Ferguson and the death of Michael Brown on Twitter: #BlackLivesMatter, #TCOT,and the evolution of collective identities

Recent events related to police brutality and the evolution of #BlackLivesMatter provides an empirical case to explore the vitality of social media data for social movements and the evolution of collective identities. Social media data provide a portal into how organizing and communicating generate narratives that survive over time. We analyse 31.65 million tweets about Ferguson across four meaningful time periods: the death of Michael Brown, the non-indictment of police officer Darren Wilson, the Department of Justice report on Ferguson, and the one year aftermath of Brown’s death. Our analysis shows that #BlackLivesMatter evolved in concert with protests opposing police brutality occurring on the ground. We also show how #TCOT (Top Conservatives on Twitter) has operated as the primary counter narrative to #BlackLivesMatter. We conclude by discussing the implications our research has for the #BlackLivesMatter movement and increased political polarization following the election of Donald Trump.     

Exploring the costs and benefits of social information use: an appraisal of current experimental evidence

Research on social learning has focused traditionally on whether animals possess the cognitive ability to learn novel motor patterns from tutors. More recently, social learning has included the use of others as sources of inadvertent social information. This type of social learning seems more taxonomically widespread and its use can more readily be approached as an economic decision. Social sampling information, however, can be tricky to use and calls for a more lucid appraisal of its costs. In this four-part review, we address these costs. Firstly, we address the possibility that only a fraction of group members are actually providing social information at any one time. Secondly, we review experimental research which shows that animals are circumspect about social information use. Thirdly, we consider the cases where social information can lead to incorrect decisions and finally, we review studies investigating the effect of social information quality. We address the possibility that using social information or not is not a binary decision and present results of a study showing that nutmeg mannikins combine both sources of information, a condition that can lead to the establishment of informational cascades. We discuss the importance of empirically investigating the economics of social information use.     

Social structure modulates the evolutionary consequences of social plasticity: A social network perspective on interacting phenotypes

Organisms express phenotypic plasticity during social interactions. Interacting phenotype theory has explored the consequences of social plasticity for evolution, but it is unclear how this theory applies to complex social structures. We adapt interacting phenotype models to general social structures to explore how the number of social connections between individuals and preference for phenotypically similar social partners affect phenotypic variation and evolution. We derive an analytical model that ignores phenotypic feedback and use simulations to test the predictions of this model. We find that adapting previous models to more general social structures does not alter their general conclusions but generates insights into the effect of social plasticity and social structure on the maintenance of phenotypic variation and evolution. Contribution of indirect genetic effects to phenotypic variance is highest when interactions occur at intermediate densities and decrease at higher densities, when individuals approach interacting with all group members, homogenizing the social environment across individuals. However, evolutionary response to selection tends to increase at greater network densities as the effects of an individual's genes are amplified through increasing effects on other group members. Preferential associations among similar individuals (homophily) increase both phenotypic variance within groups and evolutionary response to selection. Our results represent a first step in relating social network structure to the expression of social plasticity and evolutionary responses to selection.     

Opening the Black Box of Developmental Experiments: Behavioural Mechanisms Underlying Long‐Term Effects of Early Social Experience

Typically, animals spend a considerable portion of their time with social interactions involving mates, offspring, competitors and group members. The social performance during these interactions can strongly depend on the social environment individuals have experienced early in life. Despite a considerable number of experiments investigating long‐term effects of the early social environment, our understanding of the behavioural mechanisms mediating these effects is still limited, mainly for two reasons. (1) Only in few experimental studies have researchers actually observed and quantified the behaviour of their study animals during the social treatment. (2) Even if differences in social interactions between social rearing treatments are reported, these differences might not be causally linked to any observed long‐term effects later in life. The aim of this review was to investigate whether behavioural records of animals during the experimental manipulation of their social environment can help (1) identifying behavioural mechanisms involved in a long‐term effect and (2) obtaining a better understanding of the long‐term consequences of early manipulations. First, I review studies that manipulated the social environment at an early stage of the ontogeny, observed the social interactions and behaviour during the social experience phase and subsequently tested the performance in social and non‐social behavioural tasks at a later life stage. In all reviewed studies, treatment differences were reported both in social interactions during the social experience phase and in social and/or non‐social behaviours later in life. Second, I discuss four classes of behavioural mechanisms that can cause the reported long‐term effects of social experience, namely learning by experience, social learning, sensory stimulation and social cueing. I conclude that social interactions during the social experience phase should always be recorded for at least two reasons. Knowledge about how the social interactions differ between rearing treatments (1) permits researchers to formulate hypotheses about candidate mechanisms causing long‐term effects on behaviour and (2) can help to interpret unexpected outcomes of developmental experiments. Finally, I propose that as a crucial ultimate step towards understanding effects of the early social environment, we should develop targeted experiments testing for the causality of identified candidate mechanism.     

