An ape partial postcranial skeleton (KNM-NP 64631) from the Middle Miocene of Napudet, northern Kenya.

An ape partial postcranial skeleton (KNM-NP 64631) was recovered during the 2015-2021 field seasons at Napudet, a Middle Miocene (∼13 Ma) locality in northern Kenya. Bony elements representing the shoulder, elbow, hip, and ankle joints, thoracic and lumbar vertebral column, and hands and feet, offer valuable new information about the body plan and positional behaviors of Middle Miocene apes. Body mass estimates from femoral head dimensions suggest that the KNM-NP 64631 individual was smaller-bodied (c. 13-17 kg) than some Miocene taxa from eastern Africa, including Ekembo nyanzae, and probably Equatorius africanus or Kenyapithecus wickeri, and was more comparable to smaller-bodied male Nacholapithecus kerioi individuals. Similar to many Miocene apes, the KNM-NP 64631 individual had hip and hallucal tarsometatarsal joints reflecting habitual hindlimb loading in a variety of postures, a distal tibia with a large medial malleolus, an inflated humeral capitulum, probably a long lumbar spine, and a long pollical proximal phalanx relative to femoral head dimensions. The KNM-NP 64631 individual departs from most Early Miocene apes in its possession of a more steeply beveled radial head and deeper humeral zona conoidea, reflecting enhanced supinating-pronating abilities at the humeroradial joint. The KNM-NP 64631 individual also differs from Early Miocene Ekembo heseloni in having a larger elbow joint (inferred from radial head size) relative to the mediolateral width of the lumbar vertebral bodies and a more asymmetrical talar trochlea, and in these ways recalls inferred joint proportions for, and talocrural morphology of, N. kerioi. Compared to most Early Miocene apes, the KNM-NP 64631 individual likely relied on more forelimb-dominated arboreal behaviors, perhaps including vertical climbing (e.g., extended elbow, hoisting). Moreover, the Napudet ape partial postcranial skeleton suggests that an arboreally adapted body plan characterized by relatively large (here, based on joint size) forelimbs, but lacking orthograde suspensory adaptations, may not have been 'unusual' among Middle Miocene apes.

Aridity, availability of drinking water and freshwater foods, and hominin and archeological sites during the Late Pliocene-Early Pleistocene in the western region of the Turkana Basin (Kenya): A review.

Although the Turkana Basin is one of the driest regions of the East African Rift, its Plio-Pleistocene sediments are rich in freshwater vertebrates and invertebrates, providing evidence that freshwater resources were available to hominins in this region during the Plio-Pleistocene (4.2-0.7 Ma). Here we provide an overview of the hydroconnectivity of the Turkana Basin. We then review the period during which freshwater river and lake systems expanded into the western region of the Turkana Basin, where hominin and archeological sites have been discovered in sediments dating back to the Late Pliocene-Pleistocene. Freshwater conditions are reconstructed from river and lake sediments and the flora and micro- and macofauna they contain. Data synthesis suggests that drinking water and freshwater foods prevailed in the western region of the Turkana Basin at 4.20-3.98 Ma, 3.70-3.10 Ma, 2.53-2.22 Ma, then between 2.10 and 1.30 Ma and intermittently from 1.27 to 0.75 Ma. Milestones in hominin evolution occurred in this context, such as the first occurrence of Australopithecus anamensis (4.20-4.10 Ma) and Kenyanthropus platyops (3.50 Ma and 3.30-3.20 Ma), the presence of Paranthropus aethiopicus (2.53-2.45 Ma), early Homo (2.33 Ma), Paranthropus boisei (2.25 Ma and 1.77-1.72 Ma) and Homo ergaster/Homo erectus (1.75 Ma, 1.47-1.42 Ma and 1.10-0.90 Ma). Developments in hominin behavior also occurred during this timeframe, including the first known stone tools (3.30 Ma), the oldest Oldowan sites (2.34 Ma and 2.25 Ma) in the Turkana Basin, the earliest known evidence for the emergence of bifacial shaping in eastern Africa (1.80 Ma), and the first known Acheulean site (1.76 Ma). Our synthesis suggests that, diachronic variation in hydroconnectivity played a role on the amount of drinking water and freshwater foods available in the western region of the Turkana Basin, despite regional aridity.

