Why care for humanity?

Some of the most pressing challenges facing our planet-such as climate change, biodiversity loss, warfare and extreme poverty-require social cohesion and prosocial action on a global scale. How can this be achieved? Previous research suggests that identity fusion-a strong form of group cohesion motivating prosocial action-results from perceptions of shared personally transformative experiences or of common biological essence. Here, we present results from two studies with United States samples exploring each pathway to identity fusion on a global scale. Study 1 focused on globally shared motherhood experiences and found that US mothers were more fused with women around the world if they shared motherhood experiences with them, which was also reflected in money allocation behaviour. Study 2 showed that exposure to a talk about globally shared biology increased fusion with humanity at large, Americans and the extended family suggesting that fusion with humanity does not need to weaken fusion with nation or extended family. We discuss implications of our results for future research on bonding with humanity at large and for addressing collective action problems on a global scale.

Disentangling the evolutionary drivers of social complexity: A comprehensive test of hypotheses

During the Holocene, the scale and complexity of human societies increased markedly. Generations of scholars have proposed different theories explaining this expansion, which range from broadly functionalist explanations, focusing on the provision of public goods, to conflict theories, emphasizing the role of class struggle or warfare. To quantitatively test these theories, we develop a general dynamical model based on the theoretical framework of cultural macroevolution. Using this model and Seshat: Global History Databank, we test 17 potential predictor variables proxying mechanisms suggested by major theories of sociopolitical complexity (and >100,000 combinations of these predictors). The best-supported model indicates a strong causal role played by a combination of increasing agricultural productivity and invention/adoption of military technologies (most notably, iron weapons and cavalry in the first millennium BCE).

Being in a crowd bonds people via physiological synchrony

Collective events can generate intense emotions, shape group identities, and forge strong bonds. Do these effects extend to remote participation, and what are the psychological mechanisms underpinning their social power? We monitored psycho-physiological activity among groups of basketball fans who either attended games in-person (in a stadium) or watched games live on television in small groups. In-person attendance was associated with greater synchronicity in autonomic nervous system activation at the group level, which resulted in more transformative experiences and contributed to stronger identity fusion. Our findings suggest that the social effects of sports depend substantially on the inter-personal dynamics unfolding among fans, rather than being prompted simply by watching the game itself. Given the increasing prevalence of virtual experiences, this has potentially wide-reaching implications for many domains of collective human interaction.

Rise of the war machines: Charting the evolution of military technologies from the Neolithic to the Industrial Revolution

What have been the causes and consequences of technological evolution in world history? In particular, what propels innovation and diffusion of military technologies, details of which are comparatively well preserved and which are often seen as drivers of broad socio-cultural processes? Here we analyze the evolution of key military technologies in a sample of pre-industrial societies world-wide covering almost 10,000 years of history using Seshat: Global History Databank. We empirically test previously speculative theories that proposed world population size, connectivity between geographical areas of innovation and adoption, and critical enabling technological advances, such as iron metallurgy and horse riding, as central drivers of military technological evolution. We find that all of these factors are strong predictors of change in military technology, whereas state-level factors such as polity population, territorial size, or governance sophistication play no major role. We discuss how our approach can be extended to explore technological change more generally, and how our results carry important ramifications for understanding major drivers of evolution of social complexity.

Outgroup threat and the emergence of cohesive groups: A cross-cultural examination

Evolutionary models and empirical evidence suggest that outgroup threat is one of the strongest factors inducing group cohesion; however, little is known about the process of forming such cohesive groups. We investigated how outgroup threat galvanizes individuals to affiliate with others to form engaged units that are willing to act on behalf of their in-group. A total of 864 participants from six countries were randomly assigned to an outgroup threat, environmental threat, or no-threat condition. We measured the process of group formation through physical proximity and movement mirroring along with activity toward threat resolution, and found that outgroup threat induced activity and heightened mirroring in males. We also observed higher mirroring and proximity in participants who perceived the outgroup threat as a real danger, albeit the latter results were imprecisely estimated. Together, these findings help understand how sharing subtle behavioral cues influences collaborative aggregation of people under threat.

