Behavioural biologist / comparative psychologist / cognitive archaeologist / philosopher of science based at the University of Tübingen (Germany) where I work as a tenured research group leader ("Tools and Culture among Early Hominins"). In addition, I am an adjunct scientist at the Lester E. Fisher Center for the Study and Conservation of Apes.
My main research triangulates the beginnings of human cultural specialisation - as well as why this happened (and relatedly, when this happened - and how often). In particular, I use various methods and pathways to study the factors and the prehistorical beginnings that enabled the typical modern human "variant of culture": cumulative culture of know-how to supra-individual levels (i.e. know-how beyond baseline performance levels reachable by individuals in the absence of copying this or related know-how). Supervisors: Michael Tomasello and Josep Call
This chapter applies cultural evolutionary and gene-culture coevolutionary theory to chimpanzees ... more This chapter applies cultural evolutionary and gene-culture coevolutionary theory to chimpanzees by reviewing the now large body of evidence on chimpanzee social learning, culture, and traditions. It provides comparative evidence for humans to assess the similarities and differences between these two species. By asking theoretically driven questions about the nature of culture in each species, the chapter aims to assess their shared phylogenetic heritage, and to isolate the selective forces that have distinguished these lineages over the last six to nine million years. It begins with a brief introduction to gene-culture coevolutionary theory, though specific elements of the theory will be rolled out as they go along. The chapter emphasizes that the goal is to apply theoretically derived insights to the available evidence from chimpanzees, and not to provide a general review of all work on this topic. It considers whether chimpanzee social learning has been shaped by natural selection, as it appears to have been in humans, to expand and hone the behavioral repertoires of individuals by facilitating the acquisition of adaptive practices from others.
This chapter critically discusses the earliest tools and cultures of hominins—the species most cl... more This chapter critically discusses the earliest tools and cultures of hominins—the species most closely related to humans. It starts with an inferred organic tool age that would have already existed before the split of hominins from the ape lineage. It then examines the two currently fully established earliest instances of the stone tool age—the Oldowan and Acheulean. Contrary to prevalent assumptions, the cultural status of the Oldowan and most or all of the Acheulean (and the organic tool age) may have been that of ‘minimal culture’. Minimal culture shares with modern human culture and animal culture influences of some social learning types—for example, on frequencies of behaviours and tools—but, unlike human culture, it excludes cultural transmission of novel—supra-individual—behavioural and/or artefact know-how. If true, cumulative cultural transmission of know-how to supra-individual levels would then have started much later than is currently presumed.
The goal of Artificial Life research, as articulated by Chris Langton, is "to contribute to theor... more The goal of Artificial Life research, as articulated by Chris Langton, is "to contribute to theoretical biology by locating life-as-we-know-it within the larger picture of life-as-it-could-be" (1989, p.1). The study and pursuit of open-ended evolution in artificial evolutionary systems exemplifies this goal. However, open-ended evolution research is hampered by two fundamental issues; the struggle to replicate open-endedness in an artificial evolutionary system, and the fact that we only have one system (genetic evolution) from which to draw inspiration. Here we argue that cultural evolution should be seen not only as another real-world example of an open-ended evolutionary system, but that the unique qualities seen in cultural evolution provide us with a new perspective from which we can assess the fundamental properties of, and ask new questions about, open-ended evolutionary systems, especially in regard to evolved open-endedness and transitions from bounded to unbounded evolution. Here we provide an overview of culture as an evolutionary system, highlight the interesting case of human cultural evolution as an open-ended evolutionary system, and contextualise cultural evolution under the framework of (evolved) open-ended evolution. We go on to provide a set of new questions that can be asked once we consider cultural evolution within the framework of open-ended evolution, and introduce new insights that we may be able to gain about evolved open-endedness as a result of asking these questions.
After stone tools, bone tools are the most abundant tool type in the hominin
archaeological rec... more After stone tools, bone tools are the most abundant tool type in the hominin
archaeological record. However, due to their poor preservation, they are relatively
scarce, limiting our understanding of the behavioural processes that led to their
production and use. Extant primates constitute a unique source of behavioural data to
build and shape hypotheses about the potential uses that our hominin ancestors might
have given to bone tools. In this study, we investigated the behavioural responses of
two groups of captive chimpanzees (Ntotal=42) to detached and cleaned bones while
participating in a foraging task aimed at eliciting excavating behavior. Each
chimpanzee group was provided with bones of different characteristics and the two
groups differed in their respective levels of experience with tool excavation (one
group being mostly inexperienced while the other had ample experience in stick tool excavation). We found that several individuals from the inexperienced group used the
provided bones as tools during the task. No individuals from the experienced group
used bones as excavating tools. Instead, these chimpanzees performed other bone-
related behaviours (not observed in the inexperienced group), such as hammering and
tool-assisted marrow consumption. Given that previous experience in tool excavation
did not predict the use of bones as tools in the excavating task, we hypothesize that
the differences in behavior observed between the two chimpanzee groups were due to
the characteristics of the bones they were provided with. Furthermore, our results
suggest that object characteristics rather than material determine whether
chimpanzees perceive an object as a suitable excavating tool.
Many animals, and in particular great apes, show evidence of culture, in the sense of having mult... more Many animals, and in particular great apes, show evidence of culture, in the sense of having multiple innovations in multiple domains whose frequencies are influenced by social learning. But only humans show strong evidence of complex, cumulative culture, which is the product of copying and the resulting effect of cumulative cultural evolution. The reasons for this increase in complexity have recently become the subject of extensive debate. Here, we examine these reasons, relying on both comparative and paleoarcheological data. The currently best-supported inference is that culture began to be truly cumulative (and so, outside the primate range) around 500,000 years ago. We suggest that the best explanation for its onset is the emergence of verbal teaching, which not only requires language and thus probably coevolved with the latter’s evolution but also reflects the overall increase in proactive cooperation due to extensive allomaternal care. A subsequent steep increase in cumulative culture, roughly 75 ka, may reflect the rise of active novelty seeking (curiosity), which led to a dramatic range expansion and steep increase in the diversity and complexity of material culture. A final, and continuing, period of acceleration began with the Neolithic (agricultural) revolution.
