Abstract
BackgroundMajor biological and cultural innovations in late Pliocene hominin evolution are frequently linked to the spread or fluctuating presence of C4 grass in African ecosystems. Whereas the deep sea record of global climatic change provides indirect evidence for an increase in C4 vegetation with a shift towards a cooler, drier and more variable global climatic regime beginning approximately 3 million years ago (Ma), evidence for grassland-dominated ecosystems in continental Africa and hominin activities within such ecosystems have been lacking.Methodology/Principal FindingsWe report stable isotopic analyses of pedogenic carbonates and ungulate enamel, as well as faunal data from ∼2.0 Ma archeological occurrences at Kanjera South, Kenya. These document repeated hominin activities within a grassland-dominated ecosystem.Conclusions/SignificanceThese data demonstrate what hitherto had been speculated based on indirect evidence: that grassland-dominated ecosystems did in fact exist during the Plio-Pleistocene, and that early Homo was active in open settings. Comparison with other Oldowan occurrences indicates that by 2.0 Ma hominins, almost certainly of the genus Homo, used a broad spectrum of habitats in East Africa, from open grassland to riparian forest. This strongly contrasts with the habitat usage of Australopithecus, and may signal an important shift in hominin landscape usage.
Highlights
The hominin fossil and archeological records of Africa exhibit substantial anatomical and behavioral change during the PlioPleistocene (,1.5–3.0 million years ago (Ma)), including the evolution of Homo and Paranthropus, the origin of lithic technology and archeological sites, the first evidence of large mammal butchery, lower limb elongation and selection for endurance running, and thermoregulatory adaptations to hot, dry environments [1]
Evidence that grassland habitats dominated the regional ecosystem beyond the confines of our excavations is provided by large mammal frequencies, of the family Bovidae, as well as the stable isotopic composition of tooth enamel from a suite of herbivorous mammals
The reduncine bovids are indicative of edaphic grasslands and possibly woodland along the lake margin, whereas woodland is suggested by the presence of several tragelaphine bovid fossils, giraffe remains, and a Cercopithecus sp. monkey
Summary
The hominin fossil and archeological records of Africa exhibit substantial anatomical and behavioral change during the PlioPleistocene (,1.5–3.0 Ma), including the evolution of Homo and Paranthropus, the origin of lithic technology and archeological sites, the first evidence of large mammal butchery, lower limb elongation and selection for endurance running, and thermoregulatory adaptations to hot, dry environments [1]. Comparison with other Oldowan occurrences indicates that by 2.0 Ma hominins, almost certainly of the genus Homo, used a broad spectrum of habitats in East Africa, from open grassland to riparian forest.
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