Ecological stability of Late Pleistocene-to-Holocene Lesotho, southern Africa, facilitated human upland habitation

ARTICLE https://doi.org/10.1038/s43247-023-00784-8 OPEN Ecological stability of Late Pleistocene-to-Holocene Lesotho, southern Africa, facilitated human upland habitation 1234567890():,; Robert Patalano1,2 ✉, Charles Arthur3, William Christopher Carleton4,5, Sam Challis6, Genevieve Dewar 7, Kasun Gayantha5,8, Gerd Gleixner8, Jana Ilgner5, Mary Lucas5, Sara Marzo5,9, Rethabile Mokhachane6,16, Kyra Pazan 10, Diana Spurite5, Mike W. Morley 11, Adrian Parker 12, Peter Mitchell3,6, Brian A. Stewart 6,13 & Patrick Roberts 2,5,14,15 ✉ 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. 1 Department of Biological and Biomedical Sciences, School of Health and Behavioral Sciences, Bryant University, Smithfield, RI, USA. 2 isoTROPIC Research Group, Max Planck Institute of Geoanthropology, Jena, Germany. 3 School of Archaeology, University of Oxford, Oxford, UK. 4 Extreme Events Research Group, Max Planck Institute for Geoanthropology, Jena, Germany. 5 Department of Archaeology, Max Planck Institute of Geoanthropology, Jena, Germany. 6 Rock Art Research Institute, University of the Witwatersrand, Johannesburg, South Africa. 7 Department of Anthropology, University of Toronto Scarborough, Toronto, ON, Canada. 8 Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany. 9 The Roslin Institute & Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian, Edinburgh, Scotland, UK. 10 Department of Anthropology, Geography, and Ethnic Studies, California State University, Stanislaus, Turlock, CA, USA. 11 College of Humanities, Arts and Social Sciences, Flinders University, Adelaide, SA, Australia. 12 School of Social Sciences, Oxford Brookes University, Headington Campus, Oxford, UK. 13 Museum of Anthropological Archaeology and Department of Anthropology, University of Michigan, Ann Arbor, MI, USA. 14 School of Social Science, The University of Queensland, Brisbane, QLD, Australia. 15 Archaeological Studies Program, University of Philippines, Diliman, Quezon City, Philippines. 16Deceased: Rethabile Mokhachane. ✉email: ; COMMUNICATIONS EARTH & ENVIRONMENT | (2023)4:129 | https://doi.org/10.1038/s43247-023-00784-8 | www.nature.com/commsenv 1 ARTICLE H COMMUNICATIONS EARTH & ENVIRONMENT | https://doi.org/10.1038/s43247-023-00784-8 omo sapiens was adept at exploiting resources across varied climate zones and ecoregions within and beyond Africa by Marine Isotope Stage 3 (MIS 3, 57–29 ka)1. Although Late Pleistocene climatic and environmental fluctuations posed major challenges to human populations2, people exhibited complex behavioural responses to withstand and adapt to various ‘extreme’ environments and associated resource instability3–15. Mountain systems provide an important example of this, with vulnerability to climate change, cold and dry conditions, and patchy resource distributions representing potential adaptive challenges. In the Maloti-Drakensberg Mountains of Lesotho, which divide the resource-rich southern African coast from the irregularly distributed resources of the interior (Fig. 1), H. sapiens appears to have inhabited cold, rugged and ecologically variable environments at altitudes greater than 1500 m above sea level (m.a.s.l.) since at least MIS 5a, or about 80 ka10–12,14,16–19. The Maloti-Drakensberg Mountains are a particularly key geographical feature when studying human occupation across southern Africa more generally, acting as the headwaters to the region’s largest perennial rivers, the Senqu (Orange), Mohokare (Caledon), Thukela (Tugela), and Mzimvubu20, sources of abundant and persistent freshwater for much of the surrounding region. Southern African sites, including those of the Maloti-Drakensberg, have been argued to be crucial for understanding the early appearance of many key behavioural innovations including art, jewellery, and projectile weaponry21–24. However, given the historic emphasis placed on sequences from rockshelters and caves at or near the coast25,26, it is crucial to complement this with observations from the sub-continent’s topographically variable and biologically diverse interior which experienced significant climatic, environmental, and demographic changes throughout the Pleistocene27–31. Long-term proxy records from southern Africa show the potential impacts of changing plant landscape composition and hydroclimate on human populations over the Quaternary32–42. Because these environmental records are often located far from archaeological sites, however, it is important to compare these data to on-site and catchment scale (i.e., proximal) records to develop highly spatially and temporally resolved palaeoclimate and palaeoenvironmental information relevant to human evolution and behavioural change43–46. As a result, if we are to understand human adaptations to ecological variability associated with Late Quaternary climatic fluctuations in the interior of southern Africa, it is essential to examine records from archaeological sediments that can elucidate local responses of specific ecological communities and biomes to climatic change at sites where rich cultural assemblages have been recovered. Lesotho forms the core of the Maloti-Drakensberg system, with two-thirds of its land area situated at elevations higher than 2000 m.a.s.l. Topographic variability and temperature variations linked to altitude and aspect produce particularly sharp gradients of warm-loving C4 and cool-adapted C3 plants47–49. Today, C3 species flourish on the colder south-facing slopes above 2100 m.a.s.l.12,14,18, but the transition to C3-dominated vegetation only occurs around 2700 m.a.s.l. on warmer north-facing slopes49–52. As most precipitation falls during the warm summer-season, C4 plants typically have the competitive advantage at lower altitudes. The Ha Makotoko archaeological site along the Phuthiatsana River in western Lesotho (Fig. 1C and see ‘Site overview’ in ‘Methods’), documents pulsed occupation over the Late Pleistocene and Holocene16,17,53. At 10 m above the (...truncated)