Group size is a function of relative neocortical volume in nonhuman primates. Extrapolation from this regression equation yields a predicted group size for modern humans very similar to that of certain hunter-gatherer and traditional horticulturalist societies. Groups of similar size are also found in other large-scale forms of contemporary and historical society. Among primates, the cohesion of groups is maintained by social grooming; the time devoted to social grooming is linearly related to group size among the Old World monkeys and (...) apes. To maintain the stability of the large groups characteristic of humans by grooming alone would place intolerable demands on time budgets. It is suggested that (1) the evolution of large groups in the human lineage depended on the development of a more efficient method for time-sharing the processes of social bonding and that (2) language uniquely fulfills this requirement. Data on the size of conversational and other small interacting groups of humans are in line with the predictions for the relative efficiency of conversation compared to grooming as a bonding process. Analysis of a sample of human conversations shows that about 60% of time is spent gossiping about relationships and personal experiences. It is suggested that language evolved to allow individuals to learn about the behavioural characteristics of other group members more rapidly than is possible by direct observation alone. (shrink)

Science is not a great way to make money, or these days, even a job. But there are great riches in it, and in this book too. Tim Bradford, 'New Scientist'.

This paper examines social network size in contemporary Western society based on the exchange of Christmas cards. Maximum network size averaged 153.5 individuals, with a mean network size of 124.9 for those individuals explicitly contacted; these values are remarkably close to the group size of 150 predicted for humans on the basis of the size of their neocortex. Age, household type, and the relationship to the individual influence network structure, although the proportion of kin remained relatively constant at around 21%. (...) Frequency of contact between network members was primarily determined by two classes of variable: passive factors (distance, work colleague, overseas) and active factors (emotional closeness, genetic relatedness). Controlling for the influence of passive factors on contact rates allowed the hierarchical structure of human social groups to be delimited. These findings suggest that there may be cognitive constraints on network size. (shrink)

This article explores the implications of the social brain and the endorphin-based bonding mechanism that underpins it for the evolution of religion. I argue that religion evolved as one of the behavioural mechanisms designed to facilitate community bonding when humans first evolved the larger social groups of ~150 that now characterise our species. This is not a matter of facilitating cooperation, but of engineering social cohesion – a very different problem. Analysis of the size of C19th utopian communities suggests that (...) a religious basis both allowed larger groups to form and greatly enhanced their longevity. I suggest that religion evolved in two stages: an early immersive form with no formal structure based on trance-dancing (a form still evident in the rituals and practices of many hunter-gatherers) and a later form which had more formal structures and gave rise to our modern doctrinal religions. I argue that the modern doctrinal religions did not replace ancestral immersive religions but rather that the doctrinal component was overlaid on the ancient immersive form, thereby giving rise to the mystical stance that underlies all world religions. I suggest that it is this mystical stance that causes the constant upwelling of cults and sects within world religions. (shrink)

The Oxford Handbook of Evolutionary Psychology is the definitive, comprehensive, and authoritative text on this burgeoning field. With contributions from over fifty experts in the field, the range and depth of coverage is unequalled. It will be an essential resource for students and researchers in psychology.

Why and under what conditions are individuals altruistic to family and friends in their social networks? Evolutionary psychology suggests that such behaviour is primarily the product of adaptations for kin- and reciprocal altruism, dependent on the degree of genetic relatedness and exchange of benefits, respectively. For this reason, individuals are expected to be more altruistic to family members than to friends: whereas family members can be the recipients of kin and reciprocal altruism, friends can be the recipients of reciprocal altruism (...) only. However, there is a question about how the effect of kinship is implemented at the proximate psychological level. One possibility is that kinship contributes to some general measure of relationship quality (such as ‘emotional closeness’), which in turn explains altruism. Another possibility is that the effect of kinship is independent of relationship quality. The present study tests between these two possibilities. Participants (N= 111) completed a self-report questionnaire about their willingness to be altruistic, and their emotional closeness, to 12 family members and friends at different positions in their extended social networks. As expected, altruism was greater for family than friends, and greater for more central layers of the network. Crucially, the results showed that kinship made a significant unique contribution to altruism, even when controlling for the effects of emotional closeness. Thus, participants were more altruistic towards kin than would be expected if altruism was dependent on emotional closeness alone – a phenomenon we label a ‘kinship premium’. These results have implications for the ongoing debate about the extent to which kin relations and friendships are distinct kinds of social relationships, and how to measure the ‘strength of ties’ in social networks. (shrink)

