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Archive for July, 2016

We report δ13C and δ18O results from carbonate-cemented cave sediments at Malapa in South Africa. The sediments were deposited during a short-period magnetic reversal at 1.977±0.003 Ma, immediately preceding deposition of Facies D sediments that contain the type fossils of Australopithecus sediba. Values of δ13C range between -5.65 and -2.09 with an average of -4.58±0.54‰ (Vienna Pee Dee Belemnite, VPDB) and values of δ18O range between -6.14 and -3.84 with an average of -4.93±0.44‰ (VPDB).

Source: The stable isotope setting of Australopithecus sediba at Malapa, South Africa | South African Journal of Science

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The type specimen of Australopithecus sediba (MH1) is a late juvenile, prompting some commentators to suggest that had it lived to adulthood its morphology would have changed sufficiently so as to render hypotheses regarding its phylogenetic relations suspect. Considering the potentially critical position of this species with regard to the origins of the genus Homo, a deeper understanding of this change is especially vital.

Source: Developmental simulation of the adult cranial morphology of Australopithecus sediba | South African Journal of Science

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The bacteria that make their home in the intestines of modern apes and humans arose from ancient bacteria that colonized the guts of our common ancestors. Moeller et al. have developed a method to compare rapidly evolving gyrB gene sequences in fecal samples from humans and wild chimpanzees, bonobos, and gorillas (see the Perspective by Segre and Salafsky). Comparison of the gyrB phylogenies of major bacterial lineages reveals that they mostly match the apehominid phylogeny, except for some rare symbiont transfers between primate species. Gut bacteria therefore are not simply acquired from the environment, but have coevolved for millions of years with hominids to help shape our immune systems and development. Science , this issue p. [380][1]; see also p. [350][2] [1]: /lookup/doi/10.1126/science.aaf3951 [2]: /lookup/doi/10.1126/science.aag2788

Source: Cospeciation of gut microbiota with hominids

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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.This article is part of the themed issue ‘Major transitions in human evolution’.

Source: An ecometric analysis of the fossil mammal record of the Turkana Basin | Philosophical Transactions of the Royal Society B: Biological Sciences

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Source: Stable isotope dietary reconstructions of herbivore enamel reveal heterogeneous savanna ecosystems in the Plio-Pleistocene Malawi Rift

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(2016). Why is the world green? The interactions of top–down and bottom–up processes in terrestrial vegetation ecology. Plant Ecology & Diversity: Vol. 9, No. 2, pp. 127-140. doi: 10.1080/17550874.2016.1178353

Source: Why is the world green? The interactions of top–down and bottom–up processes in terrestrial vegetation ecology – Plant Ecology & Diversity – Volume 9, Issue 2

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