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Journal of Anatomy Jul 2024Extant great apes are characterized by a wide range of locomotor, postural and manipulative behaviours that each require the limbs to be used in different ways. In...
Extant great apes are characterized by a wide range of locomotor, postural and manipulative behaviours that each require the limbs to be used in different ways. In addition to external bone morphology, comparative investigation of trabecular bone, which (re-)models to reflect loads incurred during life, can provide novel insights into bone functional adaptation. Here, we use canonical holistic morphometric analysis (cHMA) to analyse the trabecular morphology in the distal femoral epiphysis of Homo sapiens (n = 26), Gorilla gorilla (n = 14), Pan troglodytes (n = 15) and Pongo sp. (n = 9). We test two predictions: (1) that differing locomotor behaviours will be reflected in differing trabecular architecture of the distal femur across Homo, Pan, Gorilla and Pongo; (2) that trabecular architecture will significantly differ between male and female Gorilla due to their different levels of arboreality but not between male and female Pan or Homo based on previous studies of locomotor behaviours. Results indicate that trabecular architecture differs among extant great apes based on their locomotor repertoires. The relative bone volume and degree of anisotropy patterns found reflect habitual use of extended knee postures during bipedalism in Homo, and habitual use of flexed knee posture during terrestrial and arboreal locomotion in Pan and Gorilla. Trabecular architecture in Pongo is consistent with a highly mobile knee joint that may vary in posture from extension to full flexion. Within Gorilla, trabecular architecture suggests a different loading of knee in extension/flexion between females and males, but no sex differences were found in Pan or Homo, supporting our predictions. Inter- and intra-specific variation in trabecular architecture of distal femur provides a comparative context to interpret knee postures and, in turn, locomotor behaviours in fossil hominins.
Topics: Animals; Male; Female; Femur; Hominidae; Humans; Cancellous Bone; Locomotion; Gorilla gorilla; Pan troglodytes
PubMed: 38381116
DOI: 10.1111/joa.14026 -
Evolutionary Anthropology Dec 2023Chimpanzees regularly hunt and consume prey smaller than themselves. It seems therefore likely that early hominins also consumed small vertebrate meat before they... (Review)
Review
Chimpanzees regularly hunt and consume prey smaller than themselves. It seems therefore likely that early hominins also consumed small vertebrate meat before they started using and producing stone tools. Research has focused on cut marks and large ungulates, but there is a small body of work that has investigated the range of bone modifications produced on small prey by chimpanzee mastication that, by analogy, can be used to identify carnivory in pre-stone tool hominins. Here, we review these works along with behavioral observations and other neo-taphonomic research. Despite some equifinality with bone modifications produced by baboons and the fact that prey species used in experiments seldom are similar to the natural prey of chimpanzees, we suggest that traces of chimpanzee mastication are sufficiently distinct from those of other predators that they can be used to investigate mastication of vertebrate prey by early hominins.
Topics: Animals; Hominidae; Pan troglodytes; Carnivory; Mammals; Vertebrates; Papio
PubMed: 37844154
DOI: 10.1002/evan.22006 -
Cognition Jul 2023How we judge the similarity between objects in the world is connected ultimately to how we represent those objects. It has been argued extensively that object...
How we judge the similarity between objects in the world is connected ultimately to how we represent those objects. It has been argued extensively that object representations in humans are 'structured' in nature, meaning that both individual features and the relations between them can influence similarity. In contrast, popular models within comparative psychology assume that nonhuman species appreciate only surface-level, featural similarities. By applying psychological models of structural and featural similarity (from conjunctive feature models to Tversky's Contrast Model) to visual similarity judgements from adult humans, chimpanzees, and gorillas, we demonstrate a cross-species sensitivity to complex structural information, particularly for stimuli that combine colour and shape. These results shed new light on the representational complexity of nonhuman apes, and the fundamental limits of featural coding in explaining object representation and similarity, which emerge strikingly across both human and nonhuman species.
Topics: Adult; Animals; Humans; Hominidae; Judgment; Pan troglodytes; Models, Psychological; Pattern Recognition, Visual
PubMed: 37104894
DOI: 10.1016/j.cognition.2023.105419 -
Anatomical Record (Hoboken, N.J. : 2007) Aug 2023For a given body mass, hominoids have longer clavicles than typical monkeys, reflecting the lateral reorientation of the hominoid glenoid. Relative length of the...
For a given body mass, hominoids have longer clavicles than typical monkeys, reflecting the lateral reorientation of the hominoid glenoid. Relative length of the clavicle varies among hominoids, with orangutans having longer clavicles than expected for body mass and gorillas and chimpanzees having shorter clavicles than expected. Modern humans conform to the general hominoid distribution, but Neandertals and Upper Paleolithic Homo sapiens have longer clavicles than expected for their size and exhibit marked positive allometry in clavicle length. Relative to clavicle length, adult and newborn humans have broader shoulders (biacromial breadths) than comparable apes, because the reduced elevation of the human shoulder swings the acromion laterally downward away from the head. Since broadened shoulders yield an increased risk of maternal and neonatal injury and/or death from shoulder dystocia during birth, we might expect hominins to manifest trends toward reduction in shoulder breadth and clavicle length. They do not, presumably because of countering selection pressures favoring a long clavicle in the adults. The marked sexual dimorphism seen in patterns of clavicular growth and static adult allometry in humans suggests that those selection pressures have disproportionately affected the males.
