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Abstract Background Captive breeding of bonobos (Pan paniscus) has proven to be successful, but maintaining genetic diversity remains a challenge. Cryopreservation of semen is an important potential tool to maintain genetic diversity by preserving current genetic material for future use, as well as facilitating the transport and exchange of genetic material. This study aimed to develop a protocol for semen collection and cryopreservation in the bonobo. Semen was collected from four healthy adult bonobos under general anesthesia during management translocation procedures. Semen collection utilizing urethral catheterization was not successful (n = 1), however, all males (n = 4) responded well to rectal probe electro-ejaculation. Immediately after collection, ejaculates were evaluated for color and admixtures, volume, motility, and concentration. Eosin-Nigrosin staining was prepared to evaluate morphology and viability. Ejaculates were split into two equal volumes and cryopreserved in two different extenders, using a one-step and a two-step approach. Ejaculates were gradually cooled to 4 °C in two hours, subsequently stored in liquid nitrogen vapor for twenty minutes (0.25 ml straws), and finally dropped into liquid nitrogen. Results Pre-freeze evaluation showed thick, white samples with an average ejaculate volume of 450 µl (100-1000 µl), total motility of 59% (40–80%), viability of 69% (38–85%) and 58% (46–72%) normal spermatozoa. Mainly head (22%) and tail (19%) defects were detected on the Eosin-Nigrosin stain. Ejaculates were highly concentrated, nevertheless, due to the coagulum that caused high viscosity and non-homogenous fractions, only estimations of concentration could be made (1000 million/ml). After 24 h of storage, the post-thaw evaluation showed a loss of quality with an average post-thaw total motility of 15% (5–25%) using the one-step freezing medium, and 19% (5–30%) using the two-step medium. Average post-thaw viability was 15% (4–24%) and 21% (15–29%), respectively. Conclusions This report on ejaculates from bonobos obtained by rectal probe electro-ejaculation shows that semen parameters of this species are not completely similar to those of its sibling species, the chimpanzee. Further studies are necessary to develop an optimal protocol for the processing and cryopreservation of bonobo spermatozoa.

The article presents a study which investigated positional behavior and terrestriality in a savanna-mosaic community of chimpanzees (Pan troglodytes schweinfurthii) in the Issa Valley, Tanzania as the first test in a living ape of the hypothesis that wooded, savanna habitats were a catalyst for terrestrial bipedalism. Topics include terrestriality in a savanna-mosaic habitat, chimpanzee terrestriality in a savanna-mosaic habitat, and the hominin arboreal niche.

Characteristics of food availability and distribution are key components of a species' ecology. Objective ecological surveying used in animal behavior research does not consider aspects of selection by the consumer and therefore may produce imprecise measures of availability. We propose a method to integrate ecological sampling of an animal's environment into existing behavioral data collection systems by using the consumer as the surveyor. Here, we evaluate the consumer‐centric method (CCM) of assessing resource availability for its ability to measure food resource abundance, distribution, and dispersion. This method catalogs feeding locations observed during behavioral observation and uses aggregated data to characterize these ecological metrics. We evaluated the CCM relative to traditional vegetation plot surveying using accumulated feeding locations across 3 years visited by a tropical frugivore, the bonobo (Pan paniscus), and compared it with data derived from over 200 vegetation plots across their 50 km2+ home ranges. We demonstrate that food species abundance estimates derived from the CCM are comparable to those derived from traditional vegetation plot sampling in less than 2 years of data collection, and agreement improved when accounting for aspects of consumer selectivity in objective vegetation plot sampling (e.g., tree size minima). Density correlated between CCM and plot‐derived estimates and was relatively insensitive to home range inclusion and other species characteristics, however, it was sensitive to sampling frequency. Agreement between the methods in relative distribution of resources performed better across species than expected by chance, although measures of dispersion correlated poorly. Once tested in other systems, the CCM may provide a robust measure of food availability for use in relative food availability indices and can be incorporated into existing observational data collection. The CCM has an advantage over traditional sampling methods as it incorporates sampling biases relevant to the consumer, thereby serving as a promising method for animal behavioral research. [ABSTRACT FROM AUTHOR]

Objectives: This study investigates patterns of bone functional adaptations in extant apes through comparing hindlimb to forelimb bone rigidity ratios in groups with varying levels of arboreality. Materials and Methods: Using CT scans, bone rigidity (J) was calculated at three regions of interest (ROI) along femoral and humeral diaphyses in Homo, Pongo, Pan, and Gorilla with further comparisons made between species and subspecies divisions within Pan and Gorilla. Results: Consistent with previous work on extant hominoids, species exhibited differences in midshaft femoral to humeral (F/H) rigidity ratios. Results of the present study confirm that these midshaft differences extend to 35% and 65% diaphyseal ROIs. Modern humans, exhibiting larger ratios, and orangutans, exhibiting smaller ratios, bracketed the intermediate African apes in comparisons. Within some African apes, limb rigidity ratios varied significantly between taxonomic groups. Eastern gorillas exhibited the highest mean ratios and chimpanzees the lowest at all three ROIs. In posthoc comparisons, chimpanzees and bonobos did not differ in relative limb rigidity ratios at any of the three ROIs. However, western gorillas were more similar to bonobos than eastern gorillas at 50% and 35% ROIs, but not at the 65% ROI. Conclusion: Species, and to a lesser extent subspecies, can be distinguished by F/H limb rigidity ratios according to broad positional behavior patterns at multiple regions of interest along the diaphyses. Similarity of bonobos and western gorillas is in line with behavioral data of bonobos being the most terrestrial of Pan species, and western gorillas the most arboreal of the Gorilla groups. [ABSTRACT FROM AUTHOR]

