A spatiotemporally explicit paleoenvironmental framework for the Middle Stone Age of eastern Africa

Abstract

Eastern Africa has played a prominent role in debates about human evolution and dispersal due to the presence of rich archaeological, palaeoanthropological and palaeoenvironmental records. However, substantial disconnects occur between the spatial and temporal resolutions of these data that complicate their integration. Here, we apply high-resolution climatic simulations of two key parameters, mean annual temperature and precipitation, and a biome model, to produce a highly refined characterisation of the environments inhabited during the eastern African Middle Stone Age. Occupations are typically found in sub-humid climates and landscapes dominated by or including tropical xerophytic shrubland. Marked expansions from these core landscapes include movement into hotter, low-altitude landscapes in Marine Isotope Stage 5 and cooler, high-altitude landscapes in Marine Isotope Stage 3, with the recurrent inhabitation of ecotones between open and forested habitats. Through our use of high-resolution climate models, we demonstrate a significant independent relationship between past precipitation and patterns of Middle Stone Age stone tool production modes overlooked by previous studies. Engagement with these models not only enables spatiotemporally explicit examination of climatic variability across Middle Stone Age occupations in eastern Africa but enables clearer characterisation of the habitats early human populations were adapted to, and how they changed through time.

Evaluating refugia in recent human evolution in Africa

“…The extent to which our use of ethnographic datasets, constrained by standard CIs, may reflect patterns of Late Pleistocene population adaptation can be tested against archaeological records. Examining the palaeoclimatic context and distribution of Late Pleistocene archaeological sites provides a direct means to refine such parameters without extrapolating from ethnographic data [77]. However, this may only be possible for those regions with the most extensive and well-dated archaeological records and thus is shaped in part by research history.…”

Longstanding behavioural stability in West Africa extends to the Middle Pleistocene at Bargny, coastal Senegal

“… 93 ), inter-regional African humidity (dark blue, PCA1 71 ); marine δ 18 O (mid blue, Atlantic stack 94 ; light blue, GeoB5928-3 95 ), n -alkane leaf wax isotopes (pink, C 31 δ 13 C, GeoB5928-3 95 ), modelled mean annual precipitation (orange, within 0.5° cell, red, delta downscaled to 0.925 km on-site location, following refs. 69 , 96 , 97 ) and synthesis of dated MSA occupations from West Africa (red diamonds; * Falémé sites; **Ounjougou sites) and other MIS 6 MSA sites across Africa (blue squares; location in N, E, or S Africa shown in parentheses). The occupation at Bargny (highlighted in purple) coincides with a peak in insolation, C4 plants and more arid environments than Late Pleistocene MSA sites in West Africa and precedes a regional shift in humidity from East to West Africa.…”

Lacustrine geoarchaeology in the central Kalahari: Implications for Middle Stone Age behaviour and adaptation in dryland conditions

“…Drylands are spaces of environmental opportunity, a facet long recognised in anthropological and archaeological research in eastern Africa (Potts, 1998;Potts and Faith, 2015). Rather than simply driving dispersal, dry and variable conditions may have facilitated adaptation, examined in an eastern African context by Grove (2016), where xerophytic dry environments are regarded as core landscapes for the MSA (Timbrell et al, 2022). In southern Africa, by contrast, dry conditions have been conceived to be an obstacle to innovation, and even to occupation, but this view is changing (Wilkins, 2020).…”