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American Journal of Biological... May 2023Chimpanzees (Pan troglodytes) possess a relatively generalized molar morphology allowing them to access a wide range of foods. Comparisons of crown and cusp morphology...
OBJECTIVES
Chimpanzees (Pan troglodytes) possess a relatively generalized molar morphology allowing them to access a wide range of foods. Comparisons of crown and cusp morphology among the four subspecies have suggested relatively large intraspecific variability. Here, we compare molar crown traits and cusp wear of two geographically close populations of Western chimpanzees, P. t. verus, to provide further information on intraspecific dental variability.
MATERIALS AND METHODS
Micro-CT reconstructions of high-resolution replicas of first and second molars of two Western chimpanzee populations from Ivory Coast (Taï National Park) and Liberia, respectively were used for this study. First, we analyzed projected tooth and cusp 2D areas as well as the occurrence of cusp six (C6) on lower molars. Second, we quantified the molar cusp wear three-dimensionally to infer how the individual cusps alter with advancing wear.
RESULTS
Both populations are similar in their molar crown morphology, except for a higher appearance rate of a C6 in Taï chimpanzees. In Taï chimpanzees, lingual cusps of upper molars and buccal cusps of lower molars possess an advanced wear pattern compared to the remaining cusps, while in Liberian chimpanzees this wear gradient is less pronounced.
DISCUSSION
The similar crown morphology between both populations fits with previous descriptions for Western chimpanzees and provides additional data on dental variation within this subspecies. The wear pattern of the Taï chimpanzees are in concordance with their observed tool rather than tooth use to open nuts/seeds, while the Liberian chimpanzees may have consumed hard food items crushed between their molars.
Topics: Animals; Pan troglodytes; Hominidae; Tooth Crown; Tooth; Crowns
PubMed: 36807569
DOI: 10.1002/ajpa.24707 -
Journal of Human Evolution Nov 2017There is broad consensus among paleoanthropologists that meat-eating played a key role in the evolution of Homo, but the details of where, when, and why are hotly...
There is broad consensus among paleoanthropologists that meat-eating played a key role in the evolution of Homo, but the details of where, when, and why are hotly debated. It has been argued that increased faunivory was causally connected with hominin adaptation to open, savanna habitats. If savanna-dwelling chimpanzees eat meat more frequently than do forest chimpanzees, it would support the notion that open, dry, seasonal habitats promote hunting or scavenging by hominoids. Here we present observational and fecal analysis data on vertebrate consumption from several localities within the dry, open Ugalla region of Tanzania. Combining these with published fecal analyses, we summarize chimpanzee vertebrate consumption rates, showing quantitatively that savanna chimpanzee populations do not differ significantly from forest populations. Compared with forest populations, savanna chimpanzees consume smaller vertebrates that are less likely to be shared, and they do so more seasonally. Analyses of chimpanzee hunting that focus exclusively on capture of forest monkeys are thus difficult to apply to chimpanzee faunivory in open-country habitats and may be misleading when used to model early hominin behavior. These findings bear on discussions of why chimpanzees hunt and suggest that increases in hominin faunivory were related to differences between hominins and chimpanzees and/or differences between modern and Pliocene savanna woodland environments.
Topics: Animals; Diet; Forests; Grassland; Pan troglodytes; Predatory Behavior; Tanzania; Vertebrates
PubMed: 29037414
DOI: 10.1016/j.jhevol.2017.09.004 -
Nature Communications Jan 2021Humans maintain extensive social ties of varying preferences, providing a range of opportunities for beneficial cooperative exchange that may promote collective action...
Humans maintain extensive social ties of varying preferences, providing a range of opportunities for beneficial cooperative exchange that may promote collective action and our unique capacity for large-scale cooperation. Similarly, non-human animals maintain differentiated social relationships that promote dyadic cooperative exchange, but their link to cooperative collective action is little known. Here, we investigate the influence of social relationship properties on male and female chimpanzee participations in a costly form of group action, intergroup encounters. We find that intergroup encounter participation increases with a greater number of other participants as well as when participants are maternal kin or social bond partners, and that these effects are independent from one another and from the likelihood to associate with certain partners. Together, strong social relationships between kin and non-kin facilitate group-level cooperation in one of our closest living relatives, suggesting that social bonds may be integral to the evolution of cooperation in our own species.
Topics: Animals; Behavior, Animal; Cooperative Behavior; Female; Group Processes; Humans; Male; Pan troglodytes; Social Behavior; Social Dominance
PubMed: 33483482
DOI: 10.1038/s41467-020-20709-9 -
Primates; Journal of Primatology Jan 2020Comparative ["evolutionary")] thanatology is devoted to investigating how animals respond to signs of death and dying, in conspecifics and other species. Responses to...