The human auditory system is capable of processing human speech even in situations when it has been heavily degraded, such as during noise-vocoding, when frequency domain-based cues to phonetic content are strongly reduced. This has contributed to arguments that speech processing is highly specialized and likely a de novo evolved trait in humans. Previous comparative research has demonstrated that a language competent chimpanzee was also capable of recognizing degraded speech, and therefore that the mechanisms underlying speech processing may not be uniquely human. However, to form a robust reconstruction of the evolutionary origins of speech processing, additional data from other closely related ape species is needed. Specifically, such data can help disentangle whether these capabilities evolved independently in humans and chimpanzees, or if they were inherited from our last common ancestor. Here we provide evidence of processing of highly varied (degraded and computer-generated) speech in a language competent bonobo, Kanzi. We took advantage of Kanzi's existing proficiency with touchscreens and his ability to report his understanding of human speech through interacting with arbitrary symbols called lexigrams. Specifically, we asked Kanzi to recognise both human (natural) and computer-generated forms of 40 highly familiar words that had been degraded (noise-vocoded and sinusoidal forms) using a match-to-sample paradigm. Results suggest that—apart from noise-vocoded computer-generated speech—Kanzi recognised both natural and computer-generated voices that had been degraded, at rates significantly above chance. Kanzi performed better with all forms of natural voice speech compared to computer-generated speech. This work provides additional support for the hypothesis that the processing apparatus necessary to deal with highly variable speech, including for the first time in nonhuman animals, computer-generated speech, may be at least as old as the last common ancestor we share with bonobos and chimpanzees. [ABSTRACT FROM AUTHOR]

Examining the relationship between food and primate social organization helps us understand how the environment shaped hominin social evolution. However, there is debate as to whether the social differences between our two closest relatives, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes), are due to differences in food availability between their respective habitats or to nonenvironmental factors. The most prominent theory is that bonobo communities have more socially cohesive, stable parties, centered on gregarious females because they evolved in food‐rich habitat where individuals, especially females, are less burdened by competition with groupmates. However, more research on bonobos in habitats with seasonal variation in food is needed. This study measured food availability and bonobo social organization at Luzaka, a new site in a seasonal forest fragment. Fruit abundance and dispersion were recorded for a year at Luzaka with the same methods used at Wamba, a bonobo site in more seasonally stable habitat and terrestrial herbaceous vegetation density was measured. At Luzaka, bonobo parties were also recorded for a year using camera traps. Fruit was more seasonal and dispersed at Luzaka than at Wamba. However, the social organization of Luzaka bonobos resembled social organization of bonobos at less seasonal sites. There were minor effects of fruit clumping on party size without effects on the proportion of females in parties suggesting that at Luzaka, the clumping of fruit slightly affected social cohesiveness but does not disproportionately affect females. Bonobo social cohesiveness and female gregariousness appears consistent and compatible with seasonal habitat. Research highlights: The female‐centered socially cohesive nature of bonobo social organization is thought to have been shaped by low competition in the food‐rich rainforests where bonobos evolved and has only been well‐studied in such habitat.This study confirmed that at the southeastern limit of the bonobo range, ripe fruit is more seasonally scarce and dispersed and investigated whether this food seasonality affected bonobo social cohesiveness and female gregariousness using camera traps.Bonobo social organization is consistent across habitat types: fruit clumping had a small positive effect on party size but fruit availability did not affect female gregariousness. [ABSTRACT FROM AUTHOR]

Oxytocin has attracted research attention due to its role in promoting social bonding. In bonobos and chimpanzees, the two species most closely related to humans, urinary oxytocin is known to correlate with key behaviours related to social bonding such as social grooming in chimpanzees and female‐female sexual behaviour in bonobos. However, no study has demonstrated that the administration of oxytocin promotes real‐life social interactions in Pan, leaving it unclear whether oxytocin is merely correlated with social behaviors or does affect them in these species. To test this, we administered nebulized oxytocin or saline placebo to a group of female bonobos and subsequently observed changes in their gross behavior during free interaction. We found an overall effect of more frequent grooming in the oxytocin condition. However, on the individual level this effect remained significant for only one participant in our follow‐up models, suggesting future work should explore interindividual variation. Our results provide some experimental support for the biobehavioural feedback loop hypothesis, which posits that some functions of the oxytocin system support the formation and maintenance of social bonds through a positive feedback loop; however, further tests with a larger number of individuals are required. Our results, at a minimum, demonstrated that oxytocin affects spontaneous, naturalistic social interactions of at least some female bonobos, adding to accumulating evidence that oxytocin modulates complex social behaviors of Pan. Highlights: We administered oxytocin or saline placebo to whole subgroups of bonobos simultaneously. Our overall model finds higher rates of grooming in the oxytocin condition, however, this was only significant in one participant in individual level analysis. This provides some support to the biobehavioural feedback loop hypothesis of oxytocin in bonobo social bonding, while future work should explore individual, group, and species level variation. [ABSTRACT FROM AUTHOR]

Previous research found that seeds of I Dialium i spp. are particularly often re-ingested by chimpanzees and gorillas, suggesting their importance in the diet of both species (Payne et al., 2008; Rogers et al., 1998). Great apes in the wild have so far only been observed to perform autocoprophagy with some rare exceptions in chimpanzees, who occasionally ingested elephant dung (Krief et al., 2005), and notion of suggested gorilla allocoprophagy, although it is not fully clear whether faeces were ingested (Masi & Breuer, 2018). Although systematic focal and scan sampling were conducted since January 2018 (in the framework of other studies), this is the first observation of coprophagy at Mbeli Baï during the last 2.5 years, thus confirming previous notions about the rarity of this behaviour in gorillas (western gorilla: Masi & Breuer, 2018; mountain gorilla: Rothman et al., 2006). Coprophagy indicates stress in lowland gorillas (Gorilla gorilla). [Extracted from the article]

