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Developmental Science May 2023Directedness and engagement during pre-verbal vocal communication play a major role in language development. What was their role in the evolution of language? This... (Observational Study)
Observational Study
Directedness and engagement during pre-verbal vocal communication play a major role in language development. What was their role in the evolution of language? This question invites us to examine these behaviours in chimpanzee vocal ontogeny. We collected observational data on infant (N = 15) and juvenile (N = 13) chimpanzees at Chimfunshi Wildlife Orphanage, Zambia. We examined the impact of age and vocalization type (grunts, whimpers, laughs and screams) on directed cues (gaze directedness and face directedness) and engagement (mutual face directedness) during vocal communication. We also assessed the impact of directed cues and engagement on social interactions by coding the behaviour of social partners before, during and after a vocalisation, and examining whether they contingently changed their behaviour in response to the vocalisation if it was directed or if engagement occurred. We found that face directed vocalisations showed a general increase during ontogeny and we observed call-type dependent effects of age for mutual face directedness. Only face directed vocalisations were significantly predictive of behavioural responses in social partners. We conclude that like young humans, young chimpanzees routinely exhibit directed behaviours and engagement during vocal communication. This social competency improves during ontogeny and benefits individuals by increasing the chances of eliciting behavioural responses from social partners. Directedness and engagement likely provide a foundation for language phylogenetically, as well as ontogenetically. RESEARCH HIGHLIGHTS: We show that directedness and engagement routinely occur during early chimpanzee vocalisations. Directedness increases throughout chimpanzee vocal ontogeny, similar to human infants. Directedness enhances social partner responsiveness, demonstrating a direct benefit to this style of communication. Directedness and engagement could provide a route towards language phylogenetically as well as ontogenetically.
Topics: Animals; Humans; Infant; Communication; Hominidae; Pan troglodytes; Vocalization, Animal; Voice
PubMed: 36222443
DOI: 10.1111/desc.13334 -
Current Biology : CB Dec 2022Humans, like many other animals, live in groups and coordinate actions with others in social settings. Such interpersonal coordination may emerge unconsciously and when...
Humans, like many other animals, live in groups and coordinate actions with others in social settings. Such interpersonal coordination may emerge unconsciously and when the goal is not the coordination of movements, as when falling into the same rhythm when walking together. Although one of our closest living relatives, the chimpanzee (Pan troglodytes), shows the ability to succeed in complex joint action tasks where coordination is the goal, little is known about simpler forms of joint action. Here, we examine whether chimpanzees spontaneously synchronize their actions with conspecifics while walking together. We collected data on individual walking behavior of two groups of chimpanzees under semi-natural conditions. In addition, we assessed social relationships to investigate potential effects on the strength of coordination. When walking with a conspecific, individuals walked faster than when alone. The relative phase was symmetrically distributed around 0° with the highest frequencies around 0, indicating a tendency to coordinate actions. Further, coordination was stronger when walking with a partner compared with two individuals walking independently. Although the inter-limb entrainment was more pronounced between individuals of similar age as a proxy for height, it was not affected by the kinship or bonding status of the walkers or the behaviors they engaged in immediately after the walk. We conclude that chimpanzees adapt their individual behavior to temporally coordinate actions with others, which might provide a basis for engaging in other more complex forms of joint action. This spontaneous form of inter-individual coordination, often called entrainment, is thus shared with humans.
Topics: Humans; Animals; Pan troglodytes; Walking
PubMed: 36270278
DOI: 10.1016/j.cub.2022.09.059 -
Science (New York, N.Y.) Oct 2020
Topics: Aging; Animals; Pan troglodytes; Social Behavior
PubMed: 33093096
DOI: 10.1126/science.abe9110 -
Journal of Comparative Psychology... May 2021For over a century now, a number of researchers have explored the evolutionary emergence of mark-making and drawing behaviors through studies in monkeys and apes, and... (Review)
Review
For over a century now, a number of researchers have explored the evolutionary emergence of mark-making and drawing behaviors through studies in monkeys and apes, and particularly in chimpanzees. Their observations and results remain relevant to this day and underline the interest of this question and the questions that remain to be answered. The present review begins by retracing the historical timeline of this specific and challenging topic from the earliest anecdotal evidence to the first systematic studies in the 1930s. We then describe how the research became more empirical through the use of stimulus figures, the examination of color choices, or even exploring outline-making processes. We discuss the use of touch screens in the 1990s, which enriched our knowledge by providing an opportunity for data collection and innovative analysis. Finally, we underline several key points that are of importance for future investigations into the mark-making process in nonhuman primates. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
Topics: Animals; Biological Evolution; Pan troglodytes; Primates
PubMed: 33252920
DOI: 10.1037/com0000251 -
Science (New York, N.Y.) Nov 2023Bonobos provide insight into the origins of partner-specific cooperation in human groups.
