3.3 million years of stone tool complexity suggests that cumulative culture began during the Middle Pleistocene

Cumulative culture, the accumulation of modifications, innovations, and improvements over generations through social learning, is a key determinant of the behavioral diversity across Homo sapiens populations and their ability to adapt to varied ecological habitats. Generations of improvements, modifications, and lucky errors allow humans to use technologies and know-how well beyond what a single naive individual could invent independently within their lifetime. The human dependence on cumulative culture may have shaped the evolution of biological and behavioral traits in the hominin lineage, including brain size, body size, life history, sociality, subsistence, and ecological niche expansion. Yet, we do not know when, in the human career, our ancestors began to depend on cumulative culture. Here, we show that hominins likely relied on a derived form of cumulative culture by at least ~600 kya, a result in line with a growing body of existing evidence. We analyzed the complexity of stone tool manufacturing sequences over the last 3.3 My of the archaeological record. We then compare these to the achievable complexity without cumulative culture, which we estimate using nonhuman primate technologies and stone tool manufacturing experiments. We find that archaeological technologies become significantly more complex than expected in the absence of cumulative culture only after ~600 kya.

Identification and quantification of projectile impact marks on bone: new experimental insights using osseous points

Shifts in projectile technology potentially document human evolutionary milestones, such as adaptations for different environments and settlement dynamics. A relatively direct proxy for projectile technology is projectile impact marks (PIM) on archaeological bones. Increasing awareness and publication of experimental data sets have recently led to more identifications of PIM in various contexts, but diagnosing PIM from other types of bone-surface modifications, quantifying them, and inferring point size and material from the bone lesions need more substantiation. Here, we focus on PIM created by osseous projectiles, asking whether these could be effectively identified and separated from lithic-tipped weapons. We further discuss the basic question raised by recent PIM research in zooarchaeology: why PIM evidence is so rare in archaeofaunal assemblages (compared to other human-induced marks), even when they are explicitly sought. We present the experimental results of shooting two ungulate carcasses with bone and antler points, replicating those used in the early Upper Paleolithic of western Eurasia. Half of our hits resulted in PIM, confirming that this modification may have been originally abundant. However, we found that the probability of a skeletal element to be modified with PIM negatively correlates with its preservation potential, and that much of the produced bone damage would not be identifiable in a typical Paleolithic faunal assemblage. This quantification problem still leaves room for an insightful qualitative study of PIM. We complement previous research in presenting several diagnostic marks that retain preservation potential and may be used to suggest osseous, rather than lithic, projectile technology.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12520-024-01944-3.

Late Acheulean occupations at Montagu Cave and the pattern of Middle Pleistocene behavioral change in Western Cape, southern Africa

Patterns of so-called modern human behavior are increasingly well documented in an abundance of Middle Stone Age archaeological sites across southern Africa. Contextualized archives directly preceding the southern African Middle Stone Age, however, remain scarce. Current understanding of the terminal Acheulean in southern Africa derives from a small number of localities that are predominantly in the central and northern interior. Many of these localities are surface and deflated contexts, others were excavated prior to the availability of modern field documentation techniques, and yet other relevant assemblages contain low numbers of characteristic artifacts relative to volume of excavated deposit. The site of Montagu Cave, situated in the diverse ecosystem of the Cape Floral Region, South Africa, contains the rare combination of archaeologically rich, laminated and deeply stratified Acheulean layers followed by a younger Middle Stone Age occupation. Yet little is known about the site owing largely to a lack of contextual information associated with the early excavations. Here we present renewed excavation of Levels 21-22 at Montagu Cave, located in the basal Acheulean sequence, including new data on site formation and ecological context, geochronology, and technological variability. We document intensive occupation of the cave by Acheulean tool-producing hominins, likely at the onset of interglacial conditions in MIS 7. New excavations at Montagu Cave suggest that, while Middle Stone Age technologies were practiced by 300 ka in several other regions of Africa, the classic Acheulean persisted later in the Fynbos Biome of the southwestern Cape. We discuss the implications of this regionalized persistence for the biogeography of African later Middle Pleistocene hominin populations, for the ecological drivers of their technological systems, and for the pattern and pace of behavioral change just prior to the proliferation of the southern African later Middle Stone Age.

Terminal ballistic analysis of impact fractures reveals the use of spearthrower 31 ky ago at Maisières-Canal, Belgium

The emergence of hunting technology in the deep past fundamentally shaped the subsistence strategies of early human populations. Hence knowing when different weapons were first introduced is important for understanding our evolutionary trajectory. The timing of the adoption of long-range weaponry remains heavily debated because preserved organic weapon components are extremely rare in the Paleolithic record and stone points are difficult to attribute reliably to weapon delivery methods without supporting organic evidence. Here, we use a refined use-wear approach to demonstrate that spearthrower was used for launching projectiles armed with tanged flint points at Maisières-Canal (Belgium) 31,000 years ago. The novelty of our approach lies in the combination of impact fracture data with terminal ballistic analysis of the mechanical stress suffered by a stone armature on impact. This stress is distinct for each weapon and visible archaeologically as fracture proportions on assemblage scale. Our reference dataset derives from a sequential experimental program that addressed individually each key parameter affecting fracture formation and successfully reproduced the archaeological fracture signal. The close match between the archaeological sample and the experimental spearthrower set extends the timeline of spearthrower use by over 10,000 years and represents the earliest reliable trace-based evidence for the utilization of long-distance weaponry in prehistoric hunting.