Plio-Pleistocene environmental variability in Africa and its implications for mammalian evolution.

Understanding the climatic drivers of environmental variability (EV) during the Plio-Pleistocene and EV's influence on mammalian macroevolution are two outstanding foci of research in African paleoclimatology and evolutionary biology. The potential effects of EV are especially relevant for testing the variability selection hypothesis, which predicts a positive relationship between EV and speciation and extinction rates in fossil mammals. Addressing these questions is stymied, however, by 1) a lack of multiple comparable EV records of sufficient temporal resolution and duration, and 2) the incompleteness of the mammalian fossil record. Here, we first compile a composite history of Pan-African EV spanning the Plio-Pleistocene, which allows us to explore which climatic variables influenced EV. We find that EV exhibits 1) a long-term trend of increasing variability since ∼3.7 Ma, coincident with rising variability in global ice volume and sea surface temperatures around Africa, and 2) a 400-ky frequency correlated with seasonal insolation variability. We then estimate speciation and extinction rates for fossil mammals from eastern Africa using a method that accounts for sampling variation. We find no statistically significant relationship between EV and estimated speciation or extinction rates across multiple spatial scales. These findings are inconsistent with the variability selection hypothesis as applied to macroevolutionary processes.

Orbital controls on eastern African hydroclimate in the Pleistocene.

Understanding eastern African paleoclimate is critical for contextualizing early human evolution, adaptation, and dispersal, yet Pleistocene climate of this region and its governing mechanisms remain poorly understood due to the lack of long, orbitally-resolved, terrestrial paleoclimate records. Here we present leaf wax hydrogen isotope records of rainfall from paleolake sediment cores from key time windows that resolve long-term trends, variations, and high-latitude effects on tropical African precipitation. Eastern African rainfall was dominantly controlled by variations in low-latitude summer insolation during most of the early and middle Pleistocene, with little evidence that glacial-interglacial cycles impacted rainfall until the late Pleistocene. We observe the influence of high-latitude-driven climate processes emerging from the last interglacial (Marine Isotope Stage 5) to the present, an interval when glacial-interglacial cycles were strong and insolation forcing was weak. Our results demonstrate a variable response of eastern African rainfall to low-latitude insolation forcing and high-latitude-driven climate change, likely related to the relative strengths of these forcings through time and a threshold in monsoon sensitivity. We observe little difference in mean rainfall between the early, middle, and late Pleistocene, which suggests that orbitally-driven climate variations likely played a more significant role than gradual change in the relationship between early humans and their environment.

Before the Acheulean: The emergence of bifacial shaping at Kokiselei 6 (1.8 Ma), West Turkana, Kenya.

We present new evidence for the emergence of biface shaping from Kokiselei 6 in the Kokiselei Site Complex (KS) in West Turkana, Kenya. This rich and well-preserved new site presents an opportunity to investigate the earliest development of biface shaping. The emergence of biface shaping in lithic technology is often used as evidence for increased and/or novel cognitive abilities that contrast prior hominins' flaking capacities. Yet, recent research reveals a story of gradual change over time in a variety of different flaking and shaping strategies. Here, we present preliminary excavation and lithic data from Kokiselei 6 that will be critical for future investigations of biface shaping emergence at KS. Kokiselei preserves the oldest known Acheulean lithic assemblage, Kokiselei 4 (1.76 Ma), as well as several older sites. Geochronological research shows that Kokiselei 6 stratigraphically underlies Kokiselei 4 and is the oldest site in the complex at 1.8 Ma. The Kokiselei 6 excavation yielded thousands of piece-plotted lithic artifacts and faunal remains. Preliminary analysis of the lithics (n = 3856) indicates a prevalence of bifacial flaking strategies alongside minimal evidence for rough biface shaping. We argue that the flaking strategies observed from bifacial cores share similar operations and abilities as those involved in the production of the roughly shaped bifaces at the site. This preliminary evidence supports existing arguments that biface shaping emerged gradually out of variability in bifacial core reduction, ultimately leading to the systematic production of bifaces characteristic of the Acheulean. Future work teasing apart the processes of technological change at KS more broadly will be critical for understanding the emergence of biface shaping. These new data add to a growing narrative that opposes long-held assumptions about hominin cognitive evolution that suggest Acheulean technology required new, and more complex, cognitive abilities and gestures.

