Middle Stone Age Research Articles

Mapping magnetism: Geophysical modelling of stratigraphic features by using in situ magnetic susceptibility measurements at Pinnacle Point 5‐6 North, South Africa

AbstractThis study utilizes geostatistical modelling of magnetic susceptibility (MS) for geophysical prospection of archaeological stratigraphy at the Middle Stone Age rock shelter site of Pinnacle Point 5‐6 North. These models are overlaid onto high‐resolution photography of the stratigraphic sequence to study the lateral and vertical changes within the magnetic signature of the archaeological sequence and correlate these changes to micromorphological interpretations previously made at the site. In situ analysis is reinforced by laboratory magnetic mineralogical analysis utilizing MS; frequency‐dependent susceptibility (χFD); isothermal remanent magnetization; and anhysteric remanent magnetization to understand the composition of the magnetic minerals creating the in situ signature. This study shows that there is consistent variation in the magnetic signatures of the sequence that can be mapped with in situ MS; there is a correlation with laboratory analysis of magnetic mineralogy, which provides insight into changes in human behaviour; and our models correlate well with micromorphological interpretations of the site.

Hydroclimatic and geochemical palaeoenvironmental records within tufa: A cool-water fluvio-lacustrine tufa system in the Wadi Dabsa volcanic setting, western Saudi Arabia

A series of uncharacterised tufa deposits within the lowland volcanic provinces of western Saudi Arabia are investigated here in order to account for their presence and to examine their utility as a palaeoenvironmental archive. The Wadi Dabsa basin, in the Harrat Al Birk, is part of the Saharo-Arabian region, where there is increasing evidence for multiple hominin dispersals during windows of reduced aridity during the last ~400 ka of the Late Quaternary. This first and detailed petrological and geochemical characterisation of these tufa carbonates is particularly important for palaeoenvironmental and climatological reconstruction at a site that contains a major concentration of Early and Middle Stone Age artefacts. We aim to determine the nature of deposition, to answer whether these are cool, freshwater tufa or hydrothermal travertine, and to establish what the tufa settings, stratigraphies and facies reveal about the hydroclimatic regime in this semi-arid environment.A widespread lacustrine-paludal and fluvial tufa system is preserved, as well as topographically-controlled tufa barrages and cascades. Observable sections, exposed by incision, reveal a thickness of tufa deposits of 3 to 6 m in places, which contain two packages of tufa-cemented conglomerate facies. This allows us to provide a conceptual model for the deposition of semi-arid tufa, based on existing type sites in the Naukluft Mountains of Namibia and the Ebro Basin of Spain. The varied topography within this volcanic harrat provides a setting at Wadi Dabsa that combines the low-lying lacustrine-paludal model from Spain with the steeper and higher-energy model from Namibia. The two tufa-cemented bedload units and the evidence for post-depositional erosion of other tufa facies indicates a shifting hydroclimatic regime, with episodes during which the basin contained water and there was steady flow in the fluvial channels, alternating with episodes of high-energy flashy flows.Geochemical analysis using 87Sr/86Sr isotopic ratios (0.7049 to 0.7056 with one sample at 0.7062) and stable carbon isotopes (−12.9 to −6.3‰) reveal that these are cool-water tufas were deposited from meteoric water that has interacted with both metamorphosed limestone in the Asir Escarpment and the mafic metavolcanic bedrock of the Wadi Dabsa Basin, without a geothermal influence. These tufa are low-concentration‑magnesium calcite, with traces of quartz (to a maximum of 3%) and other silicates. Some samples have ≤7.5% palygorskite, which along with petrological evidence for microbial filaments suggests the importance of biomineralisation by cyanobacteria within some of these tufa. Petrological analysis shows the fabrics are dominated by micrite cements with some microspar, and very little post-depositional alteration. Where samples are banded, this reflects variation in calcite crystal size as opposed to any striking variations in mineralogical composition. Oxygen stable isotopic composition (−14.6 to −1.9‰) indicates deposition from an isotopically more depleted rainfall source than the modern day, noting additional corrections for unknown past temperature and any other fractionation effects are needed. Depleted rainfall sources in this region may relate to either a far-travelled Atlantic moisture source or a higher-intensity Indian Ocean monsoon source, or some combination.