Hafted technologies likely reduced stone tool-related selective pressures acting on the hominin hand

The evolution of the hominin hand has been widely linked to the use and production of flaked stone tool technologies. After the earliest handheld flake tools emerged, shifts in hominin hand anatomy allowing for greater force during precision gripping and ease when manipulating objects in-hand are observed in the fossil record. Previous research has demonstrated how biometric traits, such as hand and digit lengths and precision grip strength, impact functional performance and ergonomic relationships when using flake and core technologies. These studies are consistent with the idea that evolutionary selective pressures would have favoured individuals better able to efficiently and effectively produce and use flaked stone tools. After the advent of composite technologies during the Middle Stone Age and Middle Palaeolithic, fossil evidence reveals differences in hand anatomy between populations, but there is minimal evidence for an increase in precision gripping capabilities. Furthermore, there is little research investigating the selective pressures, if any, impacting manual anatomy after the introduction of hafted composite stone technologies ('handles'). Here we investigated the possible influence of tool-user biometric variation on the functional performance of 420 hafted Clovis knife replicas. Our results suggest there to be no statistical relationships between biometric variables and cutting performance. Therefore, we argue that the advent of hafted stone technologies may have acted as a 'performance equaliser' within populations and removed (or reduced) selective pressures favouring forceful precision gripping capabilities, which in turn could have increased the relative importance of cultural evolutionary selective pressures in the determination of a stone tool's performance.

Atlatl use equalizes female and male projectile weapon velocity

The atlatl is a handheld, rod-shaped device that employs leverage to launch a dart, and represents a major human technological innovation. One hypothesis for forager atlatl adoption over its presumed predecessor, the thrown javelin, is that a diverse array of people could achieve equal performance results, thereby facilitating inclusive participation of more people in hunting activities. We tested this hypothesis via a systematic assessment of 2160 weapon launch events by 108 people who used both technologies. Our results show that, unlike the javelin, the atlatl equalizes the velocity of female- and male-launched projectiles. This result indicates that a javelin to atlatl transition would have promoted a unification, rather than division, of labor. Moreover, our results suggest that female and male interments with atlatl weaponry should be interpreted similarly.

The revolution that still isn't: The origins of behavioral complexity in Homo sapiens

The behavioral origins of Homo sapiens can be traced back to the first material culture produced by our species in Africa, the Middle Stone Age (MSA). Beyond this broad consensus, the origins, patterns, and causes of behavioral complexity in modern humans remain debated. Here, we consider whether recent findings continue to support popular scenarios of: (1) a modern human 'package,' (2) a gradual and 'pan-African' emergence of behavioral complexity, and (3) a direct connection to changes in the human brain. Our geographically structured review shows that decades of scientific research have continuously failed to find a discrete threshold for a complete 'modernity package' and that the concept is theoretically obsolete. Instead of a continent-wide, gradual accumulation of complex material culture, the record exhibits a predominantly asynchronous presence and duration of many innovations across different regions of Africa. The emerging pattern of behavioral complexity from the MSA conforms to an intricate mosaic characterized by spatially discrete, temporally variable, and historically contingent trajectories. This archaeological record bears no direct relation to a simplistic shift in the human brain but rather reflects similar cognitive capacities that are variably manifested. The interaction of multiple causal factors constitutes the most parsimonious explanation driving the variable expression of complex behaviors, with demographic processes such as population structure, size, and connectivity playing a key role. While much emphasis has been given to innovation and variability in the MSA record, long periods of stasis and a lack of cumulative developments argue further against a strictly gradualistic nature in the record. Instead, we are confronted with humanity's deep, variegated roots in Africa, and a dynamic metapopulation that took many millennia to reach the critical mass capable of producing the ratchet effect commonly used to define contemporary human culture. Finally, we note a weakening link between 'modern' human biology and behavior from around 300 ka ago.

The Use of Wooden Clubs and Throwing Sticks among Recent Foragers : Cross-Cultural Survey and Implications for Research on Prehistoric Weaponry

There is a popular idea that archaic humans commonly used wooden clubs as their weapons. This is not based on archaeological finds, which are minimal from the Pleistocene, but rather on a few ethnographic analogies and the association of these weapons with simple technology. This article presents the first quantitative cross-cultural analysis of the use of wooden clubs and throwing sticks for hunting and violence among foragers. Using a sample of 57 recent hunting-gathering societies from the Standard Cross-Cultural Sample, it is shown that the majority used clubs for violence (86%) and/or hunting (74%). Whereas in hunting and fishing the club usually served only as a secondary tool, 33% of societies used the club as one of their main fighting weapons. The use of throwing sticks was less frequent among the societies surveyed (12% for violence, 14% for hunting). Based on these results and other evidence, it is argued that the use of clubs by early humans was highly probable, at least in the simplest form of a crude stick. The great variation in the forms and use of clubs and throwing sticks among recent hunter-gatherers, however, indicates that they are not standardized weapons and that similar variation may have existed in the past. Many such prehistoric weapons may therefore have been quite sophisticated, multifunctional, and carried strong symbolic meaning.

