The expression of empathy in human's closest relatives, bonobos and chimpanzees: current and future directions

Empathy is a complex, multi-dimensional capacity that facilitates the sharing and understanding of others' emotions. As our closest living relatives, bonobos (Pan paniscus) and chimpanzees (P. troglodytes) provide an opportunity to explore the origins of hominin social cognition, including empathy. Despite certain assumptions that bonobos and chimpanzees may differ empathically, these species appear to overlap considerably in certain socio-emotional responses related to empathy. However, few studies have systematically tested for species variation in Pan empathic or socio-emotional tendencies. To address this, we synthesise the growing literature on Pan empathy to inform our understanding of the selection pressures that may underlie the evolution of hominin empathy, and its expression in our last common ancestor. As bonobos and chimpanzees show overlaps in their expression of complex socio-emotional phenomena such as empathy, we propose that group comparisons may be as or more meaningful than species comparisons when it comes to understanding the evolutionary pressures for such behaviour. Furthermore, key differences, such as how humans and Pan communicate, appear to distinguish how we experience empathy compared to our closest living relatives.

On some statistical and cerebral aspects of the limits of working memory capacity in anthropoid primates, with particular reference to Pan and Homo, and their significance for human evolution

Some comparative ontogenetic data imply that effective working-memory capacity develops in ways that are independent of brain size in humans. These are interpreted better from neuroscientific considerations about the continuing development of neuronal architecture in adolescents and young adults, than from one about gross brain mass which already is reached in childhood. By contrast, working-memory capacity in Pan never develops beyond that of three- or four-year-old children. The phylogenetic divergence begs the question of whether it is any longer plausible to infer from the fossil record, that over the past two million years, an ostensibly gradual increase in endocranial volumes, assigned to the genus Homo, can be correlated in a scientifically-meaningful manner with the gradual evolution of our effective executive working memory. It is argued that whereas Pan's effective working-memory capacity is relatively similar to that of its storage working-memory, our working memory is relatively larger with deeper executive control.

The measurement of ambient air moisture stable isotope composition for the accurate estimation of evaporative losses

Accurate estimation of evaporative losses from a water body, using the Craig-Gordon model and the stable hydrogen and oxygen isotope composition of water, requires knowledge of the stable isotope composition of ambient air moisture. This is rarely measured in the field, and it is usually estimated assuming that recent rainfall remains in isotopic equilibrium with atmospheric moisture. However, the ambient air moisture stable isotope composition may vary significantly at different heights above the water body. In this study, we set up outdoor pan evaporation experiments and simultaneously measured the stable isotope composition of ambient moisture in the atmosphere at three different heights. Using these measurements, we calculated evaporative losses, compared them with the observed losses in the pan, and assessed the uncertainty introduced by differences in ambient moisture measurements. Three main steps in the experimental method:•Daily water sampling from the evaporation pan for analysis of stable hydrogen and oxygen isotope compositions.•Recording the stable isotope composition of ambient air moisture at three different heights using the Picarro L2130-i system over a period of experiments.•Calculating evaporative losses from the pan using the Craig-Gordon model and ambient air stable isotope composition measured at three different levels and comparing to the observed losses.

What we know and don't know about great ape cultural communication in the wild

Following the first descriptions of culture in primates, widespread agreement has developed that the term can be applied to nonhumans as group-specific, socially learned behaviors. While behaviors such as those involving extractive tool use have been researched intensively, we propose that behaviors that are more subtle, less likely to be ecologically constrained, and more likely to be socially shaped, such as cultural forms of communication, provide compelling evidence of culture in nonhuman primates. Additionally, cultural forms of communication can provide novel insights into animal cognition such as the capacity for conformity, conventionalized meanings, arbitrariness in signal forms, and even symbolism. In this paper we focus on evidence from studies conducted on wild great apes. First, we provide a thorough review of what exactly we do know, and by extension don't know, about great ape cultural communication. We argue that detailed research on both vocal and gestural communication in wild great apes shows a more nuanced and variable repertoire than once assumed, with increasing support for group-specific variation. Second, we discuss the relevance of great ape cultural communication and its potential for illustrating evolutionary continuity for human-like cultural attributes, namely cumulative culture and symbolism. In sum, a concerted effort to examine cultural forms of communication in great apes could reveal novel evidence for cultural capacities that have thus far been heavily debated in the literature and can simultaneously contribute to an improved understanding of the complex minds of our closest living relatives.

The evolution of human fatigue resistance

Humans differ from African great apes in numerous respects, but the chief initial difference setting hominins on their unique evolutionary trajectory was habitual bipedalism. The two most widely supported selective forces for this adaptation are increased efficiency of locomotion and improved ability to feed in upright contexts. By 4 million years ago, hominins had evolved the ability to walk long distances but extreme selection for endurance capabilities likely occurred later in the genus Homo to help them forage, power scavenge and persistence hunt in hot, arid conditions. In this review we explore the hypothesis that to be effective long-distance walkers and especially runners, there would also have been a strong selective benefit among Homo to resist fatigue. Our hypothesis is that since fatigue is an important factor that limits the ability to perform endurance-based activities, fatigue resistance was likely an important target for selection during human evolution for improved endurance capabilities. We review the trade-offs between strength, power, and stamina in apes and Homo and discuss three biological systems that we hypothesize humans evolved adaptations for fatigue resistance: neurological, metabolic and thermoregulatory. We conclude that the evolution of endurance at the cost of strength and power likely also involved the evolution of mechanisms to resist fatigue.