Comparative ["evolutionary")] thanatology is devoted to investigating how animals respond to signs of death and dying, in conspecifics and other species. Responses to corpses often involve fear and confusion, and "deceased infant carrying" by females is widespread in nonhuman primates. Such behavior could result from "animacy detection malfunctions" (Gonçalves and Biro in Philos Trans R Soc (B) 373:20170263, 2018): corpses have attributes of animate agents, but-like objects-they do not act, but instead are acted upon by outside forces. Many or most nonhuman primates have core cognitive mechanisms for detecting animacy, but these might not resolve this paradox. Skeletons of conspecifics, seriously injured or ill individuals behaving oddly and not responding as expected to social acts and signals, and corpses, skeletons, and sick or injured individuals belonging to other species could trigger milder animacy detection malfunctions. A central question is whether any nonhuman primates learn from experience that death involves permanent loss of biological functionality and is universal. The relevant literature is mostly anecdotal or devoted to case studies, and this question is open. In response to calls for more information, I describe 25 cases of responses to corpses, skeletons, and mortally injured or ill individuals, both conspecifics and heterospecifics, seen during fieldwork on mountain gorillas (Gorilla beringei beringei) and chimpanzees (Pan troglodytes schweinfurthii). Observations were generally consistent with the animacy detection malfunction hypothesis, although cases of prolonged deceased infant carrying are problematic. Also, one case in gorillas apparently involved sympathetic concern for a dying individual, and sympathetic concern might have occurred in a chimpanzee case.
Topics: Animals; Death; Female; Gorilla gorilla; Male; Pan troglodytes; Rwanda; Thanatology
PubMed: 31278498
DOI: 10.1007/s10329-019-00735-y -
Communications Biology Mar 2021Much like humans, chimpanzees occupy diverse habitats and exhibit extensive behavioural variability. However, chimpanzees are recognized as a discontinuous species, with... (Comparative Study)
Comparative Study
Much like humans, chimpanzees occupy diverse habitats and exhibit extensive behavioural variability. However, chimpanzees are recognized as a discontinuous species, with four subspecies separated by historical geographic barriers. Nevertheless, their range-wide degree of genetic connectivity remains poorly resolved, mainly due to sampling limitations. By analyzing a geographically comprehensive sample set amplified at microsatellite markers that inform recent population history, we found that isolation by distance explains most of the range-wide genetic structure of chimpanzees. Furthermore, we did not identify spatial discontinuities corresponding with the recognized subspecies, suggesting that some of the subspecies-delineating geographic barriers were recently permeable to gene flow. Substantial range-wide genetic connectivity is consistent with the hypothesis that behavioural flexibility is a salient driver of chimpanzee responses to changing environmental conditions. Finally, our observation of strong local differentiation associated with recent anthropogenic pressures portends future loss of critical genetic diversity if habitat fragmentation and population isolation continue unabated.
Topics: Animal Migration; Animals; Behavior, Animal; Ecosystem; Evolution, Molecular; Gene-Environment Interaction; Genetic Variation; Genetics, Population; Genome Components; Microsatellite Repeats; Pan troglodytes; Phylogeny; Species Specificity
PubMed: 33674780
DOI: 10.1038/s42003-021-01806-x -
American Journal of Primatology Oct 2014The last common ancestor (LCA) shared by chimpanzees (Pan troglodytes) and bonobos (P. paniscus) was an Early Pleistocene African ape, which, based on the behavior of... (Review)
Review
The last common ancestor (LCA) shared by chimpanzees (Pan troglodytes) and bonobos (P. paniscus) was an Early Pleistocene African ape, which, based on the behavior of modern chimpanzees, may be assumed to be a tool-using animal. However, the character of tool use in the Pan lineage prior to the 20th century is largely unknown. Here, I use available data on wild bonobo tool use and emerging molecular estimates of demography during Pan evolution to hypothesise the plausible tool use behavior of the bonobo-chimpanzee LCA (or "Pancestor") at the start of the Pleistocene, over 2 million years ago. This method indicates that the common ancestor of living Pan apes likely used plant tools for probing, sponging, and display, but it did not use stone tools. Instead, stone tool use appears to have been independently invented by Western African chimpanzees (P. t. verus) during the Middle Pleistocene in the region of modern Liberia-Ivory Coast-Guinea, possibly as recently as 200,000-150,000 years ago. If this is the case, then the LCA of humans and chimpanzees likely also did not use stone tools, and this trait probably first emerged among hominins in Pliocene East Africa. This review also suggests that the consistently higher population sizes of Central African chimpanzees (P. t. troglodytes) over the past million years may have contributed to the increased complexity of wild tool use seen in this sub-species today.
Topics: Animals; Evolution, Molecular; Genetics, Population; Hominidae; Humans; Pan paniscus; Pan troglodytes; Tool Use Behavior
PubMed: 24710771
DOI: 10.1002/ajp.22284 -
Developmental Science Jan 2022Does comparing behavioral development between chimpanzees and humans during infancy hold the key to understanding what is uniquely human? Recent work shows that while...