Epigenetic age has emerged as an important biomarker of biological ageing. It has revealed that some tissues age faster than others, which is vital to understanding the complex phenomenon of ageing and developing effective interventions. Previous studies have demonstrated that humans exhibit heterogeneity in pace of epigenetic ageing among brain structures that are consistent with differences in structural and microanatomical deterioration. Here, we add comparative data on epigenetic brain ageing for chimpanzees, humans' closest relatives. Such comparisons can further our understanding of which aspects of human ageing are evolutionarily conserved or specific to our species, especially given that humans are distinguished by a long lifespan, large brain, and, potentially, more severe neurodegeneration with age. Specifically, we investigated epigenetic ageing of the dorsolateral prefrontal cortex and cerebellum, of humans and chimpanzees by generating genome-wide CpG methylation data and applying established epigenetic clock algorithms to produce estimates of biological age for these tissues. We found that both species exhibit relatively slow epigenetic ageing in the brain relative to blood. Between brain structures, humans show a faster rate of epigenetic ageing in the dorsolateral prefrontal cortex compared to the cerebellum, which is consistent with previous findings. Chimpanzees, in contrast, show comparable rates of epigenetic ageing in the two brain structures. Greater epigenetic change in the human dorsolateral prefrontal cortex compared to the cerebellum may reflect both the protracted development of this structure in humans and its greater age-related vulnerability to neurodegenerative pathology. [ABSTRACT FROM AUTHOR]

Background: While of predominant abundance across vertebrate genomes and significant biological implications, the relevance of short tandem repeats (STRs) (also known as microsatellites) to speciation remains largely elusive and attributed to random coincidence for the most part. Here we collected data on the whole-genome abundance of mono-, di-, and trinucleotide STRs in nine species, encompassing rodents and primates, including rat, mouse, olive baboon, gelada, macaque, gorilla, chimpanzee, bonobo, and human. The collected data were used to analyze hierarchical clustering of the STR abundances in the selected species. Results: We found massive differential STR abundances between the rodent and primate orders. In addition, while numerous STRs had random abundance across the nine selected species, the global abundance conformed to three consistent < clusters>, as follows: , , and , which coincided with the phylogenetic distances of the selected species (p < 4E-05). Exceptionally, in the trinucleotide STR compartment, human was significantly distant from all other species. Conclusion: Based on hierarchical clustering, we propose that the global abundance of STRs is non-random in rodents and primates, and probably had a determining impact on the speciation of the two orders. We also propose the STRs and STR lengths, which predominantly conformed to the phylogeny of the selected species, exemplified by (t)10, (ct)6, and (taa4). Phylogenetic and experimental platforms are warranted to further examine the observed patterns and the biological mechanisms associated with those STRs. [ABSTRACT FROM AUTHOR]

Objectives: Energetics are widely recognized to influence timing of birth in humans and other eutherian mammals, yet considerable variation exists in the relationship between energetic constraints and gestation length. In humans, poor nutrition and short inter‐gestational intervals (IGIs) are associated with shorter gestations. In other mammals, lower energy availability is usually associated with longer gestations. We investigated the predictors of gestation length, and the impact of gestation length on offspring survival, in chimpanzees, humans' closest living relatives. Materials and Methods: We used 50 years of demographic and behavioral data to estimate gestation lengths in the wild chimpanzees of Gombe National Park, Tanzania, and then used ecological and demographic data to explore the predictors and consequences of gestation length in our sample. Results: Gestation lengths were shorter for females in their early 30s (relative to younger and older females), and after short IGIs. Other predictors potentially associated with maternal energetic condition and maternal investment were not associated with gestation length. We also found that shorter gestation lengths corresponded to lower offspring survival. Discussion: Like humans, chimpanzees had shorter gestations after short IGIs, and short gestations were associated with higher offspring mortality. We consider competing explanations for the conflicting relationships between energetics and gestation length across eutherian mammals in light of these results. [ABSTRACT FROM AUTHOR]

Simple Summary: Self-directed behaviours (SDBs), such as self-scratching or self-touching, are commonly used as indicators of stress or poor welfare in animals. However, whether these behaviours truly reflect stress may depend on individual behaviour, species, context, and to which side of the body they are directed. Namely, one idea is that negative emotions are processed more frequently in the right brain, and because these nerves end in the opposite side, the following sensation is experienced in the left side of the body. Not much is known about the reliability of SDBs as indicators of stress in bonobos. Therefore, we investigated the production and asymmetry of SDBs in bonobos whilst they completed two cognitive touchscreen tasks. The most common SDB was nose wiping, followed by gentle self-scratching, then rough self-scratching. When the bonobos made incorrect responses, due to their unsuccessful experience resulting in expressions of frustration, they showed more nose wiping and rough self-scratching. Additionally, rough self-scratching was more directed to the left side of the body, suggesting a link to negative emotions. Interestingly, in one of the tasks, the bonobos gently self-scratched more frequently when they gave correct responses, possibly indicating positive emotions. These results increase our understanding of SDBs as indicators of emotion in bonobos. Self-directed behaviours (SDBs) are widely used as markers of emotional arousal in primates, and are commonly linked to negative arousal, or are used as indicators of stress or poor welfare. However, recent studies suggest that not all SDBs have the same function. Moreover, lateralisation in the production of these behaviours has been suggested to be associated with emotional processing. Hence, a better understanding of the production and the asymmetry of these displacement behaviours is needed in a wider range of species in order to confirm their reliability as indicators of emotional arousal. In the current study, we experimentally evaluated the production and asymmetry of SDBs in zoo-housed bonobos during two cognitive touchscreen tasks. Overall, nose wipes were most commonly observed, followed by gentle self-scratches, and rough self-scratches. The rates of nose wipes and rough self-scratches increased with incorrect responses, suggesting that these behaviours indicate arousal and possibly frustration. Rough self-scratching was additionally more directed towards the left hemispace after incorrect responses. In contrast, gentle self-scratching increased after correct responses in one study, possibly linking it with positive arousal. We also tested if left-handed bonobos showed greater behavioural reactivity towards incorrect responses, but found no evidence to confirm this hypothesis. Our results shed light on potential different mechanisms behind separate SDBs. We therefore provide nuance to the use of SDBs as indicator of emotional arousal in bonobos. [ABSTRACT FROM AUTHOR]

