Group Social Structure Research Articles

Indirect genetic effects for social network structure in Drosophila melanogaster.

The position an individual holds in a social network is dependent on both its direct and indirect social interactions. Because social network position is dependent on the actions and interactions of conspecifics, it is likely that the genotypic composition of individuals within a social group impacts individuals' network positions. However, we know very little about whether social network positions have a genetic basis, and even less about how the genotypic makeup of a social group impacts network positions and structure. With ample evidence indicating that network positions influence various fitness metrics, studying how direct and indirect genetic effects shape network positions is crucial for furthering our understanding of how the social environment can respond to selection and evolve. Using replicate genotypes of Drosophila melanogaster fruit flies, we created social groups that varied in their genotypic makeup. Social groups were videoed, and networks were generated using motion-tracking software. We found that both an individual's own genotype and the genotypes of conspecifics in its social group affect its position within a social network. These findings provide an early example of how indirect genetic effects and social network theory can be linked, and shed new light on how quantitative genetic variation shapes the structure of social groups. This article is part of a discussion meeting issue 'Collective behaviour through time'.

Constitutive depletion of brain serotonin differentially affects rats’ social and cognitive abilities

Central serotonin appears a promising transdiagnostic marker of psychiatric disorders and a modulator of some of their key behavioral symptoms. In adult male Tph2 -/- rats, constitutively lacking central serotonin, we tested individual's cognitive, social and non-social abilities and characterized group's social organization under classical and ethological testing conditions. Using unsupervised machine learning, we identified the functions most dependent on serotonin. Although serotonin depletion did not affect cognitive performances in classical testing, in the home-cage it induced compulsive aggression and sexual behavior, hyperactive and hypervigilant stereotyped behavior, reduced self-care and exacerbated corticosterone levels. This profile recalled symptoms of impulse control and anxiety disorders. Serotonin appeared essential for behavioral adaptation to dynamic social environments. Our animal model challenges the essential role of serotonin in decision-making, flexibility, impulsivity, and risk-taking. These findings highlight the importance of studying everyday life functions within the dynamic social living environment to model complexity in animal models.

Group composition impacts reproductive output and population viability in captive white rhinoceros

AbstractCaptive breeding programmes can play an important role in the conservation of species threatened with extinction in the wild. White rhinoceros, Ceratotherium simum, have suffered drastic declines due to illegal poaching across their range, and captive populations have the potential to safeguard this species from extinction. However, white rhinoceros birth rates in captivity have been extremely low, and there is substantial variation in breeding success between different institutions. A better understanding of the factors limiting their reproduction in captivity could improve their breeding management and conservation potential. This study used studbook data (n = 467) and comparisons with wild populations in Kenya (n = 236) to assess the breeding performance and viability of the European captive southern white rhinoceros, Ceratotherium simum simum, population. Our results show that the European population is declining 2% annually under current demographic parameters. On average, just 10% of females calved annually, in comparison to almost 40% across wild populations. To become self‐sustaining, this must increase to a minimum of 17%, though reaching this target may lead to additional management challenges. Further analyses using studbook (n = 134 individuals) and multi‐institutional questionnaire data (n = 20 institutions) suggest that modifying the social structure of captive groups could improve female breeding success. Institutions housing larger groups had proportionally greater breeding success, and females were more likely to copulate if housed with another breeding female, and more receptive to bulls if housed in a group with a lower mean age. These findings highlight the importance of considering social conditions in captive breeding programmes, particularly for species with complex social systems and low reproductive rates.

