New Oldowan locality Sare-Abururu (ca. 1.7 Ma) provides evidence of diverse hominin behaviors on the Homa Peninsula, Kenya.

The Homa Peninsula, in southwestern Kenya, continues to yield insights into Oldowan hominin landscape behaviors. The Late Pliocene locality of Nyayanga (∼3-2.6 Ma) preserves some of the oldest Oldowan tools. At the Early Pleistocene locality of Kanjera South (∼2 Ma) toolmakers procured a diversity of raw materials from over 10 km away and strategically reduced them in a grassland-dominated ecosystem. Here, we report findings from Sare-Abururu, a younger (∼1.7 Ma) Oldowan locality approximately 12 km southeast of Kanjera South and 18 km east of Nyayanga. Sare-Abururu has yielded 1754 artifacts in relatively undisturbed low-energy silts and sands. Stable isotopic analysis of pedogenic carbonates suggests that hominin activities were carried out in a grassland-dominated setting with similar vegetation structure as documented at Kanjera South. The composition of a nearby paleo-conglomerate indicates that high-quality stone raw materials were locally abundant. Toolmakers at Sare-Abururu produced angular fragments from quartz pebbles, representing a considerable contrast to the strategies used to reduce high quality raw materials at Kanjera South. Although lithic reduction at Sare-Abururu was technologically simple, toolmakers proficiently produced cutting edges, made few mistakes and exhibited a mastery of platform management, demonstrating that expedient technical strategies do not necessarily indicate a lack of skill or suitable raw materials. Lithic procurement and reduction patterns on the Homa Peninsula appear to reflect variation in local resource contexts rather than large-scale evolutionary changes in mobility, energy budget, or toolmaker cognition.

Did Early Pleistocene hominins control hammer strike angles when making stone tools?

In the study of Early Pleistocene stone artifacts, researchers have made considerable progress in reconstructing the technical decisions of hominins by examining various aspects of lithic technology, such as reduction sequences, hammer selection, platform preparation, core management, and raw material selection. By comparison, our understanding of the ways in which Early Pleistocene hominins controlled the delivery and application of percussive force during flaking remains limited. In this study, we focus on a key aspect of force delivery in stone knapping, namely the hammerstone striking angle (or the angle of blow), which has been shown to play a significant role in determining the knapping outcome. Using a dataset consists of 12 Early Pleistocene flake assemblages dated from 1.95 Ma to 1.4 Ma, we examined temporal patterns of the hammer striking angle by quantifying the bulb angle, a property of the flake's Hertzian cone that reflects the hammer striking angle used in flake production. We further included a Middle Paleolithic flake assemblage as a point of comparison from a later time period. In the Early Pleistocene dataset, we observed an increased association between the bulb angle and other flake variables related to flake size over time, a pattern similarly found in the Middle Paleolithic assemblage. These findings suggest that, towards the Oldowan-Acheulean transition, hominins began to systematically adjust the hammer striking angle in accordance with platform variables to detach flakes of different sizes more effectively, implying the development of a more comprehensive understanding of the role of the angle of blow in flake formation by ∼1.5 Ma.

Modeling Oldowan tool transport from a primate perspective.

Living nonhuman primates have long served as a referential framework for understanding various aspects of hominin biological and cultural evolution. Comparing the cognitive, social, and ecological contexts of nonhuman primate and hominin tool use has allowed researchers to identify key adaptations relevant to the evolution of hominin behavior. Although the Oldowan is often considered to be a major evolutionary milestone, it has been argued that the Oldowan is rather an extension of behaviors already present in the ape lineage. This is based on the fact that while apes move tools through repeated, unplanned, short-distance transport bouts, they produce material patterning often associated with long-distance transport, planning, and foresight in the Oldowan. Nevertheless, remain fundamental differences in how Oldowan core and flake technology and nonhuman primate tools are used. The goal of the Oldowan hominins is to produce sharp-edged flakes, whereas nonhuman primates use stone tools primarily as percussors. Here, we present an agent-based model that investigates the explanatory power of the ape tool transport model in light of these differences. The model simulates the formation of the Oldowan record under the conditions of an accumulated short-distance transport pattern, as seen in extant chimpanzees. Our results show that while ape tool transport can account for some of the variation observed in the archaeological record, factors related to use-life duration severely limit how far an Oldowan core can be moved through repeated short-distance transport bouts. Thus, the ape tool transport has limitations in its ability to explain patterns in the Oldowan. These results provide a basis for discussing adaptive processes that would have facilitated the development of the Oldowan.