Previous studies on prosociality in bonobos have reported contrasting results, which might partly be explained by differences in experimental contexts. In this study, we implement a free choice group experiment in which bonobos can provide fruit juice to their group members at a low cost for themselves. Four out of five bonobos passed a training phase and understood the setup and provisioned fruit juice in a total of 17 dyads. We show that even in this egalitarian group with a shallow hierarchy, the majority of pushing was done by the alpha female, who monopolized the setup and provided most juice to two adult females, her closest social partners. Nonetheless, the bonobos in this study pushed less frequently than the chimpanzees in the original juice-paradigm study, suggesting that bonobos might be less likely than chimpanzees to provide benefits to group members. Moreover, in half of the pushing acts, subjects obtained juice for themselves, suggesting that juice provisioning was partly driven by self-regarding behavior. Our study indicates that a more nuanced view on the prosocial food provisioning nature of bonobos is warranted but based on this case study, we suggest that the observed sex differences in providing food to friends corresponds with the socio-ecological sex difference in cooperative interactions in wild and zoo-housed bonobos. [ABSTRACT FROM AUTHOR]

Different Old World primates show conspicuous anogenital swelling, with the Maximum Swelling Phase (MSP) signaling the ovulatory phase. MSP synchronization between females has been linked to social dynamics. In bonobos, characterized by female dominance, MSP is not a fully reliable signal of fertility because it may cover anovulatory periods. We investigated whether bonobo females synchronized their MSP and whether this phenomenon was modulated by social factors. Data were collected at LaValléedesSinges (France). In the period 2009–2022, swelling cycles data were collected daily on bonobo females (N = 9). In the period 2018–2022, ethological data (aggression/affiliation/socio-sexual behaviors) were also collected. We found that: (i) females synchronized their MSP and most likely experienced MSP onset following the MSP onset in other females; (ii) synchronization increased as the years spent together by females increased; (iii) synchronization preferentially occurred between females that affiliated less; (iv) synchronization on the MSP was linked to increased female-female socio-sexual contacts, which probably favored MSP synchronization maintenance. Hence, in bonobos MSP can be modulated by social factors and its synchronization, possibly underlying autonomic contagion, might have been positively selected during evolution in relation to the benefits females obtain in terms of intra-group cohesion. [ABSTRACT FROM AUTHOR]

Human carnivory is atypical among primates. Unlike chimpanzees and bonobos, who are known to hunt smaller monkeys and eat them immediately, human foragers often cooperate to kill large animals and transport them to a safe location to be shared. While it is known that meat became an important part of the hominin diet around 2.6-2 Mya, whether intense cooperation and food sharing developed in conjunction with the regular intake of meat remains unresolved. A widespread assumption is that early hominins acquired animal protein through klepto-parasitism at felid kills. This should be testable by detecting felid-specific bone modifications and tooth marks on carcasses consumed by hominins. Here, deep learning (DL) computer vision was used to identify agency through the analysis of tooth pits and scores on bones recovered from the Early Pleistocene site of DS (Bed I, Olduvai Gorge). We present the first objective evidence of primary access to meat by hominins 1.8 Mya by showing that the most common securely detectable bone-modifying fissipeds at the site were hyenas. The absence of felid modifications in most of the carcasses analyzed indicates that hominins were the primary consumers of most animals accumulated at the site, with hyenas intervening at the post-depositional stage. This underscores the role of hominins as a prominent part of the early Pleistocene African carnivore guild. It also stresses the major (and potentially regular) role that meat played in the diet that configured the emergence of early Homo. [ABSTRACT FROM AUTHOR]

The article discusses the concept of artificial intimacy and its implications for human relationships. The author, Rob Brooks, explores the connections between artificial intimacy and sexual behavior, drawing on examples from the animal kingdom. The article also examines the impact of social media on our ability to maintain relationships and discusses the potential for virtual reality and sex robots to enhance artificial intimacy. Additionally, the author delves into the incel movement and considers how artificial intimacy may alleviate or exacerbate this social issue. The article concludes by highlighting the importance of artificial intimacy in fostering connections and its potential for further development in the future. [Extracted from the article]

"Different: Gender Through the Eyes of a Primatologist" by Frans de Waal is a book that explores human gender differences and similarities through the lens of a primatologist. The book combines storytelling and data analysis to compare human gendered behavior with that of other primates, particularly bonobos and chimpanzees, in order to determine which gendered behaviors have biological roots. De Waal argues for gender equity based on a realistic understanding of women and men, rather than assuming they are identical. While the book lacks a cohesive argument and may be confusing for some readers, it offers valuable insights into the complexity of gender and provides engaging stories and examples. [Extracted from the article]

Compared to other animals, humans supposedly excel at voluntarily controlling and strategically displaying emotional signals. Yet, new data shows that nonhuman great apes' emotion expressions may also be subject to voluntary control. A key context to further explore this is during post-conflict (PC) periods, where signalling by distressed victims may influence bystander responses, including the offering of consolation. To address this, our study investigates the signalling behaviour of sanctuary-living bonobo victims following aggression and its relation to audience composition and PC interactions. Results show that the production of paedomorphic signals by victims (regardless of age) increased their chances of receiving consolation. In adults, the production of such signals additionally reduced the risk of renewed aggression from opponents. Signal production also increased with audience size, yet strategies differed by age: while immatures reduced signalling in proximity of close-social partners, adults did so especially after receiving consolation. These results suggest that bonobos can flexibly adjust their emotion signalling to influence the outcome of PC events, and that this tendency has a developmental trajectory. Overall, these findings highlight the potential role that flexible emotion communication played in the sociality of our last common ancestor with Pan. This article is part of the theme issue 'Cognition, communication and social bonds in primates'. [ABSTRACT FROM AUTHOR]