Challenges and Prospects for the Rock Art of Mumba Rock-shelter

The Mumba rock-shelter and its surrounding landscape are places where evidences for the evolution of human cognitive behaviour and other cultural practices have been uncovered. Deep and stratified archaeological deposits recorded at Mumba have shown unique distinctive technological and behavioural traits with possible connections between Middle Stone Age (MSA), Later Stone Age (LSA), Neolithic, and Iron Age cultures. Archaeological records were found associated with symbolic-revealing objects such as ochre pigments, beads, and stone rubber stained with red ochre, which express the cognitive ability of ancestors who inhabited Mumba rock-shelter and the surrounding landscape from the MSA to the present. Ochre pigments are believed to be one of the ingredients for painted figures executed globally on Precambrian and gneiss rock-walls. Despite being a significant part of human intellectual achievements, the rock art images depicted at Mumba have been severely affected by physical weathering and anthropogenic actions. This paper explores the extent to which the rock art of Mumba reference cultural processes, conservation challenges, and prospects for future uses. The presented data were collected through in-depth documentation using modern analytical techniques such as ImageJ and Adobe Photoshop C5 softwares to trace the paintings. Two traditional systems of hunter-forager and Bantu speaking paintings were identified at Mumba. However, the conservation status of the rock art of Mumba is not ideal, which necessitates collective management approaches.

The relevance of late MSA mandibles on the emergence of modern morphology in Northern Africa

North Africa is a key area for understanding hominin population movements and the expansion of our species. It is home to the earliest currently known Homo sapiens (Jebel Irhoud) and several late Middle Stone Age (MSA) fossils, notably Kébibat, Contrebandiers 1, Dar-es-Soltane II H5 and El Harhoura. Mostly referred to as “Aterian” they fill a gap in the North African fossil record between Jebel Irhoud and Iberomaurusians. We explore morphological continuity in this region by quantifying mandibular shape using 3D (semi)landmark geometric morphometric methods in a comparative framework of late Early and Middle Pleistocene hominins (n = 15), Neanderthals (n = 27) and H. sapiens (n = 145). We discovered a set of mixed features among late MSA fossils that is in line with an accretion of modern traits through time and an ongoing masticatory gracilization process. In Northern Africa, Aterians display similarities to Iberomaurusians and recent humans in the area as well as to the Tighenif and Thomas Quarry hominins, suggesting a greater time depth for regional continuity than previously assumed. The evidence we lay out for a long-term succession of hominins and humans emphasizes North Africa’s role as source area of the earliest H. sapiens.

Portable, non-destructive colorimetry and visible reflectance spectroscopy paired with machine learning can classify experimentally heat-treated silcrete from three South African sources.

The objective of this study was to determine if visible reflectance spectroscopy and quantitative colorimetry represent viable approaches to classifying the heat treatment state of silcrete. Silcrete is a soil duricrust that has been used as toolstone since at least the Middle Stone Age. The ancient practice of heat treating silcrete prior to knapping is of considerable interest to paleolithic archaeologists because of its implications for early modern human complex cognition generally and the ability to manipulate the material properties of stone specifically. Here, we demonstrate that our quantitative, non-invasive, and portable approach to measuring color, used in conjunction with k-Nearest Neighbors “lazy” machine learning, is a highly promising method for heat treatment detection. Traditional, expert human analyst approaches typically rely upon subjective assessments of color and luster and comparison to experimental reference collections. This strongly visual method can prove quite accurate, but difficult to reproduce between different analysts. In this work, we measured percent reflectance for the visible spectrum (1018 variables) and standardized color values (CIEL*a*b*) in unheated and experimentally heat-treated silcrete specimens from three sources in South Africa. k-NN classification proved highly effective with both the spectroscopy and colorimetry data sets. An important innovation was using the heat treatment state predicted by the k-NN model for the majority of replicate observations of a single specimen to predict the heat treatment state for the specimen overall. When this majority voting approach was applied to the 746 individual observations in this study, associated with 94 discrete silcrete flakes, both spectroscopy and colorimetry k-NN models yielded 0% test set misclassification rates at the specimen level.