Apes in fiction: does the content of novels reflect primatological knowledge?

Novels about great apes and humans continue to be consistently popular with the reading public, sometimes reaching best-seller status. Media reviews of these books rarely comment on their primatological roots, nor do primatological journals review them. In a non-quantitative, pilot study, I scrutinize six prominent novels, in terms of three questions: How do the novels make use of primatology? What aspects of primatology do they use? How accurate is their use of primatology? Such novels overwhelmingly concentrate on language, with intelligence and sexuality lagging far behind; other topics, such as culture or technology, receive little or no attention. Apes in nature are rarely mentioned. Inaccuracies abound, even at the most basic level of primatological knowledge that easily could be remedied. Both authors and primatologists would benefit from more informative interaction before publication.

Information transfer efficiency differs in wild chimpanzees and bonobos, but not social cognition

Several theories have been generated to understand the socio-cognitive mechanisms underlying the unique cooperative abilities of humans. The ‘interdependence hypothesis' posits first, that the cognitive dimension of human cooperation evolved in contexts when several individuals needed to act together to achieve a common goal, like when hunting large prey. Second, the more interdependent individuals are, the more likely they are to provide services to conspecifics in other contexts. Alternatively, the ‘social tolerance hypothesis' proposes that higher social tolerance allows conspecifics to cooperate more efficiently and with a wider range of partners. We conducted the first field experimental evaluation of both hypotheses in our closest living relatives by contrasting chimpanzees to the less interdependent but more tolerant bonobos. We compared each species' performance during a cooperative task: informing conspecifics about a danger. We presented Gaboon viper models to 82 individuals from five wild communities. Chimpanzees arriving late at the snake were significantly more likely to have heard a call and less likely to startle, indicating that chimpanzees were better informed about the presence of the threat than bonobos. This stems from clear species differences in how individuals adjusted their calling decisions to the level of information already available. Chimpanzees were more likely to call and produced more alarm calls when they had not yet heard a call, whereas bonobos did so when they already heard a call. Our results confirm the link between interdependence and cooperation performance. These species differences were most likely driven by differences in motivation rather than in cognitive capacities because both species tended to consider audience knowledge in their decision to call. Our results inform theories on the evolution of human cooperation by linking inter-group competition pressure and in-group cooperative motivation and/or capability.

The Selfie View: Perioperative Photography in the Digital Age

BACKGROUND

The aesthetics of social media have become increasingly important to cosmetic surgery patients in recent years; however, aesthetic treatments have not kept pace with the desires of modern patients. The current study investigates the most common angles employed by various user cohorts when posting a selfie on social media platforms and proposes that aesthetic surgeons consider utilizing a selfie angle alongside standard pre- and postoperative photographic views.

METHODS

Full face photographs published on the social media platform Instagram™ with the tag #selfie were divided into three cohorts: female models/influencers, amateur females, and amateur males. Each cohort contained 100 photographs. The photographs were analyzed using cloud-based facial analysis software for facial pan, roll, and tilt relative to the camera.

RESULTS

One hundred photographs from each cohort were analyzed and demonstrated that amateur females (AF) take photographs from higher angles than amateur males (AM) or model females (MF). Roll-off-midline was significantly greater for AF and MF as compared to AM. The MF group had significantly a greater pan-off-midline as compared to AF and AM, while AF had significantly a greater pan-off-midline than AM.

CONCLUSIONS

Common photography practices employed within selfie photographs utilize angles not captured in standard perioperative photographs. This study supports the implementation of a selfie photograph into the standard set of pre- and postoperative photographs taken by aesthetic surgeons to evaluate the effects of interventions in the context of selfie photography. The angle employed can vary depending upon the demographic profile of the patient.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Contributions of burner, pan, meat and salt to PM emission during grilling

Grilling ground beef meat was conducted in two locations at Nazarbayev University, Kazakhstan. The experiments were designed such that only particles from beef meat were isolated. A similar experimental protocol was applied at both locations. The average particle number and mass emission rates for grilling pure meat itself (excluding particles from pan and burner) were found to be 9.4 × 10¹²(SD = 7.2 × 10¹² particle min^-1 and 7.6 × 10 (SD = 6.3 × 10) mg.min^-1, respectively. The PM emissions (number and mass) from the burner were found to be negligible compared to the pan and meat emissions. Ultrafine particle (UFP) concentrations from the heated pan itself were comparable to those of grilled meat. However, the particle mass concentrations from the pan itself were negligible. Approximately an hour of continuous heating resulted in zero emissions from the pan.

