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Dendi Lake Rockshelter is situated about 100 km west of Addis Ababa on the west-central part of the Ethiopian Plateau in the Ginchi woreda of Ethiopia’s Oromiya regional state. In October 2012, a t...

Reconstructions of climatic and environmental conditions can contribute to current debates about the factors that influenced early human dispersal within and beyond Africa. Here we analyse a 200,000-year multi-proxy paleoclimate record from Chew Bahir, a tectonic lake basin in the southern Ethiopian rift. Our record reveals two modes of climate change, both associated temporally and regionally with a specific type of human behavior. The first is a long-term trend towards greater aridity between 200,000 and 60,000 years ago, modulated by precession-driven wet-dry cycles. Here, more favorable wetter environmental conditions may have facilitated long-range human expansion into new territory, while less favorable dry periods may have led to spatial constriction and isolation of local human populations. The second mode of climate change observed since 60,000 years ago mimics millennial to centennial-scale Dansgaard-Oeschger cycles and Heinrich events. We hypothesize that human populations may have responded to these shorter climate fluctuations with local dispersal between montane and lowland habitats.

In this study, we synthesize terrestrial and marine proxy records, spanning the past 620 ky, to decipher pan-African climate variability and its drivers and potential linkages to hominin evolution. We find a tight correlation between moisture availability across Africa to El Niño Southern Ocean oscillation (ENSO) variability, a manifestation of the Walker Circulation, that was most likely driven by changes in Earth's eccentricity. Our results demonstrate that low-latitude insolation was a prominent driver of pan-African climate change during the Middle to Late Pleistocene. We argue that these low-latitude climate processes governed the dispersion and evolution of vegetation as well as mammals in eastern and western Africa by increasing resource-rich and stable ecotonal settings thought to have been important to early modern humans.

With excavated layers spanning a period from > 49 ka to ~ 36 ka, Mochena Borago Rockshelter reveals a complex sequence of Late Pleistocene human occupation punctuated by volcanic events. Fifty-nine radiocarbon ages make Mochena Borago one of the best-dated Late Pleistocene archaeological sites in eastern and northeastern Africa. However, complex site formation processes, dramatic stratigraphic differences between non-contiguous excavation areas, and “outlier” dates that appear in various parts of Mochena Borago's sequence, complicate efforts to develop a secure and detailed chronology for local and regional behavioral changes. This article focuses on contiguous squares within the Block Excavation Area (BXA) trench at the northern end of the shelter. Bayesian modeling of thirty-seven dates from six major lithostratigraphic units within the BXA yields a revised series of age ranges; these differ from the previous age model (derived from weighted means) in subtle but important ways. Perspectives gained through Bayesian analysis stimulate more careful consideration of the complex site formation processes operating at Mochena Borago, the contextual integrity of the site's robust and distinctive flaked stone artifact assemblages (lithics), and potential correlations between lithic changes and environmental events that occur on local, regional, and global scales. As these factors come into focus, Mochena Borago can serve as an important chronological benchmark to better understand human behavior in eastern and northeastern Africa around the time of the second major dispersal of Homo sapiens.

As an unambiguous indication of complex cognitive capacity, representational art presents explicit evidence for modern and symbolic human behaviour. The only examples of African figurative art dating to the Late Pleistocene comprise seven stone plaques recovered from Apollo 11 Cave in the Huns Mountains, southern Namibia. The plaques derive from a single anthropogenic layer dated by radiocarbon ( 14 C) accelerator mass spectrometry (AMS) and optically simulated luminescence (OSL) methods to c. 30 000 years ago. We present the results of digital (CIE) L*a*b* colourimetric and portable energy dispersive X-ray fluorescence (ED-XRF), Raman spectroscopic and Fourier transform infrared reflectance (FT-IR) analyses of the pigments present on the plaques. These results provide the earliest direct evidence, in Africa, for the preparation of pigment-based paint-like mixtures and their application to create prehistoric art. Our research shows that in the creation of the depictions on the plaques, the artists used black pigments derived from manganese and charcoal, red pigments likely derived from ocherous shale and white pigments possibly derived from ostrich eggshell. Additionally, these plaques provide unique evidence for the combined use of mineral- and carbon-based pigment ‘crayons’ during the African Middle Stone Age.

Our understanding of the impact of climate-driven environmental change on prehistoric human populations is hampered by the scarcity of continuous paleoenvironmental records in the vicinity of archaeological sites. Here we compare a continuous paleoclimatic record of the last 20 ka before present from the Chew Bahir basin, southwest Ethiopia, with the available archaeological record of human presence in the region. The correlation of this record with orbitally-driven insolation variations suggests a complex nonlinear response of the environment to climate forcing, reflected in several long-term and short-term transitions between wet and dry conditions, resulting in abrupt changes between favorable and unfavorable living conditions for humans. Correlating the archaeological record in the surrounding region of the Chew Bahir basin, presumably including montane and lake-marginal refugia for human populations, with our climate record suggests a complex interplay between humans and their environment during the last 20 ka. The result may contribute to our understanding of how a dynamic environment may have impacted the adaptation and dispersal of early humans in eastern Africa. (C) 2015 Elsevier Ltd. All rights reserved.

The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa—the Still Bay and Howieson's Poort industries—that are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies. We report ages for nine sites from varied climatic and ecological zones across southern Africa that show that both industries were short-lived (5000 years or less), separated by about 7000 years, and coeval with genetic estimates of population expansion and exit times. Comparison with climatic records shows that these bursts of innovative behavior cannot be explained by environmental factors alone.

During this study, the recent relations between the hydrological systems and the distribution of archaeological sites and obsidian raw material outcrops within the catchment of the Bisare River, around Mt Damota, and around Mt Sodicho in the southwestern Ethiopian Highlands were investigated. To do so, we combined geomorphological–hydrological analyses with field surveys and GIS mapping. The aim was to try to transfer these recent interrelations into the past to better understand the factors that influenced prehistoric human settlement activity. The natural geomorphodynamics in landscapes such as the southwestern Ethiopian Highlands were and still are characterized by the interplay between endogenous processes (tectonics, volcanism) and climatic fluctuations and, during the recent past, also by human activity. In the considered region, protective and potentially habitable rock shelters are found at the volcanic slopes of Mt Damota and Mt Sodicho at high elevations. In addition, in some areas recent morphodynamic processes make obsidian raw material available near the surface. However, archaeological and terrestrial paleoenvironmental archives that allow an understanding of the interplay between prehistoric settlement activity and paleoenvironmental conditions are still rare. Therefore, the surroundings of formerly occupied rock shelters were investigated to illustrate the effect of the recent fluvial morphodynamics (erosion and accumulation) on surface visibility and preservation of archaeological obsidian raw material. This recent information can be used to make assumptions about the former hydrological system and to thereby get answers to research questions such as those about the past accessibility of obsidian raw material for prehistoric humans. The results suggest that the study area is currently affected by a highly dynamic hydrological system, which is indicated by phenomena such as the formation of swamps due to sedimentation in natural depressions. In addition, wide areas of the Bisare River catchment are affected by gully erosion, which leads to land degradation but also to the exposure of the above-mentioned lithic raw material outcrops. Human influence strongly increased during the Holocene until today, especially on the mountain flanks. This in turn increased soil loss and erosion of archaeological sites, which complicates the transfer of the current morphodynamics into the past. Although it cannot be finally confirmed that prehistoric hunters and gatherers systematically used fluvially exposed raw material, based on our results it can be assumed that humans frequented this area, due to the local availability of such kind of material.