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1. Progressive aridification in East Africa over the last half million years and implications for human evolution

   https://doi.org/10.1073/pnas.1801357115  

   Owen, R. Bernhart ; Muiruri, Veronica M. ; Lowenstein, Tim K. ; Renaut, Robin W. ; Rabideaux, Nathan ; Luo, Shangde ; Deino, Alan L. ; Sier, Mark J. ; Dupont-Nivet, Guillaume ; McNulty, Emma P. ; et al ( October 2018 , Proceedings of the National Academy of Sciences)

   Evidence for Quaternary climate change in East Africa has been derived from outcrops on land and lake cores and from marine dust, leaf wax, and pollen records. These data have previously been used to evaluate the impact of climate change on hominin evolution, but correlations have proved to be difficult, given poor data continuity and the great distances between marine cores and terrestrial basins where fossil evidence is located. Here, we present continental coring evidence for progressive aridification since about 575 thousand years before present (ka), based on Lake Magadi (Kenya) sediments. This long-term drying trend was interrupted by many wet–dry cycles, with the greatest variability developing during times of high eccentricity-modulated precession. Intense aridification apparent in the Magadi record took place between 525 and 400 ka, with relatively persistent arid conditions after 350 ka and through to the present. Arid conditions in the Magadi Basin coincide with the Mid-Brunhes Event and overlap with mammalian extinctions in the South Kenya Rift between 500 and 400 ka. The 525 to 400 ka arid phase developed in the South Kenya Rift between the period when the last Acheulean tools are reported (at about 500 ka) and before the appearance of Middle Stonemore »Age artifacts (by about 320 ka). Our data suggest that increasing Middle- to Late-Pleistocene aridification and environmental variability may have been drivers in the physical and cultural evolution ofHomo sapiensin East Africa.

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2. Pleistocene climate variability in eastern Africa influenced hominin evolution

   https://doi.org/10.1038/s41561-022-01032-y  

   Foerster, Verena ; Asrat, Asfawossen ; Bronk Ramsey, Christopher ; Brown, Erik T. ; Chapot, Melissa S. ; Deino, Alan ; Duesing, Walter ; Grove, Matthew ; Hahn, Annette ; Junginger, Annett ; et al ( September 2022 , Nature Geoscience)

   Despite more than half a century of hominin fossil discoveries in eastern Africa, the regional environmental context of hominin evolution and dispersal is not well established due to the lack of continuous palaeoenvironmental records from one of the proven habitats of early human populations, particularly for the Pleistocene epoch. Here we present a 620,000-year environmental record from Chew Bahir, southern Ethiopia, which is proximal to key fossil sites. Our record documents the potential influence of different episodes of climatic variability on hominin biological and cultural transformation. The appearance of high anatomical diversity in hominin groups coincides with long-lasting and relatively stable humid conditions from ~620,000 to 275,000 yearsbp(episodes 1–6), interrupted by several abrupt and extreme hydroclimate perturbations. A pattern of pronounced climatic cyclicity transformed habitats during episodes 7–9 (~275,000–60,000 yearsbp), a crucial phase encompassing the gradual transition from Acheulean to Middle Stone Age technologies, the emergence ofHomo sapiensin eastern Africa and key human social and cultural innovations. Those accumulative innovations plus the alignment of humid pulses between northeastern Africa and the eastern Mediterranean during high-frequency climate oscillations of episodes 10–12 (~60,000–10,000 yearsbp) could have facilitated the global dispersal ofH. sapiens.
3. Early human impacts and ecosystem reorganization in southern-central Africa

   https://doi.org/10.1126/sciadv.abf9776  

   Thompson, Jessica C. ; Wright, David K. ; Ivory, Sarah J. ; Choi, Jeong-Heon ; Nightingale, Sheila ; Mackay, Alex ; Schilt, Flora ; Otárola-Castillo, Erik ; Mercader, Julio ; Forman, Steven L. ; et al ( May 2021 , Science Advances)