Topics: Male; Animals; Infant, Newborn; Humans; Shoulder; Clavicle; Biological Evolution; Hominidae; Scapula; Neanderthals; Pan troglodytes; Haplorhini
PubMed: 36594678
DOI: 10.1002/ar.25144 -
Animal Cognition Sep 2023Object interactions play an important role in human communication but the extent to which nonhuman primates incorporate objects in their social interactions remains...
Object interactions play an important role in human communication but the extent to which nonhuman primates incorporate objects in their social interactions remains unknown. To better understand the evolution of object use, this study explored how objects are used in social interactions in semi-wild chimpanzees (Pan troglodytes). We used an observational approach focusing on naturally occurring object actions where we examined their use and tested whether the production of object actions was influenced by the recipients' visual attention as well as by colony membership. The results show that chimpanzees adjusted both the type of object used, and the modality of object actions to match the visual attention of the recipient, as well as colony differences in the use of targeted object actions. These results provide empirical evidence highlighting that chimpanzees use objects in diverse ways to communicate with conspecifics and that their use may be shaped by social factors, contributing to our understanding of the evolution of human nonverbal communication, language, and tool use.
Topics: Animals; Animal Communication; Language; Nonverbal Communication; Pan troglodytes
PubMed: 37314595
DOI: 10.1007/s10071-023-01792-z -
Proceedings of the National Academy of... Dec 2023Recognition and memory of familiar conspecifics provides the foundation for complex sociality and is vital to navigating an unpredictable social world [Tibbetts and...
Recognition and memory of familiar conspecifics provides the foundation for complex sociality and is vital to navigating an unpredictable social world [Tibbetts and Dale, , 529-537 (2007)]. Human social memory incorporates content about interactions and relationships and can last for decades [Sherry and Schacter, , 439-454 (1987)]. Long-term social memory likely played a key role throughout human evolution, as our ancestors increasingly built relationships that operated across distant space and time [Malone ., , 1251-1277 (2012)]. Although individual recognition is widespread among animals and sometimes lasts for years, little is known about social memory in nonhuman apes and the shared evolutionary foundations of human social memory. In a preferential-looking eye-tracking task, we presented chimpanzees and bonobos ( = 26) with side-by-side images of a previous groupmate and a conspecific stranger of the same sex. Apes' attention was biased toward former groupmates, indicating long-term memory for past social partners. The strength of biases toward former groupmates was not impacted by the duration apart, and our results suggest that recognition may persist for at least 26 y beyond separation. We also found significant but weak evidence that, like humans, apes may remember the quality or content of these past relationships: apes' looking biases were stronger for individuals with whom they had more positive histories of social interaction. Long-lasting social memory likely provided key foundations for the evolution of human culture and sociality as they extended across time, space, and group boundaries.
Topics: Animals; Humans; Pan troglodytes; Pan paniscus; Hominidae; Social Behavior; Recognition, Psychology
PubMed: 38109542
DOI: 10.1073/pnas.2304903120 -
Journal of Comparative Psychology... Apr 2024Neophilia is a measure of individuals' attraction to novelty and is thought to provide important fitness benefits related to the acquisition of information and the...
Neophilia is a measure of individuals' attraction to novelty and is thought to provide important fitness benefits related to the acquisition of information and the ability to solve novel problems. Although neophilia is thought to vary across individuals and species, few studies have made direct comparisons to assess the factors that predict this variation. Here we operationalized neophilia as the probability of interacting with novel objects and compared the response to familiar and novel objects in 53 captive individuals belonging to seven different primate species: chimpanzees ), bonobos (), Sumatran orangutans (), gorillas (), long-tailed macaques (), tufted capuchin monkeys (), and Geoffroy's spider monkeys (). Our results showed that individuals were overall more likely to interact with novel than familiar objects. Moreover, we found no evidence that neophilia varied across individuals depending on their sex, age, and dominance rank. However, macaques were overall less likely to interact with objects (regardless of their novelty), as compared to bonobos, orangutans, gorillas, and capuchin monkeys. (PsycInfo Database Record (c) 2024 APA, all rights reserved).