Group social structure has limited impact on reproductive success in a wild mammal

Abstract The frequency and type of dyadic social interactions individuals partake in has important fitness consequences. Social network analysis is an effective tool to quantify the complexity and consequences of these behaviors on the individual level. Less work has used social networks to quantify the social structure—specific attributes of the pattern of all social interactions in a network—of animal social groups, and its fitness consequences for those individuals who comprise the group. We studied the association between social structure, quantified via five network measures, and annual reproductive success in wild, free-living female yellow-bellied marmots (Marmota flaviventer). We quantified reproductive success in two ways: (1) if an individual successfully weaned a litter and (2) how many pups were weaned. Networks were constructed from 38 968 interactions between 726 unique individuals in 137 social groups across 19 years. Using generalized linear mixed models, we found largely no relationship between either measure of reproductive success and social structure. We found a modest relationship that females residing in more fragmentable social groups (i.e., groups breakable into two or more separate groups of two or more individuals) weaned larger litters. Prior work showed that yellow-bellied marmots residing in more fragmentable groups gained body mass faster—another important fitness correlate. Interestingly, we found no strong relationships between other attributes of social group structure, suggesting that in this facultatively social mammal, the position of individuals within their group, the individual social phenotype, may be more important for fitness than the emergent group social phenotype.

Analyzing Social Factors Which Explain How the Social Context Affects Our Choice of a Code or A Variety, Whether Language, Dialect, or Style, with Examples from English- Other languages, and Libyan Arabic

People’s pronunciation, their words choice and styles mark their background (socially and culturally). So the relation between language and society is reciprocal. This relationship explains why groups speak differently in different social contexts. Language in the social context is not only a means of communication but also a means of establishing and maintain social relations. Social context accounts the language, variety, code or style that people from different background use. Theses distinct varieties determine the social structure of human groups. Actually, several factors stand behind this linguistic choice. What distinguishes man’s speech from woman’s speech which is controlled by social norms, why speakers use an appropriate register or style at home, whereas a particular language deals with government institutions, and what draws distinction between formal and casual conversation? This is the aim of this paper will be clarified. Keywords: social context, language choice, social factors, language, code, style. DOI: 10.7176/JLLL/93-01 Publication date: November 30 th 2022

Online Conspiracy Groups: Micro-Bloggers, Bots, and Coronavirus Conspiracy Talk on Twitter

Conspiracies are consequential and social, yet online conspiracy groups that consist of individuals (and bots) seeking to explain events or a system have been neglected in sociology. We extract conspiracy talk about the COVID-19 pandemic on Twitter and use the biterm topic model (BTM) to provide a descriptive baseline for the discursive and social structure of online conspiracy groups. We find that individuals enter these communities through a gateway conspiracy theory before proceeding to extreme theories, and humans adopt more diverse conspiracy theories than do bots. Event-history analyses show that individuals tweet new conspiracy theories, and tweet inconsistent theories simultaneously, when they face a threat posed by a rising COVID-19 case rate and receive attention from others via retweets. By contrast, bots are less responsive to rising case rates, but they are more consistent, as they mainly tweet about how COVID-19 was deliberately created by sinister agents. These findings suggest human beings are bricoleurs who use conspiracy theories to make sense of COVID-19, whereas bots are designed to create moral panic. Our findings suggest that conspiracy talk by individuals is defensive in nature, whereas bots engage in offense.

