Our contribution provides an overview of Wilfrid Le Gros Clark's early life and career, his developing interest in human evolution, and how invitations from Robert Broom and Louis Leakey encouraged him to visit South Africa to see the southern African hominin fossil evidence at firsthand. That experience converted Le Gros Clark from being skeptical of Dart and Broom's interpretations to being one of their foremost supporters. Le Gros Clark's conversion resulted in a brief but heated dispute involving Solly Zuckerman that led to Le Gros Clark focusing on the interpretation of the early fossil evidence for human evolution for the rest of his career, while Zuckerman shifted his attention to science policy. The combination of Le Gros Clark's considerable reputation and his steadfast support were crucial elements in the development of paleoanthropology within Africa.
Despite recent advances pushing back the earliest record of tool use, how and when it first emerged in hominins, and the extent to which it featured amongst the numerous co-existing species, remain critical questions in paleoanthropology. In addition to analyzing fossils and lithic toolkits, novel strides in understanding this might be made by studying the skeletons of the great apes, as well as more distantly related tool-using primates and applying resultant findings to the fossil record via predictive modelling. We review current methods of extrapolating tool-use capabilities in extinct and extant taxa and provide an innovative methodological framework to analyze osteological remains for evidence of percussive tool use, using chimpanzees as a case study. We propose a shift in current methodological practice, wherein both sides of the body, rather than just one, should be routinely scanned to understand of the effect percussive tool use on primate bone. Key species, including long-tailed macaques (Macaca fascicularis ssp.), capuchins (Sapajus and Cebus sp.) and chimpanzees (Pan troglodytes ssp.), all of whom engage in lithic percussion, should be the work's focus. Due to bone's dynamic ability to respond to mechanical strain, percussive forms of tool use, like nut-cracking, could cause morphological changes in the dominant hands of tool users as compared to their non-dominant hand, or the hands of primates who do not engage in percussive behaviors. However, this potential "damage signature" has not been quantified. Thus, we propose a methodology for examining the effect of percussive tool use on primate bone by scanning skeletal remains bilaterally, analyzing directional asymmetry, and using machine learning to discern patterns of variation. Long-term, our proposed methodology may be extrapolated to examine the lasting impact of tool use on the bones of extinct hominins.
A comprehensive evolutionary account of human behavior demands simultaneous consideration of biology, local ecology, and culture. Historically, evolutionary anthropology integrated these dimensions through naturalistic observations which offered direct insight into how behaviors unfold within everyday settings. However, in many contemporary contexts, traditional observations are impractical due to challenges in accessing private spaces, contributing to the decline of such methods. While evolutionary anthropologists have gradually pivoted to experimentation and larger datasets, the contextual richness afforded by direct observation is not readily replaced by other approaches. In response, and in light of renewed interest in investigating mechanisms and methodological diversification, we introduce and reflect on autophotography-a visual method in which participants document aspects of their lives through photographs-as a pragmatic, quasi‑naturalistic observational tool for evolutionary anthropology. Within its limitations, this creative, participant‑led approach may help recover some strengths of naturalistic observation while adapting to contemporary field sites.
This paper reconceptualizes fashion as a deep-time system of bodily communication rather than a byproduct of modern consumer societies. We define fashion as a socially transmitted system of bodily display in which patterned variation occurs within shared conventions of appearance. Archaeologically, fashion becomes identifiable when recurring forms of body modification and ornamentation coexist with socially meaningful differences in their selection, combination, and arrangement. From this perspective, fashion emerged through the long-term culturalization of the human body, whereby appearance became an increasingly important medium for communicating identity, affiliation, status, and social relationships. Archaeological evidence suggests that this process began at least 400,000 years ago with pigment use, intensified with the emergence of personal ornaments, and developed into regionally differentiated systems of bodily display during the Upper Paleolithic, Neolithic, and Metal Ages. Drawing on archaeological, anthropological, and cognitive approaches, we interpret this trajectory as a cultural evolutionary process involving the generation of novel forms of bodily variation, their transmission through socially learned conventions, and their persistence, transformation, or disappearance under changing social and economic conditions. We argue that fashion functioned as an externalized social memory system that reduced cognitive demands by embedding social information in material form. In this sense, fashion emerged as a cultural technology that made social information increasingly visible, interpretable, and transmissible through bodily display.