Emergent technological variation in archaeological landscapes: a primate perspective.

Archaeological evidence informs our understanding of the evolution of hominin behaviour. Such evidence is traditionally used to reconstruct hominin activities and intentions. In the Plio-Pleistocene, the presence or absence of specific tools and variation in artefact density is often used to infer foraging strategies, cognitive traits and functional activities. However, the Plio-Pleistocene archaeological record is known to be time-averaged and forms through the aggregation of repeated behavioural events over time. Thus, archaeological patterns do not reflect discrete episodes of activity, but rather the interaction of behaviour with environmental factors over time. However, little is known about how such interactions produce archaeological variation diversity. Primate archaeology can help address this research gap by providing the opportunity to observe how behaviour produces material patterns in a natural setting. This study, thus, examines how varying the material properties of stone and resource availability influence the artefactual signature of nut-cracking in a population of long-tailed macaques from Lobi Bay, Yao Noi island, Thailand. Results show that these interactions can produce a structured and diverse material signature in terms of artefact density and frequency of specific artefact types. These findings demonstrate how material patterns can emerge from long-term interactions between behaviour and environmental factors.

Simulation and social network analysis provide insight into the acquisition of tool behaviour in hybrid macaques.

The pathways through which primates acquire skills are a central focus of cultural evolution studies. The roles of social and genetic inheritance processes in skill acquisition are often confounded by environmental factors. Hybrid macaques from Koram Island (Thailand) provide an opportunity to examine the roles of inheritance and social learning to skill acquisition within a single ecological setting. These hybrids are a cross between tool-using Burmese long-tailed (Macaca fascicularis aurea) and non-tool-using common long-tailed macaques (Macaca fascicularis fascicularis). This population provides an opportunity to explore the roles of social learning and inheritance processes while being able to exclude underlying ecological factors. Here, we investigate the roles of social learning and inheritance in tool use prevalence within this population using social network analysis and simulation. Agent-based modelling (ABM) is used to generate expectations for how social/asocial learning and inheritance structure the patterning in a social network. The results of the simulation show that various transmission mechanisms can be differentiated based on associations between individuals in a social network. The results provide an investigative framework for discussing tool use transmission pathways in the Koram social network. By combining ABM, network analysis, and behavioural data from the field we can investigate the roles social learning and inheritance play in tool acquisition of wild primates.

Wild macaques challenge the origin of intentional tool production.

Intentionally produced sharp-edged stone flakes and flaked pieces are our primary evidence for the emergence of technology in our lineage. This evidence is used to decipher the earliest hominin behavior, cognition, and subsistence strategies. Here, we report on the largest lithic assemblage associated with a primate foraging behavior undertaken by long-tailed macaques (Macaca fascicularis). This behavior results in a landscape-wide record of flaked stone material, almost indistinguishable from early hominin flaked pieces and flakes. It is now clear that the production of unintentional conchoidal sharp-edged flakes can result from tool-assisted foraging in nonhominin primates. Comparisons with Plio-Pleistocene lithic assemblages, dating from 3.3 to 1.56 million years ago, show that flakes produced by macaques fall within the technological range of artifacts made by early hominins. In the absence of behavioral observations, the assemblage produced by monkeys would likely be identified as anthropogenic in origin and interpreted as evidence of intentional tool production.

Expanded geographic distribution and dietary strategies of the earliest Oldowan hominins and Paranthropus.