Archaeological evidence for thinking about possibilities in hominin evolution

The emergence of the ability to think about future possibilities must have played an influential role in human evolution, driving a range of foresightful behaviours, including preparation, communication and technological innovation. Here we review the archeological evidence for such behavioural indicators of foresight. We find the earliest signs of hominins retaining tools and transporting materials for repeated future use emerging from around 1.8 Ma. From about 0.5 Ma onwards, there are indications of technical and social changes reflecting advances in foresight. And in a third period, starting from around 140 000 years ago, hominins appear to have increasingly relied on material culture to shape the future and to exchange their ideas about possibilities. Visible signs of storytelling, even about entirely fictional scenarios, appear over the last 50 000 years. Although the current evidence suggests that there were distinct transitions in the evolution of our capacity to think about the future, we warn that issues of taphonomy and archaeological sampling are likely to skew our picture of human cognitive evolution. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.

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'.

A biomechanical investigation of the efficiency hypothesis of hafted tool technology

The transition from hand-held to hafted tool technology marked a significant shift in conceptualizing the construction and function of tools. Among other benefits, hafting is thought to have given users a significant biomechanical and physiological advantage in undertaking basic subsistence tasks compared with hand-held tools. It is assumed that addition of a handle improved the (bio)mechanical properties of a tool and upper limb by offering greater amounts of leverage, force and precision. This controlled laboratory study compares upper limb kinematics, electromyography and physiological performance during two subsistence tasks (chopping, scraping) using hafted and hand-held tools. Results show that hafted tool use elicits greater ranges of motion, greater muscle activity and greater net energy expenditure (EE) compared with hand-held equivalents. Importantly, however, these strategies resulted in reduced relative EE compared with the hand-held condition in both tasks. More specifically, the hafted axe prompted use of two well-known biomechanical strategies that help produce larger velocities at the distal end of the limb without requiring heavy muscular effort, thus improving the tool's functional efficiency and relative energy use. The energetic and biomechanical benefits of hafting arguably contributed to both the invention and spread of this technology.

The origins of human cumulative culture: from the foraging niche to collective intelligence

Various studies have investigated cognitive mechanisms underlying culture in humans and other great apes. However, the adaptive reasons for the evolution of uniquely sophisticated cumulative culture in our species remain unclear. We propose that the cultural capabilities of humans are the evolutionary result of a stepwise transition from the ape-like lifestyle of earlier hominins to the foraging niche still observed in extant hunter-gatherers. Recent ethnographic, archaeological and genetic studies have provided compelling evidence that the components of the foraging niche (social egalitarianism, sexual and social division of labour, extensive co-residence and cooperation with unrelated individuals, multilocality, fluid sociality and high between-camp mobility) engendered a unique multilevel social structure where the cognitive mechanisms underlying cultural evolution (high-fidelity transmission, innovation, teaching, recombination, ratcheting) evolved as adaptations. Therefore, multilevel sociality underlies a 'social ratchet' or irreversible task specialization splitting the burden of cultural knowledge across individuals, which may explain why human collective intelligence is uniquely able to produce sophisticated cumulative culture. The foraging niche perspective may explain why a complex gene-culture dual inheritance system evolved uniquely in humans and interprets the cultural, morphological and genetic origins of Homo sapiens as a process of recombination of innovations appearing in differentiated but interconnected populations. This article is part of a discussion meeting issue 'The emergence of collective knowledge and cumulative culture in animals, humans and machines'.

Shared intentionality, reason-giving and the evolution of human culture

The biological approach to culture focuses almost exclusively on processes of social learning, to the neglect of processes of cultural coordination including joint action and shared intentionality. In this paper, we argue that the distinctive features of human culture derive from humans' unique skills and motivations for coordinating with one another around different types of action and information. As different levels of these skills of 'shared intentionality' emerged over the last several hundred thousand years, human culture became characterized first by such things as collaborative activities and pedagogy based on cooperative communication, and then by such things as collaborative innovations and normatively structured pedagogy. As a kind of capstone of this trajectory, humans began to coordinate not just on joint actions and shared beliefs, but on the reasons for what we believe or how we act. Coordinating on reasons powered the kinds of extremely rapid innovation and stable cumulative cultural evolution especially characteristic of the human species in the last several tens of thousands of years. This article is part of a discussion meeting issue 'The emergence of collective knowledge and cumulative culture in animals, humans and machines'.

Homo sapiens origins and evolution in the Kalahari Basin, southern Africa

The Kalahari Basin, southern Africa preserves a rich archeological record of human origins and evolution spanning the Early, Middle and Late Pleistocene. Since the 1930s, several stratified and dated archeological sites have been identified and investigated, together with numerous open-air localities that provide landscape-scale perspectives. However, next to recent discoveries from nearby coastal regions, the Kalahari Basin has remained peripheral to debates about the origins of Homo sapiens. Though the interior region of southern Africa is generally considered to be less suitable for hunter-gatherer occupation than coastal and near-coastal regions, especially during glacial periods, the archeological record documents human presence in the Kalahari Basin from the Early Pleistocene onwards, and the region is not abandoned during glacial phases. Furthermore, many significant behavioral innovations have an early origin in the Kalahari Basin, which adds support to poly-centric, pan-African models for the emergence of our species.