Bonobos provide insight into the origins of partner-specific cooperation in human groups.
Topics: Animals; Humans; Pan paniscus; Pan troglodytes; Mass Behavior; Cooperative Behavior; Grooming
PubMed: 37972176
DOI: 10.1126/science.adl1813 -
Anthropologischer Anzeiger; Bericht... Jan 2023Wrist shape varies greatly across primates and previous studies indicate that the numerous morphological differences among them are related to a complex mixture of...
Wrist shape varies greatly across primates and previous studies indicate that the numerous morphological differences among them are related to a complex mixture of phylogeny and function. However, little is known about whether the variation in these various anatomical differences is linked and to what extent the wrist bones vary independently. Here, we used 3D geometric morphometrics on a sample of extant hominines (, and ), to find the model that best describes the covariation patterns among four of the eight carpals (i.e., capitate, lunate, scaphoid, and trapezium). For this purpose, 15 modular hypotheses were tested using the Covariance Ratio. Results indicate that there is a covariation structure common to all hominines, which corresponds to stronger covariation within each carpal as compared to the covariation between carpals. However, the results also indicate that that there is a degree of codependence in the variation of some carpals, which is unique in humans, chimpanzees, and gorillas, respectively. In humans there is evidence of associated shape changes between the lunate and capitate, and between the scaphoid and trapezium. This covariation between lunate and capitate is also apparent in gorillas, while chimpanzees display the greatest disassociation among carpals, showing low covariation values in all pairwise comparisons. Our analyses indicate that carpals have an important level of variational independence which might suggest a high degree of independent evolvability in the wrists of hominines, and that although weak, the structure of associated changes of these four carpals varies across genera. To our knowledge this is the first report on the patterns of modularity between these four wrist bones in the Homininae and future studies might attempt to investigate whether the anatomical shape associations among carpals are functionally related to locomotion and manipulation.
Topics: Animals; Humans; Wrist; Gorilla gorilla; Pan troglodytes; Hominidae; Carpal Bones
PubMed: 36006051
DOI: 10.1127/anthranz/2022/1558 -
Proceedings of the National Academy of... Apr 2022Admixture appears increasingly ubiquitous in the evolutionary history of various taxa, including humans. Such gene flow likely also occurred among our closest living...
Admixture appears increasingly ubiquitous in the evolutionary history of various taxa, including humans. Such gene flow likely also occurred among our closest living relatives: bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). However, our understanding of their evolutionary history has been limited by studies that do not consider all Pan lineages or do not analyze all lineages simultaneously, resulting in conflicting demographic models. Here, we investigate this gap in knowledge using nucleotide site patterns calculated from whole-genome sequences from the autosomes of 71 bonobos and chimpanzees, representing all five extant Pan lineages. We estimated demographic parameters and compared all previously proposed demographic models for this clade. We further considered sex bias in Pan evolutionary history by analyzing the site patterns from the X chromosome. We show that 1) 21% of autosomal DNA in eastern chimpanzees derives from western chimpanzee introgression and that 2) all four chimpanzee lineages share a common ancestor about 987,000 y ago, much earlier than previous estimates. In addition, we suggest that 3) there was male reproductive skew throughout Pan evolutionary history and find evidence of 4) male-biased dispersal from western to eastern chimpanzees. Collectively, these results offer insight into bonobo and chimpanzee evolutionary history and suggest considerable differences between current and historic chimpanzee biogeography.
Topics: Animals; Biological Evolution; Female; Genome; Male; Nucleotides; Pan paniscus; Pan troglodytes
PubMed: 35452306
DOI: 10.1073/pnas.2200858119 -
Journal of Human Evolution Sep 2022The calculation of morphological integration across living apes and humans may provide important insights into the potential influence of integration on evolutionary...