The oldest Oldowan tool sites, from around 2.6 million years ago, have previously been confined to Ethiopia's Afar Triangle. We describe sites at Nyayanga, Kenya, dated to 3.032 to 2.581 million years ago and expand this distribution by over 1300 kilometers. Furthermore, we found two hippopotamid butchery sites associated with mosaic vegetation and a C4 grazer-dominated fauna. Tool flaking proficiency was comparable with that of younger Oldowan assemblages, but pounding activities were more common. Tool use-wear and bone damage indicate plant and animal tissue processing. Paranthropus sp. teeth, the first from southwestern Kenya, possessed carbon isotopic values indicative of a diet rich in C4 foods. We argue that the earliest Oldowan was more widespread than previously known, used to process diverse foods including megafauna, and associated with Paranthropus from its onset.

Identifying functional and regional differences in chimpanzee stone tool technology.

The earliest hominin archaeological sites preserve a record of stone tools used for cutting and pounding. Traditionally, sharp-edged flakes were seen as the primary means by which our earliest ancestors interacted with the world. The importance of pounding tools is increasingly apparent. In some cases, they have been compared with stone hammers and anvils used by chimpanzees for nut-cracking. However, there has been little focus on providing a robust descriptive and quantitative characterization of chimpanzee stone tools, allowing for meaningful comparisons between chimpanzee groups and with archaeological artefacts. Here we apply a primate archaeological approach to characterize the range of chimpanzee nut-cracking stone tools from Djouroutou in the Taï National Park. By combining a techno-typological analysis, and two- and three-dimensional measures of damage, we identify clear differences in the location and extent of damage between nut-cracking hammerstones and anvils used at Djouroutou and when compared with other wild chimpanzee populations. Furthermore, we discuss these results in relation to interpretations of Plio-Pleistocene percussive technology. We highlight potential difficulties in identifying the underlying function of percussive artefacts based on morphological or techno-typological attributes alone. The material record from Djouroutou represents an important new datum of chimpanzee regional and material culture.

Early knapping techniques do not necessitate cultural transmission.

Early stone tool production, or knapping, techniques are claimed to be the earliest evidence for cultural transmission in the human lineage. Previous experimental studies have trained human participants to knap in conditions involving opportunities for cultural transmission. Subsequent knapping was then interpreted as evidence for a necessity of the provided cultural transmission opportunities for these techniques. However, a valid necessity claim requires showing that individual learning alone cannot lead to early knapping techniques. Here, we tested human participants (N = 28) in cultural isolation for the individual learning of early knapping techniques by providing them with relevant raw materials and a puzzle task as motivation. Twenty-five participants were technique naïve according to posttest questionnaires, yet they individually learned early knapping techniques, therewith producing and using core and flake tools. Early knapping techniques thus do not necessitate cultural transmission of know-how and could likewise have been individually derived among premodern hominins.

Modeling a primate technological niche.

The ability to modify the environment through the transport of tools has been instrumental in shaping the evolutionary success of humans. Understanding the cause-and-effect relationships between hominin behavior and the environment ultimately requires understanding of how the archaeological record forms. Observations of living primates can shed light on these interactions by investigating how tool-use behaviors produce a material record within specific environmental contexts. However, this requires reconciling data derived from primate behavioral observations with the time-averaged nature of the Plio-Pleistocene archaeological record. Here, we use an agent-based model to investigate how repeated short-distance transport events, characteristic for primate tool use, can result in significant landscape-scale patterning of material culture over time. Our results illustrate the conditions under which accumulated short-distance transport bouts can displace stone tools over long distances. We show that this widespread redistribution of tools can also increase access to tool require resources over time. As such, these results elucidate the niche construction processes associated with this pattern of tool transport. Finally, the structure of the subsequent material record largely depends on the interaction between tool transport and environmental conditions over time. Though these results have implications for inferring hominin tool transports from hominin archaeological assemblages. Furthermore, they highlight the difficulties with connecting specific behavioral processes with the patterning in the archaeological record.

Three-dimensional surface morphometry differentiates behaviour on primate percussive stone tools.