СОЦІУМ ТА ЛЮДИНА

Socialization is accomplished by a wide set of methods specific to a certain society, social stratum and age. For instance, it can include the methods of nursing a baby; the methods of encouraging and punishing in a family, age-mate groups, training or task teams; various methods and types of relations in basic life spheres (communication, games, sport) etc. The better organization of social groups is the more opportunities it provides with socializing influence on an individual. However social groups are unequal in their ability to provide influence on a personality at different stages of its ontogenetic development. Thus, family has the greatest influence at tender and preschool age. In teenage years and adolescence, the most effective influence of age-mate groups appears and grows. Status, labour collective or professional team and individual people take the central stage in adulthood. There are some factors of socialization, the value of which remains throughout an individual’s life. They are nation, mentality, ethnos. Recent years scientists attach greater importance to macro level socialization issues including natural and geographical conditions as it is determined that they have influence on formation of personality both directly and indirectly. Macro level socialization issues knowledge let comprehend the peculiarity of disclosure of general laws of development of individual as Homo sapiens. Recognition of personality activity as a dominant factor of its formation raises the question of purposeful activity, self-development of personality i.e. permanent work on self-improvement and spiritual development. The possibility to complicate tasks and creation content gradually, implementation of age and individual approach, formation of creative individuality equally to implementation of collective education and stimulation of personal self-governance through its further development are ensured by self-development. Personality as a product of life in the meantime is a living organism. The relation between social and biological things in the formation and behavior of a personality is extremely complex and has an unequal impact on it at different stages of individual development, in different situations and types of communication with other people. Courage can run into imprudent when the desire to draw attention to oneself (natural need for recognition) is stimulated. Courage prompts another people to brave life obstacles, although no one but them know about it. It is important to see the level of expression of the corresponding trait (or even to notice it). It is proved that socialization is a non-linear process of self-development of individual under the influence of social medium, the whole environment. The determine factor of socialization is not natural inclinations themselves but personal qualities formed by the external environment as a product of education and upbringing.

Experimental manipulation of food distribution alters social networks and information transmission across environments in a food-caching bird

While many animals utilize socially transmitted information, there is still much to understand about how individuals form social networks and how these networks influence social information use. Here, we tested the hypothesis that food distribution and availability can influence social structure and social information transfer when discovering novel food sources. We experimentally manipulated distribution and access to food in wild food-caching mountain chickadees, Poecile gambeli , by randomly dividing existing individuals between two feeding locations, with birds only allowed to obtain food at one of the two locations. We carried out such manipulations at multiple sites associated with two montane elevations of different environmental harshness, where birds show differing use of social information. Following 2 weeks of manipulation, we measured social networks and then introduced novel feeders to test how the manipulation affected social information use. The manipulations effectively split the resident chickadees at both elevations into two distinct communities, and when subsequently discovering novel feeders, information transmission about novel food sources followed the new, rather than the premanipulation, network structure at both elevations, although low-elevation birds used social information more than high-elevation birds. Our data show that chickadees can quickly adjust their social associations in response to short-term changes in the distribution of available resources and that these changes influence who they learn from socially when searching for food. Overall, we observed that chickadees are highly flexible in their use of social information despite their rather stable social group structure and that this information use reflects the most current social environment that individuals experience. • Mountain chickadee social networks changed during short-term resource manipulation. • Social information transmission primarily followed the most recent network edges. • Birds at high elevations showed less social information transmission.

Parochial cooperation in wild chimpanzees: a model to explain the evolution of parochial altruism.

Parochial altruism, taking individual costs to benefit the in-group and harm the out-group, has been proposed as one of the mechanisms underlying the human ability of large-scale cooperation. How parochial altruism has evolved remains unclear. In this review paper, we formulate a parochial cooperation model in small-scale groups and examine the model in wild chimpanzees. As suggested for human parochial altruism, we review evidence that the oxytocinergic system and in-group cooperation and cohesion during out-group threat are integral parts of chimpanzee collective action during intergroup competition. We expand this model by suggesting that chimpanzee parochial cooperation is supported by the social structure of chimpanzee groups which enables repeated interaction history and established social ties between co-operators. We discuss in detail the role of the oxytocinergic system in supporting parochial cooperation, a pathway that appears integral already in chimpanzees. The reviewed evidence suggests that prerequisites of human parochial altruism were probably present in the last common ancestor between Pan and Homo.This article is part of the theme issue ‘Intergroup conflict across taxa’.

