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Acknowledgements IE has received funding from the postdoctoral fellowship programme Beatriu de Pinós (2019 BP00247), funded by the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 programme of research and innovation of the European Union under the Marie Skłodowska-Curie grant agreement No. 801370. Laboratory materials for sample processing at the University of Barcelona were funded by the Ministerio de Ciencia e Innovaci on - PID 2020-119773 GB-I00. Visit to the site for sampling collection for this study was sponsored by a NRF Y-Rated Research Grant (No. 116358) to DS. PdlP was supported by a Poroulis grant through Cambridge University. PdlP thanks the action PID 2019- 1049449 GB-I00 funded by Spanish FEDER/Ministry of Science and Innovation. LB was funded by a National Geographic Explorer grant (NGS-54810R-19), DSI-NRF Centre of Excellence in Palaeosciences (Genus) grant (CEOOP 2020-1), and NRF African Origins Platform grant (No. 98824). Research by FdE is funded by the Research Council of Norway (SFF Centre for Early Sapiens Behaviour- SapienCE-project 262618), the Talents program of the University of Bordeaux (n. 191022_001), and the program “Human Past”, funded by the same university.We are grateful to Amafa for issuing us with the excavation permit (SAH 15/7645), and to SAHRA for an export permit (CaseID 15987).We thank two anonymous reviewers for their helpful comments that significantly improved the manuscript., Supplementary data to this article can be found online at https://doi.org/10.1016/j.quascirev.2022.107898., Border Cave is a well-known South African Middle and Early Later Stone Age site located in KwaZulu-Natal. The site has exceptional plant preservation, unparalleled in the African Middle Stone Age archaeological record. This study focuses on the phytolith and FTIR analysis of two Members (2 BS and 2 WA) of the under-documented post-Howiesons Poort occupations dating to ∼60 ka. These members contain complex successions of vertically overlapping, interdigitating light brown sediments, plant bedding and combustion features of various sizes. The complexity and distinctiveness of these deposits provide an excellent opportunity for the study of plant exploitation strategies and their associated human behaviour. Our taphonomic assessment inferred, through the variability of phytolith properties and minerals composing archaeological layers, that specific occupations suffered more physical weathering than others, for example in the form of trampling. The preservation of fragile and highly soluble phytoliths (eudicot leaf phytoliths) and the high frequencies of articulated phytoliths indicates that some bedding deposits experienced little disturbance after their deposition. Not all bedding layers dating to ⁓60 ka show, from a phytolith perspective, the same plant composition, which could be explained in terms of changes in human preference for the use of plants over time to construct bedding or because distinct types of living floors are represented. Finally, the systematic application of phytoliths and FTIR to the complex archaeological sequence of Border Cave confirm these analyses can be used in the future to identify bedding deposits not visible to the naked eye, and behavioural patterns obscured by diagenetic or biased processes during sampling., Programme Beatriu de Pinós (2019 BP00247), funded by the Secretary of Universities and Research (Government of Catalonia), Horizon 2020 programme of research and innovation of the European Union under the Marie Skłodowska-Curie grant agreement No. 801370, Ministerio de Ciencia e Innovación - PID 2020-119773 GB-I00, NRF Y-Rated Research Grant (No. 116358), Action PID 2019- 1049449 GB-I00 funded by Spanish FEDER/Ministry of Science and Innovation, National Geographic Explorer grant (NGS-54810R-19), DSI-NRF Centre of Excellence in Palaeosciences (Genus) grant (CEOOP 2020-1), NRF African Origins Platform grant (No. 98824), Research Council of Norway (SFF Centre for Early Sapiens Behaviour- SapienCE-project 262618), Talents program of the University of Bordeaux (n. 191022_001), Program “Human Past” University of Bordeaux, SAH 15/7645, CaseID 15987