   Modern Homo sapiens engage in substantial ecosystem modification, but it is difficult to detect the origins or early consequences of these behaviors. Archaeological, geochronological, geomorphological, and paleoenvironmental data from northern Malawi document a changing relationship between forager presence, ecosystem organization, and alluvial fan formation in the Late Pleistocene. Dense concentrations of Middle Stone Age artifacts and alluvial fan systems formed after ca. 92 thousand years ago, within a paleoecological context with no analog in the preceding half-million-year record. Archaeological data and principal coordinates analysis indicate that early anthropogenic fire relaxed seasonal constraints on ignitions, influencing vegetation composition and erosion. This operated in tandem with climate-driven changes in precipitation to culminate in an ecological transition to an early, pre-agricultural anthropogenic landscape.
4. A marine isotope stage 11 coastal Acheulian workshop with associated wood at Amanzi Springs Area 1, South Africa

   https://doi.org/10.1371/journal.pone.0273714  

   Herries, Andy I. ; Arnold, Lee J. ; Boschian, Giovanni ; Blackwood, Alexander F. ; Wilson, Coen ; Mallett, Tom ; Armstrong, Brian ; Demuro, Martina ; Petchey, Fiona ; Meredith-Williams, Matthew ; et al ( October 2022 , PLOS ONE)

   Hart, John P. (Ed.)

   Amanzi Springs is a series of inactive thermal springs located near Kariega in the Eastern Cape of South Africa. Excavations in the 1960s exposed rare, stratified Acheulian-bearing deposits that were not further investigated over the next 50 years. Reanalysis of the site and its legacy collection has led to a redefined stratigraphic context for the archaeology, a confirmed direct association between Acheulian artefacts and wood, as well as the first reliable age estimates for the site. Thermally transferred optically stimulated luminescence and post-infrared infrared stimulated luminescence dating indicates that the Acheulian deposits from the Amanzi Springs Area 1 spring eye formed during Marine Isotope Stage (MIS) 11 at ~ 404–390 ka. At this time, higher sea levels of ~13-14m would have placed Amanzi Springs around 7 km from a ria that would have formed along what is today the Swartkops River, and which likely led to spring reactivation. This makes the Amanzi Springs Area 1 assemblage an unusual occurrence of a verified late occurring, seaward, open-air Acheulian occupation. The Acheulian levels do not contain any Middle Stone Age (MSA) elements such as blades and points that have been documented in the interior of South Africa at this time. However, amore »small number of stone tools from the upper layers of the artefact zone, and originally thought of as intrusive, have been dated to ~190 ka, at the transition between MIS 7 to 6, and represent the first potential MSA identified at the site.« less
5. Early, intensive marine resource exploitation by Middle Stone Age humans at Ysterfontein 1 rockshelter, South Africa

   https://doi.org/10.1073/pnas.2020042118  

   Niespolo, Elizabeth M. ; Sharp, Warren D. ; Avery, Graham ; Dawson, Todd E. ( April 2021 , Proceedings of the National Academy of Sciences)

   Modern human behavioral innovations from the Middle Stone Age (MSA) include the earliest indicators of full coastal adaptation evidenced by shell middens, yet many MSA middens remain poorly dated. We apply²³⁰Th/U burial dating to ostrich eggshells (OES) from Ysterfontein 1 (YFT1, Western Cape, South Africa), a stratified MSA shell midden.²³⁰Th/U burial ages of YFT1 OES are relatively precise (median ± 2.7%), consistent with other age constraints, and preserve stratigraphic principles. Bayesian age–depth modeling indicates YFT1 was deposited between 119.9 to 113.1 thousand years ago (ka) (95% CI of model ages), and the entire 3.8 m thick midden may have accumulated within ∼2,300 y. Stable carbon, nitrogen, and oxygen isotopes of OES indicate that during occupation the local environment was dominated by C₃vegetation and was initially significantly wetter than at present but became drier and cooler with time. Integrating archaeological evidence with OES²³⁰Th/U ages and stable isotopes shows the following: 1) YFT1 is the oldest shell midden known, providing minimum constraints on full coastal adaptation by ∼120 ka; 2) despite rapid sea-level drop and other climatic changes during occupation, relative shellfish proportions and sizes remain similar, suggesting adaptive foraging along a changing coastline; 3) the YFT1 lithic technocomplex is similar tomore »other west coast assemblages but distinct from potentially synchronous industries along the southern African coast, suggesting human populations were fragmented between seasonal rainfall zones; and 4) accumulation rates (up to 1.8 m/ka) are much higher than previously observed for dated, stratified MSA middens, implying more intense site occupation akin to Later Stone Age middens.

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