Comparative social grooming networks in captive chimpanzees and bonobos

Despite similar dispersal patterns, models of Pan sociality emphasize sex differences in social bonding between the two species. Such disparities are attributed to hypothesized differences in environmental selective pressures that structure association patterns. However, recent research documents greater within-species variation in social bonds in both species. Here, we examine grooming networks in captive chimpanzees at the North Carolina Zoo, and captive bonobos at the Columbus Zoo. We hypothesized that male-female grooming relationships would be the strongest in both species, but that males and females of both species would not significantly differ between centrality, strength, or clustering. Via Mantel tests, we found that neither bonobos (t = - 0.070, r = - 0.009, two-tailed p = 0.942) nor chimpanzees (t = - 0.495, r = - 0.0939, two-tailed p = 0.6205) had significant differences in grooming between or within sexes. Neither species had significant sex differences in centrality, strength, or clustering. To account for idiosyncratic factors affecting grooming distribution, we examined the effect of origin, kinship, and group tenure on social network position. We found that wild-born bonobos exhibited greater eigenvector centrality (t = - 2.592, df = 9, p = 0.29) and strength (t = - 2.401; df = 9, p = 0.040), and group tenure was significantly correlated with strength (r = 0.608; N = 11, p - 0 = 0.47). None of these factors varied with social network position in chimpanzees. Our findings suggest that in captive settings, idiosyncratic factors related to individual history play a greater role in structuring social networks. Such variation may point to the behavioral flexibility inherent in fission-fusion networks, and mirror between-site variation found in wild chimpanzees. However, some idiosyncratic factors shaping captive networks may be an artifact of captivity.

Long bone cross-sectional properties reflect changes in locomotor behavior in developing chimpanzees

OBJECTIVES

Recent studies indicate that the locomotor behavior of wild chimpanzees changes during development. Before transitioning to quadrupedal knuckle-walking in adulthood, young chimpanzees engage in a significant amount of upper limb loading suspensory behavior. We investigated whether these dramatic changes in locomotion influence the strength and shape of chimpanzee long bones.

MATERIALS AND METHODS

We examined changes in chimpanzee arboreal locomotion over the course of development using behavioral data collected on wild chimpanzees. We measured the midshaft geometric properties of femora and humeri of wild-caught individuals housed in museum collections using micro computed tomographic scans.

RESULTS

Chimpanzees spent less time moving arboreally as they aged. Femoral/humeral strength ratios also increased with age, as predicted by the changing loading environment during development. Additional analyses revealed that femoral shape, but not humeral shape, varied across chimpanzee age classes. Adult femora were more elliptical compared with those of infants. This change in adult femora is consistent with the observation that adult chimpanzees spend most of their time moving terrestrially and consequently experience a less variable loading environment than do infants.

DISCUSSION

Taken together, these findings contribute to our understanding of how ontogenetic changes in function affect form. As similar changes may have characterized the behavioral and skeletal ontogeny of extinct hominoids including hominins, these findings furnish a potential means to make inferences about the behavior of fossil taxa based on the structural properties of their bones.

Rapid changes in the gut microbiome during human evolution

Humans are ecosystems containing trillions of microorganisms, but the evolutionary history of this microbiome is obscured by a lack of knowledge about microbiomes of African apes. We sequenced the gut communities of hundreds of chimpanzees, bonobos, and gorillas and developed a phylogenetic approach to reconstruct how present-day human microbiomes have diverged from those of ancestral populations. Compositional change in the microbiome was slow and clock-like during African ape diversification, but human microbiomes have deviated from the ancestral state at an accelerated rate. Relative to the microbiomes of wild apes, human microbiomes have lost ancestral microbial diversity while becoming specialized for animal-based diets. Individual wild apes cultivate more phyla, classes, orders, families, genera, and species of bacteria than do individual humans across a range of societies. These results indicate that humanity has experienced a depletion of the gut flora since diverging from Pan.

The genetic demography of a chimpanzee colony

Chimpanzees used for biomedical research must be bred in captivity because of restrictions on importation. Because they are large and expensive animals, population sizes at breeding facilities are limited. This implies that inbreeding at some level is inevitable and that genetic management techniques should be employed to minimize matings between related individuals. The purpose of this paper is to consider the genetic history of the chimpanzee colony at the Southwest Foundation for Biomedical Research (SFBR) and to suggest ways in which genetic variability may be affected by management schemes. A total of 339 chimpanzees resided at SFBR between January, 1980, and January, 1990. Although only one mating between related individuals has occurred so far, the average level of kinship in the colony and between potential breeders is increasing. Population structure techniques were employed to assess the mating patterns which have occurred and to explore the degree of change in the characteristics of potential mates. A "gene dropping" simulation method was used to predict expected levels of heterozygosity and strategies for maintaining variability by increasing the breeding portion of the population were evaluated using a simulation approach. © 1995 Wiley-Liss, Inc.