Data from various settings suggest that there is an upper limit of about four on the number of individuals who can interact in spontaneous conversation. This limit appears to be a consequence of the mechanisms of speech production and detection. There appear to be no differences between men and women in this respect, other than those introduced by women’s lighter voices.

Data on the number of adults that an individual contacts at least once a month in a set of British populations yield estimates of network sizes that correspond closely to those of the typical “sympathy group” size in humans. Men and women do not differ in their total network size, but women have more females and more kin in their networks than men do. Kin account for a significantly higher proportion of network members than would be expected by chance. The (...) number of kin in the network increases in proportion to the size of the family; as a result, people from large families have proportionately fewer non-kin in their networks, suggesting that there is either a time constraint or a cognitive constraint on network size. A small inner clique of the network functions as a support group from whom an individual is particularly likely to seek advice or assistance in time of need. Kin do not account for a significantly higher proportion of the support clique than they do for the wider network of regular social contacts for either men or women, but each sex exhibits a strong preference for members of their own sex. (shrink)

A family reconstitution study of the Krummhörn population (Ostfriesland, Germany, 1720–1874) reveals that infant mortality and children’s probabilities of marrying or emigrating unmarried are affected by the number of living same-sexed sibs in farmers’ families but not in the families of landless laborers. We interpret these results in terms of a “local resource competition” model in which resource-holding families are obliged to manipulate the reproductive future of their offspring. In contrast, families that lack resources have no need to manipulate their (...) offspring and are more likely to benefit from allowing their offspring to capitalize on whatever opportunities to reproduce present themselves. (shrink)

Cooperation for the public good is vulnerable to exploitation by free-riders because it always pays individuals to exploit the social contract for their own benefit. This problem can be resolved if free-riders are punished, but punishment is itself a public good subject to free-riding. The fear of supernatural punishment hypothesis (FSPH) proposes that belief in supernatural punishment might offer a solution to this problem by deflecting the cost of punishment onto supernatural forces and thereby incentivizing cooperation. FSPH is supported empirically (...) by ethnographic data, but this work has so far focused on (1) institutional cooperative traits which may not reflect individual choices on how to behave in everyday social interactions and (2) threat of punishment from all-powerful moralizing high gods rather than other agents capable of supernatural punishment. Here, we consider the FSPH using variables which are linked to individual interaction and expand the number of variables measuring belief in different forms of supernatural punishment. Our findings do not fit these more general FSPH predictions. We suggest there may be something special about the link between moralizing high gods and institutional enforcement of cooperation that is not captured by these other variables. (shrink)

Cooperation requires that individuals are able to identify, and preferentially associate with, others who have compatible preferences and the shared background knowledge needed to solve interpersonal coordination problems. The present study investigates the nature of such similarity within social networks, asking: What do friends have in common? And what is the relationship between similarity and altruism? The results show that similarity declines with frequency of contact; similarity in general is a significant predictor of altruism and emotional closeness; and, specifically, sharing (...) a sense of humor, hobbies and interests, moral beliefs, and being from the same area are the best predictors. These results shed light on the structure of relationships within networks and provide a possible checklist for predicting attitudes toward strangers, and in-group identification. (shrink)

When the social sciences parted company from evolutionary biology almost exactly a century ago, they did so at a time when evolutionary biology was still very much in its infancy and many key issues were unresolved. As a result, the social sciences took away with them an understanding of evolution that was in fact based on 18th- rather than 19th-century biology. I argue that contemporary evolutionary thinking has much more to offer the social sciences than most people have assumed. Contemporary (...) evolutionary research on human behaviour focuses on two main issues at the micro-social scale: understanding the trade-offs in individual decision-making and understanding the cognitive constraints that limit flexibility of decisions. I offer examples of both of these approaches. Finally, I consider the broader question of the macro-social scale. (shrink)