Debates concerning social learning in the behavioral and the developmental cognitive sciences have largely ignored the literature on social influence in the affective sciences despite having arguably the same object of study. We argue that this is a mistake and that no complete model of social learning can exclude an affective aspect. In addition, we argue that including affect can advance the somewhat stagnant debates concerning the unique characteristics of social learning in humans compared to other animals. We first review the two major bodies of literature in nonhuman animals and human development, highlighting the fact that the former has adopted a behavioral approach while the latter has adopted a cognitive approach, leading to irreconcilable differences. We then introduce a novel framework, affective social learning (ASL), that studies the way we learn about value(s). We show that all three approaches are complementary and focus, respectively, on behavior toward; cognitions concerning; and feelings about objects, events, and people in our environment. All three thus contribute to an affective, behavioral, and cognitive (ABC) story of knowledge transmission: the ABC of social learning. In particular, ASL can provide the backbone of an integrative approach to social learning. We argue that this novel perspective on social learning can allow both evolutionary continuity and ontogenetic development by lowering the cognitive thresholds that appear often too complex for other species and nonverbal infants. Yet, it can also explain some of the major achievements only found in human cultures. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Human joint action is inherently cooperative, manifested in the collaborative efforts of participants to minimize communicative trouble through interactive repair. Although interactive repair requires sophisticated cognitive abilities, it can be dissected into basic building blocks shared with non-human animal species. A review of the primate literature shows that interactionally contingent signal sequences are at least common among species of non-human great apes, suggesting a gradual evolution of repair. To pioneer a cross-species assessment of repair this paper aims at (i) identifying necessary precursors of human interactive repair; (ii) proposing a coding framework for its comparative study in humans and non-human species; and (iii) using this framework to analyse examples of interactions of humans (adults/children) and non-human great apes. We hope this paper will serve as a primer for cross-species comparisons of communicative breakdowns and how they are repaired.This article is part of the theme issue ‘Revisiting the human ‘interaction engine’: comparative approaches to social action coordination’.

Research in comparative cognition on allegedly uniquely human capacities considers the identification of these human capacities in other species as one of their main points of inquiry. Capacities are applied in their theoretical descriptions to promising empirical data. The conclusion then often is that even though, on a behavioural level, the human and nonhuman cases appear related, on a cognitive level there is no relation whatsoever because the underlying cognitive states diverge in quality. This result seems dissatisfying for two reasons: (1) there is ample empirical evidence that suggests the presence of the capacities in other species, and (2) the claim that the underlying states diverge often hinges on the reference to the theoretical definitions of these capacities only. This opinion piece focuses on the capacity of ostensive intentional communication to demonstrate that the original theoretical analyses often are not befitting a comparative endeavour and should therefore not be used as pivotal reference within comparative research. An outlook will be provided on more promising approaches to identifying ostensive communication, namely an interactive approach that will allow for ostension to not be perceived as a one-turn signalling behaviour, but as interactive, with the possibility of being established in a trial-and-error manner.This article is part of the theme issue ‘Revisiting the human ‘interaction engine’: comparative approaches to social action coordination’.

The intentional communication of affective states is a central part of human sociality and cognition. Although nonhuman primates (henceforth primates) also signal intentionally, there is a perceived chasm between their intentional versus affective forms of communication. Whereas primate vocalizations and facial expressions are traditionally viewed as involuntary 'read-outs' of affective states, gestures are considered as products of intentional control. However, this traditional view is increasingly contentious, given recent evidence of intentional signal production of primate vocalizations and facial expressions, as well as the general void of arousal-based explanations in gesture research. In this chapter, we challenge the perceived dichotomy between affective and intentional communication in primates and propose a dimensional approach, whereby primate signals can be both affective and intentional, regardless of signal modality (tactile, audible, visible) or component (gesture, facial expression, vocalization). We argue that a dimensional approach, which incorporates both affective and intentional components, would improve our knowledge on how affective and cognitive processes have jointly shaped the evolution of primate communication.

The presence of divergent and independent research traditions in the gestural and vocal domains of primate communication has resulted in major discrepancies in the definition and operationalization of cognitive concepts. However, in recent years, accumulating evidence from behavioural and neurobiological research has shown that both human and non-human primate communication is inherently multimodal. It is therefore timely to integrate the study of gestural and vocal communication. Herein, we review evidence demonstrating that there is no clear difference between primate gestures and vocalizations in the extent to which they show evidence for the presence of key language properties: intentionality, reference, iconicity and turn-taking. We also find high overlap in the neurobiological mechanisms producing primate gestures and vocalizations, as well as in ontogenetic flexibility. These findings confirm that human language had multimodal origins. Nonetheless, we note that in great apes, gestures seem to fulfil a carrying (i.e. predominantly informative) role in close-range communication, whereas the opposite holds for face-to-face interactions of humans. This suggests an evolutionary shift in the carrying role from the gestural to the vocal stream, and we explore this transition in the carrying modality. Finally, we suggest that future studies should focus on the links between complex communication, sociality and cooperative tendency to strengthen the study of language origins.

