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Post-hoc test of residuals: significant for pointed edges at p=0.024.

Investigation of Homo sapiens’ palaeogeographic expansion into African mountain environments are changing the understanding of our species’ adaptions to various extreme Pleistocene climates and habitats. Here, we present a vegetation and precipitation record from the Ha Makotoko rockshelter in western Lesotho, which extends from ~60,000 to 1,000 years ago. Stable carbon isotope ratios from plant wax biomarkers indicate a constant C3-dominated ecosystem up to about 5,000 years ago, followed by C4 grassland expansion due to increasing Holocene temperatures. Hydrogen isotope ratios indicate a drier, yet stable, Pleistocene and Early Holocene compared to a relatively wet Late Holocene. Although relatively cool and dry, the Pleistocene was ecologically reliable due to generally uniform precipitation amounts, which incentivized persistent habitation because of dependable freshwater reserves that supported rich terrestrial foods and provided prime locations for catching fish.

Melikane, a large sandstone rockshelter in the Maloti-Drakensberg Mountains of highland Lesotho, preserves an 80,000 year-old archaeological sequence including two layers (4 & 5) dated to the onset of the Last Glacial Maximum (LGM), ~ 24 kcal BP. Paleoenvironmental proxies indicate that these layers were associated with increasing aridification and changes in resource distribution. An analysis of > 17,000 lithic artifacts combining attribute and morphometric approaches reveals that these environmental changes occurred alongside the adoption of Later Stone Age (LSA) Robberg bladelet technology at the site (Layer 4), which developed out of an early microlithic industry we classify as “incipient Robberg” (Layer 5). We argue that the accelerated implementation and standardization of bladelet technology in Layer 4 was the consequence of modifying and expanding existing technologies to function in a high-stakes LGM environment. While intrasite continuities and gradual changes in flaking systems at Melikane are inconsistent with the Robberg’s arrival via population replacement or migration (cf. Bousman and Brink, 2018), shared flaking systems with penecontemporary sites also implicate a role for cultural transmission in the Robberg’s development and demand an alternate explanation for its use in nonmarginal environments. We attribute its adoption in southern Africa more broadly to the extraordinary flexibility of bladelet technology and an ongoing cycle of connectivity and isolation throughout the LGM, encouraging the development of new flaking systems and their subsequent coalescence and diffusion.

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