The Early Stone Age record preserves a rich behavioural signature of hominin stone tool making and use. The role of percussive technology in the daily subsistence strategies of our earliest ancestors has seen renewed focus recently. Studies of modern primate tool use highlight the diverse range of behaviours potentially associated with percussive technology. This has prompted significant methodological developments to characterize the associated damage marks (use-wear) on hammerstones and anvils. Little focus has, however, been paid to identifying whether these techniques can successfully differentiate between the damage patterns produced by specific and differing percussive behaviours. Here, we present a novel workflow drawing on the strengths of visual identification and three-dimensional (3D) surface quantification of use-wear. We apply this methodology firstly to characterize macaque percussive use-wear and test the efficacy of 3D surface quantification techniques in differentiating between percussive damage and natural surface topography. Secondly, we use this method to differentiate between use-wear associated with various wild macaque percussive behaviours. By combining analyst-directed, 3D surface analysis and use-wear dimensional analysis, we show that macaque percussive behaviours create specific diagnostic signatures and highlight a means of quantifiably recording such behavioural signatures in both primate and hominin contexts.

Ecological perspectives on technological diversity at Kanjera South.

The aspects of hominin behavior responsible for Oldowan stone tool variation are the focus of much debate. There is some consensus that this variation arises from a combination of ecological and cultural factors. The diversity of raw material types and technological strategies present at Kanjera South, Kenya, provide an opportunity to examine the interacting influences of ecology and culture on Oldowan stone tool variation. Here, we combine previous analyses of raw material properties, provenance, and technology with quantitative measures of core reduction intensity and tool utilization to examine the influence of both ecological and technocultural factors on stone tool variation at Kanjera South. The results of this analysis reflect a dynamic relationship between raw material properties, provenance, and hominin mobility. Exotic raw materials are generally more resistant to edge attrition compared with those available locally, which may have incentivized their transport over long distances and more extensive reduction. Cores produced on raw materials from distant sources also exhibit more complex core reduction strategies than locally acquired materials. While this pattern is partially due to the differences in the quality of knappable stone, bifacial centripetal and multifacial core reduction strategies also arise due to the continuous transport and use of exotic raw materials. Moreover, the variation in stone tool reduction is not consistent with neutral models of stone tool transport and discard. These results demonstrate that ecological factors such as raw material provenance and physical properties have strong impacts on reduction intensity and the technological strategies used by hominins.

Comparative isotopic evidence from East Turkana supports a dietary shift within the genus Homo.

It has been suggested that a shift in diet is one of the key adaptations that distinguishes the genus Homo from earlier hominins, but recent stable isotopic analyses of fossils attributed to Homo in the Turkana Basin show an increase in the consumption of C4 resources circa 1.65 million years ago, significantly after the earliest evidence for Homo in the eastern African fossil record. These data are consistent with ingesting more C4 plants, more animal tissues of C4 herbivores, or both, but it is also possible that this change reflects factors unrelated to changes in the palaeobiology of the genus Homo. Here we use new and published carbon and oxygen isotopic data (n = 999) taken from large-bodied fossil mammals, and pedogenic carbonates in fossil soils, from East Turkana in northern Kenya to investigate the context of this change in the isotope signal within Homo. By targeting taxa and temporal intervals unrepresented or undersampled in previous analyses, we were able to conduct the first comprehensive analysis of the ecological context of hominin diet at East Turkana during a period crucial for detecting any dietary and related behavioural differences between early Homo (H. habilis and/or H. rudolfensis) and Homo erectus. Our analyses suggest that the genus Homo underwent a dietary shift (as indicated by δ13Cena and δ18Oena values) that is (1) unrelated to changes in the East Turkana vegetation community and (2) unlike patterns found in other East Turkana large mammals, including Paranthropus and Theropithecus. These data suggest that within the Turkana Basin a dietary shift occurred well after we see the first evidence of early Homo in the region.

Earliest known Oldowan artifacts at >2.58 Ma from Ledi-Geraru, Ethiopia, highlight early technological diversity.

