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During the Covid-19 pandemic we increasingly turned to technology to stay in touch with our family, friends, and colleagues. Even as lockdowns and restrictions ease many are encouraging us to embrace the replacement of face-to-face encounters with technologically mediated ones. Yet, as philosophers of technology have highlighted, technology can transform the situations we find ourselves in. Drawing insights from the phenomenology of sociality, we consider how digitally-enabled forms of communication and sociality impact our experience of one another. In particular, we draw attention to the way in which our embodied experience of one another is altered when we meet in digital spaces, taking as our focus the themes of perceptual access, intercorporeality, shared space, transitional spaces, and self-presentation. In light of the way in which technological mediation alters various dimensions of our social encounters, we argue that digital encounters constitute their own forms of sociality requiring their own phenomenological analysis. We conclude our paper by raising some broader concerns about the very framework of thinking about digitally and non-digitally mediated social encounters simply in terms of replacement.

Throughout the world people differ in the magnitude with which they value strong family ties or heightened religiosity. We propose that this cross-cultural variation is a result of a contingent psychological adaptation that facilitates in-group assortative sociality in the face of high levels of parasite-stress while devaluing in-group assortative sociality in areas with low levels of parasite-stress. This is because in-group assortative sociality is more important for the avoidance of infection from novel parasites and for the management of infection in regions with high levels of parasite-stress compared with regions of low infectious disease stress. We examined this hypothesis by testing the predictions that there would be a positive association between parasite-stress and strength of family ties or religiosity. We conducted this study by comparing among nations and among states in the United States of America. We found for both the international and the interstate analyses that in-group assortative sociality was positively associated with parasite-stress. This was true when controlling for potentially confounding factors such as human freedom and economic development. The findings support the parasite-stress theory of sociality, that is, the proposal that parasite-stress is central to the evolution of social life in humans and other animals.

Behaviors of introduced species can change with context and can impact local ecosystems in negative and positive ways. Warbling White-eye (Zosterops japonicus), Red-billed Leiothrix (Leiothrix lutea), and Red-whiskered Bulbul (Pycnonotus jocosus) are introduced species at several locations globally, including O‘ahu, Hawai‘i, where they are responsible for the majority of seed dispersal. To understand how behaviors of introduced species vary across ecological contexts and impact local seed dispersal, it is important to identify the circumstances under which individuals engage in foraging and social behaviors, examine interspecific variation in these behaviors, and compare behaviors across localities. From 2015 to 2017 on O‘ahu, we used radio telemetry to track 68 individuals year-round and conducted 459 behavioral observations to examine how often they forage on specific foods (insects, fruit) and employ specific social behaviors (alone, with a mate, mixed-species foraging aggregation, conspecific foraging aggregation). In their native ranges, these three omnivorous species exhibit social foraging in conspecific or mixed-species aggregations. Here, all species were observed in mixed-species aggregations consisting of only introduced species, suggesting that the behavior of social foraging has been maintained from their native ranges even though the species assemblages are different. All species foraged on fruit and insects on O‘ahu, but P. jocosus shifted away from primarily foraging on fruits during of the breeding season. Thus, L. lutea and Z. japonicus contribute to seed dispersal more consistently throughout the year compared to P. jocosus. All species participated in aggregations outside of the breeding season, and these aggregations primarily foraged on fruit, which suggests the potential for longer distance seed dispersal events outside of the breeding season. These results suggest that flexibility in social and foraging behaviors across the year and across ecological contexts may influence how introduced species integrate into novel communities and impact local seed dispersal. Los comportamientos de las especies introducidas pueden cambiar en función del contexto y repercutir en los ecosistemas locales de forma negativa y positiva. El mejiro (Zosterops japonicus), el leiótrix piquirrojo (Leiothrix lutea) y el bulbul orfeo (Pycnonotus jocosus) son especies introducidas en varios lugares del mundo, entre ellos O‘ahu (Hawai‘i), donde son responsables de la mayor parte de la dispersión de semillas. Para comprender cómo varían los comportamientos de las especies introducidas en los distintos contextos ecológicos y cómo influyen en la dispersión local de semillas, es importante identificar las circunstancias en las que los individuos adoptan diferentes comportamientos sociales y de búsqueda de alimento, examinar la variación interespecífica de estos comportamientos y comparar los comportamientos entre localidades. De 2015 a 2017 en O‘ahu, usamos radiotelemetría para rastrear a 68 individuos durante todo el año y realizamos 459 observaciones de comportamiento para examinar la frecuencia con la que se alimentan de insectos vs. frutas y la frecuencia con la que emplean comportamientos sociales específicos (solos, con la pareja, en agregación de forrajeo multi-especie, en agregación de forrajeo de una sola especie). En sus áreas de distribución nativas, estas tres especies omnívoras se alimentan socialmente en agregaciones multi-especie o de una sola especie. Observamos a todas las especies en agregaciones multi-especie formadas únicamente por especies introducidas, lo que sugiere que el comportamiento de búsqueda social de alimento se ha mantenido en sus áreas de distribución nativas aunque los ensambles de especies sean diferentes. Todas las especies se alimentaron de fruta e insectos en O‘ahu, pero P. jocosus dejó de alimentarse principalmente de fruta durante la época de cría. Entonces, L. lutea y Z. japonicus contribuyen a la dispersión de semillas de forma más constante que a lo largo del año. Todas las especies participaron en agregaciones fuera de la época de cría, y estas agregaciones se alimentaron principalmente de frutos, lo que sugiere la posibilidad de que se produzcan eventos de dispersión de semillas a mayor distancia fuera de la época de cría. Estos resultados sugieren que la flexibilidad en los comportamientos sociales y de forrajeo a lo largo del año y en distintos contextos ecológicos puede influir en la forma en que las especies introducidas se integran en las nuevas comunidades, con repercusiones para la dispersión local de semillas. PALABRAS CLAVE agregaciones de forrajeo; omnívoro; dispersión de semillas; especies introducidas