A review of the social behaviour of the giraffe Giraffa camelopardalis: a misunderstood but socially complex species

1. Until around 2000, giraffe Giraffa camelopardalis were believed to have no social structure. Despite a resurgence of interest in giraffe behaviour in around 2010, most studies are of isolated populations, making it difficult to draw general conclusions. Although it is now well established that giraffe social organisation is non-random, there is little consensus as to what influences preferred and avoided associations or the underpinning mechanisms.
2. We test two hypotheses: first, giraffe have a complex cooperative social system, exhibited by 1) stable groups of females, 2) offspring that stay in their natal group for part or all of their lives, 3) support by non-mothers in rearing young, and 4) non-reproductive females in the group; and second, giraffe form matrilineal societies, evidenced by 1) male dispersal, 2) female philopatry, 3) assistance in raising or protecting offspring, and 4) individual benefits gained from social foraging.
3. We reviewed 404 papers on giraffe behaviour and social organisation; captive studies were included where they supplemented information from free-living populations.
4. We show that giraffe exhibit many of the features typical of mammals with complex cooperative social systems and matrilineal societies. However, the social complexity hypothesis posits that such species also require complex communication systems to regulate interactions and relations among group members; giraffe communication systems are poorly understood.
5. Quantifying the fitness and survival benefits of the giraffe’s social organisation is necessary to ensure its long-term survival. Giraffe numbers have declined by 40% since 1985, they have been declared extinct in seven (possibly nine) countries and are listed as Vulnerable by the International Union for Conservation of Nature. We identify research areas that will advance our understanding of giraffe behaviour and conservation requirements.

     

Processing power limits social group size: computational evidence for the cognitive costs of sociality

Sociality is primarily a coordination problem. However, the social (or communication) complexity hypothesis suggests that the kinds of information that can be acquired and processed may limit the size and/or complexity of social groups that a species can maintain. We use an agent-based model to test the hypothesis that the complexity of information processed influences the computational demands involved. We show that successive increases in the kinds of information processed allow organisms to break through the glass ceilings that otherwise limit the size of social groups: larger groups can only be achieved at the cost of more sophisticated kinds of information processing that are disadvantageous when optimal group size is small. These results simultaneously support both the social brain and the social complexity hypotheses.     

A demographic analysis of the membership of the American Society of Primatologists: 1992

Rank differences in the production of vocalizations by wild, semihabituated, unprovisioned chimpanzees were investigated during a 10-month study in the Kibale Forest, Uganda. Vocalization rates were calculated from data collected during 230 hours of focal-animal sampling on adult females, adult males, and subadult males. Rates were calculated according to whether individuals were alone, with adult females only, or in mixed parties, and the results were compared with published data collected at the Gombe provisioning area. Adult females and low-ranking adult and sub-adult males were generally quiet except when they were in mixed parties, whereas high-ranking males vocalized in all social contexts. These results were in partial contrast to data collected at Gombe, which indicated that vocal production was similar across all age and sex classes. Vocal production at Gombe did, however, resemble that from mixed parties at Kibale, suggesting that the provisioning area at Gombe was comparable to a natural socioecological context occurring at large fruiting trees. It is suggested that low-ranking chimpanzees refrain from loud vocalizing when they are alone or with females only in order to avoid attracting feeding competition and/or potentially aggressive males. These individuals may vocalize when they are associating with high-ranking males in order to advertise the presence of large parties and to deter other individuals from joining them. The use of loud, interparty calls by high-ranking males, when alone or with others, is consistent with the greater sociality of adult male chimpanzees. Loud calling might be advantageous for adult males in attracting mates or allies. © 1993 Wiley-Liss, Inc.     