MicroRNAs as biomarkers of atrophic scarring in acne: a cross-sectional analysis of 41 patients

BACKGROUND

Acne is the commonest inflammatory dermatosis seen worldwide. Atrophic acne scarring is a frequent complication, which can arise from acne of any severity. Micro (mi)RNAs are noncoding RNA molecules of 19-25 nucleotides that function as post-transcriptomic mediators of gene expression. They have demonstrated differential expression in various pathologies, such as eczema and psoriasis, allowing for a unique miRNA 'signature' profile to be established for different disease states.

AIM

To establish a miRNA signature for acne, and acne-associated atrophic scarring and to identify if a pattern of circulating miRNA is evident in patients who are prone to scarring.

METHODS

In total, 41 participants were consecutively recruited to this study. Circulating miRNA was quantified from plasma samples in all 41 patients, while in 8 patients, and in a further validation cohort of 9 patients, whole miRNAome was undertaken from tissue specimens, which included lesional, normal and where present, scarred skin.

RESULTS

Three miRNAs, miR-223, miR-21 and miR-150, were statistically significantly overexpressed in acne lesions, and notably, in clinically uninvolved skin in participants prone to scarring. In this subgroup, we also found statistically significantly elevated levels of circulating miRNA-21 and miRNA-150.

CONCLUSION

The presence of elevated levels of these specific miRNAs in the serum of patients with acne raises the potential of a blood test to identify those at risk of scarring, allowing for earlier intervention with effective therapy.

Preverbal infants expect agents exhibiting counterintuitive capacities to gain access to contested resources

Claims to supernatural power have been used as a basis for authority in a wide range of societies, but little is known about developmental origins of the link between supernatural power and worldly authority. Here, we show that 12- to 16-month-old infants expect agents exhibiting counterintuitive capacities to win out in a two-way standoff over a contested resource. Infants watched two agents gain a reward using either physically intuitive or physically counterintuitive methods, the latter involving simple forms of levitation or teleportation. Infants looked longer, indicating surprise, when the physically intuitive agent subsequently outcompeted a physically counterintuitive agent in securing a reward. Control experiments indicated that infants’ expectations were not simply motived by the efficiency of agents in pursuing their goals, but specifically the deployment of counterintuitive capacities. This suggests that the link between supernatural power and worldly authority has early origins in development.

The Development of Identity Fusion

The fusion of personal and group identities can lead to self-sacrificial progroup behavior, from acts of charity to violent extremism. Two pathways to identity fusion-via shared biology and shared experiences-have been proposed. In this article, we elucidate a new developmental account of the origins and mechanisms of these two pathways to identity fusion from childhood to adulthood. Whereas fusion based on shared biology occurs from early childhood cued by phenotypic similarity, fusion based on episodic memories of shared experiences is not possible until midadolescence and relies on suitable bonding experiences (e.g., painful initiation rituals, emotionally intense team sports). The critical development that enables fusion based on shared experiences is autobiographical reasoning, which entails connecting one's past experiences to the present self. Autobiographical reasoning begins in adolescence, which may explain the flourishing of fusion in late adolescence and young adulthood relative to other life periods. Fusion via either pathway is linked to strong progroup behavior. We outline a program of empirical research on the development of identity fusion while addressing relevant methodological challenges. A developmental framework may help foster efforts to harness identity fusion for peaceful rather than violent forms of self-sacrifice for the group.