Did Pleistocene Africans use the spearthrower-and-dart?

Archeologists commonly suppose that among complex projectile weapons humans use as subsistence aids, the spearthrower-and-dart preceded bow-and-arrow use. And yet, neither ethnographic nor archeological records furnish any robust evidence for spearthrower-and-dart use in Africa. Instead, evidence grows apace for ever-more ancient bow-and-arrow use. Here we explore these findings and their implications for models of early Homo sapiens behavior.

Foragers and Their Tools: Risk, Technology and Complexity

The subsistence technology of forager communities has varied greatly over space and time. This paper (i) reviews briefly the main causal factors the literature identifies as responsible for this variation; (ii) analyzes in some detail the most prominent idea in the literature on spatial variation:Complex technology is an adaptive response to elevated risks of subsistence failure; (iii) it argues that the alleged empirical support for this hypothesis depends on dubious proxies of risk; (iv) it argues that it fails to explain the subsistence technologies of desert foragers, who generally live with simple technologies in high-risk environments; (v) it offers an alternative analysis, based on the reduced opportunity costs of complex technologies in highly seasonal environments, on the high value of typical forager targets in those environments and their relatively predictable location in space and time; and (v) the paper concludes with a conjecture about the role of environmental variation in toolkit change over deep time.

Causal Reasoning and Event Cognition as Evolutionary Determinants of Language Structure

The aim of this article is to provide an evolutionarily grounded explanation of central aspects of the structure of language. It begins with an account of the evolution of human causal reasoning. A comparison between humans and non-human primates suggests that human causal cognition is based on reasoning about the underlying forces that are involved in events, while other primates hardly understand external forces. This is illustrated by an analysis of the causal cognition required for early hominin tool use. Second, the thinking concerning forces in causation is used to motivate a model of human event cognition. A mental representation of an event contains two vectors representing a cause as well as a result but also entities such as agents, patients, instruments and locations. The fundamental connection between event representations and language is that declarative sentences express events (or states). The event structure also explains why sentences are constituted of noun phrases and verb phrases. Finally, the components of the event representation show up in language, where causes and effects are expressed by verbs, agents and patients by nouns (modified by adjectives), locations by prepositions, etc. Thus, the evolution of the complexity of mental event representations also provides insight into the evolution of the structure of language.

Exploring variability in lithic armature discard in the archaeological record

The invention of projectile technology had important ramifications for hominin evolution. However, the number of stone points that could have been used as projectiles fluctuates in archaeological assemblages, making it difficult to define when projectile technology was first widely adopted and how its usage changed over time. Here we use an agent-based model to simulate a hunter-gatherer foraging system where armatures are dropped according to their usage. We explore the impact of interactions between human behaviors and the environmental constraints of a data-informed landscape on the distribution and number of lithic armatures found in archaeological assemblages. We ran 2400 simulations modeling different population sizes, rates of hunting with projectiles, and tool curation levels. For each simulation, we recorded the location of dropped armatures and calculated the number and percentage of used armatures that were discarded at habitation camps vs. lost during hunting. We used linear regression to identify the demographic, behavioral, and environmental factor(s) that best explained changes in these numbers and percentages. The model results show that in a well-controlled environment, most armatures used as projectile weapons are lost or discarded at hunting sites; only ∼4.5% of used armatures (or ∼2 armatures per year of simulation) are discarded in habitation camps where they would likely be excavated. These findings suggest that even rare hafted armatures found in the Early and Middle Stone Age could indicate a well-established use of such tools. Our model shows that interactions between reoccupation of archaeological sites, population size, rate of hunting with projectile weapons, and tool curation levels strongly influence the count of lithic armatures found in archaeological assemblages. Therefore, we argue that fluctuations in the counts of armatures documented at archaeological sites should be evaluated within their demographic and environmental contexts to better understand if they reflect spatiotemporal changes in hunting behavior.

Complexity and sophistication of Early Middle Paleolithic flint tools revealed through use-wear analysis of tools from Misliya Cave, Mount Carmel, Israel

The Early Middle Paleolithic (EMP) is a less-studied phase of the Levantine Middle Paleolithic, attributable to the small number of sites discovered. Drawing on the dense archaeological accumulations at Misliya Cave, Mount Carmel, Israel, the present study seeks to trace EMP daily activities and behavioral patterns through the prism of use-wear analysis. The emergence of the laminar and Levallois technologies that form the EMP toolkit is investigated to reveal other dimensions of tool novelties. Through microscopic analyses, integrated with experimentation, the most outstanding aspect revealed in this study is the extensive evidence of hafting, which included the use of binding together with various techniques for tool design. A unique treatment was identified, never reported before, entailing the abrasion of cortical surfaces and protruding dorsal ridges. Other aspects include the clear preference for pointed tools as a leading morphological trend and the use of retouch as a mean to create durable working edges and facilitate grip arrangements. The analysis demonstrates the venue of use-wear to trace a wide variety of practices, including consumption-related (processing hunted game and edible plants) and craft-related (hide processing, woodworking, and perhaps stone working) activities that otherwise hardly leave a trace in the archaeological record. By exploring these features, the research provides important insights into early hominin behavior and way of life during the EMP, emphasizing the novelties brought by the earliest Homo sapiens out of Africa.

