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This study was supported by the Leverhulme Trust grant 2016–21 (Nature and impacts of Middle Pleistocene volcanism in the Ethiopian Rift). KF was supported by the UK's Natural Environment Research Council (NERC) grant NE/L013932/1 (RiftVolc: The Past, Present and Future of Rift Volcanism in the Main Ethiopian Rift), a Boise Fund grant from the Department of Zoology, University of Oxford, and acknowledges Fonds de Recherche Scientifique – FNRS MIS grant F.4515.20. Tephra work on the Chew Bahir cores in the Cambridge Tephra Lab by AA, AP and CL was made possible by NERC grant NE/K014560/1. Ar–Ar dating was supported by grants NIGFSC IP-1683-1116 and IP-1680-1116. The iCRAG lab is supported by SFI 13/RC/2092. The Main Ethiopian Rift (MER) is renowned as a focus of investigations into human origins. It is also the site of many large volcanic calderas, whose eruptions have spanned the timeframe of speciation, cultural innovation, and dispersal of our species. Yet, despite their significance for dating human fossils and cultural materials, the timing and geochemical signatures of some of the largest eruptions have remained poorly constrained at best. Here, through a programme of field surveys, geochemical analysis and 40Ar/39Ar dating, we report the ages of MER ignimbrites and link them to widespread tephra layers found in sequences of archaeological and paleoenvironmental significance. We date major eruptions of Fentale (76 ± 18 ka), Shala (ca. 145–155 ka), Kone (184 ± 42 ka and ca. 200 ± 12 ka) and Gedemsa (251 ± 47 ka) volcanoes, and correlate a suite of regionally important tephra horizons. Geochemical analysis highlights the predominantly peralkaline rhyolitic melt compositions (7.5–12 wt% Na2O + K2O, 70–76 wt% SiO2) across the central MER and remarkable similarity in incompatible trace element ratios, limiting the correlation of deposits via glass composition alone. However, by integrating stratigraphic and geochronological evidence from proximal deposits, lake sediment cores and distal outcrops at archaeological sites, we have traced ash layers associated with the ca. 177 ka Corbetti, ca. 145–155 ka Shala and ca. 108 ka Bora-Baricha-Tullu-Moye eruptions across southern Ethiopia. In addition to strengthening the tephrochronological framework that supports paleoenvironmental and archaeological work in the region, our findings have wider implications for evaluating the hypothesis of a middle Pleistocene ‘ignimbrite flare-up’ in the MER, and for evaluating the impacts of these great eruptions on landscapes, hydrology, and human ecology. Publisher PDF

The North Atlantic region experienced abrupt high-amplitude cooling at the onset of the Younger Dryas stadial. However, due to chronological uncertainties in the available terrestrial records it is unclear whether terrestrial ecosystem response to this event was instantaneous and spatially synchronous, or whether regional or time-transgressive lags existed. Here we use new palynological results from a robustly dated lake sediment sequence retrieved from lake Hämelsee (north Germany) to show that vegetation change started at 12,820 cal. yr BP, concurrent with the onset of changes in local climate. A comparison of the Hämelsee results to a compilation of precisely dated palynological records shows instant and, within decadal-scale dating uncertainty, synchronous response of the terrestrial plant community to Late-Glacial climate change across northwest Europe. The results indicate that the environmental impact of climate cooling was more severe than previously thought and illustrates the sensitivity of natural terrestrial ecosystems to external forcing.

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.

We present a multidisciplinary dating approach - including radiocarbon, Uranium/Thorium series (U/Th), paleomagnetism, single-grain optically stimulated luminescence (OSL), polymineral fine-grain infrared stimulated luminescence (IRSL) and tephrochronology - used for the development of an age model for the Cañizar de Villarquemado sequence (VIL) for the last ca. 135 ka. We describe the protocols used for each technique and discuss the positive and negative results, as well as their implications for interpreting the VIL sequence and for dating similar terrestrial records. In spite of the negative results of some techniques, particularly due to the absence of adequate sample material or insufficient analytical precision, the multi-technique strategy employed here is essential to maximize the chances of obtaining robust age models in terrestrial sequences. The final Bayesian age model for VIL sequence includes 16 AMS 14C ages, 9 single-grain quartz OSL ages and 5 previously published polymineral fine-grain IRSL ages, and the accuracy and resolution of the model are improved by incorporating information related to changes in accumulation rate, as revealed by detailed sedimentological analyses. The main paleohydrological and vegetation changes in the sequence are coherent with global Marine Isotope Stage (MIS) 6 to 1 transitions since the penultimate Termination, although some regional idiosyncrasies are evident, such as higher moisture variability than expected, an abrupt inception of the last glacial cycle and a resilient response of vegetation in Mediterranean continental Iberia in both Terminations. © 2019, Funding for El Cañizar de Villarquemado sequence research was provided by DINAMO ( CGL-BOS 2009–07992 ), DINAMO2 ( CGL-BOS 2012–33063 ), DINAMO 3 ( ) IBERIANPALEOFLORA ( CGL-BOS 2012–31717) and GRACCIE-CONSOLIDER ( CSD2007-00067 ) projects, provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT ) and by the Aragon Government ( DGA project, 2005–2006 ). Tephrochronology research was supported by the UK Natural Environment Research Council consortium RESET (NE/E015670/1 ). The single-grain OSL dating research was supported by Australian Research Council ( ARC ) Future Fellowship project FT130100195 and Discovery Early Career Researcher Award DE160100743 . The work of BMB was supported by the IGNEX project ( 249894 ), funded by the FRIMEDBIO program of The Research Council of Norway. Graciela Gil-Romera is funded by the DFG project FOR 2358 “ Mountain Exile Hypothesis ”. We are grateful to two anonymous reviewers whose comments and suggestions improved the manuscript.