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 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.

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.

Mate selection has important fitness implications and thus has been a prominent focus across the evolutionary social sciences. However, despite ample evidence that human mate selection is uniquely shaped by others, existing research allocates outsized attention to individual preferences. Here, we take stock of the implications of arranged marriage, highlighting measurement issues that obscure continua of parental influence and likely drive inconsistency in the downstream literature. Focusing on parent-offspring conflict over spouse selection, we find (i) culturally widespread evidence of conflicting preferences, but limited evidence that conflict impacts realized spouse selection, (ii) parental approval predicts marriage outcomes more so than parental control, and (iii) that key predictions about socioecological variation in the form and consequences of conflict remain largely untested. We conclude that a more satisfying account of human mating will require refined measurement of its social embeddedness, greater focus on conflict negotiation, and continued cross-cultural research.

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 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 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.

We focus on three researchers-Davidson Black, Franz Weidenreich and Ralph von Koenigswald-who have made major contributions to the recovery of the fossil record of the hominin taxon now known as Homo erectus. Black was responsible for the recognition of Sinanthropus pekinensis and for the recovery of the initial hypodigm from Choukoutien*. Almost all of the original S. pekinensis fossils were lost during the Second World War, but the precise documentation and meticulous descriptions prepared by Franz Weidenreich substantially mitigate their loss. An earlier article in this series focused on Eugène Dubois' recovery of the type specimen of Pithecanthropus erectus from Trinil in Java, and while a few additional specimens from Trinil were recognized, the majority of the Javan hypodigm of P. erectus was recovered thanks to initiatives led or encouraged by Ralph von Koenigswald.

Fossil and artefactual evidence shows Homo sapiens in Eurasia well before 75 ka. However, genetic evidence suggests all extant non-African populations derive almost all of their ancestry from a dispersal that only diverged in the last 60-50 ka. In northern Eurasia, the Upper Paleolithic with its laminar blade knapping provides an archeological signature of this dispersal, but no equivalent is yet established for southern Asia, Wallacea, and Sahul. This paper suggests that lithic miniaturization may provide such a signature as it appears across these southern regions from around 50 ka. It can be traced back to the southwestern edge of Asia at 55 ka, and then coastal east Africa at 68 ka. In both these cases it is also associated with laminar blade technology. Lithic miniaturization is implicated in behaviors including bow-and-arrow hunting, compound tools, hair-shaving, and scarification. The ecological and social implications of these behaviors may have given later Homo sapiens a competitive advantage over both other hominins and earlier dispersals of our own species.

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.