Borderlands History in the Southwestern Historical Quarterly

Borderlands History in the Southwestern Historical Quarterly Omar Valerio-Jiménez (bio) Click for larger view View full resolution First page of the July 1912 issue of the Southwestern Historical Quarterly, which subtly notes the publication's name change. University of North Texas Libraries, the Portal to Texas History, https://texashistory.unt.edu. [End Page 408] For over a century, the Southwestern Historical Quarterly (including the time between 1897 and 1912 when it was known as the Quarterly of the Texas State Historical Association) has been a venue for borderlands scholarship on Texas and the surrounding regions. While the number of articles on borderlands topics have waxed and waned over the years, the journal has consistently promoted scholarship on the Spanish and Mexican periods of the region's history. The Quarterly has featured articles by some of the most renowned borderlands scholars, such as Herbert Bolton, who helped establish the field, but it has also been an avenue for emerging scholars whose research has appeared as journal articles before their books were published. The journal has also published articles by various non-academics whose interests in the state's early history led to contributions to the borderlands field.1 Among the first articles in what [End Page 409] would become known as borderlands history that appeared in the Quarterly were studies focused on Indigenous nations, imperial rivalries, and Spanish exploration.2 The first articles on Indigenous nations were mainly descriptive. They focused on identifying which Native groups lived in what is now Texas, their social organization, the languages spoken by each nation, and their displacement by Anglo Americans. Reflecting the attitudes of Anglo Americans in the late 1890s, these articles demonstrate a Eurocentric bias and advance pernicious stereotypes of Indigenous nations. While discussing the presence of Caddo, Alabama-Coushatta, Lipan Apaches, Comanches, Tonkawas, Karankawas, and others in the region that became Texas, Martin McHenry Kenney lauded the advances in comparative philology that allowed scholars to trace human migrations by analyzing language. Using "tribes" to refer to the Indigenous nations, Kenney discussed the "advance toward civilization" of "savage people."3 He also described alliances among various Indigenous nations and briefly explained their internal social structure of matriarchal and patriarchal groups. Kenney's perspective on "progress" and "civilization" led him to conclude, "There is no instance of a tribe, as such, adopting the political or social organization of civilization."4 But perhaps his most troubling statement is about the Karankawa Indians of the Texas Gulf Coast, when he writes, "The first and worst of these was the Carankawa, inhabiting along the coast from Galveston westward–a tribe of cannibals, noted for their gigantic stature and hideous aspect. … their language was an almost inarticulate guttural, impossible of imitation, and the lowest form of human speech."5 Some articles on Indigenous nations contain important insights despite their Eurocentric interpretations. The essay by Kenney mentioned above notes the advanced skills required to create arrowheads with "uniform construction." The author gestures to the elaborate trade networks among Indigenous nations that led Native groups in western and northwestern Texas to acquire flint rock to make arrowheads. Noting that this flint rock originated in Arkansas and Alabama, the author notes that expansive trade among non-sedentary Indigenous people brought this rock [End Page 410] material to Texas.6 The different types of materials exchanged in such trade networks are not discussed, nor is the possibility that these materials were exchanged among various Indigenous nations from their source to their ultimate destination. This article also speculates about the purpose of earthen mounds in East Texas and references Spanish colonists' accounts of them. Notwithstanding the author's acknowledgement that these mounds took considerable skill and time to complete, the author disparages Indigenous nations by arguing that it was unlikely they were descendants of the mound builders because these nations had a "habitual indisposition to labor."7 The author concludes that "prehistoric races" of Indigenous peoples became "extinct" because they had failed to develop agriculture. Other articles focused on the forced removal of the Cherokee Indians from the American Southeast to Texas and eventually to Indian Territory in present-day Oklahoma. These essays described the Cherokees' acculturation...

Group and individual social network metrics are robust to changes in resource distribution in experimental populations of forked fungus beetles.