In animals with slow ontogeny and long- term maternal investment, immatures are likely to experience the birth of a younger sibling before reaching maturity. In these species, the birth of a sibling marks a major event in an offspring's early life as the older siblings experience a decrease in maternal support. The transition to siblinghood (TTS) is often considered to be stressful for the older offspring, but physiological evidence is lacking. To explore the TTS in wild bonobos, we investigated physiological changes in urinary cortisol (stress response), neopterin (cell-mediated immunity), and total triiodothyronine (T3, metabolic rate), as well as changes in behaviors that reflect the mother--offspring relationship. Following a sibling's birth, urinary cortisol levels of the older offspring increased fivefold, independent of their age, and remained elevated for 7 months. The cortisol level increase was associated with declining neopterin levels; however, T3 levels and behavioral measures did not change. Our results indicate that the TTS is accompanied by elevated cortisol levels and that this change does not coincide with nutritional weaning and attainment of physical independence. Our results suggest that bonobos and humans experience TTS in similar ways and that this developmental event may have emerged in the last common ancestor. [ABSTRACT FROM AUTHOR]

Simple Summary: Generally male mammals are more aggressive than their female peers. In these males, aggressive behavior is linked to levels of androgens; higher levels of testosterone are predictive of higher aggression rates or more severe aggression. There are some species where the pattern of sex-specific aggression is reversed, and it was hypothesized that high levels of androgens may be responsible for social dominance and aggressiveness in these females. Studies so far found that females of species with sex-reversed aggression patterns (e.g., spotted hyenas and ring-tailed lemurs) had lower plasma testosterone levels than their male peers, but a precursor of testosterone, androstenedione, was comparable or even higher in females than in males. This supported the idea that selection for female aggressiveness may be facilitated through augmented androgen secretion. Here we show that in two sister species, bonobos and chimpanzees, that differ in terms of sex-specific aggression patterns, females have lower plasma testosterone levels and higher plasma androstenedione levels than their male peers. Thus, our data do not support a theory of a role of female androgen levels on the expression of sex-specific patterns of aggression. In most animals, males are considered more aggressive, in terms of frequency and intensity of aggressive behaviors, than their female peers. However, in several species this widespread male-biased aggression pattern is either extenuated, absent, or even sex-reversed. Studies investigating potential neuro-physiological mechanisms driving the selection for female aggression in these species have revealed an important, but not exclusive role of androgens in the expression of the observed sex-specific behavioral patterns. Two very closely related mammalian species that markedly differ in the expression and degree of sex-specific aggression are the two Pan species, where the chimpanzee societies are male-dominated while in bonobos sex-biased aggression patterns are alleviated. Using liquid chromatography–mass spectrometry (LC-MS) methods, we measured levels of plasma testosterone and androstenedione levels in male and female zoo-housed bonobos (N = 21; 12 females, 9 males) and chimpanzees (N = 41; 27 females, 14 males). Our results show comparable absolute and relative intersexual patterns of blood androgen levels in both species of Pan. Plasma testosterone levels were higher in males (bonobos: females: average 0.53 ± 0.30 ng/mL; males 6.70 ± 2.93 ng/mL; chimpanzees: females: average 0.40 ± 0.23 ng/mL; males 5.84 ± 3.63 ng/mL) and plasma androstenedione levels were higher in females of either species (bonobos: females: average 1.83 ± 0.87 ng/mL; males 1.13 ± 0.44 ng/mL; chimpanzees: females: average 1.84 ± 0.92 ng/mL; males 1.22 ± 0.55 ng/mL). The latter result speaks against a role of androstenedione in the mediation of heightened female aggression, as had been suggested based on studies in other mammal species where females are dominant and show high levels of female aggressiveness. [ABSTRACT FROM AUTHOR]

The adenoviruses (AdVs) isolated from humans are taxonomically grouped in seven different species in the Mastadenovirus genus (HAdV-A through G). AdVs isolated from apes are often included in one of the human AdV species. Here we describe the sequence analyses of ten new AdVs that are related to the HAdV-C species and that were isolated from healthy western lowland gorillas, bonobos, chimpanzees, and orangutans kept in Dutch zoos. We analyzed these viruses and compared their genome sequences to those of human- and ape-derived AdV sequences in the NCBI GenBank database. Our data demonstrated that the ape-derived viruses clustering to HAdV-C are markedly distinct from the human HAdV-C species in the size and nucleotide composition (%GC) of their genome, differ in the amino-acid sequence of AdV proteins, and have longer RGD-loops in their penton-base proteins. The viruses form three well-separated clades (the human, the gorilla, and the combined group of the bonobo and chimpanzee viruses), and we propose that these should each be given species-level ranks. The Ad-lumc005 AdV isolated from orangutans was found to be very similar to the gorilla AdVs, and bootstrap inference provided evidence of recombination between the orangutan AdV and the gorilla AdVs. This suggests that this virus may not be a genuine orangutan AdV but may have been transferred from a gorilla to an orangutan host. [ABSTRACT FROM AUTHOR]

Facial expressions are key to navigating social group life. The Power Asymmetry Hypothesis of Motivational Emancipation predicts that the type of social organization shapes the meaning of communicative displays in relation to an individual's dominance rank. The bared‐teeth (BT) display represents one of the most widely observed communicative signals across primate species. Studies in macaques indicate that the BT display in despotic species is often performed unidirectionally, from low‐ to high‐ranking individuals (signaling submission), whereas the BT display in egalitarian species is usually produced irrespective of dominance (mainly signaling affiliation and appeasement). Despite its widespread presence, research connecting BT displays to the power asymmetry hypothesis outside the Macaca genus remains scarce. To extend this knowledge, we investigated the production of BT in relation to social dominance in dyadic interactions (N = 11,377 events) of 11 captive bonobos (Pan paniscus). Although adult bonobos were more despotic than previously suggested in the literature, BT displays were produced irrespective of dominance rank. Moreover, while adults produced the BT exclusively during socio‐sexual interactions, especially during periods of social tension, immature bonobos produced the BT in a wider number of contexts. As such, the results indicate that the communicative meaning of the BT display is consistent with signaling appeasement, especially in periods of social tension. Moreover, the BT display does not seem to signal social status, supporting the prediction for species with a high degree of social tolerance. These results advance our understanding of the origins of communicative signals and their relation to species' social systems. Research Highlight: Adult bonobos use bared‐teeth (BT) displays irrespectively of dominance rank, during sexual behaviors, when tensions are high.Juvenile bonobos use the BT in wider contexts, suggesting an adjustment of display rules over bonobo development. [ABSTRACT FROM AUTHOR]

