Paleoecology of the Serengeti during the Oldowan-Acheulean transition at Olduvai Gorge, Tanzania : The mammal and fish evidence

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 similar to 1.7-1.4 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 1.85-1.80 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 large mammal 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 community was robust, and comparisons with the Serengeti community indicate that the fundamental structure of food webs 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. (C) 2017 Published by Elsevier Ltd.Peer reviewe

Paleoecology of the Serengeti during the oldowan-Acheulean transition at Olduvai Gorge, Tanzania: The mammal and fish evidence

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 large mammal 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 community was robust, and comparisons with the Serengeti community indicate that the fundamental structure of food webs 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.Fieldwork by OGAP is authorized by the National Museum of Tanzania, Tanzanian Antiquities, and COSTECH, and the Ngorongoro Conservation Authority, and was funded by the NSF (BCS-0852292) and a European Research Council Starting Grant (283366). FB was supported by the German Research Foundation (DFG, grant number BI 1879/1-1). AS was funded by the LaScArBx (Universite de Bordeaux), a research program supported by the Agence Nationale de la Recherche, France (ANR-10-LABX-52), and a SYNTHESYS grant (DE-TAF-5741). SV was supported by a post-doctoral fellowship from the Alexander von Humboldt Foundation. LW was funded by the Swedish Research Council.Peer reviewe

Fossil fish remains from the Pliocene Kanapoi site, Kenya

Volume: 498Start Page: 21End Page: 3

Human Activities and Site Formation at Modern Lake Margin Foraging Camps in Kenya

Interpretation of archaeological sites with predominantly freshwater fish and reptile remains has been impeded by lack of documentation of how humans process such vertebrates, of bone modifications resulting from such handling, and of physical characteristics of sites produced by these activities. We report on 19 contemporary foraging camps on the shore of Lake Turkana, Kenya, with the creation, abandonment, and resulting faunal assemblages of 7 of these more closely described. Variable processing activities created a range of site structures but cross-assemblage regularities in patterns of bone surface modification and element frequencies are perceptible. Most sites were very large, with special-purpose activity areas peripheral to the main residential area. Site structure and size depended mainly on specific subsistence activities carried out and features of the camp locale rather than upon the number of occupants or duration of occupation. Sites can be classified as base camps or as fish production camps, with consistent differences in site structure and bone assemblage characteristics

The ethnoarchaeology of reptile remains at a Lake Turkana occupation site, Kenya

The role of reptiles in hominid hunter-gatherer subsistence in Pleistocene Africa has been largely overlooked. This study examines the reptile component of a modern lake shore camp (site 20) assemblage of low archaeological visibility. Site 20, located on the eastern shore of Lake Turkana, has been observed from its creation to burial. The site is an ideal modern analogue for the interpretation of African prehistoric archaeological sites. Patterns of element loss, and patterns of bone modifications, namely burn, cut and slice marks, are examined. From this baseline data, three conclusions are drawn regarding the interpretability of reptile remains found at archaeological lakeside sites: (1) the MNI of crocodile remains at a site is likely to be similar to the original number of individuals which contributed to the deposited assemblage; (2) the MNI estimates of the turtle component will be much less than the original number of individuals in the deposited assemblage; and (3) patterns of bone modifications can be related to hominid food procurement and processing activities

Arrival order and release from competition does not explain why haplochromine cichlids radiated in Lake Victoria

The frequent occurrence of adaptive radiations on oceanic islands and in lakes is often attributed to ecological opportunity resulting from release from competition where arrival order among lineages predicts which lineage radiates. This priority effect occurs when the lineage that arrives first expands its niche breadth and diversifies into a set of ecological specialists with associated monopolization of the resources. Later-arriving species do not experience ecological opportunity and do not radiate. While theoretical support and evi- dence from microbial experiments for priority effects are strong, empirical evidence in nature is difficult to obtain. Lake Victoria (LV) is home to an exceptional adaptive radiation of haplochromine cichlid fishes, where 20 trophic guilds and several hundred species emerged in just 15 000 years, the age of the modern lake that was preceded by a complete desiccation lasting several thousand years. However, while about 50 other lineages of teleost fish also have established populations in the lake, none of them has produced more than two species and most of them did not speciate at all. Here, we test if the ancestors of the haplochromine radiation indeed arrived prior to the most competent potential competitors, ‘tilapias’ and cyprinids, both of which have made rapid radiations in other African lakes. We assess LV sediment core intervals from just before the desiccation and just after refilling for the presence of fossil fish teeth. We show that all three lineages were present when modern LV began to fill with water. We conclude that the haplochro- mines’ extraordinary radiation unfolded in the presence of potentially competing lineages and cannot be attributed to a simple priority effect

LV96_6A_ms_data from Arrival order and release from competition does not explain why haplochromine cichlids radiated in Lake Victoria

Table S1 - Magnetic susceptibility data generated at Laccore, University of Minnesota, from sections 2 to 5 of core LV96_6