Humans possess some unique social-cognitive skills and motivations, involving such things as joint attention, cooperative communication, dual-level collaboration and cultural learning. These are almost certainly adaptations for humans' especially complex sociocultural lives. The common assumption has been that these unique skills and motivations emerge in human infancy and early childhood as preparations for the challenges of adult life, for example, in collaborative foraging. In the current paper, I propose that the curiously early emergence of these skills in infancy––well before they are needed in adulthood––along with other pieces of evidence (such as almost exclusive use with adults not peers) suggests that aspects of the evolution of these skills represent ontogenetic adaptations to the unique socio-ecological challenges human infants face in the context of a regime of cooperative breeding and childcare. This article is part of the theme issue ‘Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals’.

The question as to why primates have evolved unusually large brains has received much attention, with many alternative proposals all supported by evidence. We review the main hypotheses, the assumptions they make and the evidence for and against them. Taking as our starting point the fact that every hypothesis has sound empirical evidence to support it, we argue that the hypotheses are best interpreted in terms of a framework of evolutionary causes (selection factors), consequences (evolutionary windows of opportunity) and constraints (usually physiological limitations requiring resolution if large brains are to evolve). Explanations for brain evolution in birds and mammals generally, and primates in particular, have to be seen against the backdrop of the challenges involved with the evolution of coordinated, cohesive, bonded social groups that require novel social behaviours for their resolution, together with the specialized cognition and neural substrates that underpin this. A crucial, but frequently overlooked, issue is that fact that the evolution of large brains required energetic, physiological and time budget constraints to be overcome. In some cases, this was reflected in the evolution of ‘smart foraging’ and technical intelligence, but in many cases required the evolution of behavioural competences (such as coalition formation) that required novel cognitive skills. These may all have been supported by a domain-general form of cognition that can be used in many different contexts. This article is part of the themed issue ‘Physiological determinants of social behaviour in animals’.

Many species use social interactions to cope with challenges in their environment and a growing number of studies show that individuals which are well-connected to their group have higher fitness than socially isolated individuals. However, there are many ways to be ‘well-connected’ and it is unclear which aspects of sociality drive fitness benefits. Being well-connected can be conceptualized in four main ways: individuals can be socially integrated by engaging in a high rate of social behaviour or having many partners; they can have strong and stable connections to favoured partners; they can indirectly connect to the broader group structure; or directly engage in a high rate of beneficial behaviours, such as grooming. In this study, we use survival models and long-term data in adult female rhesus macaques ( Macaca mulatta ) to compare the fitness outcomes of multiple measures of social connectedness. Females that maintained strong connections to favoured partners had the highest relative survival probability, as did females well-integrated owing to forming many weak connections. We found no survival benefits to being structurally well-connected or engaging in high rates of grooming. Being well-connected to favoured partners could provide fitness benefits by, for example, increasing the efficacy of coordinated or mutualistic behaviours.