Language is inherently relational, prompting comparative studies to prioritize social, gregarious, and voluble primates as evolutionary models. By prevailing theory, solitary and dispersed primates ought to be silent or communicatively impoverished, but this is often presumed, not empirically verified, with these species' capacities seldom being brought to bear on evolutionary theories based on social drivers. This skewed sampling could mask other valuable but hitherto disregarded sources of information and inference obfuscated by the spotlights of the social stage. Orangutans-the only hominids living without permanent social groups-are also the only nonhuman primate known to share with humans two hallmark features of language: displaced vocal reference (where mothers delay alarm calls to teach offspring about past predator encounters) and vocal hierarchies (with vocal motifs nested in self-similar motifs). The description of such traits in the most private and reserved great ape highlights a hidden precondition for vocal evolution: extended and elaborated vocal patterns and functions, which epitomize vocal sophistication, are time-sensitive and require attentive listening without interruption for correct processing. The functional benefits of elaborate and complex sound combinations partly depend on receivers being capable of vocal suppression and impulse control in response to others. Conversely, species with frequent, rapid and reactive social chatter incur "town square taxes" that interrupt and constrain, rather than promote, vocal elaboration and complex patterning. Silence remains a critical but undertheorized resource for fostering communicative and cognitive sophistication, helping reframe the (a)social prerequisites for primate vocal evolution and the emergence of language amongst ancestral hominids.
Hominin evolution made physical activity obligatory for survival. Modern environments decoupled effort from ecological returns, generating an evolutionary mismatch that favors energy conservation over voluntary movement. This review distinguishes between subsistence-based physical activity, the ancestral condition directly coupled to survival, and discretionary exercise, a voluntary behavior performed in the absence of immediate metabolic necessity. It delineates a neuro-evolutionary framework characterizing discretionary exercise as the functional repurposing of neural systems originally shaped for subsistence, operating through evolutionarily conserved effort-reward valuation circuitry that computes context-dependent cost-benefit trade-offs. Three complementary evolutionary pathways mediate this process: homeostatic compensation, where exercise reinstates ancestral physiological maintenance signals; costly signaling, where exercise functions as an honest phenotypic display of quality; and reward recoding, where human mesocorticolimbic circuitry attributes abstract significance and reward to physical exertion. These mechanisms explain how neurobiological exaptation and cultural mediation enable sustained voluntary effort in contemporary populations despite the absence of ecological necessity.
Prehistoric "symbolic" artifacts remain incompletely explained by semiotic models, which emphasize representational meaning but offer limited insight into how such materials emerged and spread across Pleistocene populations. This article develops a cultural evolutionary framework that reconceives early ornaments, pigments, figurines, and related materials as opaque social instruments (OSIs): culturally transmitted, socially functional traits whose coordinating effects typically exceed users' explicit understanding of their roles. A heuristic distinction is introduced between participation-embedded OSIs, whose efficacy derives from embodied participation in shared, interactionally dense practices, and frame-embedded OSIs, whose efficacy depends more heavily on publicly stabilized interpretive frames and role structures that extend across contexts and generations. Because these modes operate under different transmission environments and selective pressures, they are expected to generate distinct patterns of reproduction, contextual embedding, and archeological visibility. Reframing prehistoric "symbolic" materials as OSIs shifts explanatory focus from encoded meaning to social coordination, functional opacity, and transmission dynamics, offering a mechanistic account of how materially mediated practices became reproducible components of Pleistocene social systems.
The pronounced neurological immaturity, yet increased birthweight of human neonates relative to other primates, known as secondary altriciality, is traditionally attributed to obstetric constraints arising from pelvic adaptations for bipedal locomotion and childbirth-the so-called obstetrical dilemma. The Energetics of Gestation and Growth (EGG) hypothesis instead attributes it to a constrained maternal metabolism. We tested the assumptions of the EGG hypothesis with hypothetical maternofetal dyads using empirical data on maternal metabolic scope and fetal growth. Our results revealed no consistent relationship between fetal and maternal patterns with birth timing. Moreover, there is no evidence that cortisol, the presumed proximate birth mechanism under the EGG hypothesis, is involved in birth timing in humans, thus questioning that metabolic limitations can serve as its trigger. Finally, we propose that secondary altriciality does not result from simple shifts in birth timing but from heterochronic growth patterns related to obstetric constraints.