Author Correction: New infant cranium from the African Miocene sheds light on ape evolution.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Hominin fire use in the Okote member at Koobi Fora, Kenya: New evidence for the old debate.

Hominin fire use in the early Pleistocene has been debated since the early 1970s when consolidated reddened sediment patches were identified at FxJj20 East and Main, Koobi Fora, Kenya. Since then, researchers have argued for evidence of early Pleistocene fire use at a handful of archaeological sites with evidence of combustion. Some argue that morphological evidence of early Homo erectus fossils indicates a dietary shift to higher quality food sources, which could be achieved by cooking. Others contend that fire use does not become a regular behavior until later, in the middle Pleistocene, when archaeological sites begin to show regular evidence for fire use. An early date for hominin control of fire would help to explain the grade changes seen with the appearance of H. erectus, while a later date would mean that fire would have had little influence on the early development of the lineage. Early hominins would have encountered fire regularly on the landscape, increasing the possibility of hominins interacting with and habituating to natural landscape fire. Only a detailed understanding of the patterns of controlled and natural fires can lead to understanding of early hominin fire use. We present new work on the evidence of fire at the FxJj20 Site complex in Koobi Fora, dated to 1.5 Ma. We highlight evidence of burning found on site through Fourier Transform Infrared spectrometry, and describe ongoing work to investigate the association of hominin behavior and fire evidence. We present data supporting the hypothesis that the site is undisturbed and discuss spatial relationships showing burned material associated with non-burned material. We present data on a type of stone fragment, the Thermal Curve Fragment (TCF), which is indicative of knapped material being exposed to high heat. Finally, we suggest future directions on the topic of fire in the early Pleistocene.

Relevance of the eastern African coastal forest for early hominin biogeography.

The influence of climate change on hominin evolution is much debated. Two issues hamper our understanding of this process: the limited hominin fossil record, and incomplete knowledge about hominin spatial occupation of Africa. Here, we analyze the presently known hominin fossil distribution pattern and explore the potential geographic distribution of hominins between ∼4.5 and ∼2.5 Ma. We focus on assessing the relevance of the Coastal Forest of Eastern Africa (CFEA) along the Indian Ocean as a core area for early hominin evolution. Based on biogeographic-phylogeographic data we propose the coastal refuge hypothesis: the CFEA provided a refugium for early hominins in periods of variable climate and strong seasonality during eccentricity maxima. From this refuge, evolved species could disperse inland (e.g. to rift basins) via vegetated humid corridors, whenever onset of stable climate periods with low seasonality during eccentricity minima allowed expansion out of the coastal enclave. We develop a conceptual model in time and space, comparing predictions with climatic and hominin fossil records. The results imply that: 1) between ∼4.5 and 3 Ma, ongoing (mostly anagenetic) hominin evolution occurred in the CFEA, punctuated by inland dispersal events at ∼4.4, 4.2, 3.8, 3.5, and 3.2 Ma; 2) before ∼3 Ma, the Afar Basin was a (sub)core area often connected to and relatively similar to the CFEA, while other inland areas were more or less marginal for early hominin habitation; 3) after ∼3 Ma, Northern Hemisphere Glaciation exerted strong influence by causing latitudinal contraction of the CFEA, leading to habitat fragmentation, isolation of hominin populations and possible cladogenetic evolution. A major challenge for the coastal refuge model is the fact that at present, no (hominin) fossils are known from the CFEA. We consider how this can be explained, and possibly overcome with targeted search efforts. Furthermore we discuss how the model can be tested, e.g. with molecular phylogeography approaches, and used to predict new hominin fossil locations. With this study, we hope to contribute a fresh perspective to the climate-evolution debate, emphasizing the role of climatic stability, length of dry season and vegetation cover to facilitate connectivity between hominin core and marginal habitats.