Replication is an important tool used to test and develop scientific theories. Areas of biomedica... more Replication is an important tool used to test and develop scientific theories. Areas of biomedical and psychological research have experienced a replication crisis, in which many published findings failed to replicate. Following this, many other scientific disciplines have been interested in the robustness of their own findings. This chapter examines replication in primate cognitive studies. First, it discusses the frequency and success of replication studies in primate cognition and explores the challenges
researchers face when designing and interpreting replication studies across the wide range of research designs used across the field. Next, it discusses the type of research that can probe the robustness of published findings, especially when replication studies are difficult to perform. The chapter concludes with a discussion of different roles that replication can have in primate cognition research.
An understanding of ape culture offers important insights into the evolution of human culture. Th... more An understanding of ape culture offers important insights into the evolution of human culture. This chapter presents the argument that ape tool cultures consist of socially-mediated branching chains of individually-derived behaviors (‘latent solutions’) and presents the hypothesis that the evolved motivations and skills of apes potentially enable them to individually create all tool behaviors shown by any other conspecific. Through non-copying observational learning mechanisms, each individual becomes sufficiently likely to express the latent solution variants shown in their group. But even with social mediation, each chimpanzee still must generate the underlying behavior individually (i.e. reinnovate it). Ultimately, reinnovation arises due to an interplay between environmental factors, motivation and skill. While the resulting uniformity of behavior within chimpanzee groups can create the illusion that their culture requires copying, we review the evidence and conclude this is not the case. Furthermore, latent solutions are not limited to chimpanzees – they may underlie the cultures of many other animals, and presumably those of earlier hominins. While our own species also possesses a ‘zone of latent solutions,’ the additional behaviors and technology that we use and produce today cannot occur unless they are culturally transmitted: they are not only cumulative, but truly culture-dependent traits.
Body-pockets are areas afforded by bodies that can be used to hold and/or transport objects to so... more Body-pockets are areas afforded by bodies that can be used to hold and/or transport objects to solve transport problems. Several lines of evidence – from animals (such as apes) to modern humans – point toward the likely use of body-pockets by all hominins. Here we highlight the neglect in the literature of accounting for hominin body-pocket usage. We argue that it is likely that body-pockets were used – at least sometimes – by hominins, and that, specifically, bipedal hominin body-pocket usage would have included the use of armpit-pockets. Hominins would have, at least sometimes, held and/or transported objects such as artefacts, including stone artefacts. This is the body-pocket / armpit-pocket hypothesis. Additionally, and independently of the body-pocket hypothesis more generally, we speculate that body-pocket usage could have influenced also aspects of the forms of carried objects – indirectly (via selecting) and/or directly (via forming). Three mutually exclusive theoretical possibilities remain. Possibility 1 (i.e. the current status quo): Any hominin body-pocket influence on objects’ forms was absent – or never sufficiently large to have left any recognisable pattern today. Possibility 2: There was a hominin body-pocket influence on objects’ forms, and this influence – while perhaps small – was large enough, at least sometimes and/or in some cases, to be recognisable today. Possibility 3 (the body-pocket fitting hypothesis): There was a hominin body-pocket influence on objects’ forms, and this influence was so large that it best explains large or complete parts of these forms completely. In our manuscript we tentatively reject Possibility 3. As for the remaining possibilities, Possibility 1 currently proved more parsimonious than Possibility 2. While we present data that is consistent with Possibility 2, no strong evidence was found to support it – rendering it a speculative and weak hypothesis. We outline possible future examinations of the body-pocket fitting hypothesis, but we conclude that the current status quo (i.e. Possibility 1) regarding the sources of hominin artefact forms remains unchanged.
It remains unclear when and why the ability to copy actions evolved and also its uniqueness to hu... more It remains unclear when and why the ability to copy actions evolved and also its uniqueness to humans. Thus far, a lack of valid evidence for spontaneous action copying by other apes supports the view that only humans spontaneously copy actions. However, wild apes have access to multiple demonstrators and have been demonstrated to be affected by majority influences, thus raising the possibility that ape action copying might require a majority ratio of demonstrators to observers. We tested for spontaneous ape action copying across all four non-human great ape species using a demonstrator majority. Nineteen captive mother-reared apes (across 4 species) were tested (Raage=9-52; Mage=18.63; ♀=14; ♂=5). All failed to copy the demonstrated actions, despite observing it in a majority influence condition. We conclude that culture in non-human great apes is more likely supported by variants of social learning which regulate frequencies, rather than forms, of observed behaviours.
We argue that imitation, in addition to the typical roles it plays in culture, additionally suppo... more We argue that imitation, in addition to the typical roles it plays in culture, additionally supports the social transmission and recombination of world models. We propose a learning pathway called “model-based assimilation”, which uses imitation to shape the statics of experience, and “hijacks” existing individual learning mechanisms supporting model-based learning (e.g., hippocampal replay). This pathway is computationally cheaper than explicit Theory of Mind inference, but nevertheless allows for the social recombination of knowledge across multiple brains. Our theory provides important insights into why our close relative, the chimpanzee, imitates poorly and why humans acquired cumulative culture.