Band of mothers: Childbirth as a female bonding experience

Does the experience of childbirth create social bonds among first-time mothers? Previous research suggests that sharing emotionally intense or painful experiences with others leads to “identity fusion,” a visceral feeling of oneness with a group that predicts strong forms of prosocial action and self-sacrifice for other group members. This study compared identity fusion with other mothers during pregnancy versus after childbirth in a sample of 164 U.S. women. Eighty-nine mothers in our sample were pregnant with their firstborn, and 75 mothers had given birth to their firstborn up to 6 months prior to the time of data collection. Results demonstrated that identity fusion with other mothers was higher for postpartum mothers than for antenatal mothers. As predicted, among postpartum mothers, those who thought that their childbirth was more painful than a typical childbirth experience reported greater identity fusion with mothers who reported having had a very difficult birth. Postpartum mothers’ ruminative thought about the birth mediated the association between level of dysphoria and identity fusion, and identity fusion moderated the association between postpartum mothers’ ruminative and reflective thought about the birth and their posttraumatic growth in complex ways. These findings provide evidence that perceived sharedness of the childbirth experience and thoughts about the birth are important to the process of identity fusion with other mothers, and highlight the importance of post-event processing for psychological health.

Ritual, fusion, and conflict: The roots of agro-pastoral violence in rural Cameroon

Herder–farmer conflicts in West Africa have caused thousands of deaths in recent years. Many conflicts are triggered by localized events that rapidly spiral out of control. What leads specific interpersonal conflicts to scale up into intergroup violence? We propose that such conflicts are rooted in identity and ritual dynamics. We present evidence that participants in Mambila traditions of masquerade initiation in Cameroon report especially strong identity fusion, a visceral sense of oneness with the ingroup. Results showed that men strongly fused to their ethnic ingroup were especially willing to fight and die for it. Overall, our findings provide evidence that when ordinary conflicts develop between groups that differ sharply on ethnic and religious lines, there is grave risk that fused persons will escalate violence. Understanding these processes may inform future development of new strategies to prevent or ameliorate intergroup conflicts of this kind.

Ritual morphospace revisited: the form, function and factor structure of ritual practice

Human rituals exhibit bewildering diversity, from the Mauritian Kavadi to Catholic communion. Is this diversity infinitely plastic or are there some general dimensions along which ritual features vary? We analyse two cross-cultural datasets: one drawn from the anthropological record and another novel contemporary dataset, to examine whether a consistent underlying set of latent dimensions in ritual structure and experiences can be detected. First, we conduct a factor analysis on 651 rituals from 74 cultural groups, in which 102 binary variables are coded. We find a reliable set of dimensions emerged, which provide potential candidates for foundational elements of ritual form. Notably, we find that the expression of features associated with dysphoric and euphoric experiences in rituals appears to be largely orthogonal. Second, we follow-up with a pre-registered factor analysis examining contemporary ritual experiences of 779 individuals from Japan, India and the US. We find supporting evidence that ritual experiences are clustered in relatively orthogonal euphoric, dysphoric, frequency and cognitive dimensions. Our findings suggest that there are important regularities in the diversity of ritual expression and experience observed across both time and culture. We discuss the implications of these findings for cognitive theories of ritual and cultural evolution.

This article is part of the theme issue ‘Ritual renaissance: new insights into the most human of behaviours'.

Exploring the Pathways Between Transformative Group Experiences and Identity Fusion

A growing body of evidence suggests that two distinct forms of group alignment are possible: identification and fusion (the former asserts that group and personal identity are distinct, while the latter asserts group and personal identities are functionally equivalent and mutually reinforcing). Among highly fused individuals, group identity taps directly into personal agency and so any attack on the group is perceived as a personal attack and motivates a willingness to fight and possibly even die as a defensive response. As such, identity fusion is relevant in explaining violent extremism, including suicidal terrorist attacks. Identity fusion is theorized to arise as a result from experiences which are (1) perceived as shared and (2) transformative, however evidence for this relationship remains limited. Here, we present a pre-registered study in which we examine the role of transformativeness and perceived sharedness of group-defining events in generating identity fusion. We find that both of these factors are predictive of identity fusion but that the relationship with transformativeness was more consistent than perceived sharedness across analyses in a sample of Indonesian Muslims.

