Search

The African Middle Stone Age (MSA, typical range ~ 320–30 ka) has been the subject of intense research interest in recent decades as a culture-chronological Unit associated with the emergence and dispersal of our species. Recent results of this work have shown that sites designated as “MSA” contain common approaches to lithic reduction, but that within this rubric, there is much diversity in overall assemblage characteristics and the timing of their appearance across the continent. As researchers recover more data from more sites, especially from undersampled geographic regions, this more complex picture of the MSA reveals technological and other behavioral diversity in early modern human populations that may inform about the ultimate success of our species. Here we add to this growing database by describing the environmental context and characteristics of two concentrations of stone artifacts from the late MSA (~ 43–21 ka) open-air locality of Chaminade-I (CHA-I), near the town of Karonga in northern Malawi. The CHA-I lithic artifacts show a flexible approach to stone tool production and use that is common to assemblages in Karonga but distinctive from MSA sites reported elsewhere. Radial and minimally reduced cores typify an unelaborated lithic assemblage, in which raw material choice is driven by toolstone clast size and shape rather than preferential use or treatment of specific materials, as found in MSA assemblages in the East African Rift, South Africa, and the North African coast. Lithic reduction at CHA-I took place within a woody, riparian context embedded within a more open woodland landscape. Most artifacts occurred in near-channel sandy deposits dated to ~ 41 ka, and were buried under alluvial fan deposits that began aggrading by at least ~ 21 ka and continued beyond ~ 5.5 ka within a grassy, open landscape. The site’s late MSA age and lack of elaboration in lithic technology challenges straightforward ideas of increasing complexity in human technological behavior over time and provides important insight into the diversity of MSA technologies and the environmental conditions in which they existed.

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. Introduction Results - Geochronology and geomorphology - Archaeology - Paleoclimate and environment reconstruction - Paleoenvironmental analysis Discussion Material and methods - Fieldwork survey, excavation, and profile documentation - OSL dating - Lithic analysis - Micromorphology and carbonate dating - Phytolith analysis - Statistical methods

The Southern Montane Forest-Grassland mosaic ecosystem in the humid subtropics southern Rift Valley of Africa comprised the environmental context for a large area in which modern human evolution and dispersal occurred. Variable climatic conditions during the Late Pleistocene have ranged between humid and hyperarid, changing the character of the ecosystem and transforming it at different points in time into a barrier, a refuge, and a corridor between southern and eastern African populations. Alluvial fans presently blanket the areas adjacent to major river systems, which were key areas of prehistoric human habitation. These sets of variables have created conditions that are both challenging and advantageous to conduct archaeological research. Lateritic soil development has resulted in poor organic preservation and facilitated insect bioturbation, which has demanded an integrated micro-macro scale approach to building a reliable geochronology. An integrated field and analytical methodology has also been employed to identify the nature and degree of post-depositional movement in alluvial deposits, which preserve a wide range of spatial integrity levels in buried stone artifact assemblages between 47 and 30 ka in Karonga, northern Malawi. This paper describes the methodological advances taken toward understanding open-air Middle Stone Age archaeology in sub-tropical Africa, and explores the inferential potential for understanding Pleistocene human ecology in the important southern Rift Valley region.