The propensity to teach is vital to human cultural evolution and to our ecological dominance of the planet, but its cognitive foundations remain poorly understood. Traditional explanations argue that teaching hinges on particular cognitive pre-requisites, such as Theory of Mind. However, such explanations conflate the function of teaching-promoting learning in others-with how it is achieved, and overlook the role of comparatively simple mechanisms like the heuristics known to underpin teaching in some non-human animals. We propose a novel framework integrating evolutionary and psychological perspectives to understand the diversity of teaching by focusing on the cognitive requirements for flexibility and sensitivity to pupil needs. Synthesizing theory and evidence across disciplines, our framework evaluates the contributions of different mechanisms in determining who and what is taught, and how teaching is achieved. This allows us to understand the cognitive foundations of teaching across different species, in diverse human societies, and neurodiverse populations.
The postcanine teeth of mangabeys (members of Cercocebus and Lophocebus) have figured prominently in discussions about the relationship between hard-object feeding and dental form. Grey-cheeked mangabeys (Lophocebus albigena) and sooty mangabeys (Cercocebus atys) both have thickly enameled posterior teeth. Thick enamel in the former is argued to be response to fallback consumption of hard-object foods, whereas in the latter, this feature is thought to have evolved in response to routine consumption of hard-object foods year-round. Our recent analyses reveal aspects of dental form beyond thick enamel that render C. atys posterior teeth better suited to process hard-object foods and resist fracture than those of L. albigena. We argue that the different feeding regimes of these two mangabey species had different effects on the evolution of their posterior teeth. Here, we detail these differences within the context of the fallback food paradigm. These results may ultimately help us detect modes of hard-object feeding in the fossil record.
The Acheulean represents the longest cultural period known to human history, lasting globally for more than 1.75 million years. It may have emerged as early as 1.95 Ma in Africa, spreading throughout much of the continent and then into Eurasia and lasting up to 350-200 ka in western Europe and South Asia, and even later in eastern Asia. Originally defined in the 1870s, the term Acheulean is one of the earliest and most contested classifications in prehistoric archaeology. Almost 150 years after its first appearance, it remains a source of continuous debate. This paper summarizes roundtable discussions that took place at the Musée de l'Homme (Paris) in November 2025 that focused on the meaning of the Acheulean and the diversity of its manifestations across Eurasia. Some 20 researchers, from various institutions across Europe, Asia, and the Pacific participated in this event, during which it became clear that the Acheulean had different meanings to the participants. Among the major points raised during the meeting was the question of how different specialists differentiate the Acheulean from the older Oldowan techno-complex, with specificities emerging from each of their respective regions of study. The geographic origins and hominin species' attribution of the Acheulean toolmakers were also brought to the fore since important questions have been raised in the last decades by the growing record of hominin taxa that existed during this timeframe across Eurasia and the relatively late arrival of this techno-complex in Europe. These issues become even more important when we consider the recent evidence emanating out of Asia, which indicates that hominins were present well before their earliest appearance in Europe. The purpose of this paper is not only to make a statement regarding how to define the Acheulean, but also to illustrate its diversity across Eurasia.
Primate tongue morphology and function are critical to understanding the evolution of feeding, swallowing, and vocalization. In this paper, we examine the primate tongue as a muscular hydrostat with regionally specialized neuromuscular compartments. We integrate anatomical, kinematic, and biomechanical modeling approaches to analyze how muscle architecture and fiber orientation drive complex tongue deformations during functional behaviors. We evaluate the hydraulic mechanisms underlying tongue-base retraction, highlight species-specific adaptations in macaques and humans, and review primate tongue kinematics across distinct feeding stages. Finally, we synthesize recent advances in biomechanical modeling and experimental studies of tongue kinematics and their contributions to advancing three-dimensional analyses of tongue movement during feeding and speech.