Drama, at least according to the Aristotelian view, is effective inasmuch as it successfully mirrors real aspects of human behavior. This leads to the hypothesis that successful dramas will portray fictional social networks that have the same properties as those typical of human beings across ages and cultures. We outline a methodology for investigating this hypothesis and use it to examine ten of Shakespeare’s plays. The cliques and groups portrayed in the plays correspond closely to those which have been observed (...) in spontaneous human interaction, including in hunter-gatherer societies, and the networks of the plays exhibit “small world” properties of the type which have been observed in many human-made and natural systems. (shrink)

Heroism is apparently nonadaptive in Darwinian terms, so why does it exist at all? Risk-taking and heroic behavior are predominantly male tendencies, and literature and legend reflect this. This study explores the possibility that heroism persists in many human cultures owing to a female preference for risk-prone rather than risk-averse males as sexual partners, and it suggests that such a preference may be exploited as a male mating strategy. It also attempts to quantify the relative influences of altruism and bravery (...) in the evolution of heroism. Our study found that females do prefer risk-prone brave males to risk-averse non-brave males, and that men are aware of this preference. Bravery in a male was shown to be the stronger factor influencing female choice of short-term partners, long-term partners, and male friends, with altruism playing a lesser part in their choice. Altruism was deemed important in long-term relationships and friendships, but for short-term liaisons, non-altruists were preferred to altruists. Heroism may therefore have evolved owing to a female preference for brave, risk-prone males because risk-taking acts as an honest cue for "good genes." Altruism was judged to be a less influential factor in the evolution of heroism than bravery and a demonstrated willingness to take risks. (shrink)

Hyperlink cinema is an emergent film genre that seeks to push the boundaries of the medium in order to mirror contemporary life in the globalized community. Films in the genre thus create an interacting network across space and time in such a way as to suggest that people’s lives can intersect on scales that would not have been possible without modern technologies of travel and communication. This allows us to test the hypothesis that new kinds of media might permit us (...) to break through the natural cognitive constraints that limit the number and quality of social relationships we can manage in the conventional face-to-face world. We used network analysis to test this hypothesis with data from 12 hyperlink films, using 10 motion pictures from a more conventional film genre as a control. We found few differences between hyperlink cinema films and the control genre, and few differences between hyperlink cinema films and either the real world or classical drama (e.g., Shakespeare’s plays). Conversation group size seems to be especially resilient to alteration. It seems that, despite many efficiency advantages, modern media are unable to circumvent the constraints imposed by our evolved psychology. (shrink)

The original book chapter does not have an abstract. However, I have written an abstract for this repository: Religious life encompasses a wide diversity of situations for which the emotional tone is on a continuum from extreme euphoria to extreme dysphoria. In this book chapter, we propose the novel hypothesis that euphoria and dysphoria have distinctly separate functional consequences for religious evolution and survivability. This is due to the differential cognitive states that are created in euphoric and dysphoric situations. Based (...) on readings from religious studies and cognitive psychology, we propose that euphoria in religion is conducive to social bonding and situations needing lateral thinking and creativity; whereas dysphoria in religion is conducive to situations where precision and analogical reasoning are necessary. (shrink)

Previous empirical studies have suggested that language is primarily used to exchange social information, but our evidence on this derives mainly from English speakers. We present data from a study of natural conversations among Farsi speakers in Iran and show that not only are conversation groups the same size as those observed in Europe and North America, but people also talk predominantly about social topics. We argue that these results reinforce the suggestion that language most likely evolved for the transmission (...) of information about the social world. We also explore sex differences in conversational behavior: while the pattern is broadly similar between the sexes, men may be more sensitive than women are to discussing some topics in the presence of many other people. (shrink)