PubMed: 38573676
DOI: 10.1037/com0000377 -
Physics of Life Reviews Jul 2023A prerequisite for copying innovative behaviour faithfully is the capacity of observers' brains, regarded as 'hierarchically mechanistic minds', to overcome cognitive... (Review)
Review
A prerequisite for copying innovative behaviour faithfully is the capacity of observers' brains, regarded as 'hierarchically mechanistic minds', to overcome cognitive 'surprisal' (see 2.), by maximising the evidence for their internal models, through active inference. Unlike modern humans, chimpanzees and other great apes show considerable limitations in their ability, or 'Zone of Bounded Surprisal', to overcome cognitive surprisal induced by innovative or unorthodox behaviour that rarely, therefore, is copied precisely or accurately. Most can copy adequately what is within their phenotypically habitual behavioural repertoire, in which technology plays scant part. Widespread intra- and intergenerational social transmission of complex technological innovations is not a hall-mark of great-ape taxa. 3 Ma, precursors of the genus Homo made stone artefacts, and stone-flaking likely was habitual before 2 Ma. After that time, early Homo erectus has left traces of technological innovations, though faithful copying of these and their intra- and intergenerational social transmission were rare before 1 Ma. This likely owed to a cerebral infrastructure of interconnected neuronal systems more limited than ours. Brains were smaller in size than ours, and cerebral neuronal systems ceased to develop when early Homo erectus attained full adult maturity by the mid-teen years, whereas its development continues until our mid-twenties nowadays. Pleistocene Homo underwent remarkable evolutionary adaptation of neurobiological propensities, and cerebral aspects are discussed that, it is proposed here, plausibly, were fundamental for faithful copying, which underpinned social transmission of technologies, cumulative learning, and culture. Here, observers' responses to an innovation are more important for ensuring its transmission than is an innovator's production of it, because, by themselves, the minimal cognitive prerequisites that are needed for encoding and assimilating innovations are insufficient for practical outcomes to accumulate and spread intra- and intergenerationally.
Topics: Adult; Animals; Adolescent; Humans; Pan troglodytes; Hominidae; Brain; Learning; Technology
PubMed: 36931123
DOI: 10.1016/j.plrev.2023.02.005 -
Learning & Behavior Dec 2023The outcome of an action often occurs after a delay. One solution for learning appropriate actions from delayed outcomes is to rely on a chain of state transitions....
The outcome of an action often occurs after a delay. One solution for learning appropriate actions from delayed outcomes is to rely on a chain of state transitions. Another solution, which does not rest on state transitions, is to use an eligibility trace (ET) that directly bridges a current outcome and multiple past actions via transient memories. Previous studies revealed that humans (Homo sapiens) learned appropriate actions in a behavioral task in which solutions based on the ET were effective but transition-based solutions were ineffective. This suggests that ET may be used in human learning systems. However, no studies have examined nonhuman animals with an equivalent behavioral task. We designed a task for nonhuman animals following a previous human study. In each trial, participants chose one of two stimuli that were randomly selected from three stimulus types: a stimulus associated with a food reward delivered immediately, a stimulus associated with a reward delivered after a few trials, and a stimulus associated with no reward. The presented stimuli did not vary according to the participants' choices. To maximize the total reward, participants had to learn the value of the stimulus associated with a delayed reward. Five chimpanzees (Pan troglodytes) performed the task using a touchscreen. Two chimpanzees were able to learn successfully, indicating that learning mechanisms that do not depend on state transitions were involved in the learning processes. The current study extends previous ET research by proposing a behavioral task and providing empirical data from chimpanzees.
Topics: Humans; Animals; Pan troglodytes; Learning; Reinforcement, Psychology; Reward; Food
PubMed: 37369920
DOI: 10.3758/s13420-023-00591-3 -
Proceedings of the National Academy of... May 2024The aryl hydrocarbon receptor (AHR) is a transcription factor that has many functions in mammals. Its best known function is that it binds aromatic hydrocarbons and...
The aryl hydrocarbon receptor (AHR) is a transcription factor that has many functions in mammals. Its best known function is that it binds aromatic hydrocarbons and induces the expression of cytochrome P450 genes, which encode enzymes that metabolize aromatic hydrocarbons and other substrates. All present-day humans carry an amino acid substitution at position 381 in the AHR that occurred after the divergence of modern humans from Neandertals and Denisovans. Previous studies that have expressed the ancestral and modern versions of AHR from expression vectors have yielded conflicting results with regard to their activities. Here, we use genome editing to modify the endogenous gene so that it encodes to the ancestral, Neandertal-like AHR protein in human cells. In the absence of exogenous ligands, the expression of AHR target genes is higher in cells expressing the ancestral AHR than in cells expressing the modern AHR, and similar to the expression in chimpanzee cells. Furthermore, the modern human AHR needs higher doses of three ligands than the ancestral AHR to induce the expression of target genes. Thus, the ability of AHR to induce the expression of many of its target genes is reduced in modern humans.
Topics: Receptors, Aryl Hydrocarbon; Humans; Gene Editing; Animals; Basic Helix-Loop-Helix Transcription Factors; Evolution, Molecular; Pan troglodytes; Neanderthals; Ligands
PubMed: 38739836
DOI: 10.1073/pnas.2402159121