Formation of long‐lasting galls by overwintered nymphs in the Japanese aphid Quadrartus yoshinomiyai (Hemiptera: Aphididae: Hormaphidinae)

This paper examines the life history of a generation of galls created by the aphid Quadrartus yoshinomiyai (Hormaphidinae: Nipponaphidini) on its primary host plant, Distylium racemosum. First‐instar fundatrix nymphs of Q. yoshinomiyai initiated galls on stems of developing shoots in early April and incipient enclosed galls were found from later the same month. The galls lasted for up to 14 months, during which they grew to maturity, opened in early or mid‐April of the following year and dried up by the end of June. First‐instar fundatrix nymphs were found on winter buds, indicating that they hatched from eggs in autumn and overwintered as nymphs. These results suggest that Q. yoshinomiyai has a three‐year life cycle.     

Social learning and evolution: the cultural intelligence hypothesis

If social learning is more efficient than independent individual exploration, animals should learn vital cultural skills exclusively, and routine skills faster, through social learning, provided they actually use social learning preferentially. Animals with opportunities for social learning indeed do so. Moreover, more frequent opportunities for social learning should boost an individual's repertoire of learned skills. This prediction is confirmed by comparisons among wild great ape populations and by social deprivation and enculturation experiments. These findings shaped the cultural intelligence hypothesis, which complements the traditional benefit hypotheses for the evolution of intelligence by specifying the conditions in which these benefits can be reaped. The evolutionary version of the hypothesis argues that species with frequent opportunities for social learning should more readily respond to selection for a greater number of learned skills. Because improved social learning also improves asocial learning, the hypothesis predicts a positive interspecific correlation between social-learning performance and individual learning ability. Variation among primates supports this prediction. The hypothesis also predicts that more heavily cultural species should be more intelligent. Preliminary tests involving birds and mammals support this prediction too. The cultural intelligence hypothesis can also account for the unusual cognitive abilities of humans, as well as our unique mechanisms of skill transfer.     

Social ties at work: Roma migrants and the community dynamics

This research examines how the internal social dynamics of Roma communities at home shape their propensity to migrate. It is theoretically grounded in the literature on social capital and focuses on two core concepts: ‘migration-rich’ and ‘migration-poor’ communities. The research is based on in-depth interviews and informal discussions with Roma from six (mainly rural) communities of Transylvania (Romania) and includes qualitative data gathered from migrants as well as from people who did not migrate. The findings challenge existing conceptualizations of Roma migration as either explained by poverty alone or by cultural arguments (such as nomadism). This paper indicates that even in the context of severe poverty, social networks are actually decisive for migration. It demonstrates that the patterns of migration tend to be community-specific and shaped by a locally shared culture (ethos) on migration. The research suggests policy choices according to the community profile and its internal dynamics.     

Neural and social correlates of attitudinal brokerage: using the complete social networks of two entire villages

To avoid polarization and maintain small-worldness in society, people who act as attitudinal brokers are critical. These people maintain social ties with people who have dissimilar and even incompatible attitudes. Based on resting-state functional magnetic resonance imaging (n = 139) and the complete social networks from two Korean villages (n = 1508), we investigated the individual-level neural capacity and social-level structural opportunity for attitudinal brokerage regarding gender role attitudes. First, using a connectome-based predictive model, we successfully identified the brain functional connectivity that predicts attitudinal diversity of respondents'' social network members. Brain regions that contributed most to the prediction included mentalizing regions known to be recruited in reading and understanding others’ belief states. This result was corroborated by leave-one-out cross-validation, fivefold cross-validation and external validation where the brain connectivity identified in one village was used to predict the attitudinal diversity in another independent village. Second, the association between functional connectivity and attitudinal diversity of social network members was contingent on a specific position in a social network, namely, the structural brokerage position where people have ties with two people who are not otherwise connected.     