Devoted fans release more cortisol when watching live soccer matches

Why do some sports fans experience intense emotions when watching live matches? Identity fusion is a strong form of group alignment in which personal and group identities are activated synergistically to produce a visceral sense of 'oneness' with one's team. Here we examine the role of fusion (using a three-item state measure with high internal validity) in elevating salivary cortisol levels while watching football (n = 41). Our evidence was gathered at field laboratories during the 2014 sFIFA World Cup in Natal, Brazil, with live screenings of two Brazilian victories (Colombia, 2-1; Chile, 1-1 with penalties), and the historic semi-final loss to Germany (1-7). We replicated previous studies showing that salivary cortisol concentrations fluctuate during live football events and are related to group membershipbut we also extended them by showing that identity fusion is even more strongly related to cortisol concentrations than identification. We found an interaction between match outcome and cortisol, such that watching a loss, i.e. dysphoria, was associated with particularly high cortisol concentrations. While women were more fused to the team than men, there were no other gender effects. Taken together, these findings suggest that identity fusion modulates physiological reactivity, resulting in distinct psycho-physiological profiles during stressful events.

An effective digital tourniquet utilising a fenestrated limb tourniquet

We describe a safe and effective digital tourniquet utilising a fenestrated limb tourniquet which would normally be used for venepuncture.

Fusion and Reform

Recent theoretical advances in anthropology and group psychology suggest that sharing self-defining experiences creates identity fusion, a powerful form of social glue motivating prosocial action. Here, we present results of in-depth interviews with a sample of 31 inmates of an Australian prison and explore the theoretical implications of this work for interventions designed to reduce recidivism amongst ex-off enders. Our approach focusses on the implications of fusion theory both for desistance amongst released prisoners and for reinclusion into the community. We consider various ways in which existing interventions could be enhanced by applying this new theoretical knowledge and harnessing the bonding power of shared experience. We also point to features of current practice throughout the criminal justice system that encourage the adoption of inauthentic identities and thereby obstruct the potential for fusion to energise and embolden efforts at reform.

Complex societies precede moralizing gods throughout world history

The origins of religion and of complex societies represent evolutionary puzzles^1-8. The 'moralizing gods' hypothesis offers a solution to both puzzles by proposing that belief in morally concerned supernatural agents culturally evolved to facilitate cooperation among strangers in large-scale societies^9-13. Although previous research has suggested an association between the presence of moralizing gods and social complexity^3,6,7,9-18, the relationship between the two is disputed^9-13,19-24, and attempts to establish causality have been hampered by limitations in the availability of detailed global longitudinal data. To overcome these limitations, here we systematically coded records from 414 societies that span the past 10,000 years from 30 regions around the world, using 51 measures of social complexity and 4 measures of supernatural enforcement of morality. Our analyses not only confirm the association between moralizing gods and social complexity, but also reveal that moralizing gods follow-rather than precede-large increases in social complexity. Contrary to previous predictions^9,12,16,18, powerful moralizing 'big gods' and prosocial supernatural punishment tend to appear only after the emergence of 'megasocieties' with populations of more than around one million people. Moralizing gods are not a prerequisite for the evolution of social complexity, but they may help to sustain and expand complex multi-ethnic empires after they have become established. By contrast, rituals that facilitate the standardization of religious traditions across large populations^25,26 generally precede the appearance of moralizing gods. This suggests that ritual practices were more important than the particular content of religious belief to the initial rise of social complexity.