Among non-human primates, male dominance rank is not necessarily a good indicator of mating success, and relationships between male dominance rank and mating or reproductive success are affected by female behavior and sexual states implying their probability of conception. Although comparisons of the behavior of male chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) suggest that the effect of male dominance rank on mating success is expected to be less prominent in bonobos, recent genetic studies have shown that high-ranking male reproductive skew is higher in bonobos than in chimpanzees. One possible reason for the higher reproductive skew in bonobos could be that female behavior and their sexual states may have much more influence on male mating and reproductive success in bonobos than in chimpanzees. In the current study on bonobos, we conducted focal animal observation of females and analyzed the influence of female sexual swelling, the number of days after parturition, and dominance rank of males on female associations, and copulation with adult males. Our results showed that females with maximum swelling (MS) had more proximity with high-ranking males and copulated more frequently with higher-ranking males than with lower-ranking males. Females for whom longer time had elapsed since parturition, and therefore had higher probabilities of conception, had 5-m proximity with adult males more frequently than females whom shorter time had elapsed since parturition, but did not have more copulation with adult males. Females with MS had proximity and copulated with high-ranking males frequently, which partly explains why the reproductive skew is so high in bonobos. These results are discussed in relation to previous hypotheses on the influence of long-lasting mother–son relationships on mating success of males and on the contribution of female receptivity during non-conceptive nursing periods to moderate intermale aggression in bonobos. [ABSTRACT FROM AUTHOR]

Central and eastern chimpanzees are infected with Simian Immunodeficiency Virus (SIV) in the wild, typically without developing acute immunodeficiency. Yet the recent zoonotic transmission of chimpanzee SIV to humans, which were naïve to the virus, gave rise to the Human Immunodeficiency Virus (HIV), which causes AIDS and is responsible for one of the deadliest pandemics in human history. Chimpanzees have been infected with SIV for tens of thousands of years and have likely evolved to reduce its pathogenicity, becoming semi-natural hosts that largely tolerate the virus. In support of this view, central and eastern chimpanzees show evidence of positive selection in genes involved in SIV/HIV cell entry and immune response to SIV, respectively. We hypothesise that the population first infected by SIV would have experienced the strongest selective pressure to control the lethal potential of zoonotic SIV, and that population genetics will reveal those first critical adaptations. With that aim we used population genomics to investigate signatures of positive selection in the common ancestor of central-eastern chimpanzees. The genes with signatures of positive selection in the ancestral population are significantly enriched in SIV-related genes, especially those involved in the immune response to SIV and those encoding for host genes that physically interact with SIV/HIV (VIPs). This supports a scenario where SIV first infected the central-eastern ancestor and where this population was under strong pressure to adapt to zoonotic SIV. Interestingly, integrating these genes with candidates of positive selection in the two infected subspecies reveals novel patterns of adaptation to SIV. Specifically, we observe evidence of positive selection in numerous steps of the biological pathway responsible for T-helper cell differentiation, including CD4 and multiple genes that SIV/HIV use to infect and control host cells. This pathway is active only in CD4+ cells which SIV/HIV infects, and it plays a crucial role in shaping the immune response so it can efficiently control the virus. Our results confirm the importance of SIV as a selective factor, identify specific genetic changes that may have allowed our closest living relatives to reduce SIV's pathogenicity, and demonstrate the potential of population genomics to reveal the evolutionary mechanisms used by naïve hosts to reduce the pathogenicity of zoonotic pathogens. Author summary: Chimpanzees are at the origin of HIV-1, a virus that generates an incurable disease and that generated a pandemic that has claimed 35 million lives. Chimpanzees have evolved to control the pathogenicity of the virus, which does not typically develop into AIDS in the same way as in humans. Identifying the genetic adaptations responsible for this process provides critical knowledge about SIV and HIV. Our analysis of chimpanzee genetic adaptations identified specific genes and molecular pathways involved in adaptation to SIV, providing important insights into the mechanisms that likely allowed our closest living relatives to control SIV/HIV. Further, we establish SIV as a strong and recurrent selective pressure in central and eastern chimpanzees, two important subspecies of large mammals that are currently endangered. [ABSTRACT FROM AUTHOR]

Human beings are highly familiar over-learnt social targets, with similar physical facial morphology between perceiver and target. But does experience with or similarity to a social target determine whether we can accurately infer emotions from their facial displays? Here, we test this question across two studies by having human participants infer emotions from facial displays of: dogs, a highly experienced social target but with relatively dissimilar facial morphology; panins (chimpanzees/bonobos), inexperienced social targets, but close genetic relatives with a more similar facial morphology; and humans. We find that people are more accurate inferring emotions from facial displays of dogs compared to panins, though they are most accurate for human faces. However, we also find an effect of emotion, such that people vary in their ability to infer different emotional states from different species' facial displays, with anger more accurately inferred than happiness across species, perhaps hinting at an evolutionary bias towards detecting threat. These results not only compare emotion inferences from human and animal faces but provide initial evidence that experience with a non-human animal affects inferring emotion from facial displays. [ABSTRACT FROM AUTHOR]

