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The Olorgesailie basin in the southern Kenya rift valley contains sediments dating back to 1.2 million years ago, preserving a long archaeological record of human activity and environmental conditions. Three papers present the oldest East African evidence of the Middle Stone Age (MSA) and elucidate the system of technology and behavior associated with the origin of Homo sapiens . Potts et al. present evidence for the demise of Acheulean technology that preceded the MSA and describe variations in late Acheulean hominin behavior that anticipate MSA characteristics. The transition to the MSA was accompanied by turnover of large mammals and large-scale landscape change. Brooks et al. establish that ∼320,000 to 305,000 years ago, the populations in eastern Africa underwent a technological shift upon procurement of distantly sourced obsidian for toolmaking, indicating the early development of social exchange. Deino et al. provide the chronological underpinning for these discoveries. Science , this issue p. 86 , p. 90 , p. 95 Social, technological, and subsistence behaviors and pigment use emerged during human evolution more than 300,000 years ago. Previous research suggests that the complex symbolic, technological, and socioeconomic behaviors that typify Homo sapiens had roots in the middle Pleistocene <200,000 years ago, but data bearing on human behavioral origins are limited. We present a series of excavated Middle Stone Age sites from the Olorgesailie basin, southern Kenya, dating from ≥295,000 to ~320,000 years ago by argon-40/argon-39 and uranium-series methods. Hominins at these sites made prepared cores and points, exploited iron-rich rocks to obtain red pigment, and procured stone tool materials from ≥25- to 50-kilometer distances. Associated fauna suggests a broad resource strategy that included large and small prey. These practices imply notable changes in how individuals and groups related to the landscape and to one another and provide documentation relevant to human social and cognitive evolution.

Exchange networks created by Neolithic pastoral transhumance have been central to explaining the distant transport of obsidian since chemical analysis was first used to attribute Near Eastern artifacts to their volcanic origins in the 1960s. Since then, critical reassessments of floral, faunal, and chronological data have upended long-held interpretations regarding the emergence of food production and have demonstrated that far-traveled, nomadic pastoralists were more myth than reality, at least during the Neolithic. Despite debates regarding their proposed conveyance mechanisms, obsidian artifacts’ transport has received relatively little attention compared with zooarchaeological and archaeobotanical lines of investigation. The rise of nondestructive and portable instruments permits entire obsidian assemblages to be traced to their sources, renewing their significance in elucidating connections among early pastoral and agricultural communities. Here we share our findings about the obsidian artifacts excavated from the sites of Ali Kosh and Chagha Sefid in the southern Zagros. In the 1960s and 1970s, 28 obsidian artifacts from the sites were destructively tested, and the remainder were sorted by color. Our results emphasize a dynamic, accelerating connectivity among the Early and Late Neolithic communities. Here we propose and support an alternative model for obsidian distribution among more settled communities. In brief, diversity in the obsidian assemblage accelerated diachronically, an invisible trend in the earlier studies. Our model of increasing population densities is supported by archaeological data and computational simulations, offering insights regarding the Neolithic Demographic Transition in the Zagros, an equivalent of which is commonly thought to have occurred around the world.

Context The reasons for the intermittent human use of harsh Afroalpine environments in prehistory remain unclear. High-resolution glacial and archaeological chronologies from Ethiopia’s Bale Mountains now offer insights into landscape change and human adaptations at high altitudes. Objectives This study investigates the behavioral signatures of human occupation in Africa’s largest alpine environment around 15,000 years ago, focusing on local site use and integration into regional networks amid deglaciation and the abrupt onset of African Humid Period wet conditions. Methods This research integrates surface exposure dating of moraine boulders and radiocarbon dating of archaeological rock shelter deposits with detailed analyses of lithic materials from three stratified sites in the Bale Mountains. We use multivariate statistical analyses of electron microprobe data to determine the geochemical provenance of obsidian artifacts. Lithic technological analysis is based on systematic recording of artifact attributes to reconstruct key stages of production. Functional analyses include use-wear and residue studies conducted using stereomicroscopy, reflected light microscopy, and scanning electron microscopy (SEM–EDX). Results This study provides a detailed reconstruction of the final deglaciation phase in the Bale Mountains and identifies distinct patterns of lithic acquisition, production, and use across three contemporaneous sites. Dimtu, located on the formerly glaciated plateau and representing the highest known stratified archaeological site in Africa, is distinguished by a focus on the production of rare but specific pointed flakes. Simbero exhibits standardized backed tool production and evidence of hafting, while the Webi Gestro assemblage includes bladelets and notched tools; wear on unretouched bladelets indicates their use in transverse and longitudinal motions for processing activities and possibly as projectile elements. Geochemical results reveal obsidian exchange between high altitudes and lowlands, suggesting extensive social networks reinforced by technological and behavioral parallels. Conclusions Human strategies at high altitudes closely mirror contemporaneous lowland behavior, revealing synchronous patterns across ecological zones. Similar patterns during other periods point to broader systemic dynamics. Conventional refugium-based explanations fail to fully capture these patterns, highlighting the need to examine diachronic shifts in the scale, connectivity, and intensity of prehistoric networks across ecozones.

The Olorgesailie basin in the southern Kenya rift valley contains sediments dating back to 1.2 million years ago, preserving a long archaeological record of human activity and environmental conditions. Three papers present the oldest East African evidence of the Middle Stone Age (MSA) and elucidate the system of technology and behavior associated with the origin of Homo sapiens . Potts et al. present evidence for the demise of Acheulean technology that preceded the MSA and describe variations in late Acheulean hominin behavior that anticipate MSA characteristics. The transition to the MSA was accompanied by turnover of large mammals and large-scale landscape change. Brooks et al. establish that ∼320,000 to 305,000 years ago, the populations in eastern Africa underwent a technological shift upon procurement of distantly sourced obsidian for toolmaking, indicating the early development of social exchange. Deino et al. provide the chronological underpinning for these discoveries. Science , this issue p. 86 , p. 90 , p. 95 Changes in fauna, landscapes, and climate were associated with novel adaptive behaviors in the earliest Homo sapiens . Development of the African Middle Stone Age (MSA) before 300,000 years ago raises the question of how environmental change influenced the evolution of behaviors characteristic of early Homo sapiens . We used temporally well-constrained sedimentological and paleoenvironmental data to investigate environmental dynamics before and after the appearance of the early MSA in the Olorgesailie basin, Kenya. In contrast to the Acheulean archeological record in the same basin, MSA sites are associated with a markedly different faunal community, more pronounced erosion-deposition cycles, tectonic activity, and enhanced wet-dry variability. Aspects of Acheulean technology in this region imply that, as early as 615,000 years ago, greater stone material selectivity and wider resource procurement coincided with an increased pace of land-lake fluctuation, potentially anticipating the adaptability of MSA hominins.

Sourced from the Tyrrhenian Islands and exchanged over long distances, obsidian was used widely across prehistoric Western Europe. An obsidian core and bladelets from a newly discovered rockshelter site in south-eastern Spain, however, raised the possibility of an unrecognised mainland source of obsidian. EDXRF analysis of the Early Magdalenian finds from La Boja links them to a source 125km to the south-west. The artefacts were discarded during two brief activity phases at the site, indicating that obsidian procurement was integral to the technological choices of the site's users. The specificities of the technocomplex may explain the unique nature of this occurrence.