Experimental replication of stone tools is an important method for understanding the context and ... more Experimental replication of stone tools is an important method for understanding the context and production of prehistoric technologies. In scientific undertakings, experimental control is a valuable and necessary means of ensuring that confounding variables are not influencing the outcomes of the study. One way that researchers can exert control in knapping experiments is to standardize the type, form, and size of raw materials that are provided to the knappers. Though measures to standardize materials are already part of archaeological practice, specific protocols, let alone comparisons between standardization techniques, are rarely openly reported. Consequently, independent laboratories often repeat the same trial-and-error process for selecting the ‘right’ material for testing. We investigate a variety of techniques and raw materials (e.g., hand-knapped flint, machine-cut basalt, manufactured glass, and porcelain). Each material was evaluated for their validity, reliability, and ease of standardization. Here, we have outlined the raw material tests we performed, providing information on the individual approaches, as well as comparisons between the techniques and materials according to both validity and reliability, along with their costs and our own recommendations. This text is intended as a serviceable guide
on raw material standardization for knapping experiments, including previously pursued avenues and means that are as-of-yet undescribed in the experimental archaeology literature. We include additional considerations for techniques that were not included in this study or which are presently not widely available and/or affordable. Future potential in this field would benefit from advances in the relevant technologies and in methodological approaches.
Range et al. (2007, Current Biology, 17,868-872) found that dogs, Canis familiaris, copy others’... more Range et al. (2007, Current Biology, 17,868-872) found that dogs, Canis familiaris, copy others’ means to achieve a goal more often when those means are the rational solution to a problem than when they are irrational. In our first experiment, we added a further control condition and failed to replicate this result, suggesting that dogs in the previous study may have been distracted in the irrational condition rather than selectively attending to the irrational nature of the action. In a second experiment, the demonstrator used an unusual means (an extended leg) to communicate the location of food, either rationally (her hands were occupied) or irrationally (she could have used her hand). Dogs succeeded in finding the food irrespective of whether the leg action was rational or irrational. Our results suggest that dogs do not distinguish rational from irrational acts, instead simply being proficient at monitoring human behavioural patterns.
Ape knapping experiments complement human knapping experiments as a source of behavioural data to... more Ape knapping experiments complement human knapping experiments as a source of behavioural data to build hypotheses about the learning mechanisms underlying the acquisition of knapping skills in extinct hominins. In addition, ape knapping experiments provide information regarding the stone-related behaviours that could have preceded the systematic production and use of sharp stones in our lineage. In this chapter we review previous ape knapping experiments with a focus on those that tested apes' abilities to socially learn from human demonstrators. Two studies, investigating one orangutan and one bonobo, concluded that both apes could socially learn sharp stone tool-making and use from human demonstrations. These results were interpreted as evidence of the reliance of early hominins on social learning to acquire knapping skills. However, alternative explanations exist. We provide novel data from two experiments investigating the abilities of the two previously untested great ape species (chimpanzees and gorillas) to learn knapping from human demonstrations. Contrary to the previous studies, the chimpanzees and gorillas in our experiments did not acquire sharp stone tool-making or use socially from human demonstrations. However, the apes we tested frequently manipulated the testing materials and two chimpanzees engaged in two events of lithic percussion involving an active hammer (although these actions did not lead to flake detachment). Our results suggest that the observation of human demonstrations is insufficient for the tested apes to acquire knapping abilities. This disparity in results between studies is unlikely to be explained by species differences in tool-use proficiency but rather by the particular rearing background of the previously tested individuals. We discuss how our previous results on both the individual and social learning abilities of unenculturated, untrained orangutans compare to our new results on gorillas and chimpanzees. In addition, we comment on the general implications of ape knapping experiments for understanding the likely origin and maintenance of knapping skills in pre-modern hominins.
Studies suggest that being mimicked can positively affect human social interactions, not only in ... more Studies suggest that being mimicked can positively affect human social interactions, not only in adults but also in children and even in individuals with atypical social competences. Outside of the human species, however, little is still known about this so-called ‘social glue function’ of mimicry; with only two studies—both on primates—testing whether other animals can show increased affiliation towards humans who mimic them. The present paper provides two pioneer studies on whether dogs—a domesticated species strongly attached to humans—show increased preference toward humans who display matching behaviour (walking). Results from both studies, including several tests, evidenced no preference of dogs for the human experimenter who matched the dogs’ walk. Methodological issues are discussed and a number of new routes of experimentation are proposed that we hope will prove valuable for future studies.
While culture is widespread in the animal kingdom, human culture has been claimed to be special d... more While culture is widespread in the animal kingdom, human culture has been claimed to be special due to being cumulative. It is currently debated which cognitive abilities support cumulative culture, but behavior copying is one of the main abilities proposed. One important source of contention is the presence or absence of behavior copying in our closest living relatives, non-human great apes (apes) – especially given that their behavior does not show clear signs of cumulation. Those who claim that apes copy behavior often base this claim on the existence of stable ape cultures in the wild. We developed an individual-based model to test whether ape cultural patterns can both
emerge and stabilize in absence of any behavior copying, when only allowing for a well-supported alternative social learning mechanism, socially-mediated reinnovation, where only the frequency of reinnovation is under social influence, but the form of the behavior is not. Our model reflects wild ape life conditions, including physiological and behavioral needs, demographic and spatial features, and possible genetic and ecological variation between populations. Our results show that, under a wide range of values of parameters, we fully reproduce the defining features of wild ape cultural
patterns. Overall, our results show that ape cultures can emerge and stabilize without behavior copying. Ape cultures do not show the signatures of behavior copying abilities, lending support to the notion that behavior copying is, among apes, unique in the human lineage. It therefore remains an open question when and why behaviour copying evolved in hominins.