Parasites and their social hosts form many different relationships. But what kind of selection regimes are important? A look at the parameters that determine fitness of the two parties suggests that social hosts differ from solitary ones primarily in the structure of transmission pathways. Because transmission is, both, the physical encounter of a new host and infecting it, several different elements determine parasite transmission success. These include spatial distance, genetic distance, or the temporal and ecological niche overlaps. Combing these elements into a ‘generalized transmission distance’ that determines parasite fitness aids in the identification of the critical steps. For example, short-distance transmission to genetically similar hosts within the social group is the most frequent process under sociality. Therefore, spatio-genetical distances are the main driver of parasite fitness. Vice versa, the generalized distance identifies the critical host defences. In this case, host defences should be primarily selected to defend against the within-group spread of an infection, especially among closely related group members.

Abstract Aggression is costly, and animals have evolved tactics to mitigate these costs. Submission signals are an underappreciated example of such adaptations. Here we review submissive behaviour, with an emphasis on non-primates. We highlight the design of submission signals and how such signals can reduce costs. Animal societies necessitate frequent social interactions, which can increase the probability of conflict. Where maintaining group proximity is essential, animals cannot avoid aggression by fleeing. Mutual interest between group members may also select for efficient conflict avoidance and resolution mechanisms. As a result, submission signals may be especially well developed among group living species, helping social animals to overcome potential costs of recurring conflict that could otherwise counter the benefits of group living. Therefore, submission signalling can be a crucial aspect of social living and is deserving of specific attention within the broader context of social evolution and communication.

An important element in understanding the evolution of human sociality is to understand the factors that governed the evolution of social organisation in our closest living relatives. The ‘social brain hypothesis’ proposes that the complex social world of primates is especially cognitively demanding, and that this imposed intense selection pressure for increasingly large brains. Group size in primates is strongly correlated with brain size but exactly what makes larger groups more ‘socially complex’ than smaller groups is still poorly understood. Chimpanzees and Gorillas are among our closest living relatives and they exhibit remarkable diversity in various aspects of their social organisation both within and across species. They are thus excellent species in which to investigate patterns of sociality and social complexity in primates, and to inform models of human social evolution. We propose a program of research that will provide the first systematic insight into how social structure differs in small, medium and large groups of Chimpanzees and Gorillas, to explore what makes larger groups more socially complex than smaller groups. Further, we propose to investigate how these variations in social structure in different size groups are affected by the social organisation of the species. Chimpanzees live in a fluid fission-fusion social system, whereas Gorillas have more stable, cohesive groups. To carry out both the within and between species comparisons, we advocate use of social network analysis, which provides a novel way to describe and compare social structure. This program of research will therefore lead to a new, systematic way of comparing social complexity across species, something that is lacking in current comparative studies of social structure. Considering that hominins were likely characterized by a fission-fusion social structure, comparing the social complexity of such systems with that of more stable groups may yield valuable insights into the evolution of human sociality.

Members of a social species need to make appropriate decisions about who, how, and when to interact with others in their group. However, it has been difficult for researchers to detect the inputs to these decisions and, in particular, how much information individuals actually have about their social context. We present a method that can serve as a social assay to quantify how patterns of aggression depend upon information about the ranks of individuals within social dominance hierarchies. Applied to existing data on aggression in 172 social groups across 85 species in 23 orders, it reveals three main patterns of rank-dependent social dominance: the downward heuristic (aggress uniformly against lower-ranked opponents), close competitors (aggress against opponents ranked slightly below self), and bullying (aggress against opponents ranked much lower than self). The majority of the groups (133 groups, 77%) follow a downward heuristic, but a significant minority (38 groups, 22%) show more complex social dominance patterns (close competitors or bullying) consistent with higher levels of social information use. These patterns are not phylogenetically constrained and different groups within the same species can use different patterns, suggesting that heuristic use may depend on context and the structuring of aggression by social information should not be considered a fixed characteristic of a species. Our approach provides opportunities to study the use of social information within and across species and the evolution of social complexity and cognition.