A West African Middle Stone Age site dated to the beginning of MIS 5: Archaeology, chronology, and paleoenvironment of the Ravin Blanc I (eastern Senegal)

The Ravin Blanc I archaeological occurrence, dated to MIS 5, provides unprecedented data on the Middle Stone Age (MSA) of West Africa since well-contextualized archaeological sites pre-dating MIS 4/3 are extremely rare for this region. The combined approach on geomorphology, phytolith analysis, and OSL date estimations offers a solid framework for the MSA industry comprised in the Ravin Blanc I sedimentary sequence. The paleoenvironmental reconstruction further emphasizes on the local effects of the global increase in moisture characterizing the beginning of the Upper Pleistocene as well as the later shift to more arid conditions. The lithic industry, comprised in the lower part of the sequence and dated to MIS 5e, shows core reduction sequences among which Levallois methods are minor, as well as an original tool-kit composition, among which pieces with single wide abrupt notches, side-scrapers made by inverse retouch, and a few large crudely shaped bifacial tools. The Ravin Blanc I assemblage has neither a chronologically equivalent site to serve comparisons nor a clear techno-typological correspondent in West Africa. However, the industry represents an early MSA technology that could either retain influences from the southern West African 'Sangoan' or show reminiscences of the preceding local Acheulean. A larger-scale assessment of behavioral dynamics at work at the transition period between the Middle to Upper Pleistocene is discussed in view of integrating this new site to the global perception of this important period in the MSA evolutionary trajectories.

The ripples of modernity: How we can extend paleoanthropology with the extended evolutionary synthesis

Contemporary understandings of paleoanthropological data illustrate that the search for a line defining, or a specific point designating, "modern human" is problematic. Here we lend support to the argument for the need to look for patterns in the paleoanthropological record that indicate how multiple evolutionary processes intersected to form the human niche, a concept critical to assessing the development and processes involved in the emergence of a contemporary human phenotype. We suggest that incorporating key elements of the Extended Evolutionary Synthesis (EES) into our endeavors offers a better and more integrative toolkit for modeling and assessing the evolution of the genus Homo. To illustrate our points, we highlight how aspects of the genetic exchanges, morphology, and material culture of the later Pleistocene complicate the concept of "modern" human behavior and suggest that multiple evolutionary patterns, processes, and pathways intersected to form the human niche.

Carrying capacity, population density and the later Pleistocene expression of backed artefact manufacturing traditions in Africa

As is the case today, both climate variability and population density influenced human behavioural change in the past. The mechanisms underpinning later Pleistocene human behavioural evolution, however, remain contested. Many complex behaviours evolved in Africa, but early evidence for these behaviours varies both spatially and temporally. Scientists have not been able to explain this flickering pattern, which is present even in sites and regions clearly occupied by Homo sapiens. To explore this pattern, here the presence and frequency of evidence for backed stone artefact production are modelled against climate-driven, time-series population density estimates (Timmermann and Friedrich. 2016 Nature 538, 92. (doi:10.1038/nature19365)), in all known African Late Pleistocene archaeological sites (n = 116 sites, n = 409 assemblages, n = 893 dates). In addition, a moving-window, site density population estimate is included at the scale of southern Africa. Backed stone artefacts are argued in many archaeological contexts to have functioned in elaborate technologies like composite weapons and, in the African Pleistocene, are accepted proxies for cultural complexity. They show a broad but sporadic distribution in Africa, prior to their association with Homo sapiens dispersing into Europe 45-40 ka. Two independent population estimates explain this pattern and potentially implicate the interaction of climate change and demography in the expression of cultural complexity in African Pleistocene Homo sapiens. This article is part of the theme issue 'Cross-disciplinary approaches to prehistoric demography'.

Learner-driven innovation in the stone tool technology of early Homo sapiens

Current perspectives of stone tool technology tend to emphasize homogeneity in tool forms and core reduction strategies across time and space. This homogeneity is understood to represent shared cultural traditions that are passed down through the generations. This represents a top-down perspective on how and why stone tools are manufactured that largely restricts technological agency to experts, adults and teachers. However, just as bottom-up processes driven by children and youth influence technological innovation today, they are likely to have played a role in the past. This paper considers evidence from the archaeological record of early Homo sapiens' lithic technology in Africa that may attest to our long history of bottom-up social learning processes and learner-driven innovation. This evidence includes the role of emulative social learning in generating assemblages with diverse reduction strategies, a high degree of technological fragmentation across southern Africa during some time periods, and technological convergence through the Pleistocene. Counter to some perspectives on the uniqueness of our species, our ability to learn independently, to 'break the rules' and to play, as opposed to conforming to top-down influences, may also account for our technological success.