Nut-cracking is often cited as one of the most complex behaviours observed in wild
chimpanzees.... more Nut-cracking is often cited as one of the most complex behaviours observed in wild
chimpanzees. However, the cognitive mechanisms behind its acquisition are still
debated. The current null hypothesis is that the form of nut-cracking behaviour relies
on variants of social learning, with some researchers arguing, more precisely, that
copying variants of social learning mechanisms are necessary. However, to date, very
few experiments have directly investigated the potentially sufficient role of individual
learning in explaining the behavioural form of nut-cracking. Despite this, the available
data provides some evidence for the spontaneous acquisition of nut-cracking by
chimpanzees; later group acquisition was then found to be at least facilitated by
(unspecified) variants of social learning. The latter findings are in line with both
suggested hypotheses, i.e., that copying social learning is required and that other (non-
copying) social learning mechanisms are at play. Here we present the first study which
focused (initially) on the role of individual learning for the acquisition of the nut-
cracking behavioural form in chimpanzees. We tested task-naïve chimpanzees (N = 13)
with an extended baseline condition to examine whether the behaviour would emerge
spontaneously. After the baseline condition (which was unsuccessful), we tested for
the role of social learning by providing social information in a step-wise fashion,
culminating in a full action demonstration of nut-cracking by a human demonstrator
(this last condition made it possible for the observers to copy all actions underlying
the behaviour). Despite the opportunities to individually and/or socially learn nut-
cracking, none of the chimpanzees tested here cracked nuts using tools in any of the
conditions in our study; thus, providing no conclusive evidence for either competing
hypothesis. We conclude that this failure was the product of an interplay of factors,
including behavioural conservatism and the existence of a potential sensitive learning
period for nut-cracking in chimpanzees. The possibility remains that nut-cracking is
a behaviour that chimpanzees can individually learn. However, this behaviour might
only be acquired when chimpanzees are still inside their sensitive learning period, and
when ecological and developmental conditions allow for it. The possibility remains
that nut-cracking is an example of a culture dependent trait in non-human great apes.
Recommendations for future research projects to address this question are considered.
This chapter applies cultural evolutionary and gene-culture coevolutionary theory to chimpanzees ... more This chapter applies cultural evolutionary and gene-culture coevolutionary theory to chimpanzees by reviewing the now large body of evidence on chimpanzee social learning, culture, and traditions. It provides comparative evidence for humans to assess the similarities and differences between these two species. By asking theoretically driven questions about the nature of culture in each species, the chapter aims to assess their shared phylogenetic heritage, and to isolate the selective forces that have distinguished these lineages over the last six to nine million years. It begins with a brief introduction to gene-culture coevolutionary theory, though specific elements of the theory will be rolled out as they go along. The chapter emphasizes that the goal is to apply theoretically derived insights to the available evidence from chimpanzees, and not to provide a general review of all work on this topic. It considers whether chimpanzee social learning has been shaped by natural selection, as it appears to have been in humans, to expand and hone the behavioral repertoires of individuals by facilitating the acquisition of adaptive practices from others.
This chapter critically discusses the earliest tools and cultures of hominins—the species most cl... more This chapter critically discusses the earliest tools and cultures of hominins—the species most closely related to humans. It starts with an inferred organic tool age that would have already existed before the split of hominins from the ape lineage. It then examines the two currently fully established earliest instances of the stone tool age—the Oldowan and Acheulean. Contrary to prevalent assumptions, the cultural status of the Oldowan and most or all of the Acheulean (and the organic tool age) may have been that of ‘minimal culture’. Minimal culture shares with modern human culture and animal culture influences of some social learning types—for example, on frequencies of behaviours and tools—but, unlike human culture, it excludes cultural transmission of novel—supra-individual—behavioural and/or artefact know-how. If true, cumulative cultural transmission of know-how to supra-individual levels would then have started much later than is currently presumed.
The goal of Artificial Life research, as articulated by Chris Langton, is "to contribute to theor... more The goal of Artificial Life research, as articulated by Chris Langton, is "to contribute to theoretical biology by locating life-as-we-know-it within the larger picture of life-as-it-could-be" (1989, p.1). The study and pursuit of open-ended evolution in artificial evolutionary systems exemplifies this goal. However, open-ended evolution research is hampered by two fundamental issues; the struggle to replicate open-endedness in an artificial evolutionary system, and the fact that we only have one system (genetic evolution) from which to draw inspiration. Here we argue that cultural evolution should be seen not only as another real-world example of an open-ended evolutionary system, but that the unique qualities seen in cultural evolution provide us with a new perspective from which we can assess the fundamental properties of, and ask new questions about, open-ended evolutionary systems, especially in regard to evolved open-endedness and transitions from bounded to unbounded evolution. Here we provide an overview of culture as an evolutionary system, highlight the interesting case of human cultural evolution as an open-ended evolutionary system, and contextualise cultural evolution under the framework of (evolved) open-ended evolution. We go on to provide a set of new questions that can be asked once we consider cultural evolution within the framework of open-ended evolution, and introduce new insights that we may be able to gain about evolved open-endedness as a result of asking these questions.
After stone tools, bone tools are the most abundant tool type in the hominin
archaeological rec... more After stone tools, bone tools are the most abundant tool type in the hominin
archaeological record. However, due to their poor preservation, they are relatively
scarce, limiting our understanding of the behavioural processes that led to their
production and use. Extant primates constitute a unique source of behavioural data to
build and shape hypotheses about the potential uses that our hominin ancestors might
have given to bone tools. In this study, we investigated the behavioural responses of
two groups of captive chimpanzees (Ntotal=42) to detached and cleaned bones while
participating in a foraging task aimed at eliciting excavating behavior. Each
chimpanzee group was provided with bones of different characteristics and the two
groups differed in their respective levels of experience with tool excavation (one
group being mostly inexperienced while the other had ample experience in stick tool excavation). We found that several individuals from the inexperienced group used the
provided bones as tools during the task. No individuals from the experienced group
used bones as excavating tools. Instead, these chimpanzees performed other bone-
related behaviours (not observed in the inexperienced group), such as hammering and
tool-assisted marrow consumption. Given that previous experience in tool excavation
did not predict the use of bones as tools in the excavating task, we hypothesize that
the differences in behavior observed between the two chimpanzee groups were due to
the characteristics of the bones they were provided with. Furthermore, our results
suggest that object characteristics rather than material determine whether
chimpanzees perceive an object as a suitable excavating tool.
