Early LGM Environments Accelerated the MSA/LSA Transition in Southern African Highlands: the Robberg’s Emergence at Melikane (Lesotho)

Abstract

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 aridi cation 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 aking systems at Melikane are inconsistent with the Robberg's arrival via population replacement or migration (cf. Bousman and Brink, 2018), shared aking 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 exibility of bladelet technology and an ongoing cycle of connectivity and isolation throughout the LGM, encouraging the development of new aking systems and their subsequent coalescence and diffusion. population incursions from further north. Sampson (1974) modi ed this idea, asserting that microlithic industries had origins in southern Zambia and Rhodesia (Zimbabwe). J.D. Clark (1959) andHumphreys (1972) were among others advocating for migration theories. Models incorporating climate became more popular in the second half of the twentieth century: J. D. Clark (1974) and Phillipson (1976Phillipson ( , 1977 suggested that microlithic technology evolved independently in many areas, taking forms most advantageous to the local environment. H.J. Deacon (1976) proposed that microlithic techniques arrived though diffusion and were then modi ed to suit environmental conditions. Mitchell's (1988) hypothesis, speci c to the Maloti-Drakensberg mountains of highland Lesotho, implicated the LGM as an impetus for microlithization, positing that microlithic technologies were adaptive in "time-stressed" environments (Torrence, 1983). By the end of the twentieth century, "gradualist" theories rejected a sudden population replacement or migration entirely. Built on sites with long occupation histories like Sehonghong, Umhlatuzana, and Rose Cottage Cave, these hypotheses recognized intrasite continuities and subtle temporal trends (A.