Although curiosity has huge implications for human creativity and learning, its evolutionary roots and function in animals remain poorly understood. Modern humans, who lack natural predators, thrive with curiosity, but our ancestors faced more hazardous environments that would not necessarily favor individual curiosity. Instead, being curious may have undergone selection in interaction with sociality. Our closest living relatives, the great apes (henceforth apes) have evolved facing conditions more like human ancestors and as such, can help us understand the functions of curiosity and its expression in non‐human species. In this study, we defined curiosity as a combination of behavioral traits like neophilia, exploration diversity, and prolonged interest in exploring novelty and compared it, under similar captive environments across four ape species (N = 101): Pan troglodytes, Pan paniscus, Pongo abelii, and Pongo pygmaeus. Results revealed that curiosity followed a linear gradient across the four species in accordance with their sociality. We propose the social curiosity hypothesis to explain the observed pattern, reflecting those individuals in highly social species, like bonobos and chimpanzees, regularly are accompanied by conspecifics, and thereby accustomed to an abundance of social cues, leading to inhibited curiosity when alone, compared to more solitary orangutans. As such, our study implies that ape curiosity evolved interlinked with sociality. Further, a subset of the sample (N = 46) enabled us to examine if curiosity benefits problem‐solving skills, but our data did not support such link. [ABSTRACT FROM AUTHOR]

Ape language acquisition studies have demonstrated that apes can learn arbitrary mappings between different auditory or visual patterns and concepts, satisfying the definition of symbol use. The extent to which apes understand aspects of grammar is less well accepted. On the production side, several studies have shown that apes sometimes combine two or more symbols together, in non-random patterns. However, this is quite limited compared to human language production. On the comprehension side, much greater abilities have been reported in apes. One of the most famous examples is Kanzi, a bonobo who reportedly responded correctly to a large number of novel commands. However, based on his performance on a small subset of reversible sentences--where the understanding of English syntax was critical--the extent to which he demonstrated grammatical knowledge has been questioned. Using a randomization study it is shown here that his performance actually vastly exceeds random chance, supporting the contention that he does in fact understand word order grammatical rules in English. This of course represents only one aspect of English grammar, and does not suggest he has completely human grammatical abilities. However, it does show that he understands one of the arbitrary grammatical devices used in many languages: The use of word order to code argument relations. It also removes from serious consideration the view that apes lack any kind of grammatical ability. From an evolutionary perspective, Kanzi's ability is most likely to result from homologous brain circuitry, although this is ultimately an empirical question. [ABSTRACT FROM AUTHOR]

Introduction. Amyloid plaques are one of the neuropathological markers of Alzheimer's disease, formed by peptide fragments that are deposited, derived from the protease cut of the enzyme γ-secretase, of which presenilin-1 is the subunit with the active site, it is possible to investigate at the evolutionary level what happens with this protein in a sample of hominids. Materials and methods. structural biology study is carried out to evaluate changes in the structure of the proteins modeled with the Phyre2 software and primary sequence alignments with Jalview from the hominids Pongo abelii, Pan troglodytes, Pan paniscus, Gorilla gorilla, Homo sapiens and two species used in biological tests as Macaca fascicularis, Macaca mulatta. Results. It was found that the primary sequences of isoform 467 presented very high percentages of identity with T-Coffee 2.0 of 99.57 % on average, within its primary sequence in the pairwise alignment and at the three-dimensional level, with the Needleman- Wunsch algorithm, slight changes were found in the structure at the loop level, but very conserved between species, which was also reflected in standard deviation values of the models of less than 5 Å. Conclusions. Finally, no significant changes were found at the structural level in the protein with protease function, so for the hominin sample there were no evolutionary changes, at least for this protein, and in perspective, the other components of the enzyme gamma-secretase remain to evaluate. [ABSTRACT FROM AUTHOR]

Simple Summary: Zoo visitors can have a positive, negative, or neutral impact on animals. Primates are cognitively very advanced and their interactions with human visitors are complex. The COVID-19 pandemic led to a prolonged absence of visitors in zoos. This enabled an opportunity to compare how primates behaved when the zoo was open to visitors as opposed to when it was closed. We studied four primate species housed in the UK: bonobos, chimpanzees, and western lowland gorillas held at Twycross Zoo and olive baboons held at Knowsley Safari. Bonobos and gorillas spent less time alone when facilities were open to the public. Gorillas also spent less time resting when the facility was open to the public. Chimpanzees ate more and engaged more with enrichment when the zoo was open to the public. Olive baboons performed less sexual and dominance behaviour and approached visitor cars more frequently when the safari park was opened to the public than the ranger's vehicle during closure periods. The results suggest that the zoo closures had variable impacts on the primates and that the closure periods were neither "negative" or "positive" for all of the studied species. There are likely to be differences between individuals due to prior experiences. We recommend that future work seeks to understand the impact individual differences and animal environments have on animals' experiences with visitors. Primates are some of the most cognitively advanced species held in zoos, and their interactions with visitors are complex. The COVID-19 pandemic provided a unique opportunity to understand the impact of zoo visitors on animals, in comparison to "empty zoos". This study sought to understand the impact of facility closures and subsequent reopenings on behavioural and physiological parameters of welfare in four primate species housed in the UK: bonobos (Pan paniscus) (n = 8), chimpanzees (Pan troglodytes) (n = 11), and western lowland gorillas (Gorilla gorilla gorilla) (n = 6) held at Twycross Zoo (TZ); and olive baboons (Papio anubis) (n = 192) held at Knowsley Safari (KS). Behavioural data were collected from April–September 2020 (KS) and November 2020–January 2021 (TZ). Faecal samples were collected during morning checks from October–November (TZ) and July–November 2020 (KS). Faecal glucocorticoid metabolites (FGMs) were measured using ELISA kits. Statistical analysis for behavioural observations was undertaken using general linear models. Enclosure usage was assessed using t-tests and Mann–Whitney U-tests as appropriate. Bonobos and gorillas spent less time alone when facilities were open to the public (p = 0.004, p = 0.02 respectively). Gorillas spent less time resting when the facility was open to the public (p = 0.04), and chimpanzees engaged in more feeding (p = 0.02) and engagement with enrichment (p = 0.03) when the zoo was open to the public than when it was closed. Olive baboons performed less sexual and dominance behaviour and approached visitor cars more frequently when the safari park was opened to the public than they did the ranger's vehicle during closure periods. There were no significant changes in physiological parameters for any of the study species. The results suggest variable impacts of the zoo closures on zoo-housed primates. We recommend future work that seeks to understand the impact of individual-level differences on "visitor effects" and that differences between animal experiences in zoos and safari parks are further explored in a range of species. [ABSTRACT FROM AUTHOR]