Many animals, and in particular great apes, show evidence of culture, in the sense of having mult... more Many animals, and in particular great apes, show evidence of culture, in the sense of having multiple innovations in multiple domains whose frequencies are influenced by social learning. But only humans show strong evidence of complex, cumulative culture, which is the product of copying and the resulting effect of cumulative cultural evolution. The reasons for this increase in complexity have recently become the subject of extensive debate. Here, we examine these reasons, relying on both comparative and paleoarcheological data. The currently best-supported inference is that culture began to be truly cumulative (and so, outside the primate range) around 500,000 years ago. We suggest that the best explanation for its onset is the emergence of verbal teaching, which not only requires language and thus probably coevolved with the latter’s evolution but also reflects the overall increase in proactive cooperation due to extensive allomaternal care. A subsequent steep increase in cumulative culture, roughly 75 ka, may reflect the rise of active novelty seeking (curiosity), which led to a dramatic range expansion and steep increase in the diversity and complexity of material culture. A final, and continuing, period of acceleration began with the Neolithic (agricultural) revolution.
Replication is an important tool used to test and develop scientific theories. Areas of biomedica... more Replication is an important tool used to test and develop scientific theories. Areas of biomedical and psychological research have experienced a replication crisis, in which many published findings failed to replicate. Following this, many other scientific disciplines have been interested in the robustness of their own findings. This chapter examines replication in primate cognitive studies. First, it discusses the frequency and success of replication studies in primate cognition and explores the challenges
researchers face when designing and interpreting replication studies across the wide range of research designs used across the field. Next, it discusses the type of research that can probe the robustness of published findings, especially when replication studies are difficult to perform. The chapter concludes with a discussion of different roles that replication can have in primate cognition research.
An understanding of ape culture offers important insights into the evolution of human culture. Th... more An understanding of ape culture offers important insights into the evolution of human culture. This chapter presents the argument that ape tool cultures consist of socially-mediated branching chains of individually-derived behaviors (‘latent solutions’) and presents the hypothesis that the evolved motivations and skills of apes potentially enable them to individually create all tool behaviors shown by any other conspecific. Through non-copying observational learning mechanisms, each individual becomes sufficiently likely to express the latent solution variants shown in their group. But even with social mediation, each chimpanzee still must generate the underlying behavior individually (i.e. reinnovate it). Ultimately, reinnovation arises due to an interplay between environmental factors, motivation and skill. While the resulting uniformity of behavior within chimpanzee groups can create the illusion that their culture requires copying, we review the evidence and conclude this is not the case. Furthermore, latent solutions are not limited to chimpanzees – they may underlie the cultures of many other animals, and presumably those of earlier hominins. While our own species also possesses a ‘zone of latent solutions,’ the additional behaviors and technology that we use and produce today cannot occur unless they are culturally transmitted: they are not only cumulative, but truly culture-dependent traits.
Body-pockets are areas afforded by bodies that can be used to hold and/or transport objects to so... more Body-pockets are areas afforded by bodies that can be used to hold and/or transport objects to solve transport problems. Several lines of evidence – from animals (such as apes) to modern humans – point toward the likely use of body-pockets by all hominins. Here we highlight the neglect in the literature of accounting for hominin body-pocket usage. We argue that it is likely that body-pockets were used – at least sometimes – by hominins, and that, specifically, bipedal hominin body-pocket usage would have included the use of armpit-pockets. Hominins would have, at least sometimes, held and/or transported objects such as artefacts, including stone artefacts. This is the body-pocket / armpit-pocket hypothesis. Additionally, and independently of the body-pocket hypothesis more generally, we speculate that body-pocket usage could have influenced also aspects of the forms of carried objects – indirectly (via selecting) and/or directly (via forming). Three mutually exclusive theoretical possibilities remain. Possibility 1 (i.e. the current status quo): Any hominin body-pocket influence on objects’ forms was absent – or never sufficiently large to have left any recognisable pattern today. Possibility 2: There was a hominin body-pocket influence on objects’ forms, and this influence – while perhaps small – was large enough, at least sometimes and/or in some cases, to be recognisable today. Possibility 3 (the body-pocket fitting hypothesis): There was a hominin body-pocket influence on objects’ forms, and this influence was so large that it best explains large or complete parts of these forms completely. In our manuscript we tentatively reject Possibility 3. As for the remaining possibilities, Possibility 1 currently proved more parsimonious than Possibility 2. While we present data that is consistent with Possibility 2, no strong evidence was found to support it – rendering it a speculative and weak hypothesis. We outline possible future examinations of the body-pocket fitting hypothesis, but we conclude that the current status quo (i.e. Possibility 1) regarding the sources of hominin artefact forms remains unchanged.
It remains unclear when and why the ability to copy actions evolved and also its uniqueness to hu... more It remains unclear when and why the ability to copy actions evolved and also its uniqueness to humans. Thus far, a lack of valid evidence for spontaneous action copying by other apes supports the view that only humans spontaneously copy actions. However, wild apes have access to multiple demonstrators and have been demonstrated to be affected by majority influences, thus raising the possibility that ape action copying might require a majority ratio of demonstrators to observers. We tested for spontaneous ape action copying across all four non-human great ape species using a demonstrator majority. Nineteen captive mother-reared apes (across 4 species) were tested (Raage=9-52; Mage=18.63; ♀=14; ♂=5). All failed to copy the demonstrated actions, despite observing it in a majority influence condition. We conclude that culture in non-human great apes is more likely supported by variants of social learning which regulate frequencies, rather than forms, of observed behaviours.
