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Abstract In 2017, a hemimandible (MW5-B208), corresponding to the Ethiopian wolf (Canis simensis), was found in a stratigraphically-controlled and radio-isotopically-dated sequence of the Melka Wakena paleoanthropological site-complex, on the Southeastern Ethiopian Highlands, ~ 2300 m above sea level. The specimen is the first and unique Pleistocene fossil of this species. Our data provide an unambiguous minimum age of 1.6–1.4 Ma for the species’ presence in Africa and constitutes the first empirical evidence that supports molecular interpretations. Currently,C. simensisis one of the most endangered carnivore species of Africa. Bioclimate niche modeling applied to the time frame indicated by the fossil suggests that the lineage of the Ethiopian wolf faced severe survival challenges in the past, with consecutive drastic geographic range contractions during warmer periods. These models help to describe future scenarios for the survival of the species. Projections ranging from most pessimistic to most optimistic future climatic scenarios indicate significant reduction of the already-deteriorating territories suitable for the Ethiopian Wolf, increasing the threat to the specie’s future survival. Additionally, the recovery of the Melka Wakena fossil underscores the importance of work outside the East African Rift System in research of early human origins and associated biodiversity on the African continent. 

Abstract Terrestrial‐marine dust fluxes, pedogenic carbonate δ¹³C values, and various paleovegetation proxies suggest that Africa experienced gradual cooling and drying across the Pliocene‐Pleistocene (Plio‐Pleistocene) boundary (2.58 million years ago [Ma]). However, the timing, magnitude, resolution, and relative influences of orbitally‐driven changes in high latitude glaciations and low latitude insolation differ by region and proxy. To disentangle these forcings and investigate equatorial eastern African climate across the Plio‐Pleistocene boundary, we generated a high‐resolution (∼3,000‐year) data set of compound‐specificn‐alkane leaf wax δ²H values—a robust proxy for atmospheric circulation and precipitation amount—from the HSPDP‐BTB13‐1A core, which spans a ∼3.3–2.6 Ma sequence in the Baringo‐Tugen Hills‐Barsemoi Basin of central Kenya. In combination with the physical sedimentology, our data indicate that precipitation varied strongly with orbital obliquity, not precession, during the late Pliocene, perhaps imparted by variations in the cross‐equatorial insolation gradient. We also observe a marked shift toward wetter conditions beginning ∼3 Ma that corresponds with global cooling, drying in western Australia, and a steepening of the west‐east zonal Indian Ocean (IO) sea surface temperature (SST) gradient. We propose that northward migration of the Subtropical Front reduced Agulhas current leakage, warming the western IO and causing changes in the IO zonal SST gradient at 3 Ma, a process that has been observed in the latest Pleistocene‐Holocene but not over longer timescales. Thus, the late Cenozoic moisture history of eastern Africa is driven by a complex mixture of low‐latitude insolation, the IO SST gradient, and teleconnections to distal high‐latitude cooling. 

Significance We have developed an Africa-wide synthesis of paleoenvironmental variability over the Plio-Pleistocene. We show that there is strong evidence for orbital forcing of variability during this time that is superimposed on a longer trend of increasing environmental variability, supporting a combination of both low- and high-latitude drivers of variability. We combine these results with robust estimates of mammalian speciation and extinction rates and find that variability is not significantly correlated with these rates. These findings do not currently support a link between environmental variability and turnover and thus fail to corroborate predictions derived from the variability selection hypothesis. 

Significance Understanding the evolution, dispersals, behaviors, and ecologies of early AfricanHomo sapiensrequires accurate geochronological placement of fossils and artifacts. We introduce open-air occurrences of such remains in sediments of the Middle Awash study area in Ethiopia. We describe the stratigraphic and depositional contexts of our discoveries and demonstrate the effectiveness of recently developed uranium-series dating of ostrich eggshell at validating and bridging across more traditional radioisotopic methods (¹⁴C and⁴⁰Ar/³⁹Ar).Homo sapiensfossils and associated Middle Stone Age artifacts are placed at >158 and ∼96 ka. Later Stone Age occurrences are dated to ∼21 to 24 ka and ∼31 to 32 ka, firmly dating the upper portion of one of the longest records of human evolution. 

Abstract 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. 

Abstract Lake Magadi is an internally drained, saline and alkaline terminal sump in the southern Kenya Rift. Geochemistry of samples from an ~200 m core representing the past ~1 m.y. of the lake's history shows some of the highest concentrations of transition metals and metalloids ever reported from lacustrine sediment, including redox-sensitive elements molybdenum, arsenic, and vanadium. Elevated concentrations of these elements represent times when the lake's hypolimnion was euxinic—that is, anoxic, saline, and sulfide-rich. Euxinia was common after ca. 700 ka, and after that tended to occur during intervals of high orbital eccentricity. These were likely times when high-frequency hydrologic changes favored repeated episodes of euxinia and sulfide precipitation. High-amplitude environmental fluctuations at peak eccentricity likely impacted water balance in terrestrial habitats and resource availability for early hominins. These are associated with important events in human evolution, including the first appearance of Middle Stone Age technology between ca. 500 and 320 ka in the southern Kenya Rift. 

Abstract Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish^1–3and Herto^4,5in Ethiopia, have drawn on a variety of chronometric evidence, including⁴⁰Ar/³⁹Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I^3,6,7, and around 160–155 kyr for the Herto hominins^5,8. However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged^6,8. Here we report geochemical analyses that link the Kamoya’s Hominid Site (KHS) Tuff⁹, which conclusively overlies the member of the Omo-Kibish Formation that contains Omo I, with a major explosive eruption of Shala volcano in the Main Ethiopian Rift. By dating the proximal deposits of this eruption, we obtain a new minimum age for the Omo fossils of 233 ± 22 kyr. Contrary to previous arguments^6,8, we also show that the KHS Tuff does not correlate with another widespread tephra layer, the Waidedo Vitric Tuff, and therefore cannot anchor a minimum age for the Herto fossils. Shifting the age of the oldest knownHomo sapiensfossils in eastern Africa to before around 200 thousand years ago is consistent with independent evidence for greater antiquity of the modern human lineage¹⁰.