| 1. |
- 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. |
- Fortelius, Mikael, et al.
(författare)
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An ecometric analysis of the fossil mammal record of the Turkana Basin
- 2016
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 371
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Tidskriftsartikel (refereegranskat)abstract
- Although ecometric methods have been used to analyse fossil mammal faunas and environments of Eurasia and North America, such methods have not yet been applied to the rich fossil mammal record of eastern Africa. Here we report results from analysis of a combined dataset spanning east and west Turkana from Kenya between 7 and 1 million years ago (Ma). We provide temporally and spatially resolved estimates of temperature and precipitation and discuss their relationship to patterns of faunal change, and propose a new hypothesis to explain the lack of a temperature trend. We suggest that the regionally arid Turkana Basin may between 4 and 2 Ma have acted as a ‘species factory’, generating ecological adaptations in advance of the global trend. We show a persistent difference between the eastern and western sides of the Turkana Basin and suggest that the wetlands of the shallow eastern side could have provided additional humidity to the terrestrial ecosystems. Pending further research, a transient episode of faunal change centred at the time of the KBS Member (1.87–1.53 Ma), may be equally plausibly attributed to climate change or to a top-down ecological cascade initiated by the entry of technologically sophisticated humans.
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| 3. |
- Hempel, Elisabeth, et al.
(författare)
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Blue Turns to Gray : Paleogenomic Insights into the Evolutionary History and Extinction of the Blue Antelope (Hippotragus leucophaeus)
- 2022
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 39:12
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Tidskriftsartikel (refereegranskat)abstract
- The blue antelope (Hippotragus leucophaeus) is the only large African mammal species to have become extinct in historical times, yet no nuclear genomic information is available for this species. A recent study showed that many alleged blue antelope museum specimens are either roan (Hippotragus equinus) or sable (Hippotragus niger) antelopes, further reducing the possibilities for obtaining genomic information for this extinct species. While the blue antelope has a rich fossil record from South Africa, climatic conditions in the region are generally unfavorable to the preservation of ancient DNA. Nevertheless, we recovered two blue antelope draft genomes, one at 3.4× mean coverage from a historical specimen (∼200 years old) and one at 2.1× mean coverage from a fossil specimen dating to 9,800–9,300 cal years BP, making it currently the oldest paleogenome from Africa. Phylogenomic analyses show that blue and sable antelope are sister species, confirming previous mitogenomic results, and demonstrate ancient gene flow from roan into blue antelope. We show that blue antelope genomic diversity was much lower than in roan and sable antelope, indicative of a low population size since at least the early Holocene. This supports observations from the fossil record documenting major decreases in the abundance of blue antelope after the Pleistocene–Holocene transition. Finally, the persistence of this species throughout the Holocene despite low population size suggests that colonial-era human impact was likely the decisive factor in the blue antelope's extinction.
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| 4. |
- Hempel, Elisabeth, et al.
(författare)
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Identifying the true number of specimens of the extinct blue antelope (Hippotragus leucophaeus)
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:2100
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Tidskriftsartikel (refereegranskat)abstract
- Native to southern Africa, the blue antelope (Hippotragus leucophaeus) is the only large African mammal species known to have become extinct in historical times. However, it was poorly documented prior to its extinction ~ 1800 AD, and many of the small number of museum specimens attributed to it are taxonomically contentious. This places limitations on our understanding of its morphology, ecology, and the mechanisms responsible for its demise. We retrieved genetic information from ten of the sixteen putative blue antelope museum specimens using both shotgun sequencing and mitochondrial genome target capture in an attempt to resolve the uncertainty surrounding the identification of these specimens. We found that only four of the ten investigated specimens, and not a single skull, represent the blue antelope. This indicates that the true number of historical museum specimens of the blue antelope is even smaller than previously thought, and therefore hardly any reference material is available for morphometric, comparative and genetic studies. Our study highlights how genetics can be used to identify rare species in natural history collections where other methods may fail or when records are scarce. Additionally, we present an improved mitochondrial reference genome for the blue antelope as well as one complete and two partial mitochondrial genomes. A first analysis of these mitochondrial genomes indicates low levels of maternal genetic diversity in the ‘museum population’, possibly confirming previous results that blue antelope population size was already low at the time of the European colonization of South Africa.
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| 5. |
- 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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| 6. |
- Westbury, V, Michael, et al.
(författare)
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Hyena paleogenomes reveal a complex evolutionary history of cross-continental gene flow between spotted and cave hyena
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:11
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Tidskriftsartikel (refereegranskat)abstract
- The genus Crocuta (African spotted and Eurasian cave hyenas) includes several closely related extinct and extant lineages. The relationships among these lineages, however, are contentious. Through the generation of population-level paleogenomes from late Pleistocene Eurasian cave hyena and genomes from modern African spotted hyena, we reveal the cross-continental evolutionary relationships between these enigmatic hyena lineages. We find a deep divergence (similar to 2.5 Ma) between African and Eurasian Crocuta populations, suggesting that ancestral Crocuta left Africa around the same time as early Homo. Moreover, we find discordance between nuclear and mitochondrial phylogenies and evidence for bidirectional gene flow between African and Eurasian Crocuta after the lineages split, which may have complicated prior taxonomic classifications. Last, we find a number of introgressed loci that attained high frequencies within the recipient lineage, suggesting some level of adaptive advantage from admixture.
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