The manufacture of flaked stone artifacts represents a major milestone in the technology of the human lineage. Although the earliest production of primitive stone tools, predating the genus Homo and emphasizing percussive activities, has been reported at 3.3 million years ago (Ma) from Lomekwi, Kenya, the systematic production of sharp-edged stone tools is unknown before the 2.58-2.55 Ma Oldowan assemblages from Gona, Ethiopia. The organized production of Oldowan stone artifacts is part of a suite of characteristics that is often associated with the adaptive grade shift linked to the genus Homo Recent discoveries from Ledi-Geraru (LG), Ethiopia, place the first occurrence of Homo ∼250 thousand years earlier than the Oldowan at Gona. Here, we describe a substantial assemblage of systematically flaked stone tools excavated in situ from a stratigraphically constrained context [Bokol Dora 1, (BD 1) hereafter] at LG bracketed between 2.61 and 2.58 Ma. Although perhaps more primitive in some respects, quantitative analysis suggests the BD 1 assemblage fits more closely with the variability previously described for the Oldowan than with the earlier Lomekwian or with stone tools produced by modern nonhuman primates. These differences suggest that hominin technology is distinctly different from generalized tool use that may be a shared feature of much of the primate lineage. The BD 1 assemblage, near the origin of our genus, provides a link between behavioral adaptations-in the form of flaked stone artifacts-and the biological evolution of our ancestors.

Pleistocene animal communities of a 1.5 million-year-old lake margin grassland and their relationship to Homo erectus paleoecology.

The ecological and selective forces that sparked the emergence of Homo's adaptive strategy remain poorly understood. New fossil and archaeological finds call into question previous interpretations of the grade shift that drove our ancestors' evolutionary split from the australopiths. Furthermore, issues of taphonomy and scale have limited reconstructions of the hominin habitats and faunal communities that define the environmental context of these behavioral changes. The multiple ∼1.5 Ma track surfaces from the Okote Member of the Koobi Fora Formation at East Turkana provide unique windows for examining hominin interactions with the paleoenvironment and associated faunas at high spatiotemporal resolution. These surfaces preserve the tracks of many animals, including cf. Homo erectus. Here, we examine the structure of the animal community that inhabited this landscape, considering effects of preservation bias by comparing the composition of the track assemblage to a skeletal assemblage from the same time and place. We find that the track and skeletal assemblages are similar in their representation of the vertebrate paleocommunity, with comparable levels of taxonomic richness and diversity. Evenness (equitability of the number of individuals per taxon) differs between the two assemblages due to the very different circumstances of body fossil versus track preservation. Both samples represent diverse groups of taxa including numerous water-dependent species, consistent with geological interpretations of the track site environments. Comparisons of these assemblages also show a pattern of non-random hominin association with a marginal lacustrine habitat relative to other vertebrates in the track assemblage. This evidence is consistent with behavior that included access to aquatic foods and possibly hunting by H. erectus in lake margins/edaphic grasslands. Such behaviors may signal the emergence of the adaptative strategies that define our genus.

Pleistocene footprints show intensive use of lake margin habitats by Homo erectus groups.

Reconstructing hominin paleoecology is critical for understanding our ancestors' diets, social organizations and interactions with other animals. Most paleoecological models lack fine-scale resolution due to fossil hominin scarcity and the time-averaged accumulation of faunal assemblages. Here we present data from 481 fossil tracks from northwestern Kenya, including 97 hominin footprints attributed to Homo erectus. These tracks are found in multiple sedimentary layers spanning approximately 20 thousand years. Taphonomic experiments show that each of these trackways represents minutes to no more than a few days in the lives of the individuals moving across these paleolandscapes. The geology and associated vertebrate fauna place these tracks in a deltaic setting, near a lakeshore bordered by open grasslands. Hominin footprints are disproportionately abundant in this lake margin environment, relative to hominin skeletal fossil frequency in the same deposits. Accounting for preservation bias, this abundance of hominin footprints indicates repeated use of lakeshore habitats by Homo erectus. Clusters of very large prints moving in the same direction further suggest these hominins traversed this lakeshore in multi-male groups. Such reliance on near water environments, and possibly aquatic-linked foods, may have influenced hominin foraging behavior and migratory routes across and out of Africa.