Oldest Evidence of Toolmaking Hominins in a Grassland-Dominated Ecosystem

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.

Change and variability in Plio-Pleistocene climates: modelling the hominin response

“…With the true nature of the Dikika evidence still in contention (Dominguez-Rodrigo et al, 2010;McPherron et al, 2010), it is currently prudent to assign the earliest Oldowan a date of around 2.6 mya (Semaw, 2000;Semaw et al, 1997Semaw et al, , 2003. Following this initial date, a series of important Oldowan localities appear between 2.5 and 2 mya in the Hadar, Middle Awash and Omo areas of Ethiopia, on the west banks of Lake Turkana and at Kanjera in Kenya, and in the Upper Semliki Valley, Democratic Republic of Congo (Chavaillon, 1976;de Heinzelin et al, 1999;Goldman-Neuman and Hovers, 2009;Harris et al, 1987Harris et al, , 1990Hovers, 2009;Howell et al, 1987;Kimbel et al, 1996;Plummer et al, 1999Plummer et al, , 2009Roche et al, 1999). The Oldowan occurs in habitats ranging from riverine forest and grassy woodlands at Olduvai (Sikes, 1994) to open context savanna environments at Kanjera (de Lumley and Beyene, 2004;Plummer et al, 1999Plummer et al, , 2009, ultimately occurring over a latitudinal span of some 80 .…”

“…Following this initial date, a series of important Oldowan localities appear between 2.5 and 2 mya in the Hadar, Middle Awash and Omo areas of Ethiopia, on the west banks of Lake Turkana and at Kanjera in Kenya, and in the Upper Semliki Valley, Democratic Republic of Congo (Chavaillon, 1976;de Heinzelin et al, 1999;Goldman-Neuman and Hovers, 2009;Harris et al, 1987Harris et al, , 1990Hovers, 2009;Howell et al, 1987;Kimbel et al, 1996;Plummer et al, 1999Plummer et al, , 2009Roche et al, 1999). The Oldowan occurs in habitats ranging from riverine forest and grassy woodlands at Olduvai (Sikes, 1994) to open context savanna environments at Kanjera (de Lumley and Beyene, 2004;Plummer et al, 1999Plummer et al, , 2009, ultimately occurring over a latitudinal span of some 80 . A case can clearly be made, therefore, that this initial mastery of stone technology provided not only a stimulus to spatial expansion towards novel environments, but also a means of adapting to temporal habitat fluctuations in situ (Grove, in press).…”

Environment and Climate of Early Human Evolution

“…Vegetation is a key component of habitat and the selection pressures on all terrestrial organisms, as it can affect diet, shelter, body plan, mobility, and predator-prey interactions. In studies of human evolution, vegetation has been important in considering the reasons for the development of terrestrial lifestyles, bipedalism, dietary change, and stone tool use (Domínguez-Rodrigo 2014, Plummer et al 2009, Wheeler 1991, White et al 2009). The nature of vegetation change in Africa has been recently reviewed (Bonnefille 2010, Barboni 2014, Jacobs et al 2010, and the reader should consult these texts for more thorough treatments.…”

Old stones' song: Use-wear experiments and analysis of the Oldowan quartz and quartzite assemblage from Kanjera South (Kenya)

“…It has been argued that the Kanjera artifacts were made by a species of Homo (Plummer, 2004;Plummer et al, 2009a), and their age at ~ 2 Ma may indicate that either very early H. erectus or a taxon that preceded it was making wooden tools.…”