Social interactions drive many important ecological and evolutionary processes. It is therefore essential to understand the intrinsic and extrinsic factors that underlie social patterns. A central tenet of the field of behavioural ecology is the expectation that the distribution of resources shapes patterns of social interactions.We combined experimental manipulations with social network analyses to ask how patterns of resource distribution influence complex social interactions.We experimentally manipulated the distribution of an essential food and reproductive resource in semi‐natural populations of forked fungus beetles Bolitotherus cornutus. We aggregated resources into discrete clumps in half of the populations and evenly dispersed resources in the other half. We then observed social interactions between individually marked beetles. Half‐way through the experiment, we reversed the resource distribution in each population, allowing us to control any demographic or behavioural differences between our experimental populations. At the end of the experiment, we compared individual and group social network characteristics between the two resource distribution treatments.We found a statistically significant but quantitatively small effect of resource distribution on individual social network position and detected no effect on group social network structure. Individual connectivity (individual strength) and individual cliquishness (local clustering coefficient) increased in environments with clumped resources, but this difference explained very little of the variance in individual social network position. Individual centrality (individual betweenness) and measures of overall social structure (network density, average shortest path length and global clustering coefficient) did not differ between environments with dramatically different distributions of resources.Our results illustrate that the resource environment, despite being fundamental to our understanding of social systems, does not always play a central role in shaping social interactions. Instead, our results suggest that sex differences and temporally fluctuating environmental conditions may be more important in determining patterns of social interactions.

Social behavior mediates the use of social and personal information in wild jays

The factors favoring the evolution of certain cognitive abilities in animals remain unclear. Social learning is a cognitive ability that reduces the cost of acquiring personal information and forms the foundation for cultural behavior. Theory predicts the evolutionary pressures to evolve social learning should be greater in more social species. However, research testing this theory has primarily occurred in captivity, where artificial environments can affect performance and yield conflicting results. We compared the use of social and personal information, and the social learning mechanisms used by wild, asocial California scrub-jays and social Mexican jays. We trained demonstrators to solve one door on a multi-door task, then measured the behavior of naïve conspecifics towards the task. If social learning occurs, observations of demonstrators will change the rate that naïve individuals interact with each door. We found both species socially learned, though personal information had a much greater effect on behavior in the asocial species while social information was more important for the social species. Additionally, both species used social information to avoid, rather than copy, conspecifics. Our findings demonstrate that while complex social group structures may be unnecessary for the evolution of social learning, it does affect the use of social versus personal information.

Flexible group cohesion and coordination, but robust leader-follower roles, in a wild social primate using urban space.

Collective behaviour has a critical influence on group social structure and organization, individual fitness and social evolution, but we know little about whether and how it changes in anthropogenic environments. Here, we show multiple and varying effects of urban space-use upon group-level processes in a primate generalist-the chacma baboon (Papio ursinus)-within a managed wild population living at the urban edge in the City of Cape Town, South Africa. In natural space, we observe baboon-typical patterns of collective behaviour. By contrast, in urban space (where there are increased risks, but increased potential for high-quality food rewards), baboons show extreme flexibility in collective behaviour, with changes in spatial cohesion and association networks, travel speeds and group coordination. However, leader-follower roles remain robust across natural and urban space, with adult males having a disproportionate influence on the movement of group members. Their important role in the group's collective behaviour complements existing research and supports the management tactic employed by field rangers of curbing the movements of adult males, which indirectly deters the majority of the group from urban space. Our findings highlight both flexibility and robustness in collective behaviour when groups are presented with novel resources and heightened risks.

Abundance, distribution and behaviour of humpback whales (

Context Previous research has shown the presence of an endangered humpback whale population breeding off the Pacific coast of Central America. However, little is known about the density, size, social-group structure and spatial habitat use of this subpopulation. Aim The study goal was to characterise a potential breeding subpopulation of humpback whales in the waters off Nicaragua. Five objectives were used to achieve this goal: (1) estimate abundance, (2) determine encounter rates, (3) define group composition, (4) assess distribution, and (5) document habitat-use patterns. Method Boat-based surveys were conducted between November and April at two study sites along the Pacific coast of Nicaragua in the winters of 2004–2008 and 2016–2020. Key result Inter-annual mark–recapture estimates did not yield a reliable estimate of abundance. Encounter rates were lower for the northern study site than for the southern site. Group composition consisted of groups with calves, singers and competitive males. Conclusion These results confirmed that Nicaragua is a breeding area based on known breeding-ground behaviours observed in other areas, and similar environmental characteristics. Implication Distinct habitats were found at the two study sites, suggesting that Central American humpback whales might use different areas within the broader Central American breeding range according to their needs and activity.