The calculation of morphological integration across living apes and humans may provide important insights into the potential influence of integration on evolutionary trajectories in the hominid lineage. Here, we quantify magnitudes of morphological integration among and within elements of the midfoot in great apes and humans to examine the link between locomotor differences and trait covariance. We test the hypothesis that the medial elements of the great ape foot are less morphologically integrated with one another compared to humans based on their abducted halluces, and aim to determine how adaptations for midfoot mobility/stiffness and locomotor specialization influence magnitudes of morphological integration. The study sample is composed of all cuneiforms, the navicular, the cuboid, and metatarsals 1-5 of Homo sapiens (n = 80), Pan troglodytes (n = 63), Gorilla gorilla (n = 39), and Pongo sp. (n = 41). Morphological integration was quantified using the integration coefficient of variation of interlandmark distances organized into sets of a priori-defined modules. Magnitudes of integration across these modules were then compared against sets of random traits from the whole midfoot. Results show that all nonhuman apes have less integrated medial elements, whereas humans have highly integrated medial elements, suggesting a link between hallucal abduction and reduced levels of morphological integration. However, we find considerable variation in magnitudes of morphological integration across metatarsals 2-5, the intermediate and lateral cuneiform, the cuboid, and navicular, emphasizing the influence of functional and nonfunctional factors in magnitudes of integration. Lastly, we find that humans and orangutans show the lowest overall magnitudes of integration in the midfoot, which may be related to their highly specialized functions, and suggest a link between strong diversifying selection and reduced magnitudes of morphological integration.
Topics: Animals; Foot; Gorilla gorilla; Hominidae; Humans; Pan troglodytes; Pongo; Pongo pygmaeus
PubMed: 35940157
DOI: 10.1016/j.jhevol.2022.103231 -
American Journal of Physical... Apr 2021The Giles hypothesis posits that differences in the cranial morphology of Pan troglodytes and Gorilla gorilla are largely the result of allometric scaling. However,...
OBJECTIVES
The Giles hypothesis posits that differences in the cranial morphology of Pan troglodytes and Gorilla gorilla are largely the result of allometric scaling. However, previous support for the Giles hypothesis was based on bivariate plots of linear measurements. This investigation uses geometric morphometric methods to retest this hypothesis and its prediction that extending the ontogenetic trajectory of a chimpanzee would produce an adult gorilla-like cranial morphology.
MATERIALS AND METHODS
Forty-three 3D cranial landmarks were collected from an ontogenetic series of 76 Pan troglodytes and 58 Gorilla gorilla specimens. Ontogenetic trajectories of cranial shape change were computed via multivariate regression of Procrustes aligned coordinates against LnCS (size vector) and molar eruption stage (developmental vector). These two vectors were then used in developmental simulations to extend the ontogenetic trajectories of adult chimpanzees. Allometric trajectories of chimpanzees and gorillas were also directly compared using Procrustes ANOVA.
RESULTS
Pan and Gorilla significantly differ in their allometric trajectories, and none of the Pan developmental simulations resembled actual adult gorillas. Additionally, the more the Pan developmental vector was extended, the more morphologically distinct the simulations became from actual adult gorillas.
DISCUSSION
Taken together, these results do not support the Giles hypothesis that allometric scaling is primarily responsible for observed morphological differences between chimpanzee and gorilla crania. This investigation demonstrates that neither "growing" a chimpanzee to the size of a gorilla, nor extending a chimpanzee's developmental shape trajectory will result in an adult gorilla-like cranial morphology as they differ in their patterns of allometry.
Topics: Animals; Anthropology, Physical; Biological Evolution; Cephalometry; Female; Gorilla gorilla; Male; Pan troglodytes; Skull
PubMed: 33393687
DOI: 10.1002/ajpa.24219 -
Nature Communications Sep 2020Large brains and behavioural innovation are positively correlated, species-specific traits, associated with the behavioural flexibility animals need for adapting to...
Large brains and behavioural innovation are positively correlated, species-specific traits, associated with the behavioural flexibility animals need for adapting to seasonal and unpredictable habitats. Similar ecological challenges would have been important drivers throughout human evolution. However, studies examining the influence of environmental variability on within-species behavioural diversity are lacking despite the critical assumption that population diversification precedes genetic divergence and speciation. Here, using a dataset of 144 wild chimpanzee (Pan troglodytes) communities, we show that chimpanzees exhibit greater behavioural diversity in environments with more variability - in both recent and historical timescales. Notably, distance from Pleistocene forest refugia is associated with the presence of a larger number of behavioural traits, including both tool and non-tool use behaviours. Since more than half of the behaviours investigated are also likely to be cultural, we suggest that environmental variability was a critical evolutionary force promoting the behavioural, as well as cultural diversification of great apes.
Topics: Animals; Behavior, Animal; Ecosystem; Environment; Female; Forests; Male; Pan troglodytes; Tool Use Behavior
PubMed: 32934202
DOI: 10.1038/s41467-020-18176-3