We argue that imitation, in addition to the typical roles it plays in culture, additionally suppo... more We argue that imitation, in addition to the typical roles it plays in culture, additionally supports the social transmission and recombination of world models. We propose a learning pathway called “model-based assimilation”, which uses imitation to shape the statics of experience, and “hijacks” existing individual learning mechanisms supporting model-based learning (e.g., hippocampal replay). This pathway is computationally cheaper than explicit Theory of Mind inference, but nevertheless allows for the social recombination of knowledge across multiple brains. Our theory provides important insights into why our close relative, the chimpanzee, imitates poorly and why humans acquired cumulative culture.
Experimental replication of stone tools is an important method for understanding the context and ... more Experimental replication of stone tools is an important method for understanding the context and production of prehistoric technologies. In scientific undertakings, experimental control is a valuable and necessary means of ensuring that confounding variables are not influencing the outcomes of the study. One way that researchers can exert control in knapping experiments is to standardize the type, form, and size of raw materials that are provided to the knappers. Though measures to standardize materials are already part of archaeological practice, specific protocols, let alone comparisons between standardization techniques, are rarely openly reported. Consequently, independent laboratories often repeat the same trial-and-error process for selecting the ‘right’ material for testing. We investigate a variety of techniques and raw materials (e.g., hand-knapped flint, machine-cut basalt, manufactured glass, and porcelain). Each material was evaluated for their validity, reliability, and ease of standardization. Here, we have outlined the raw material tests we performed, providing information on the individual approaches, as well as comparisons between the techniques and materials according to both validity and reliability, along with their costs and our own recommendations. This text is intended as a serviceable guide
on raw material standardization for knapping experiments, including previously pursued avenues and means that are as-of-yet undescribed in the experimental archaeology literature. We include additional considerations for techniques that were not included in this study or which are presently not widely available and/or affordable. Future potential in this field would benefit from advances in the relevant technologies and in methodological approaches.
Range et al. (2007, Current Biology, 17,868-872) found that dogs, Canis familiaris, copy others’... more Range et al. (2007, Current Biology, 17,868-872) found that dogs, Canis familiaris, copy others’ means to achieve a goal more often when those means are the rational solution to a problem than when they are irrational. In our first experiment, we added a further control condition and failed to replicate this result, suggesting that dogs in the previous study may have been distracted in the irrational condition rather than selectively attending to the irrational nature of the action. In a second experiment, the demonstrator used an unusual means (an extended leg) to communicate the location of food, either rationally (her hands were occupied) or irrationally (she could have used her hand). Dogs succeeded in finding the food irrespective of whether the leg action was rational or irrational. Our results suggest that dogs do not distinguish rational from irrational acts, instead simply being proficient at monitoring human behavioural patterns.
Ape knapping experiments complement human knapping experiments as a source of behavioural data to... more Ape knapping experiments complement human knapping experiments as a source of behavioural data to build hypotheses about the learning mechanisms underlying the acquisition of knapping skills in extinct hominins. In addition, ape knapping experiments provide information regarding the stone-related behaviours that could have preceded the systematic production and use of sharp stones in our lineage. In this chapter we review previous ape knapping experiments with a focus on those that tested apes' abilities to socially learn from human demonstrators. Two studies, investigating one orangutan and one bonobo, concluded that both apes could socially learn sharp stone tool-making and use from human demonstrations. These results were interpreted as evidence of the reliance of early hominins on social learning to acquire knapping skills. However, alternative explanations exist. We provide novel data from two experiments investigating the abilities of the two previously untested great ape species (chimpanzees and gorillas) to learn knapping from human demonstrations. Contrary to the previous studies, the chimpanzees and gorillas in our experiments did not acquire sharp stone tool-making or use socially from human demonstrations. However, the apes we tested frequently manipulated the testing materials and two chimpanzees engaged in two events of lithic percussion involving an active hammer (although these actions did not lead to flake detachment). Our results suggest that the observation of human demonstrations is insufficient for the tested apes to acquire knapping abilities. This disparity in results between studies is unlikely to be explained by species differences in tool-use proficiency but rather by the particular rearing background of the previously tested individuals. We discuss how our previous results on both the individual and social learning abilities of unenculturated, untrained orangutans compare to our new results on gorillas and chimpanzees. In addition, we comment on the general implications of ape knapping experiments for understanding the likely origin and maintenance of knapping skills in pre-modern hominins.
Studies suggest that being mimicked can positively affect human social interactions, not only in ... more Studies suggest that being mimicked can positively affect human social interactions, not only in adults but also in children and even in individuals with atypical social competences. Outside of the human species, however, little is still known about this so-called ‘social glue function’ of mimicry; with only two studies—both on primates—testing whether other animals can show increased affiliation towards humans who mimic them. The present paper provides two pioneer studies on whether dogs—a domesticated species strongly attached to humans—show increased preference toward humans who display matching behaviour (walking). Results from both studies, including several tests, evidenced no preference of dogs for the human experimenter who matched the dogs’ walk. Methodological issues are discussed and a number of new routes of experimentation are proposed that we hope will prove valuable for future studies.