Groups and Emotional Arousal Mediate Neural Synchrony and Perceived Ritual Efficacy

We present the first neurophysiological signatures showing distinctive effects of group social context and emotional arousal on cultural perceptions, such as the efficacy of religious rituals. Using a novel protocol, EEG data were simultaneously recorded from ethnic Chinese religious believers in group and individual settings as they rated the perceived efficacy of low, medium, and high arousal spirit-medium rituals presented as video clips. Neural oscillatory patterns were then analyzed for these perceptual judgements, categorized as low, medium, and high efficacy. The results revealed distinct neural signatures and behavioral patterns between the experimental conditions. Arousal levels predicted ratings of ritual efficacy. Increased efficacy was marked by suppressed alpha and beta power, regardless of group or individual setting. In groups, efficacy ratings converged. Individual setting showed increased within-participant phase synchronization in alpha and beta bands, while group setting enhanced between-participant theta phase synchronization. This reflected group participants' orientation toward a common perspective and social coordination. These findings suggest that co-presence in groups leads to a social-tuning effect supported by between-participant theta phase synchrony. Together these neural synchrony patterns reveal how collective rituals have both individual and communal dimensions. The emotionality of spirit-medium rituals drives individual perceptions of efficacy, while co-presence in groups signals the significance of an event and socially tunes enhanced agreement in perceptual ratings. In other words, mass gatherings may foster social cohesion without necessarily requiring group-size scaling limitations of direct face-to-face interaction. This could have implications for the scaling computability of synchrony in large groups as well as for humanistic studies in areas such as symbolic interactionism.

Examining memory for ritualized gesture in complex causal sequences

Humans have created and maintained an exponentially large and sophisticated behavioral corpus over evolutionary time. In no small part this was achieved due to our tendency to imitate behaviours rather than to emulate outcomes. This tendency, however, can lead to inefficiency and redundancy in our behavioral repertoires. Drawing on evidence from multiple fields of psychology, we propose two novel competing hypotheses. The 'catalyst hypothesis' suggests that low (but not high) proportions of ritualized gesture in instrumental action sequences will improve subsequent recall of the entire action sequence (without itself enhancing the instrumental utility of the sequence). Conversely, the 'cost hypothesis' suggests that increasing proportions of ritualized gesture will impair recall, due to the introduction of cognitive load. The null hypothesis states that ritualized gestures are neither beneficial nor costly. In a pre-registered experiment, we presented participants with multiple versions of two complicated 2-min action sequences in which we varied the proportion of ritualized gesture. We then quantified the influence ritualized gesture had on recall for individuals gestures, overall outcomes, and described detail. We found clear evidence that high proportions of ritualized gestures impair recall for individual gestures and overall success, and weak evidence that low proportions increase overall success. At present, we may reject the null, but cannot rule out either of our competing hypotheses. We discuss potential implications for cultural evolution, and generate competing predictions that allow for adjudication between Ritual Modes theory (Whitehouse, 2004) and the 'Cognitive Resource Depletion' account of Religious Interaction (Schjoedt et al., 2013). All files (including data and syntax) are freely available at https://osf.io/spz68/.

Positive experiences of high arousal martial arts rituals are linked to identity fusion and costly pro-group actions

A cross‐sectional study was conducted with 605 practitioners of Brazilian Jiu Jitsu (BJJ) to test the hypothesis that high arousal rituals promote social cohesion, primarily through identity fusion. BJJ promotion rituals are rare, highly emotional ritual events that often feature gruelling belt‐whipping gauntlets. We used the variation in such experiences to examine whether more gruelling rituals were associated with identity fusion and pro‐group behaviour. We found no differences between those who had undergone belt‐whipping and those who had not and no evidence of a correlation between pain and social cohesion. However, across the full sample we found that positive, but not negative, affective experiences of promotional rituals were associated with identity fusion and that this mediated pro‐group action. These findings provide new evidence concerning the social functions of collective rituals and highlight the importance of addressing the potentially diverging subjective experiences of painful rituals.