Site fragmentation, hominin mobility and LCT variability reflected in the early Acheulean record of the Okote Member, at Koobi Fora, Kenya.

From its initial appearance at ∼1.7 Ma, the Acheulean was prevalent through a vast chronological span of hominin behavioural evolution that lasted nearly 1.5 million years. The origins and production patterns of large bifacial cutting tools ('LCTs') - the marker of the Acheulean techno-complex - and the systematic changes in this behaviour through time are gaining increasing interest in paleoanthropology. Here we provide a synthesis of early Acheulean LCT variation in a landscape context by analysing assemblages from four different quasi-contemporaneous (∼1.4 Ma) sites from the Koobi Fora Formation. We characterize this variation using both 3D geometric morphometric and descriptive approaches. The expansive lateral exposures of fluvial and lacustrine sediments, as well as the associated tephrostratigraphy of the Koobi Fora Formation provide the landscape context that enables these comparative analyses. Our study demonstrates that when multiple contemporaneous early Acheulean localities are analysed together, a broader picture of LCT variability is elucidated. Four sites at Koobi Fora appear to represent a single system of lithic economy, characterized by a discrete trajectory of changes in LCT size and shape. These sites have ranges of LCT forms which appear to represent different but overlapping stages on a single reduction trajectory. Certain sites exhibit the full reduction trajectory while others exhibit only fragments of this trajectory. Other inter-site lithic proxies further complement these patterns in LCT variability. We explore patterns of site function, mobility and hominin landscape use, all of which may be suggestive of a depth of planning in early Acheulean hominins wherein technological activities were undertaken in substantial anticipation of future needs.

New infant cranium from the African Miocene sheds light on ape evolution.

The evolutionary history of extant hominoids (humans and apes) remains poorly understood. The African fossil record during the crucial time period, the Miocene epoch, largely comprises isolated jaws and teeth, and little is known about ape cranial evolution. Here we report on the, to our knowledge, most complete fossil ape cranium yet described, recovered from the 13 million-year-old Middle Miocene site of Napudet, Kenya. The infant specimen, KNM-NP 59050, is assigned to a new species of Nyanzapithecus on the basis of its unerupted permanent teeth, visualized by synchrotron imaging. Its ear canal has a fully ossified tubular ectotympanic, a derived feature linking the species with crown catarrhines. Although it resembles some hylobatids in aspects of its morphology and dental development, it possesses no definitive hylobatid synapomorphies. The combined evidence suggests that nyanzapithecines were stem hominoids close to the origin of extant apes, and that hylobatid-like facial features evolved multiple times during catarrhine evolution.

A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya.

Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial-lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure (ca 5-100% C4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25-30% more C4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C3-C4 to C4-dominated ecosystems. The proportion of C4-based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61-97% C4 vegetation on the landscape.This article is part of the themed issue 'Major transitions in human evolution'.

3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya.

Human evolutionary scholars have long supposed that the earliest stone tools were made by the genus Homo and that this technological development was directly linked to climate change and the spread of savannah grasslands. New fieldwork in West Turkana, Kenya, has identified evidence of much earlier hominin technological behaviour. We report the discovery of Lomekwi 3, a 3.3-million-year-old archaeological site where in situ stone artefacts occur in spatiotemporal association with Pliocene hominin fossils in a wooded palaeoenvironment. The Lomekwi 3 knappers, with a developing understanding of stone's fracture properties, combined core reduction with battering activities. Given the implications of the Lomekwi 3 assemblage for models aiming to converge environmental change, hominin evolution and technological origins, we propose for it the name 'Lomekwian', which predates the Oldowan by 700,000 years and marks a new beginning to the known archaeological record.

Associated ilium and femur from Koobi Fora, Kenya, and postcranial diversity in early Homo.