Introduction: Social Complexity and the Bow in the Prehistoric North American Record

This Special Issue of Evolutionary Anthropology grew out of a symposium at the 2012 Society for American Archaeology (SAA) meeting in Memphis, Tennessee (April 18–22). The goal of the symposium was to explore what we will argue is one of the most important and promising opportunities in the global archeological enterprise. In late prehistoric North America, the initial rise of cultures of strikingly enhanced complexity and the local introduction of a novel weapon technology, the bow, apparently correlate intimately in a diverse set of independent cases across the continent, as originally pointed out by Blitz. 1 If this empirical relationship ultimately proves robust, it gives us an unprecedented opportunity to evaluate hypotheses for the causal processes producing social complexity and, by extension, to assess the possibility of a universal theory of history. The rise of comparably complex cultures was much more recent in North America than it was elsewhere and the resulting fresher archeological record is relatively well explored. These and other features make prehistoric North America a unique empirical environment. Together, the symposium and this issue have brought together outstanding investigators with both empirical and theoretical expertise. The strong cross‐feeding and extended interactions between these investigators have given us all the opportunity to advance the promising exploration of what we call the North American Neolithic transitions. Our goal in this paper is to contextualize this issue.     

It is not only group size: Soldiers also modulate the tolerance to insecticide in termites (Blattodea: Isoptera)

The survivorship of social insects is known to increase with group size, even in situations of stress, such as starvation and exposure to insecticides. However, in termites, studies have been undertaken only with workers, disregarding the possible effect of soldiers. The role of soldiers in the termite colonies goes beyond defense, mainly in Nasutitermes species. It is already known that soldiers initiate the foraging as well as improve the decision-making of food resources. Here, we evaluated the effect of group size and the presence of soldiers on exposure to sublethal doses of the insecticide imidacloprid in Nasutitermes corniger (Termitidae: Nasutitermitinae). To do so, toxicity bioassays were undertaken initially to determine the dose of the insecticide required to kill 50% of the N. corniger population (LD₅₀) to be used in the main experiments. Survival bioassays were then carried out with termite groups, with and without soldiers, in different sizes (6, 10, 14, 22, 26, 30 and 60), exposed and nonexposed to insecticide. In general, the mean time to death of termites increases linearly with group size. However, the mean time to death in groups with soldiers was significantly longer only in groups exposed to the insecticide. Our results indicate that soldiers can help to increase the tolerance of nasute termite groups to insecticides, in addition to the group size, as already shown in the previous study. The size of the group and social context could, therefore, modulate behavioral and/or physiological responses that enhance the ability to survive under stressful situations.     

Foundress behaviors and interactions in polygynous colonies of the haplometrotic Japanese paper wasp Polistes snelleni (Hymenoptera: Vespidae)

Only two out of 959 pre‐emergence colonies of the paper wasp Polistes snelleni de Saussure surveyed between 1989 and 1996 in Sapporo, northern Japan, were found to be two‐foundress colonies, and the others were single‐foundress colonies. The two foundresses in one of the two colonies showed neither aggressive dominance behavior nor clear division of labor between them during a total of approximately 30 h in the first half of the pre‐emergence stage. Although both of the foundresses foraged for pulp and laid eggs, only one foundress foraged for prey and delivered it to the other.     

Calves as social hubs: dynamics of the social network within sperm whale units

It is hypothesized that the primary function of permanent social relationships among female sperm whales (Physeter macrocephalus) is to provide allomothers for calves at the surface while mothers make foraging dives. In order to investigate how reciprocity of allocare within units of sperm whales facilitates group living, we constructed weighted social networks based on yearly matrices of associations (2005–2010) and correlated them across years, through changes in age and social role, to study changes in social relationships within seven sperm whale units. Pairs of association matrices from sequential years showed a greater positive correlation than expected by chance, but as the time lag increased, the correlation coefficients decreased. Over all units considered, calves had high values for all measured network statistics, while mothers had intermediate values for most of the measures, but high values for connectedness and affinity. Mothers showed sharp drops in strength and connectedness in the first year of their new calves'' lives. These broad patterns appear to be consistent across units. Calves appeared to be significant nodes in the network of the social unit, and thus provide quantitative support for the theory in which communal care acts as the evolutionary force behind group formation in this species.