Versatile use of microliths as a technological advantage in the miniaturization of Late Pleistocene toolkits: The case study of Neve David, Israel

The miniaturization of stone tools, as reflected through the systematic production of bladelets and bladelet tools (microliths), characterized many industries of the Late Pleistocene, with the Levantine Epipalaeolithic serving as a well-studied example. It is commonly held that microliths were used as modular inserts in composite projectiles, while their incorporation in other tools for different tasks is generally overlooked, the latter aspect being the main focus of this paper. We present here a more inclusive approach through a case study of the Geometric Kebaran (Middle Epipalaeolithic, ca. 18,500–15,000 cal BP) site of Neve David, Mount Carmel, Israel. Recent excavations at the site exposed a variety of features, and one well-preserved shallow pit provided a large lithic assemblage with ca. 90 microliths. We studied this assemblage using both the low- and high- magnification use-wear protocols, accompanied by a range of experiments. Our results show that a) the fragmentation rate is very high in this assemblage (ca. 90%), b) most of the microliths have identifiable use-wear, c) the microliths were commonly used as inserts in composite projectiles, d) many microliths were used for functions not related to weaponry and hunting, such as wood-working, weed harvesting and meat processing. These findings strongly support the suggestion that the small insets, regardless of their specific type (trapeze, rectangle, backed/retouched bladelet), were used in a wide variety of composite tools. We argue that such a versatile approach and flexibility in the use of microliths reflect a technological advantage where a minimal set of microlithic types, produced in large numbers, could provide the required elements for weapons, as well as for a variety of cutting, processing and harvesting tools needed for mundane tasks at a large Middle Epipalaeolithic camp.

Innovation, life history and social networks in human evolution

There is a famous puzzle about the first 3 million years of archaeologically visible human technological history. The pace of change, of innovation and its uptake, is extraordinarily slow. In particular, the famous handaxes of the Acheulian technological tradition first appeared about 1.7 Ma, and persisted with little change until about 800 ka, perhaps even longer. In this paper, I will offer an explanation of that stasis based in the life history and network characteristics that we infer (on phylogenetic grounds) to have characterized earlier human species. The core ideas are that (i) especially in earlier periods of hominin evolution, we are likely to find archaeological traces only of widespread and persisting technologies and practices; (ii) the record is not a record of the rate of innovation, but the rate of innovations establishing in a landscape; (iii) innovations are extremely vulnerable to stochastic loss while confined to the communities in which they are made and established; (iv) the export of innovation from the local group is sharply constrained if there is a general pattern of hostility and suspicion between groups, or even if there is just little contact between adults of adjoining groups. That pattern is typical of great apes and likely, therefore, to have characterized at least early hominin social lives. Innovations are unlikely to spread by adult-to-adult interactions across community boundaries. (v) Chimpanzees and bonobos are characterized by male philopatry and subadult female dispersal; that is, therefore, the most likely early hominin pattern. If so, the only innovations at all likely to expand beyond the point of origin are those acquired by subadult females, and ones that can be expressed by those females, at high enough frequency and salience for them to spread, in the bands that the females join. These are very serious filters on the spread of innovation. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.

Early Levallois core technology between Marine Isotope Stage 12 and 9 in Western Europe

Early Levallois core technology is usually dated in Europe to the end of Marine Isotope Stage (MIS) 9 and particularly from the beginning of MIS 8 to MIS 6. This technology is considered as one of the markers of the transition from lower to Middle Paleolithic or from Mode 2 to Mode 3. Recent discoveries show that some lithic innovations actually appeared earlier in western Europe, from MIS 12 to MIS 9, contemporaneous with changes in subsistence strategies and the first appearance of early Neanderthal anatomical features. Among these discoveries, there is the iconic Levallois core technology. A selection of well-dated assemblages in the United Kingdom, France, and Italy dated from MIS 12 to 9, which include both cores and flakes with Levallois features, has been described and compared with the aim of characterizing this technology. The conclusion supports the interpretation that several technical features may be attributed to a Levallois technology similar to those observed in younger Middle Paleolithic sites, distinct from the main associated core technologies in each level. Some features in the sample of sites suggest a gradual transformation of existing core technologies. The small evidence of Levallois could indicate occasional local innovations from different technological backgrounds and would explain the diversity of Levallois methods that is observed from MIS 12. The technological roots of Levallois technology in the Middle Pleistocene would suggest a multiregional origin and diffusion in Europe and early evidence of regionalization of local traditions through Europe from MIS 12 to 9. The relationships of Levallois technology with new needs and behaviors are discussed, such as flake preference, functional reasons related to hunting and hafting, an increase in the use of mental templates in European populations, and changes in the structure of hominin groups adapting to climatic and environmental changes.