Morphological, biometric and taphonomic analyses of Holocene gerbils from Guenfouda (Eastern Morocco) and first mention of Gerbillus henleyi in a fossil record

ABSTRACT The Guenfouda cave, located in eastern Morocco, has yielded an abundant macro- and microvertebrate fauna associated with a rich lithic industry attributed to several cultures (Middle Stone Age, Later Stone Age and Neolithic). Among the microfauna, on the basis of new morphological and biometric data of the upper and lower first molars, we identified two gerbillines of the genus Gerbillus collected from the upper levels of an Holocene age. Gerbillus henleyi is here identified for the first time in the fossil record of North Africa, while G. campestris has been cited previously at this site and in many other Pleistocene and Holocene sites in the Maghreb. The taphonomic study concluded that a medium-sized nocturnal predator (possibly Tyto alba) was likely to be the source of the accumulation of small mammals in the filling of the Guenfouda cave. The palaeoecological reconstruction based on the whole faunal spectrum indicates a semi-open steppic landscape, with patches of more wooded areas and water ponds or streams, which is also characteristic for this region at present.

The Middle Stone Age in the Eastern Desert. EDAR 135 — a buried early MIS 5 horizon from Sudan

ABSTRACT Middle Stone Age (MSA) lithic artefacts coming from dated layers preserved in their original stratigraphic position are still rare in Northeast Africa in general and in Sudan in particular. This paper aims to present the results of technological and functional analyses of an assemblage coming from a stratigraphic context, i.e. the upper level of the EDAR (Eastern Desert – Atbara River) 135 site, discovered in an abandoned gold mining pit in the Sudanese Eastern Desert, approximately 70 km east of the town of Atbara. The assemblage, which is based on locally available quartz and rhyolite, comes from a layer bracketed by OSL dates of 116 ± 13 and 125 ± 11 kya. Such dating places it within Marine Isotope Stage 5e–5d. Analysis of the assemblage revealed several characteristics that seem to set it apart from other MSA Northeast African inventories. Among these, the dominance of simple, non-predetermined core reduction strategies and expedient tool types, coupled with the lack of traces of Nubian Levallois technique, are the most conspicuous. Micro-traces of use on animal and plant matter were preserved on some of the tools. EDAR 135 is part of a newly discovered complex of sites that confirms the presence of Middle and Late Pleistocene hominins along one of the possible routes out of Africa towards Eurasia.

The final MSA of eastern South Africa: a comparative study between Umbeli Belli and Sibhudu

ABSTRACT The end of the Middle Stone Age in southern Africa, often called the final MSA (∼40–28 ka), represents one of the most understudied technocomplexes in this part of the world. Researchers have often focused on earlier time periods associated with Marine Isotope Stage 4 or have emphasised the transition between the Middle and the Later Stone Age. Thus, the final MSA has been poorly understood and, at least in KwaZulu-Natal, only a few chrono-cultural markers called hollow-based points are known for it. Since 2016, excavations at Umbeli Belli rock shelter have produced new insights into this period. The site provides one of the most accurately dated sequences for the final MSA, spanning four geological horizons, respectively GH7, GH8, GH9 and GH10, that date to between 29.9 ± 2.3 and 40.3 ± 3.5 ka. Significant technological and typological variations are evident between those horizons, raising questions about the mechanisms behind them. A direct comparative analysis with the final MSA layers Coffee – Espresso at Sibhudu, which date to ∼38 ka, places these results in the regional archaeological context. The analysis shows first that the final MSA encompasses diachronic variability within relatively short time frames at Umbeli Belli. Secondly, it reveals several distinct chronological discrepancies between Sibhudu and Umbeli Belli. A detailed review of the environmental setting of the research area helps to explain these changes.

Investigating the effect of diagenesis on ESR dating of Middle Stone Age tooth samples from the open-air site of Lovedale, Free State, South Africa

Teeth are usually targeted for dating archaeological sites because they are less prone to dissolution, in comparison with bones. However, despite this apparent resistance, teeth do undergo diagenesis, which needs to be accounted for in order to obtain accurate ages. In particular, the uptake of trace elements such as uranium in dental tissues needs to be considered for dose rate determination when dated using electron spin resonance (ESR). Characterising the mineralogy and structural integrity of samples prior to dating may thus provide important information related to their state of preservation, especially in the case of teeth whose U content can significantly affect the dose rate.

