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- Bibi, Faysal, et al.
(författare)
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Paleoecology of the Serengeti during the Oldowan-Acheulean transition at Olduvai Gorge, Tanzania: The mammal and fish evidence
- 2017
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Ingår i: Journal of Human Evolution. - : Elsevier BV. - 0047-2484 .- 1095-8606.
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Tidskriftsartikel (refereegranskat)abstract
- Eight years of excavation work by the Olduvai Geochronology and Archaeology Project (OGAP) has produced a rich vertebrate fauna from several sites within Bed II, Olduvai Gorge, Tanzania. Study of these as well as recently re-organized collections from Mary Leakey's 1972 HWK EE excavations here provides a synthetic view of the faunal community of Olduvai during Middle Bed II at ~1.7e1.4 Ma, an interval that captures the local transition from Oldowan to Acheulean technology. We expand the faunal list for this interval, name a new bovid species, clarify the evolution of several mammalian lineages, and record new local first and last appearances. Compositions of the fish and large mammal assemblages support previous indications for the dominance of open and seasonal grassland habitats at the margins of an alkaline lake. Fish diversity is low and dominated by cichlids, which indicates strongly saline conditions. The taphonomy of the fish assemblages supports reconstructions of fluctuating lake levels with mass die-offs in evaporating pools. The mammals are dominated by grazing bovids and equids. Habitats remained consistently dry and open throughout the entire Bed II sequence, with no major turnover or paleoecological changes taking place. Rather, wooded and wet habitats had already given way to drier and more open habitats by the top of Bed I, at 1.85e1.80 Ma. This ecological change is close to the age of the Oldowan-Acheulean transition in Kenya and Ethiopia, but precedes the local transition in Middle Bed II. The Middle Bed II largemammal community is much richer in species and includes a much larger number of large-bodied species (>300 kg) than the modern Serengeti. This reflects the severity of Pleistocene extinctions on African large mammals, with the loss of large species fitting a pattern typical of defaunation or ‘downsizing’ by human disturbance. However, trophic network (food web) analyses show that the Middle Bed II communitywas robust, and comparisons with the Serengeti community indicate that the fundamental structure of foodwebs remained intact despite Pleistocene extinctions. The presence of a generalized meateating hominin in the Middle Bed II community would have increased competition among carnivores and vulnerability among herbivores, but the high generality and interconnectedness of the Middle Bed II food web suggests this community was buffered against extinctions caused by trophic interactions.
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| 2. |
- Rowan, John, et al.
(författare)
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Early Pleistocene large mammals from Maka’amitalu, Hadar, lower Awash Valley, Ethiopia
- 2022
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Ingår i: PeerJ. - Corte Medera : PeerJ. - 2167-8359. ; 10, s. e13210-e13210
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Tidskriftsartikel (refereegranskat)abstract
- The Early Pleistocene was a critical time period in the evolution of eastern Africanmammal faunas, but fossil assemblages sampling this interval are poorly known fromEthiopia’s Afar Depression. Field work by the Hadar Research Project in theBusidima Formation exposures (~2.7–0.8 Ma) of Hadar in the lower Awash Valley,resulted in the recovery of an early Homo maxilla (A.L. 666-1) with associated stonetools and fauna from the Maka’amitalu basin in the 1990s. These assemblages aredated to ~2.35 Ma by the Bouroukie Tuff 3 (BKT-3). Continued work by the HadarResearch Project over the last two decades has greatly expanded the faunal collection.Here, we provide a comprehensive account of the Maka’amitalu large mammals(Artiodactyla, Carnivora, Perissodactyla, Primates, and Proboscidea) and discusstheir paleoecological and biochronological significance. The size of the Maka’amitalu assemblage is small compared to those from the Hadar Formation (3.45–2.95 Ma)and Ledi-Geraru (2.8–2.6 Ma) but includes at least 20 taxa. Bovids, suids, andTheropithecus are common in terms of both species richness and abundance, whereascarnivorans, equids, and megaherbivores are rare. While the taxonomic compositionof the Maka’amitalu fauna indicates significant species turnover from the HadarFormation and Ledi-Geraru deposits, turnover seems to have occurred at a constantrate through time as taxonomic dissimilarity between adjacent fossil assemblages isstrongly predicted by their age difference. A similar pattern characterizes functionalecological turnover, with only subtle changes in dietary proportions, body sizeproportions, and bovid abundances across the composite lower Awash sequence.Biochronological comparisons with other sites in eastern Africa suggest that the taxarecovered from the Maka’amitalu are broadly consistent with the reported age of theBKT-3 tuff. Considering the age of BKT-3 and biochronology, a range of 2.4–1.9 Mais most likely for the faunal assemblage.
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