Not on my team: Medial prefrontal cortex responses to ingroup fusion and unfair monetary divisions

OBJECTIVE

People are highly attuned to fairness, with people willingly suffering personal costs to prevent others benefitting from unfair acts. Are fairness judgments influenced by group alignments? A new theory posits that we favor ingroups and denigrate members of rival outgroups when our personal identity is fused to a group. Although the mPFC has been separately implicated in group membership and fairness processing, it is unclear whether group alignments affect medial prefrontal cortex (mPFC) activity in response to fairness. Here, we examine the contribution of different regions of the mPFC to processing from ingroup and outgroup members and test whether its response differs depending on how fused we are to an ingroup.

METHODS

Subjects performed rounds of the Ultimatum Game, being offered fair or unfair divisions of money from supporters of the same soccer team (ingroup), the fiercest rival (outgroup) or neutral individuals whilst undergoing functional Magnetic Resonance Imaging (fMRI).

RESULTS

Strikingly, people willingly suffered personal costs to prevent outgroup members benefitting from both unfair and fair offers. Activity across dorsal and ventral (VMPFC) portions of the mPFC reflected an interaction between fairness and group membership. VMPFC activity in particular was consistent with it coding one's fusion to a group, with the fairness by group membership interaction correlating with the extent that the responder's identity was fused to the ingroup.

CONCLUSIONS

The influence of fusion on social behavior therefore seems to be linked to processing in the VMPFC.

The evolution of extreme cooperation via shared dysphoric experiences

Willingness to lay down one's life for a group of non-kin, well documented historically and ethnographically, represents an evolutionary puzzle. Building on research in social psychology, we develop a mathematical model showing how conditioning cooperation on previous shared experience can allow individually costly pro-group behavior to evolve. The model generates a series of predictions that we then test empirically in a range of special sample populations (including military veterans, college fraternity/sorority members, football fans, martial arts practitioners, and twins). Our empirical results show that sharing painful experiences produces "identity fusion" - a visceral sense of oneness - which in turn can motivate self-sacrifice, including willingness to fight and die for the group. Practically, our account of how shared dysphoric experiences produce identity fusion helps us better understand such pressing social issues as suicide terrorism, holy wars, sectarian violence, gang-related violence, and other forms of intergroup conflict.

Rituals Improve Children's Ability to Delay Gratification

To be accepted into social groups, individuals must internalize and reproduce appropriate group conventions, such as rituals. The copying of such rigid and socially stipulated behavioral sequences places heavy demands on executive function. Given previous research showing that challenging executive functioning improves it, it was hypothesized that engagement in ritualistic behaviors improves children's executive functioning, in turn improving their ability to delay gratification. A 3-month circle time games intervention with 210 schoolchildren (M_age  = 7.78 years, SD = 1.47) in two contrasting cultural environments (Slovakia and Vanuatu) was conducted. The intervention improved children's executive function and in turn their ability to delay gratification. Moreover, these effects were amplified when the intervention task was imbued with ritual, rather than instrumental, cues.

Incipient Social Groups: An Analysis via In-Vivo Behavioral Tracking

Social psychology is fundamentally the study of individuals in groups, yet there remain basic unanswered questions about group formation, structure, and change. We argue that the problem is methodological. Until recently, there was no way to track who was interacting with whom with anything approximating valid resolution and scale. In the current study we describe a new method that applies recent advances in image-based tracking to study incipient group formation and evolution with experimental precision and control. In this method, which we term “in vivo behavioral tracking,” we track individuals’ movements with a high definition video camera mounted atop a large field laboratory. We report results of an initial study that quantifies the composition, structure, and size of the incipient groups. We also apply in-vivo spatial tracking to study participants’ tendency to cooperate as a function of their embeddedness in those crowds. We find that participants form groups of seven on average, are more likely to approach others of similar attractiveness and (to a lesser extent) gender, and that participants’ gender and attractiveness are both associated with their proximity to the spatial center of groups (such that women and attractive individuals are more likely than men and unattractive individuals to end up in the center of their groups). Furthermore, participants’ proximity to others early in the study predicted the effort they exerted in a subsequent cooperative task, suggesting that submergence in a crowd may predict social loafing. We conclude that in vivo behavioral tracking is a uniquely powerful new tool for answering longstanding, fundamental questions about group dynamics.