The Human Genome Project, together with the subsequent advent of diverse repositories for storing, sharing, and analyzing biological data, represented a revolution in the way genetic research is conducted. The overwhelming landscape of omics data resources available today provides an exceptional opportunity to drive innovations in human genetics. Here, we report an updated compilation of 117 open-access and active resources containing DNA, RNA, protein and phenotypic data, viewed through the lens of a population geneticist. A deep inspection of these resources from both spatial and temporal perspectives allows us to identify trends in the use of large-scale biological data, as well as the current and future challenges in the field-including the implementation of new technologies, the call for greater diversity in the sampled populations, and the imperative role of bioethics. Addressing these issues requires the integration of biology and medicine, along with the crucial insights gained from population-based research.
Reproduction is a complex process, and microbes play a far greater role than previously imagined. This review explores the ways that microbiomes influence the rich tapestry of reproductive processes and outcomes within the primate lineage, including pre-copulatory and post-copulatory mechanisms. We discuss microbiomes in a sexual selection framework, specifically how they might influence mate choice and sexual competition across multiple sensory modalities. We then consider how copulatory behavior and mating systems may in turn shape reproductive microbiomes. Moving to post-copulatory processes, we discuss the potential impact of microbes on cryptic choice and sperm competition and call for additional research in this area. Finally, we explore the influence of microbes on pregnancy outcomes, emphasizing evolutionary perspectives often overlooked in clinical research. Importantly, we compare human studies to those on nonhuman primates, bridging the two areas of inquiry and outlining future research directions. Our aim is to highlight the vast potential for microbes to contribute to all stages of reproduction, and to inspire creative, synthetic future research that moves forward this fascinating area of inquiry.
How primates sense, cognize, and respond to death, and are affected by it, are broad research themes within primate thanatology. When primate thanatology adopts a comparative framework, it can illuminate the diversity and evolutionary continuity of psycho-neuro-emotional responses to death and dying across primate species, including humans. Evolutionary or comparative thanatology has recently gained momentum, but it lacks methodological consistency, quantitative rigor, and coherent reporting standards. We attempt to address the lack of standardized approaches by introducing an individual-level comparative framework and employing standard ethological methods, accompanied by well-defined behavioral variables. We argue that the proposed framework can capture individual-specific responses to conspecific death and enable hypothesis-driven studies. The framework is essential to examine the large number of hypotheses that have accumulated in the field.
Why do rituals persist in human societies despite their frequent and observable failures to produce intended outcomes? This paper advances a two-part argument to explain this resilience. First, at the individual level, I argue that belief in ritual efficacy is maintained through Bayesian-rational processes, where the invocation of auxiliary hypotheses absorbs disconfirming evidence and shields central beliefs from significant revision. Importantly, such protection is not complete. Each failure produces a small but non-zero erosion of individual confidence. Second, I address the resulting population-level puzzle: why does such incremental doubt not accumulate into widespread skepticism and the eventual collapse of ritual systems? I argue that social features and informational dynamics (e.g., memory biases, the underreporting of failure, pluralistic ignorance) as well as the protective "design" of rituals themselves systematically inhibit the aggregation of doubt across individuals and generations. By linking individual cognition with population dynamics, this account explains the remarkable resilience of ritual systems in the face of persistent empirical failure.
The evolution of laryngeal air sacs in hominins has been a subject of considerable debate, with particular attention given to the inferred presence of air sacs in Australopithecus afarensis and inferred absence in Middle and Upper Pleistocene hominins. We challenge several assumptions prevalent in relevant discourse and assert that (1) while exhibiting morphological similarity, it cannot be ruled out that relationships between hyoid morphology and air sac morphology in extant African great apes may reflect convergence; (2) while the only known A. afarensis hyoid exhibits "ape-like" bulla, this feature may have persisted following the loss of air sacs, and not be indicative of their presence per se; (3) because there are currently only five known hominin hyoid bones represented in the fossil record (with a single specimen predating the Middle Pleistocene) the evidential basis for interpreting air sac presence or absence is minimal; and (4) inferences toward a role of sexual selection and communicative behavior in explicating the loss of air sacs in the hominin lineage are undermined by the atypical sexual dimorphism patterns in early hominins. We advocate for a cautious approach to interpreting hominin behavior and evolution which prioritizes data over speculation, and underscore the need for rigorous evidence when constructing evolutionary narratives about early hominin vocal anatomy and its evolution.