Human occupation of the semi-arid grasslands of South Africa during MIS 4: New archaeological and paleoecological evidence from Lovedale, Free State

Marine Isotope Stage (MIS) 5 and 4 are periods of major cultural innovations in the Middle Stone Age (MSA) of southern Africa. While extensive data is available for the coast, far less is known about the interior, in particular its central plateau. This is likely due to the large geographic extent of this area and a general paucity of caves and rock shelters that can provide long stratigraphic sequences and environmental records. The lack of information and systematic research has hindered our understanding of regional variation and patterns of human dispersal within the subcontinent. Our research at the open-air MSA site of Lovedale situated on the Modder River addresses this issue. Using sediment micromorphology, infrared spectroscopy of bones and sediments, phytolith and faunal analyses, as well as luminescence dating, we have reconstructed the evolution of paleoenvironments in this region at specific points over the last ∼80,000 years. Our results help contextualize human occupation and hunting strategies associated with a pre-Howiesons Poort technology that occurred in a wetland environment during a short-lived warm, dry period dated to ∼70 ka. These results show that humans settled the grasslands of the central interior at the onset of MIS 4 and confirm the importance of wetlands in human subsistence strategies, especially in times of climatic stress.

A late Middle Pleistocene Middle Stone Age sequence identified at Wadi Lazalim in southern Tunisia

The late Middle Pleistocene, starting at around 300 ka, witnessed large-scale biological and cultural dynamics in hominin evolution across Africa including the onset of the Middle Stone Age that is closely associated with the evolution of our species—Homo sapiens. However, archaeological and geochronological data of its earliest appearance are scarce. Here we report on the late Middle Pleistocene sequence of Wadi Lazalim, in the Sahara of Southern Tunisia, which has yielded evidence for human occupations bracketed between ca. 300–130 ka. Wadi Lazalim contributes valuable information on the spread of early MSA technocomplexes across North Africa, that likely were an expression of large-scale diffusion processes.

Anthropogenic fire fingerprints in Late Pleistocene and Holocene sediments of Sodmein Cave, Egypt

Sodmein Cave in Egypt is an exceptional archive for the study of past human behavior and anthropogenic fire history. Stratified remains of human occupation were excavated, ranging from the Middle Stone Age to the Neolithic. Hearths were repeatedly detected throughout the stratigraphy, with the lowest Pleistocene level having particularly large fire pits. This study is the first to apply a black carbon (BC) method on sediments bearing archaeology from the last 120,000 years. The method oxidizes BC to benzene polycarboxylic acids (BPCA) as a proxy for fire residue input. We detected significant changes in BC amounts throughout the stratigraphy; the highest contents in the form of two distinctive peaks were found in samples corresponding to the beginning of the Late Pleistocene (3.3 and 2.2 g BC kg−1, respectively), indicating frequent burning. In the overlying layers, BC remained low (on average: 0.2 g BC kg−1) until the beginning of the Holocene, when contents increased, and human influence became visible again (1.7 g BC kg−1). Also, BPCA composition as a proxy for changes in fire temperature changed significantly over the stratigraphy. In the Pleistocene, residues of hotter fires were predominantly found, while the Holocene was characterised by a change to low-temperature fires. Variations in BC input and source are in agreement with the archaeological results, demonstrating the varying intensities and recurrence of human visits to the shelter during the last 120,000 years, but also show the potential to resolve different phases of human occupation more finely, when the archaeological findings are accompanied by geochemical BC analyses.

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

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.

Riddles wrapped inside an enigma. Lupemban MSA technology as a rainforest adaptation: revisiting the lanceolate point.