Shared Negative Experiences Lead to Identity Fusion via Personal Reflection

Across three studies, we examined the role of shared negative experiences in the formation of strong social bonds—identity fusion—previously associated with individuals' willingness to self-sacrifice for the sake of their groups. Studies 1 and 2 were correlational studies conducted on two different populations. In Study 1, we found that the extent to which Northern Irish Republicans and Unionists experienced shared negative experiences was associated with levels of identity fusion, and that this relationship was mediated by their reflection on these experiences. In Study 2, we replicated this finding among Bostonians, looking at their experiences of the 2013 Boston Marathon Bombings. These correlational studies provide initial evidence for the plausibility of our causal model; however, an experiment was required for a more direct test. Thus, in Study 3, we experimentally manipulated the salience of the Boston Marathon Bombings, and found that this increased state levels of identity fusion among those who experienced it negatively. Taken together, these three studies provide evidence that shared negative experience leads to identity fusion, and that this process involves personal reflection.

In-Group Ostracism Increases High-Fidelity Imitation in Early Childhood

The Cyberball paradigm was used to examine the hypothesis that children use high-fidelity imitation as a reinclusion behavior in response to being ostracized by in-group members. Children ( N = 176; 5- to 6-year-olds) were either included or excluded by in- or out-group members and then shown a video of an in-group or an out-group member enacting a social convention. Participants who were excluded by their in-group engaged in higher-fidelity imitation than those who were included by their in-group. Children who were included by an out-group and those who were excluded by an out-group showed no difference in imitative fidelity. Children ostracized by in-group members also displayed increased anxiety relative to children ostracized by out-group members. The data are consistent with the proposal that high-fidelity imitation functions as reinclusion behavior in the context of in-group ostracism.

A Life-Cycle Model of Human Social Groups Produces a U-Shaped Distribution in Group Size

One of the central puzzles in the study of sociocultural evolution is how and why transitions from small-scale human groups to large-scale, hierarchically more complex ones occurred. Here we develop a spatially explicit agent-based model as a first step towards understanding the ecological dynamics of small and large-scale human groups. By analogy with the interactions between single-celled and multicellular organisms, we build a theory of group lifecycles as an emergent property of single cell demographic and expansion behaviours. We find that once the transition from small-scale to large-scale groups occurs, a few large-scale groups continue expanding while small-scale groups gradually become scarcer, and large-scale groups become larger in size and fewer in number over time. Demographic and expansion behaviours of groups are largely influenced by the distribution and availability of resources. Our results conform to a pattern of human political change in which religions and nation states come to be represented by a few large units and many smaller ones. Future enhancements of the model should include decision-making rules and probabilities of fragmentation for large-scale societies. We suggest that the synthesis of population ecology and social evolution will generate increasingly plausible models of human group dynamics.

Religion and morality

The relationship between religion and morality has long been hotly debated. Does religion make us more moral? Is it necessary for morality? Do moral inclinations emerge independently of religious intuitions? These debates, which nowadays rumble on in scientific journals as well as in public life, have frequently been marred by a series of conceptual confusions and limitations. Many scientific investigations have failed to decompose "religion" and "morality" into theoretically grounded elements; have adopted parochial conceptions of key concepts-in particular, sanitized conceptions of "prosocial" behavior; and have neglected to consider the complex interplay between cognition and culture. We argue that to make progress, the categories "religion" and "morality" must be fractionated into a set of biologically and psychologically cogent traits, revealing the cognitive foundations that shape and constrain relevant cultural variants. We adopt this fractionating strategy, setting out an encompassing evolutionary framework within which to situate and evaluate relevant evidence. Our goals are twofold: to produce a detailed picture of the current state of the field, and to provide a road map for future research on the relationship between religion and morality.