A case study of the construction of inter-embedded multi-ethnic community of urban migrants in Nanyang

As the domestic interprovincial migrants, Uygur traders have been engaged in the Hetian jade trade from Xinjiang Uygur Autonomous Region to the city of Nanyang in Henan Province. Having lived in the private rented houses around the market in the early days, they moved into the government-built public rental housing in 2017, an independently managed community. They have maintained their past residential pattern of living around the market, and gradually develop the community into an inter-embedded multi-ethnic community together with other ethnic groups. Through the history of the formation of the Uygur community in Nanyang Stone Town, this paper presents the process of interaction between the ethnic minority migrants and the local community, examines the responses and influence of the market, society, government, and individuals in this process, aiming to understand how the minority community was formed, to deepen understanding of the “inter-embedded multi-ethnic community", and, in turn, to promote research and reflection on the development of the ethnic community during urbanization in China. This study suggests that such communities surrounding the market are socially extended based on inter-embedded livelihood. The open national market is the core of the social structure of inter-embedded ethnic groups, and market exchange is one of the main relations generated in the current interactions between the ethnic groups. The government’s efforts to build inter-embedded communities are conducive to transforming the relationships among ethnic groups from limited interaction to comprehensive and balanced development. Moreover, the improvement of common living environments and increase in exchanges are conducive to upgrading interactions between individuals to extensive and in-depth exchanges among different ethnic groups.

Social status modulates the behavioral and physiological consequences of a chemical pollutant in animal groups.

The social environment (i.e., the suite of social interactions that occur among individuals that can result in variation in social ranks) is a commonly overlooked aspect of biology when scientists evaluate the effects of chemical contaminants. The social environment, however, represents the arena in which individual-level performance shapes group- or population-level outcomes and may therefore mediate many of the ultimate consequences of chemicals for wildlife. Here, we evaluated the role that the social environment plays in determining the consequences of pollutant exposure. We exposed groups of juvenile brown trout (Salmo trutta) to an emerging pharmaceutical pollutant that is commonly detected in freshwaters (the benzodiazepine, oxazepam) and allowed them to form dominance hierarchies. Exposure affected dominant and subordinate fish differently, causing fish to become less aggressive at high doses and subordinate fish to become more competitively successful at low doses. These perturbations had further consequences for growth, fin damage, and survival. Exposure also modulated physiological stress in the hierarchy, and social status itself affected how much oxazepam was absorbed in tissues, potentially creating a dynamic feedback loop that further influences the asymmetric effects of exposure on differing social statuses. Many effects followed a "U-shaped" dose-response curve, highlighting the importance of nonlinear, low-dose effects. Altogether, we show that social structure in animal groups can interact with and modulate the effects of an environmental contaminant. We underscore the need to account for an organism's natural ecological context, including their social environment, in future experiments and environmental risk assessments to predict the effects of chemical contaminants on wildlife.

Transitioning to civilian life: The importance of social group engagement and identity among Australian Defence Force veterans.

Veterans transitioning to civilian life after leaving the military face unique health concerns. Although there is a significant body of research exploring veterans' experiences of transition and predictors of well-being, there are limited studies examining how social group engagement influences veterans' transition. We explored how Australian Defence Force veterans' social group engagement and identity influenced their adjustment to civilian life and well-being. Forty Australian veterans (85% male; mean age = 37 years, range = 25-57 years) took part in in-depth, semi-structured interviews. Participants completed two mapping tasks (a social network map and life course map) that provided a visual component to the interviews. Interview transcripts were analysed thematically and interpreted by adopting a social identity approach. Joining the military involved a process of socialisation into military culture that for most participants led to the development of a military identity. An abrupt or difficult discharge from defence was often associated with a negative impact on social group engagement and well-being in civilian life. Veterans' social group memberships may act not only as positive psychological resources during transition but also as a potential source of conflict, especially when trying to re-engage with civilian groups with different norms or beliefs. Military values inscribed within a veteran's sense of self, including a strong sense of service, altruism and giving back to their community, may operate as positive resources and promote social group engagement. Engaging with supportive social groups can support transition to civilian life. Reintegration may be improved via effective linkage with programmes (e.g. volunteering, ex-service support organisations) that offer supportive social networks and draw upon veterans' desire to give back to community. Social mapping tasks that visualise veterans' social group structures may be useful for clinicians to explore the roles and conflicts associated with veterans' social group memberships during transition.