During the evolution of hominins, it is generally accepted that there was a shift in postcranial morphology between Australopithecus and the genus Homo. Given the scarcity of associated remains of early Homo, however, relatively little is known about early Homo postcranial morphology. There are hints of postcranial diversity among species, but our knowledge of the nature and extent of potential differences is limited. Here we present a new associated partial ilium and femur from Koobi Fora, Kenya, dating to 1.9 Ma (millions of years ago) that is clearly attributable to the genus Homo but documents a pattern of morphology not seen in eastern African early Homo erectus. The ilium and proximal femur share distinctive anatomy found only in Homo. However, the geometry of the femoral midshaft and contour of the pelvic inlet do not resemble that of any specimens attributed to H. erectus from eastern Africa. This new fossil confirms the presence of at least two postcranial morphotypes within early Homo, and documents diversity in postcranial morphology among early Homo species that may reflect underlying body form and/or adaptive differences.

Improved age control on early Homo fossils from the upper Burgi Member at Koobi Fora, Kenya.

To address questions regarding the evolutionary origin, radiation and dispersal of the genus Homo, it is crucial to be able to place the occurrence of hominin fossils in a high-resolution chronological framework. The period around 2 Ma (millions of years ago) in eastern Africa is of particular interest as it is at this time that a more substantial fossil record of the genus Homo is first found. Here we combine magnetostratigraphy and strontium (Sr) isotope stratigraphy to improve age control on hominin-bearing upper Burgi (UBU) deposits in Areas 105 and 131 on the Karari Ridge in the eastern Turkana Basin (Kenya). We identify the base of the Olduvai subchron (bC2n) plus a short isolated interval of consistently normal polarity that we interpret to be the Pre-Olduvai event. Combined with precession-forced (~20 kyr [thousands of years]) wet-dry climate cycles resolved by Sr isotope ratios, the magnetostratigraphic data allow us to construct an age model for the UBU deposits. We provide detailed age constraints for 15 hominin fossils from Area 131, showing that key specimens such as cranium KNM-ER 1470, partial face KNM-ER 62000 and mandibles KNM-ER 1482, KNM-ER 1801, and KNM-ER 1802 can be constrained between 1.945 ± 0.004 and 2.058 ± 0.034 Ma, and thus older than previously estimated. The new ages are consistent with a temporal overlap of two species of early Homo that can be distinguished by their facial morphology. Further, our results show that in this time interval, hominins occurred throughout the wet-dry climate cycles, supporting the hypothesis that the lacustrine Turkana Basin was a refugium during regionally dry periods. By establishing the observed first appearance datum of a marine-derived stingray in UBU deposits at 2.058 ± 0.034 Ma, we show that at this time the Turkana Basin was hydrographically connected to the Indian Ocean, facilitating dispersal of fauna between these areas. From a biogeographical perspective, we propose that the Indian Ocean coastal strip should be considered as a possible source area for one or more of the multiple Homo species in the Turkana Basin from over 2 Ma onwards.

Pedogenic carbonate stable isotopic evidence for wooded habitat preference of early Pleistocene tool makers in the Turkana Basin.

The origin and evolution of early Pleistocene hominin lithic technologies in Africa occurred within the context of savanna grassland ecosystems. The Nachukui Formation of the Turkana Basin in northern Kenya, containing Oldowan and Acheulean tool assemblages and fossil evidence for early members of Homo and Paranthropus, provides an extensive spatial and temporal paleosol record of early Pleistocene savanna flora. Here we present new carbon isotopic (δ(13)CVPDB) values of pedogenic carbonates (68 nodules, 193 analyses) from the Nachukui Formation in order to characterize past vegetation structure and change through time. We compared three members (Kalochoro, Kaitio, and Natoo) at five locations spanning 2.4-1.4Ma and sampled in proximity to hominin archaeological and paleontological sites. Our results indicate diverse habitats showing a mosaic pattern of vegetation cover at each location yet demonstrate grassland expansion through time influenced by paleogeography. Kalochoro floodplains occurred adjacent to large river systems, and paleosols show evidence of C3 woodlands averaging 46-50% woody cover. Kaitio habitats were located along smaller rivers and lake margins. Paleosols yielded evidence for reduced portions of woody vegetation averaging 34-37% woody cover. Natoo environments had the highest percentage of grasslands averaging 21% woody cover near a diminishing Lake Turkana precursor. We also compared paleosol δ(13)CVPDB values of lithic archaeological sites with paleosol δ(13)CVPDB values of all environments available to hominins at 2.4-1.4Ma in the Nachukui and Koobi Fora Formations. Grassy environments became more widespread during this interval; woody canopy cover mean percentages steadily decreased by 12%. However, significantly more wooded savanna habitats were present in the vicinity of lithic archaeological sites and did not mirror the basin-wide trend of grassland spread. Hominin lithic archaeological sites consistently demonstrated woody cover circa 40% throughout our study interval and were 4-12% more woody than coeval basin environs. We propose that Turkana Basin early tool makers may have preferred a more wooded portion of the savanna ecosystem to reduce heat stress and to gain differential access to potable water, raw materials, animal carcasses, and edible plants.