Debates concerning social learning in the behavioral and the developmental cognitive sciences have largely ignored the literature on social influence in the affective sciences despite having arguably the same object of study. We argue that this is a mistake and that no complete model of social learning can exclude an affective aspect. In addition, we argue that affect can allow bridging of the debates of the unique characteristics of social learning in humans compared to other animals. We first review the two major bodies of literature in non-human animals and human development, highlighting the fact that the former has adopted a behavioral approach while the latter has adopted a cognitive approach, leading to irreconcilable differences. We then introduce a novel framework, affective social learning (ASL), that studies the way we learn about value(s). We show that all three approaches are complementary and focus, respectively, on behavior towards, cognitions concerning, and feelings about objects, events and people in our environment. All three thus contribute to an affective, behavioral and cognitive story of knowledge transmission: the ABC of social learning. In particular, ASL can provide the backbone of an integrative approach to social learning. We argue that this novel perspective on social learning can allow both evolutionary continuity and ontogenetic development by lowering the cognitive thresholds that appear often too complex for other species and non-verbal infants. Yet, it can also explain some of the major achievements only found in human cultures.

Early plant use is seldom described in the archaeological record because of poor preservation. We report the discovery of grass bedding used to create comfortable areas for sleeping and working by people who lived in Border Cave at least 200,000 years ago. Sheaves of grass belonging to the broad-leafed Panicoideae subfamily were placed near the back of the cave on ash layers that were often remnants of bedding burned for site maintenance. This strategy is one forerunner of more-complex behavior that is archaeologically discernible from ~100,000 years ago.

Using fire experiments, we investigate claims that black organic residues on lithics found in Stone Age sites are markers for heat treatment of rocks in the embers of aboveground wood fires. We buried sedges overlain with lithics and bone to replicate plant bedding sometimes found in archaeological sites. Small fires were lit over the material buried under a mixture of coarse- and medium-grained sand. Black carbonised residues formed on several lithics that were in direct contact with buried sedges that burned below the fire. FTIR, Raman and preliminary GC–MS measurements were made on dried and burnt sedge, burnt bone, and on a prominent black residue that formed on one quartz piece that had been in contact with buried fresh sedge when it was heated. Importantly, we were able to confirm the spontaneous and accidental transfer of organic compounds to lithics buried and heated underground in the presence of plant material. This means that carbonised organic residues are not useful markers for determining whether heat treatment of rocks took place above or below ground. Our preliminary experiments imply that further work should be done to investigate the causes of the residues formed on lithics underground.

The concept of functional reference has been used to isolate potentially referential vocal signals in animal communication. However, its relatedness to the phenomenon of reference in human language has recently been brought into question. While some researchers have suggested abandoning the concept of functional reference altogether, others advocate a revision of its definition to include contextual cues that play a role in signal production and perception. Empirical and theoretical work on functional reference has also put much emphasis on how the receiver understands the referential signal. However, reference, as defined in the linguistic literature, is an action of the producer, and therefore, any definition describing reference in non-human animals must also focus on the producer. To successfully determine whether a signal is used to refer, we suggest an approach from the field of pragmatics, taking a closer look at specific situations of signal production, specifically at the factors that influence the production of a signal by an individual. We define the concept of signaller's reference to identify intentional acts of reference produced by a signaller independently of the communicative modality, and illustrate it with a case study of the hoo vocalizations produced by wild chimpanzees during travel. This novel framework introduces an intentional approach to referentiality. It may therefore permit a closer comparison of human and non-human animal referential behaviour and underlying cognitive processes, allowing us to identify what may have emerged solely in the human lineage.

The Middle Stone Age (MSA) is associated with early behavioral innovations, expansions of modern humans within and out of Africa, and occasional population bottlenecks. Several innovations in the MSA are seen in an archaeological sequence in the rock shelter Sibudu (South Africa). At ~77,000 years ago, people constructed plant bedding from sedges and other monocotyledons topped with aromatic leaves containing insecticidal and larvicidal chemicals. Beginning at ~73,000 years ago, bedding was burned, presumably for site maintenance. By ~58,000 years ago, bedding construction, burning, and other forms of site use and maintenance intensified, suggesting that settlement strategies changed. Behavioral differences between ~77,000 and 58,000 years ago may coincide with population fluctuations in Africa.