Understanding stone tool-making skill acquisition: Experimental methods and evolutionary implications

Despite its theoretical importance, the process of stone tool-making skill acquisition remains understudied and poorly understood. The challenges and costs of skill learning constitute an oft-neglected factor in the evaluation of alternative adaptive strategies and a potential source of bias in cultural transmission. Similarly, theory and data indicate that the most salient neural and cognitive demands of stone tool-making should occur during learning rather than expert performance. Unfortunately, the behavioral complexity and extensive learning requirements that make stone knapping skill acquisition an interesting object of study are the very features that make it so challenging to investigate experimentally. Here we present results from a multidisciplinary study of Late Acheulean handaxe-making skill acquisition involving twenty-six naïve participants and up to 90 hours training over several months, accompanied by a battery of psychometric, behavioral, and neuroimaging assessments. In this initial report, we derive a robust quantitative skill metric for the experimental handaxes using machine learning algorithms, reconstruct a group-level learning curve, and explore sources of individual variation in learning outcomes. Results identify particular cognitive targets of selection on the efficiency or reliability of tool-making skill acquisition, quantify learning costs, highlight the likely importance of social support, motivation, persistence, and self-control in knapping skill acquisition, and illustrate methods for reliably reconstructing ancient learning processes from archaeological evidence.

One size does not fit all: Group size and the late middle Pleistocene prehistoric archive

The role of demography is often suggested to be a key factor in both biological and cultural evolution. Recent research has shown that the linkage between population size and cultural evolution is not straightforward and emerges from the interplay of many demographic, economic, social and ecological variables. Formal modelling has yielded interesting insights into the complex relationship between population structure, intergroup connectedness, and magnitude and extent of population extinctions. Such studies have highlighted the importance of effective (as opposed to census) population size in transmission processes. At the same time, it remained unclear how such insights can be applied to material culture phenomena in the prehistoric record, especially for deeper prehistory. In this paper we approach the issue of population sizes during the time of the Lower to Middle Paleolithic transition through the proxy of regional trajectories of lithic technological change, identified in the archaeological records from Africa, the Levant, Southwestern and Northwestern Europe. Our discussion of the results takes into consideration the constraints inherent to the archaeological record of deep time - e.g., preservation bias, time-averaging and the incomplete nature of the archaeological record - and of extrapolation from discrete archaeological case studies to an evolutionary time scale. We suggest that technological trajectories of change over this transitional period reflect the robustness of transmission networks. Our results show differences in the pattern and rate of cultural transmission in these regions, from which we infer that information networks, and their underlying effective population sizes, also differed.

Zoon politikon: The evolutionary origins of human socio-political systems

We deploy the most up-to-date evidence available in various behavioral fields in support of the following hypothesis: The emergence of bipedalism and cooperative breeding in the hominin line, together with environmental developments that made a diet of meat from large animals adaptive, as well as cultural innovations in the form of fire, cooking, and lethal weapons, created a niche for hominins in which there was a significant advantage to individuals with the ability to communicate and persuade in a moral context. These forces added a unique political dimension to human social life which, through gene-culture coevolution, became Homo ludens-Man, the game player-with the power to conserve and transform the social order. Homo sapiens became, in the words of Aristotle's Nicomachean Ethics, a zoon politikon.

The origins and early elaboration of projectile technology

The ability of Homo sapiens to kill prey at a distance is arguably one of the catalysts for our current ecological dominance. Many researchers have suggested its origins lie in the African Middle Stone Age or the European Middle Palaeolithic (∼300-30 thousand years ago), but the perishable components of armatures rarely preserve. Most research on this subject therefore emphasises analysis of armature tip size, shape, and diagnostic impacts or residues. Other lines of evidence have included human skeletal anatomy or analyses of the species composition of faunal assemblages. Projectile Impact Marks (PIMs) on archaeofaunal remains offer an ideal complement to this work, but their potential has been restricted mainly to the later Eurasian zooarchaeological record. A review of current evidence and approaches shows that systematic PIM research could add much to our understanding of early projectile technology, especially in Africa.

Causal Cognition, Force Dynamics and Early Hunting Technologies

With this contribution we analyze ancient hunting technologies as one way to explore the development of causal cognition in the hominin lineage. Building on earlier work, we separate seven grades of causal thinking. By looking at variations in force dynamics as a central element in causal cognition, we analyze the thinking required for different hunting technologies such as stabbing spears, throwing spears, launching atlatl darts, shooting arrows with a bow, and the use of poisoned arrows. Our interpretation demonstrates that there is an interplay between the extension of human body through technology and expanding our cognitive abilities to reason about causes. It adds content and dimension to the trend of including embodied cognition in evolutionary studies and in the interpretation of the archeological record. Our method could explain variation in technology sets between archaic and modern human groups.

Sports and the human brain: an evolutionary perspective

An evolutionary perspective helps explain a conundrum faced by sports neurologists: why is the human brain dependent on physical activity to function optimally, yet simultaneously susceptible to harm from particular types of athletics? For millions of years, human bodies and brains co-evolved to meet the physical and cognitive demands of the uniquely human subsistence strategy of hunting and gathering. Natural selection favored bodies with adaptations for endurance-based physical activity patterns, whereas brains were selected to be big and powerful to navigate the complex cultural and ecologic landscapes of hunter-gatherers. Human brains require physical activity to function optimally because their physiology evolved among individuals who were rarely able to avoid regular physical activity. Moreover, because energy from food was limited, human brains, like most energetically costly physiologic systems, evolved to require stimuli from physical activity to adjust capacity to demand. Consequently, human brains are poorly adapted to excessive physical inactivity. In addition, while brain enlargement during human evolution was vital to successful hunting and gathering, it came at the cost of a decreased ability to withstand brain accelerations and decelerations, which commonly occur during contact/collision sports.