While culture is widespread in the animal kingdom, human culture has been claimed to be special d... more While culture is widespread in the animal kingdom, human culture has been claimed to be special due to being cumulative. It is currently debated which cognitive abilities support cumulative culture, but behavior copying is one of the main abilities proposed. One important source of contention is the presence or absence of behavior copying in our closest living relatives, non-human great apes (apes) – especially given that their behavior does not show clear signs of cumulation. Those who claim that apes copy behavior often base this claim on the existence of stable ape cultures in the wild. We developed an individual-based model to test whether ape cultural patterns can both
emerge and stabilize in absence of any behavior copying, when only allowing for a well-supported alternative social learning mechanism, socially-mediated reinnovation, where only the frequency of reinnovation is under social influence, but the form of the behavior is not. Our model reflects wild ape life conditions, including physiological and behavioral needs, demographic and spatial features, and possible genetic and ecological variation between populations. Our results show that, under a wide range of values of parameters, we fully reproduce the defining features of wild ape cultural
patterns. Overall, our results show that ape cultures can emerge and stabilize without behavior copying. Ape cultures do not show the signatures of behavior copying abilities, lending support to the notion that behavior copying is, among apes, unique in the human lineage. It therefore remains an open question when and why behaviour copying evolved in hominins.
Nut-cracking is often cited as one of the most complex behaviours observed in wild
chimpanzees.... more Nut-cracking is often cited as one of the most complex behaviours observed in wild
chimpanzees. However, the cognitive mechanisms behind its acquisition are still
debated. The current null hypothesis is that the form of nut-cracking behaviour relies
on variants of social learning, with some researchers arguing, more precisely, that
copying variants of social learning mechanisms are necessary. However, to date, very
few experiments have directly investigated the potentially sufficient role of individual
learning in explaining the behavioural form of nut-cracking. Despite this, the available
data provides some evidence for the spontaneous acquisition of nut-cracking by
chimpanzees; later group acquisition was then found to be at least facilitated by
(unspecified) variants of social learning. The latter findings are in line with both
suggested hypotheses, i.e., that copying social learning is required and that other (non-
copying) social learning mechanisms are at play. Here we present the first study which
focused (initially) on the role of individual learning for the acquisition of the nut-
cracking behavioural form in chimpanzees. We tested task-naïve chimpanzees (N = 13)
with an extended baseline condition to examine whether the behaviour would emerge
spontaneously. After the baseline condition (which was unsuccessful), we tested for
the role of social learning by providing social information in a step-wise fashion,
culminating in a full action demonstration of nut-cracking by a human demonstrator
(this last condition made it possible for the observers to copy all actions underlying
the behaviour). Despite the opportunities to individually and/or socially learn nut-
cracking, none of the chimpanzees tested here cracked nuts using tools in any of the
conditions in our study; thus, providing no conclusive evidence for either competing
hypothesis. We conclude that this failure was the product of an interplay of factors,
including behavioural conservatism and the existence of a potential sensitive learning
period for nut-cracking in chimpanzees. The possibility remains that nut-cracking is
a behaviour that chimpanzees can individually learn. However, this behaviour might
only be acquired when chimpanzees are still inside their sensitive learning period, and
when ecological and developmental conditions allow for it. The possibility remains
that nut-cracking is an example of a culture dependent trait in non-human great apes.
Recommendations for future research projects to address this question are considered.
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archaeological record. However, due to their poor preservation, they are relatively
scarce, limiting our understanding of the behavioural processes that led to their
production and use. Extant primates constitute a unique source of behavioural data to
build and shape hypotheses about the potential uses that our hominin ancestors might
have given to bone tools. In this study, we investigated the behavioural responses of
two groups of captive chimpanzees (Ntotal=42) to detached and cleaned bones while
participating in a foraging task aimed at eliciting excavating behavior. Each
chimpanzee group was provided with bones of different characteristics and the two
groups differed in their respective levels of experience with tool excavation (one
group being mostly inexperienced while the other had ample experience in stick tool excavation). We found that several individuals from the inexperienced group used the
provided bones as tools during the task. No individuals from the experienced group
used bones as excavating tools. Instead, these chimpanzees performed other bone-
related behaviours (not observed in the inexperienced group), such as hammering and
tool-assisted marrow consumption. Given that previous experience in tool excavation
did not predict the use of bones as tools in the excavating task, we hypothesize that
the differences in behavior observed between the two chimpanzee groups were due to
the characteristics of the bones they were provided with. Furthermore, our results
suggest that object characteristics rather than material determine whether
chimpanzees perceive an object as a suitable excavating tool.
researchers face when designing and interpreting replication studies across the wide range of research designs used across the field. Next, it discusses the type of research that can probe the robustness of published findings, especially when replication studies are difficult to perform. The chapter concludes with a discussion of different roles that replication can have in primate cognition research.
on raw material standardization for knapping experiments, including previously pursued avenues and means that are as-of-yet undescribed in the experimental archaeology literature. We include additional considerations for techniques that were not included in this study or which are presently not widely available and/or affordable. Future potential in this field would benefit from advances in the relevant technologies and in methodological approaches.
emerge and stabilize in absence of any behavior copying, when only allowing for a well-supported alternative social learning mechanism, socially-mediated reinnovation, where only the frequency of reinnovation is under social influence, but the form of the behavior is not. Our model reflects wild ape life conditions, including physiological and behavioral needs, demographic and spatial features, and possible genetic and ecological variation between populations. Our results show that, under a wide range of values of parameters, we fully reproduce the defining features of wild ape cultural
patterns. Overall, our results show that ape cultures can emerge and stabilize without behavior copying. Ape cultures do not show the signatures of behavior copying abilities, lending support to the notion that behavior copying is, among apes, unique in the human lineage. It therefore remains an open question when and why behaviour copying evolved in hominins.
