reed, 2008). Suid microwear patterns imprinted on enamel surfaces are of considerable importance and can reveal significant information. "
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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.
    Full-text · Article · Apr 2015 · Palaeogeography Palaeoclimatology Palaeoecology
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