Technological complexity and the global dispersal of modern humans

Anatomically modern humans (Homo sapiens) dispersed out of Africa roughly 120,000 years ago and again after 75,000 years ago. The early dispersal was geographically restricted to the Arabian Peninsula, Levant, and possibly parts of southern Asia. The later dispersal was ultimately global in scope, including areas not previously occupied by Homo. One explanation for the contrast between the two out-of-Africa dispersals is that the modern humans who expanded into Eurasia 120,000 years ago lacked the functionally and structurally complex technology of recent hunter-gatherers. This technology, which includes, for example, mechanical projectiles, snares and traps, and sewn clothing, provides not only expanded dietary breadth and increased rates of foraging efficiency and success in places where plant and animal productivity is low, but protection from cold weather in places where winter temperatures are low. The absence of complex technology before 75,000 years ago also may explain why modern humans in the Levant did not develop sedentary settlements and agriculture 120,000 years ago (i.e., during the Last Interglacial).

Fitting handled objects into apertures by 17- to 36-month-old children: The dynamics of spatial coordination

Handled artifacts are ubiquitous in human technology, but how young children engage in spatially coordinated behaviors with these artifacts is not well understood. To address this issue, children (N = 30) from 17-36 months were studied with motion tracking technology as they fit the distal segment of a handled artifact into a slot. The handle was orthogonal to the distal segment. Results revealed developmental differences in prospective control tied to the artifact's spatial structure. Although all children accomplished fitting, younger children first oriented the handle and then the distal segment (and only after the distal segment contacted the slot), whereas children by 3 years of age oriented the handle and distal segment simultaneously in different spatial planes, prior to the distal segment contacting the slot. Choosing an effective grip posture proved difficult for all children. Results are discussed in terms of how children begin to relate their actions to the 3-dimensional spatial structure of handled objects and the prospective control of object movement in multiple spatial planes. (PsycINFO Database Record

Occasional, obligatory, and habitual stone tool use in hominin evolution

Archeologists have long assumed that earlier hominins were obligatory stone tool users. This assumption is deeply embedded in traditional ways of describing the lithic record. This paper argues that lithic evidence dating before 1.7 Ma reflects occasional stone tool use, much like that practiced by nonhuman primates except that it involved flaked-stone cutting tools. Evidence younger than 0.3 Ma is more congruent with obligatory stone tool use, like that among recent humans. The onset of habitual stone tool use at about 1.7 Ma appears correlated with increased hominin logistical mobility (carrying things). The onset of obligatory stone tool use after 0.3 Ma may be linked to the evolution of spoken language. Viewing the lithic evidence dating between 0.3-1.7 Ma as habitual stone tool use explains previously inexplicable aspects of the Early-Middle Pleistocene lithic record.

Evidence of a chimpanzee-sized ancestor of humans but a gibbon-sized ancestor of apes

Body mass directly affects how an animal relates to its environment and has a wide range of biological implications. However, little is known about the mass of the last common ancestor (LCA) of humans and chimpanzees, hominids (great apes and humans), or hominoids (all apes and humans), which is needed to evaluate numerous paleobiological hypotheses at and prior to the root of our lineage. Here we use phylogenetic comparative methods and data from primates including humans, fossil hominins, and a wide sample of fossil primates including Miocene apes from Africa, Europe, and Asia to test alternative hypotheses of body mass evolution. Our results suggest, contrary to previous suggestions, that the LCA of all hominoids lived in an environment that favored a gibbon-like size, but a series of selective regime shifts, possibly due to resource availability, led to a decrease and then increase in body mass in early hominins from a chimpanzee-sized LCA.The pattern of body size evolution in hominids can provide insight into historical human ecology. Here, Grabowski and Jungers use comparative phylogenetic analysis to reconstruct the likely size of the ancestor of humans and chimpanzees and the evolutionary history of selection on body size in primates.

The discovery of fire by humans: a long and convoluted process

Numbers of animal species react to the natural phenomenon of fire, but only humans have learnt to control it and to make it at will. Natural fires caused overwhelmingly by lightning are highly evident on many landscapes. Birds such as hawks, and some other predators, are alert to opportunities to catch animals including invertebrates disturbed by such fires and similar benefits are likely to underlie the first human involvements with fires. Early hominins would undoubtedly have been aware of such fires, as are savanna chimpanzees in the present. Rather than as an event, the discovery of fire use may be seen as a set of processes happening over the long term. Eventually, fire became embedded in human behaviour, so that it is involved in almost all advanced technologies. Fire has also influenced human biology, assisting in providing the high-quality diet which has fuelled the increase in brain size through the Pleistocene. Direct evidence of early fire in archaeology remains rare, but from 1.5 Ma onward surprising numbers of sites preserve some evidence of burnt material. By the Middle Pleistocene, recognizable hearths demonstrate a social and economic focus on many sites. The evidence of archaeological sites has to be evaluated against postulates of biological models such as the ‘cooking hypothesis' or the ‘social brain’, and questions of social cooperation and the origins of language. Although much remains to be worked out, it is plain that fire control has had a major impact in the course of human evolution.

This article is part of the themed issue ‘The interaction of fire and mankind’.