The Central African Stone Age is very poorly known when compared to the higher-resolution records of East and Southern Africa. Early Stone Age (ESA) archaeology is effectively absent from the rainforest zone, with the early Middle Stone Age (MSA) Lupemban industry representing the earliest sustained archaeological signature. Uranium-series dates of approximately 265 ka BP for the Lupemban at Twin Rivers (Zambia), although queried, suggest a precocious late Middle Pleistocene dispersal of early Homo sapiens into the equatorial rainforest belt. Lupemban palaeohabitat interactions and attendant behavioural and technological repertoires are key to its evolutionary significance, but investigation is hampered by the widespread vertical disturbance of stratigraphic profiles and the formation of 'stone-lines'. The Lupemban takes in a range of implement types and technologies, including core-axes, prepared core technology (PCT) points, blades and backed blades. But it is the elongated bifacial lanceolate point-some exquisitely made and many exceeding 30 cm in length-that defines the industry. Remarkably, unequivocal examples of these iconic artefacts have never been the focus of detailed techno-typological scrutiny. In this paper, I advance understanding of the Lupemban by initiating a re-consideration of lanceolate points at Kalambo Falls, Zambia, and discuss their implications for the Lupemban's evolutionary significance. This article is part of the theme issue 'Tropical forests in the deep human past'.

The climate and vegetation backdrop to hominin evolution in Africa.

The most profound shift in the African hydroclimate of the last 1 million years occurred around 300 thousand years (ka) ago. This change in African hydroclimate is manifest as an east-west change in moisture balance that cannot be fully explained through linkages to high latitude climate systems. The east-west shift is, instead, probably driven by a shift in the tropical Walker Circulation related to sea surface temperature change driven by orbital forcing. Comparing records of past vegetation change, and hominin evolution and development, with this breakpoint in the climate system is challenging owing to the paucity of study sites available and uncertainties regarding the dating of records. Notwithstanding these uncertainties we find that, broadly speaking, both vegetation and hominins change around 300 ka. The vegetative backdrop suggests that relative abundance of vegetative resources shifted from western to eastern Africa, although resources would have persisted across the continent. The climatic and vegetation changes probably provided challenges for hominins and are broadly coincident with the appearance of Homo sapiens (ca 315 ka) and the emergence of Middle Stone Age technology. The concomitant changes in climate, vegetation and hominin evolution suggest that these factors are closely intertwined. This article is part of the theme issue 'Tropical forests in the deep human past'.

Environmental influences on human innovation and behavioural diversity in southern Africa 92-80 thousand years ago.

Africa's Middle Stone Age preserves sporadic evidence for novel behaviours among early modern humans, prompting a range of questions about the influence of social and environmental factors on patterns of human behavioural evolution. Here we document a suite of novel adaptations dating approximately 92-80 thousand years before the present at the archaeological site Varsche Rivier 003 (VR003), located in southern Africa's arid Succulent Karoo biome. Distinctive innovations include the production of ostrich eggshell artefacts, long-distance transportation of marine molluscs and systematic use of heat shatter in stone tool production, none of which occur in coeval assemblages at sites in more humid, well-studied regions immediately to the south. The appearance of these novelties at VR003 corresponds with a period of reduced regional wind strength and enhanced summer rainfall, and all of them disappear with increasing winter rainfall dominance after 80 thousand years before the present, following which a pattern of technological similarity emerges at sites throughout the broader region. The results indicate complex and environmentally contingent processes of innovation and cultural transmission in southern Africa during the Middle Stone Age.

Predetermined Refinement: the Earliest Levallois of the Kapthurin Formation

Levallois technology characterizes the Middle Stone Age/Middle Palaeolithic, but one of its earliest manifestations is from the preceding Acheulean of the Kapthurin Formation, in the Rift Valley of east Africa. Here, ~ 400 ka, hominins were creating large flake blank handaxes and cleavers through Levallois knapping. Comparing these tools with other Rift Valley Acheulean assemblages made on large flakes shows those of the Kapthurin Formation are distinguished by their thinness. This was achieved through symmetrical centripetal preparation of gentle upper surface convexities on the Levallois cores, the creation of a protruding facetted platform, and proximal bevelling of the upper surface. A large elongate flake blank was struck from the facetted platform, then finished with marginal trimming to create the symmetrical and regular edge of the handaxe or cleaver. As they were used for the creation of handaxes and cleavers, the Kapthurin Acheulean Levallois cores and flakes are much larger than that of the Middle Stone Age, with overshot flakes from excessive force a more frequent error. The Acheulean Levallois is further distinguished from those of the Middle Stone Age by the lack of recurrent flaking, with cores apparently producing only a single preferential flake without any repreparation of the main flaking surface, despite the cores being big enough for further large blank removals, and even if the preferential removal overshot and was abandoned. The key advantage offered by Levallois in general is large thin elongate flakes. In its Kapthurin Acheulean manifestation, Levallois was used to create an individual tool, but in the Middle Stone Age it was often used to make toolkits.