Patriarchy is historical. To transcend the society and science that emerged within it, it is necessary to broaden the gaze, and take a journey from our primate ancestors and the organizational heritage that our species continued most of its experience, as the sustenance of a very probable Paleolithic matriarchal order whose transformation would have created the conditions of possibility for the emergence of the Patriarchal Illusion. And appreciate, in this intersection, matriality as a source to reinvent ourselves in the present and generate a civilizing proposal and post-patriarchal knowledge. [ABSTRACT FROM AUTHOR]

Comparative behavioral studies of hand use amongst primate species, including humans, have been central in research on evolutionary mechanisms. In particular, the manipulative abilities of our closest relatives, the chimpanzee (Pan troglodytes), have been widely described in various contexts, showing a high level of dexterity both in zoo and in natural conditions. In contrast, the study of bonobos' manipulative abilities has almost exclusively been carried out in experimental contexts related to tool use. The objective of the present study is to describe the richness of the manipulative repertoire of zoo‐housed bonobos, in a spontaneous feeding context including various physical substrates to gain a larger insight into our evolutionary past. Our study describes a great variety of grasping postures and grip associations in bonobos, close to the range of manipulative repertoire in chimpanzees, confirming that the two species are not markedly different in terms of cognitive and morphological constraints associated with food manipulation. We also observed differences in manipulative behaviors between juveniles and adults, indicating a greater diversity in grip associations and grasping postures used in isolation with age, and a sex‐biased use of tools with females using tools more often than males. These results are consistent with the previous results in the Pan genus and reinforce the hypothesis that the evolutionary mechanisms underlying the flexibility of manipulative behaviors are shared by both species and that these ecological strategies would have already evolved in their common ancestor. Research highlights: Our study provides a description of a large manipulative repertoire, from precision to power grips, including 22 grasping postures, while individuals fed on foods of different shapes and sizes and on different substrates.Our results show an enrichment of the manipulative repertoire from juveniles to adult individuals.We described a spontaneous use of tools with a female bias and the use of specific grasping postures for this context. [ABSTRACT FROM AUTHOR]

Sociality is widespread among group-living primates and is beneficial in many ways. Sociality amongst female bonobos (Pan paniscus) has been proposed to have evolved as a female counterstrategy to male infanticide and sexual coercion. In male-philopatric bonobo societies, females mostly form relationships with unrelated females. Among these social relationships, it has been proposed that females with infants (also referred to as mothers) tend to have strong relationships with each other (mother-bonding hypothesis). In this paper, we use the case of an infant death in a group of wild bonobos in the Kokolopori Bonobo Reserve, Democratic Republic of Congo, to test this hypothesis. By using dyadic sociality indices for grooming, proximity, and aggression, we investigated whether the infant death influenced dyadic relationships the mother had with other group members. Before the infant death, grooming index (GI) and proximity index (PI) scores were the highest between the focal mother and another mother. After the death, the relationship of this mother dyad weakened, as indicated by lower GI and PI scores, whereas the relationship of another mother dyad became stronger. Aggression index scores among the mothers were comparable before and after the death, suggesting that changes in mother affiliative relationships were not a by-product of changes in overall interaction frequencies. Also, PI scores increased between the focal mother and three non-mothers after the death. Collectively, the shift in social dynamics between the focal mother and other group members after the infant death partially supported the mother-bonding hypothesis. [ABSTRACT FROM AUTHOR]

In this article I am trying to look at the complex and robust subject of "A Chronology of Human Evolution and Comparative Insights from Sikhism" from available literature. First, I collected the scattered scientific literature about evolution of humans at different stages, thereafter, I linked that information to make continuous research starting from the evolution of organic molecules from inorganic matter, which gave rise to the evolution of Deoxyribonucleic Acid (DNA) and ribonucleic Acid (RNA) leading to the evolution of life as Single cell. Further linkage about evolution continued till I reached to the evolution of bonobos, chimpanzees, gorillas, and orangutans and finally to Hominins which gave rise to the evolution of genus Homo and ultimately to Homo sapiens, the human. Along with that the comparative Insights from Sikhism was discussed. [ABSTRACT FROM AUTHOR]

• PEMFC parameters are accurately identified using the SaBO algorithm. • Investigations with two available PEMFCs to confirm the SaBO's stability. • Comparative analysis with recent robust algorithms has been conducted. • Comprehensive statistical analysis is performed. • Minimum error values between experimental and forecasted data are obtained. The present study introduces an efficient Self-Adaptive Bonobo Optimizer (SaBO) for identifying the unknown parameters of the proton exchange membrane fuel cell (PEMFC). A comparative analysis between recent robust approaches, such as Gradient-based Optimizer (GBO), Bald Eagle Search Algorithm, and Rime-Ice algorithm (RIME), has been introduced. The basic concept is to minimize the mean bias error between the measured and predicted stack voltage. The main results show that although the techniques were close, in contrast, the SaBO optimizer provides a better superiority than GBO, BES, and RIME for an optimum forecast of the PEMFCs model. Moreover, the best fitness was achieved with the SaBO at 0.0367 (V) for the Heliocentris FC-50, and 0.1150 (V) for Nexa® 1200, also, with the minimum deviation of 0.0027 & 0.0172, and high efficiency. These achievements denote that the SaBO algorithm is more stable and robust for PEMFC parameter estimation. [ABSTRACT FROM AUTHOR]