One of the more compelling features of Denis Dutton’s The Art Instinct is its theoretical parsimony. Utilizing what essentially amounts to one explanatory principle—that of Darwinian selection—Dutton advances a theory of aesthetics that is at once general enough to account for cross-cultural variations in artistic production and sufficiently nuanced to promote insights into individual artworks. In doing this, Dutton’s work could not offer a greater contrast to some of the more vocal trends in contemporary aesthetic theory, where ponderous theorizing and (...) rebarbative jargons have violently opposed the idea—otherwise so modest—that aesthetic activities might draw on the evolved capacities of the human imagination. On .. (shrink)

The study of church growth has historically been divided into two strands of research: the Church Growth Movement and the Social Science approach. This article argues that Dunbar’s Social Brain Hypothesis represents a legitimate and fruitful third strand in the study of church growth, sharing features of both previous strands but identical with neither. We argue that five predictions derived from the Social Brain Hypothesis are accurately borne out in the empirical and practical church growth literature: that larger congregations lead (...) to lower active engagement from members; that single-leader congregations are limited to around 150 members; that congregations of 150 are further stratified into smaller functioning groups; that congregations expanding beyond 150 members undergo internal tensions and are forced to reorganise; and that congregations larger than 150 will require structural sub-divisions to retain active member involvement. While these assertions are reflected in the church growth literature and articulate the common sense assumptions of church growth experts, the Social Brain Hypothesis offers a coherent theoretical framework which unifies these observations and thereby represents a distinctive contribution to church growth studies. (shrink)

This study examines the socioeconomic and familial background of Irish Catholic priests born between 1867 and 1911. Previous research has hypothesized that lack of marriage opportunities may influence adoption of celibacy as part of a religious institution. The present study traced data from Irish seminary registries for 46 Catholic priests born in County Limerick, Ireland, using 1901 Irish Census returns and Land Valuation records. Priests were more likely to originate from landholding backgrounds, and with landholdings greater in size and wealth (...) than the local average. Priests were found to originate from families with more sons than the national average, but with similar numbers of daughters. These findings are discussed in relation to competition for resources and lineage survival strategies. (shrink)

I argue that, while Finlay et al, are correct to suggest that there are developmental regularities (or constraints) acting on brain component evolution, they are incorrect to infer from this that a developmental explanation necessarily implies that structural changes preceded functional use. Developmental and functional (adaptationist) explanations are complementary, not alternatives.

For as long as history has been with us, religion has been a feature of human life. There is no known culture for which we have an ethnographic or an archaeological record that does not have some form of religion. Even in the secular societies that have become more common in the past few centuries, there are people who consider themselves religious and aspire to practise the rituals of their religion. These religions vary in form, style and size from small (...) cults numbering a few hundred people centred around a charismatic leader to worldwide organizations numbering tens, or even hundreds, of millions of adherents with representations in every country. Some, like Buddhism, take an individualistic stance (your salvation is entirely in your own hands), some like the older Abrahamic religions view salvation as more of a collective activity through the performance of appropriate rituals, and a few (Judaism is one) have no formal concept of an afterlife. Some like Christianity and Islam believe in a single all- powerful God. (shrink)

In my target article, I argued (1) that the relationship between neocortical size and group size in primates implies that there is a cognitive limit on the size of human groups, and (2) that time constraints forced the evolution of language as a more efficient means of bonding the large groups that humans evolved. The doubts about these claims raised by these additional commentaries largely reflect misinterpretation of my original claims.

Striedter's account of human brain evolution fails on two key counts. First, he confuses developmental constraints with selection explanations in the initial jump in hominid brain size around two MYA. Second, he misunderstands the Machiavellian Intelligence explanation.

While the evidence that cetaceans exhibit behaviours that are every bit as cultural as those recognised in chimpanzees is unequivocal, I argue that it is unlikely that either taxon has the social cognitive mechanisms required to underpin the more advanced forms of culture characteristic of humans (namely those that depend on shared meaning).