Larval ecology, dispersal, and the evolution of sociality in the sea

AbstractIndividual decisions about whether or not to disperse shape the kin structure of social groups, promoting or disrupting the evolution of sociality via kin selection. It is often assumed that the great dispersal potential of marine larvae driven by ocean currents disrupts kin association and, as a consequence, reduces the chances that social groups in the sea form via kin selection. Yet, accumulating evidence indicates that the larval dispersal process is not as random as previously assumed and that different mechanisms can promote kin associations in marine species. Here, we review recent findings in the marine larval ecology literature, emphasizing key aspects of larval development that may limit or promote dispersal and the evolution of sociality in the sea. We find ample evidence that marine larvae settle closer to home than has been previously assumed. A variety of different mechanisms, including lack of planktonic dispersal, limited larval duration, larvae traveling together, variability in reproductive success, and behavioral and physical processes, can generate kin association in marine species and potentially lead to the formation of social groups via kin selection. Uncovering post‐settlement dispersal patterns is also important for understanding how groups of unrelated individuals are formed. By integrating different larval dispersal strategies into the dual benefit framework for the evolution of sociality, we provide examples of alternative pathways for the evolution of sociality in marine species. Finally, we discuss how the increased use of parentage analysis in marine species will provide an opportunity for investigating whether kin selection is indeed much rarer in marine than terrestrial species. Ultimately, determining the role that dispersal and kin selection play in the evolution of sociality in marine species will require an increased effort to gather both behavioral and genetic data for the same species.

The Human Sleep Paradox: The Unexpected Sleeping Habits ofHomo sapiens

The human sleep pattern is paradoxical. Sleep is vital for optimal physical and cognitive performance, yet humans sleep the least of all primates. In addition, consolidated and continuous monophasic sleep is evidently advantageous, yet emerging comparative data sets from small-scale societies show that the phasing of the human pattern of sleep–wake activity is highly variable and characterized by significant nighttime activity. To reconcile these phenomena, the social sleep hypothesis proposes that extant traits of human sleep emerged because of social and technological niche construction. Specifically, sleep sites function as a type of social shelter by way of an extended structure of social groups that increases fitness. Short, high-quality, and flexibly timed sleep likely originated as a response to predation risks while sleeping terrestrially. This practice may have been a necessary preadaptation for migration out of Africa and for survival in ecological niches that penetrate latitudes with the greatest seasonal variation in light and temperature on the planet.

Selection on heritable social network positions is context-dependent in Drosophila melanogaster

Social group structure is highly variable and can be important for nearly every aspect of behavior and its fitness consequences. Group structure can be modeled using social network analysis, but we know little about the evolutionary factors shaping and maintaining variation in how individuals are embedded within their networks (i.e., network position). While network position is a pervasive target of selection, it remains unclear whether network position is heritable and can respond to selection. Furthermore, it is unclear how environmental factors interact with genotypic effects on network positions, or how environmental factors shape selection on heritable network structure. Here we show multiple measures of social network position are heritable, using replicate genotypes and replicate social groups of Drosophila melanogaster flies. Our results indicate genotypic differences in network position are largely robust to changes in the environment flies experience, though some measures of network position do vary across environments. We also show selection on multiple network position metrics depends on the environmental context they are expressed in, laying the groundwork for better understanding how spatio-temporal variation in selection contributes to the evolution of variable social group structure.