Does comparing behavioral development between chimpanzees and humans during infancy hold the key to understanding what is uniquely human? Recent work shows that while many behaviors emerge at similar ages in chimpanzees, human infants develop behavioral traits underpinning our prosocial and ultra-cooperative nature at a much accelerated rate.
Topics: Animals; Hominidae; Humans; Infant; Pan troglodytes
PubMed: 34184373
DOI: 10.1111/desc.13142 -
Folia Primatologica; International... 2019To improve our understanding of the evolutionary origins of culture and technology in humans, it is vital that we document the full extent of behavioural diversity in...
To improve our understanding of the evolutionary origins of culture and technology in humans, it is vital that we document the full extent of behavioural diversity in our great ape relatives. About half of the world's remaining chimpanzees (Pan spp.) live in the Democratic Republic of Congo (DRC), yet until now we have known almost nothing about their behaviour. Here we describe the insect-related tool technology of Bili-Uéré chimpanzees (Pan troglodytes schweinfurthii) inhabiting an area of at least a 50,000-km2 area in northern DRC, as well as their percussive technology associated with food processing. Over a 12-year period, we documented chimpanzee tools and artefacts at 20 survey areas and gathered data on dung, feeding remains and sleeping nests. We describe a new chimpanzee tool kit: long probes used to harvest epigaeic driver ants (Dorylus spp.), short probes used to extract ponerine ants and the arboreal nests of stingless bees, wands to dip for D. kohli and stout digging sticks used to access underground meliponine bee nests. Epigaeic Dorylus tools were significantly longer than the other tool types, and D. kohli tools were significantly thinner. Tools classified as terrestrial honey-digging sticks were a significant predictor for brushed and blunted tool ends, consistent with their presumed use. We describe two potential new tool types, an "ant scoop" and a "fruit hammer." We document an extensive percussive technology used to process termite mounds of Cubitermes sp. and Thoracotermes macrothorax and hard-shelled fruits such as Strychnos, along with evidence of the pounding open of African giant snails and tortoises. We encountered some geographic variation in behaviour: we found honey-digging tools, long driver ant probes and fruit-pounding sites only to the north of the Uele River; there were more epigaeic Dorylus tools to the north and more ponerine ant tools to the south. We found no evidence of termite-fishing, despite the availability of Macrotermes muelleri mounds throughout the region. This lack of evidence is consistent with the results of dung washes, which revealed a substantial proportion of driver ants, but no evidence of Macrotermes or other termites. Our results allow us to describe a new chimpanzee behavioural complex, characterised by a general similarity of multiple behaviours across a large, ecologically diverse region but with subtle differences in prey choice and techniques. We propose that this widespread and related suite of behaviours be referred to as the Bili-Uéré Chimpanzee Behavioural Realm. Possible explanations for this pattern are a recent chimpanzee expansion across the region and the interconnectedness of this population across at least the entirety of northern DRC.
Topics: Animals; Ants; Bees; Democratic Republic of the Congo; Feeding Behavior; Female; Male; Pan troglodytes; Tool Use Behavior
PubMed: 30799412
DOI: 10.1159/000492998 -
Current Biology : CB May 2024A new paper shows that rates of aggression are higher, and rates of coalition formation are lower, among male bonobos than among male chimpanzees. These findings are...
A new paper shows that rates of aggression are higher, and rates of coalition formation are lower, among male bonobos than among male chimpanzees. These findings are noteworthy because they challenge the view that female bonobos' preferences for less aggressive males favored a reduction in male aggression and an increase in social tolerance.
Topics: Animals; Pan paniscus; Aggression; Male; Female; Pan troglodytes; Behavior, Animal; Social Behavior
PubMed: 38714164
DOI: 10.1016/j.cub.2024.03.056 -
Current Biology : CB Aug 2019Garcia and Dunn [1] raise some interesting and valuable points regarding our recent paper in Current Biology[2]. As Garcia and Dunn [1] point out, cross-species...
Garcia and Dunn [1] raise some interesting and valuable points regarding our recent paper in Current Biology[2]. As Garcia and Dunn [1] point out, cross-species variation in vocal and anatomical relations allows for the identification of relevant outliers from the body size - fundamental frequency (f) regression. However, this depends on the premise that the chosen or available f and body size values are typical of the species. A motivation for our study [2] was in part to improve the accuracy of such estimates by providing more data per species compared to previous studies. We address each point of their critique by controlling for cross-species body size variation using body weights for chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), addressing potential call variation in different subspecies of Pan troglodytes, measuring minimum f as well as maximum f and possible effects caused by different larynx fixation methods.
Topics: Animals; Larynx; Pan paniscus; Pan troglodytes
PubMed: 31386846
DOI: 10.1016/j.cub.2019.06.023