chimpanzees. However, the cognitive mechanisms behind its acquisition are still
debated. The current null hypothesis is that the form of nut-cracking behaviour relies
on variants of social learning, with some researchers arguing, more precisely, that
copying variants of social learning mechanisms are necessary. However, to date, very
few experiments have directly investigated the potentially sufficient role of individual
learning in explaining the behavioural form of nut-cracking. Despite this, the available
data provides some evidence for the spontaneous acquisition of nut-cracking by
chimpanzees; later group acquisition was then found to be at least facilitated by
(unspecified) variants of social learning. The latter findings are in line with both
suggested hypotheses, i.e., that copying social learning is required and that other (non-
copying) social learning mechanisms are at play. Here we present the first study which
focused (initially) on the role of individual learning for the acquisition of the nut-
cracking behavioural form in chimpanzees. We tested task-naïve chimpanzees (N = 13)
with an extended baseline condition to examine whether the behaviour would emerge
spontaneously. After the baseline condition (which was unsuccessful), we tested for
the role of social learning by providing social information in a step-wise fashion,
culminating in a full action demonstration of nut-cracking by a human demonstrator
(this last condition made it possible for the observers to copy all actions underlying
the behaviour). Despite the opportunities to individually and/or socially learn nut-
cracking, none of the chimpanzees tested here cracked nuts using tools in any of the
conditions in our study; thus, providing no conclusive evidence for either competing
hypothesis. We conclude that this failure was the product of an interplay of factors,
including behavioural conservatism and the existence of a potential sensitive learning
period for nut-cracking in chimpanzees. The possibility remains that nut-cracking is
a behaviour that chimpanzees can individually learn. However, this behaviour might
only be acquired when chimpanzees are still inside their sensitive learning period, and
when ecological and developmental conditions allow for it. The possibility remains
that nut-cracking is an example of a culture dependent trait in non-human great apes.
Recommendations for future research projects to address this question are considered.
archaeological record. However, due to their poor preservation, they are relatively
scarce, limiting our understanding of the behavioural processes that led to their
production and use. Extant primates constitute a unique source of behavioural data to
build and shape hypotheses about the potential uses that our hominin ancestors might
have given to bone tools. In this study, we investigated the behavioural responses of
two groups of captive chimpanzees (Ntotal=42) to detached and cleaned bones while
participating in a foraging task aimed at eliciting excavating behavior. Each
chimpanzee group was provided with bones of different characteristics and the two
groups differed in their respective levels of experience with tool excavation (one
group being mostly inexperienced while the other had ample experience in stick tool excavation). We found that several individuals from the inexperienced group used the
provided bones as tools during the task. No individuals from the experienced group
used bones as excavating tools. Instead, these chimpanzees performed other bone-
related behaviours (not observed in the inexperienced group), such as hammering and
tool-assisted marrow consumption. Given that previous experience in tool excavation
did not predict the use of bones as tools in the excavating task, we hypothesize that
the differences in behavior observed between the two chimpanzee groups were due to
the characteristics of the bones they were provided with. Furthermore, our results
suggest that object characteristics rather than material determine whether
chimpanzees perceive an object as a suitable excavating tool.
researchers face when designing and interpreting replication studies across the wide range of research designs used across the field. Next, it discusses the type of research that can probe the robustness of published findings, especially when replication studies are difficult to perform. The chapter concludes with a discussion of different roles that replication can have in primate cognition research.
on raw material standardization for knapping experiments, including previously pursued avenues and means that are as-of-yet undescribed in the experimental archaeology literature. We include additional considerations for techniques that were not included in this study or which are presently not widely available and/or affordable. Future potential in this field would benefit from advances in the relevant technologies and in methodological approaches.
emerge and stabilize in absence of any behavior copying, when only allowing for a well-supported alternative social learning mechanism, socially-mediated reinnovation, where only the frequency of reinnovation is under social influence, but the form of the behavior is not. Our model reflects wild ape life conditions, including physiological and behavioral needs, demographic and spatial features, and possible genetic and ecological variation between populations. Our results show that, under a wide range of values of parameters, we fully reproduce the defining features of wild ape cultural
patterns. Overall, our results show that ape cultures can emerge and stabilize without behavior copying. Ape cultures do not show the signatures of behavior copying abilities, lending support to the notion that behavior copying is, among apes, unique in the human lineage. It therefore remains an open question when and why behaviour copying evolved in hominins.
chimpanzees. However, the cognitive mechanisms behind its acquisition are still
debated. The current null hypothesis is that the form of nut-cracking behaviour relies
on variants of social learning, with some researchers arguing, more precisely, that
copying variants of social learning mechanisms are necessary. However, to date, very
few experiments have directly investigated the potentially sufficient role of individual
learning in explaining the behavioural form of nut-cracking. Despite this, the available
data provides some evidence for the spontaneous acquisition of nut-cracking by
chimpanzees; later group acquisition was then found to be at least facilitated by
(unspecified) variants of social learning. The latter findings are in line with both
suggested hypotheses, i.e., that copying social learning is required and that other (non-
copying) social learning mechanisms are at play. Here we present the first study which
focused (initially) on the role of individual learning for the acquisition of the nut-
cracking behavioural form in chimpanzees. We tested task-naïve chimpanzees (N = 13)
with an extended baseline condition to examine whether the behaviour would emerge
spontaneously. After the baseline condition (which was unsuccessful), we tested for
the role of social learning by providing social information in a step-wise fashion,
culminating in a full action demonstration of nut-cracking by a human demonstrator
(this last condition made it possible for the observers to copy all actions underlying
the behaviour). Despite the opportunities to individually and/or socially learn nut-
cracking, none of the chimpanzees tested here cracked nuts using tools in any of the
conditions in our study; thus, providing no conclusive evidence for either competing
hypothesis. We conclude that this failure was the product of an interplay of factors,
including behavioural conservatism and the existence of a potential sensitive learning
period for nut-cracking in chimpanzees. The possibility remains that nut-cracking is
a behaviour that chimpanzees can individually learn. However, this behaviour might
only be acquired when chimpanzees are still inside their sensitive learning period, and
when ecological and developmental conditions allow for it. The possibility remains
that nut-cracking is an example of a culture dependent trait in non-human great apes.
Recommendations for future research projects to address this question are considered.