New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo.

Since its discovery in 1972 (ref. 1), the cranium KNM-ER 1470 has been at the centre of the debate over the number of species of early Homo present in the early Pleistocene epoch of eastern Africa. KNM-ER 1470 stands out among other specimens attributed to early Homo because of its larger size, and its flat and subnasally orthognathic face with anteriorly placed maxillary zygomatic roots. This singular morphology and the incomplete preservation of the fossil have led to different views as to whether KNM-ER 1470 can be accommodated within a single species of early Homo that is highly variable because of sexual, geographical and temporal factors, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation. Here we report on three newly discovered fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470 but is notably smaller. It preserves previously unknown morphology, including moderately sized, mesiodistally long postcanine teeth. The nearly complete mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental arcade that is short anteroposteriorly and flat across the front, with small incisors; these features are consistent with the arcade morphology of KNM-ER 1470 and KNM-ER 62000. The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa.

A geological history of the Turkana Basin.

The Turkana Basin preserves a long and detailed record of biotic evolution, cultural development, and rift valley geology in its sedimentary strata. Before the formation of the modern basin, Cretaceous fluvial systems, Paleogene lakes, and Oligo-Miocene volcano-sedimentary sequences left fossil-bearing strata in the region. These deposits were in part related to an early system of rift basins that stretched from Sudan to the Indian Ocean. The present-day basin has its origins in Pliocene tectonic developments of the modern rift, with subsidence making room for more than one kilometer of Plio-Pleistocene strata. Much of this sequence belongs to the Omo Group, richly fossiliferous sediments associated with the ancestral Omo River and its tributaries. Modern Lake Turkana has a record stretching back more than 200 thousand years, with earlier lake phases throughout the Plio-Pleistocene. The geologic history of the basin is one of dynamic landscapes responding to environmental influences, including tectonics, volcanic activity and climate.

An earlier origin for the Acheulian.

The Acheulian is one of the first defined prehistoric techno-complexes and is characterized by shaped bifacial stone tools. It probably originated in Africa, spreading to Europe and Asia perhaps as early as ∼1 million years (Myr) ago. The origin of the Acheulian is thought to have closely coincided with major changes in human brain evolution, allowing for further technological developments. Nonetheless, the emergence of the Acheulian remains unclear because well-dated sites older than 1.4 Myr ago are scarce. Here we report on the lithic assemblage and geological context for the Kokiselei 4 archaeological site from the Nachukui formation (West Turkana, Kenya) that bears characteristic early Acheulian tools and pushes the first appearance datum for this stone-age technology back to 1.76 Myr ago. Moreover, co-occurrence of Oldowan and Acheulian artefacts at the Kokiselei site complex indicates that the two technologies are not mutually exclusive time-successive components of an evolving cultural lineage, and suggests that the Acheulian was either imported from another location yet to be identified or originated from Oldowan hominins at this vicinity. In either case, the Acheulian did not accompany the first human dispersal from Africa despite being available at the time. This may indicate that multiple groups of hominins distinguished by separate stone-tool-making behaviours and dispersal strategies coexisted in Africa at 1.76 Myr ago.