An improved chronology for the Middle Stone Age at El Mnasra cave, Morocco.

North African coastal Middle Stone Age (MSA) sites are key to study the development and expansion of early H. sapiens. El Mnasra cave on the Atlantic coast of Morocco (Témara region) is a crucial site associated with MSA archaeological materials considered advanced cognitive hallmarks of behavioural innovation, such as numerous Nassariidae perforated shells, hematite pigments, bones industry and coastal resources exploitation. We provide new trapped-charges dates (OSL and combined US-ESR ages). Our Bayesian modelling strengthens the new lithostratigraphic interpretation of the cave stratigraphic units (US) and we propose an updated chronostratigraphic model for the Middle Stone Age archaeo-sequence of El Mnasra Cave. We confirm a human presence between 124–104 ka, earlier than what the previous OSL and US-ESR data showed. Our time range intervals allowed us to also extend the age of the MSA occupations considerably to the MIS 4/3 (~62–30 ka), marked by the disappearance of the Nassariidae perforated shells. Outstandingly, our model pushed back the age of the largest record of Nassariidae perforated shells and placed the age of their use by the Aterian groups at El Mnasra from the MIS 5d-5b (~115–94 ka).

Technological diversity in the Late Pleistocene of the Nyanza Rift, Kenya: Archaeological excavations at Kapsarok 1 and Anderea’s Farm 1

The archaeological record of Late Pleistocene Africa is characterized by behavioral diversity and change, notably the technological shift from the Middle Stone Age (MSA) to Later Stone Age (LSA). Recent research shows the MSA-LSA transition was a spatially and temporally complex process. Understanding this transition requires a composite record of archaeological sites from precise chronological and stratigraphic contexts within multiple regions. Here we present excavation and analysis of two open-air Late Pleistocene sites in chronological and geographic association: Anderea’s Farm 1 (GrJe-8) and Kapsarok 1 (GrJe-9), from the Nyanza Rift, Kenya. Volcanic ash correlations of artifact-bearing sediments provide ages of ∼ 45–36 ka for Anderea’s Farm 1 (GrJe-8) and ∼ 50 ka for Kapsarok 1 (GrJe-9). Locally procured lavas were used to produce different stone tools by disparate technological methods. Lithic production at Anderea’s Farm 1 focused on the manufacture of short irregular flakes using expedient and discoidal methods, and tools are dominated by heavy-duty types. In contrast, Kapsarok 1 is characterized by elongated and convergent blanks produced using hierarchical core technologies. Viewed together, Kapsarok 1 and Anderea’s Farm 1 emphasizes high diversity in Late Pleistocene technology of the Victoria Basin. We argue these different technologies are most parsimoniously interpreted as expressions of a broad and flexible behavioral repertoire. Further, our results emphasize how excavation and analysis of open-air archaeological sites in secure chronological and stratigraphic contexts provides the means to sample the necessary range of human behaviours across a landscape commensurate with past forager geographic ranges.

Une vue d’ensemble sur Melka Kunture, grand complexe de sites pléistocènes dans la vallée supérieure de l’Awash (Éthiopie)

Melka Kunture is a cluster of Pleistocene sites, extending over ⁓100 km2 between 2000 and 2200m asl, in the upper Awash Valley of Ethiopia. Starting around 2 million-years ago, the archaeological sequence includes sites with lithic productions of the Oldowan, Early Acheulean, middle Acheulean, final Acheulean, Early Middle Stone Age, Middle Stone Age and Late Stone Age. All over the Pleistocene, the climate was rainy and cooler than at the lower elevations of the Rift Valley, allowing the development of Afromontane vegetation. Hippopotamuses are ubiquitous and dominant in terms of biomass, but Alcelaphini are well represented, notably with genus Connochaetes and genus Damaliscus. Hominin fossils have been discovered in association with the Oldowan, the Early Acheulean, the middle Acheulean and the Early Middle Stone Age. Animal tracks and hominin footprints have also been documented, the latter ones in layers dated between 1.2 and 0.7 million-years.