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In this review, we reorganize the concept and highlight the importance of prestige in humans and non-human animals by introducing key characteristics of dominance and prestige and related theories. Previous studies with non-human animals have mainly focused on dominance, presuming prestige as a human-unique social trait. However, to deepen our understanding of the evolution of prestige, comparative studies with non-human animals, especially our evolutionary closest relatives, chimpanzees and bonobos, are essential. We propose the direction of future studies to investigate how prestige has emerged as a viable strategy for gaining social rank while diverging from dominance, which will establish a foundation for investigating the impact of prestige on propensities towards large-scale cooperation and cumulative culture which are still considered unique to humans. Such comparative viewpoints on prestige, along with some hypotheses of species differences, will provide powerful guidance for understanding the evolution of social hierarchies. • Both dominance and prestige are utilized as a viable strategy for acquiring higher social rank in human social hierarchy. • In non-human animals, only dominance, but not prestige, has been assumed as a viable strategy for attaining social rank. • Exploring prestige-like traits in non-human animals may provide insights into the evolution of human social hierarchy. • We propose hypotheses about possible differences in prestige between chimpanzees and bonobos. [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 has found that oxytocin (OT) is associated with intergroup behaviour in humans as well as wild chimpanzees, and that exogenous OT affects Pan social attention. The two Pan species, bonobos and chimpanzees, differ drastically from one another in their intensity of intergroup competition, with lethal intergroup aggression often led by males in chimpanzees and more tolerant associations often centered around females in bonobos. However, it remains unclear how exogenous OT changes the two species' responses to ingroup and outgroup individuals. In this study, after intranasal administration of nebulized OT or placebo control, chimpanzees and bonobos viewed image pairs of ingroup and outgroup conspecifics while their eye movements were tracked with an eye-tracker. Although the overall effect of OT was small, we found that OT shifted bonobos' and chimpanzees' attention to outgroup images of the sex primarily involved in intergroup encounters in each species. Specifically, OT selectively shifted attention towards outgroup photos of female conspecifics in bonobos, and those of outgroup male conspecifics in chimpanzees. This suggests that OT generally promotes outgroup attention in both bonobos and chimpanzees but this effect is restricted to the sex most relevant in intergroup relations. These results suggest that, although OT may have a generally conserved role in hominid intergroup behaviour, it may act in species-relevant ways under the influence of their socio-ecological backgrounds. • Oxytocin (OT) is known to promote ingroup-outgroup psychology in humans. • We tested how OT affects bonobo and chimpanzee gaze to ingroup and outgroup images. • In both species, OT promoted outgroup attention. • However, this effect was restricted to sex more relevant to intergroup encounters. • This suggests a common evolutionary role of OT, acting in species-relevant ways. [ABSTRACT FROM AUTHOR]