Human Social Evolution Research Articles

Male cooperation for breeding opportunities contributes to the evolution of multilevel societies.

A small number of primate species including snub-nosed monkeys (colobines), geladas (papionins) and humans live in multilevel societies (MLSs), in which multiple one-male polygamous units (OMUs) coexist to form a band, and non-breeding males associate in bachelor groups. Phylogenetic reconstructions indicate that the papionin MLS appears to have evolved through internal fissioning of large mixed-sex groups, whereas the colobine MLS evolved through the aggregation of small, isolated OMUs. However, how agonistic males maintain tolerance under intensive competition over limited breeding opportunities remains unclear. Using a combination of behavioural analysis, satellite telemetry and genetic data, we quantified the social network of males in a bachelor group of golden snub-nosed monkeys. The results show a strong effect of kinship on social bonds among bachelors. Their interactions ranged from cooperation to agonism, and were regulated by access to mating partners. We suggest that an ‘arms race’ between breeding males' collective defence against usurpation attempts by bachelor males and bachelor males' aggregative offence to obtain reproductive opportunities has selected for larger group size on both sides. The results provide insight into the role that kin selection plays in shaping inter-male cohesion which facilities the evolution of multilevel societies. These findings have implications for understanding human social evolution, as male–male bonds are a hallmark of small- and large-scale human societies.

From Pleistocene to Holocene: the prehistory of southwest Asia in evolutionary context

In this paper I seek to show how cultural niche construction theory offers the potential to extend the human evolutionary story beyond the Pleistocene, through the Neolithic, towards the kind of very large-scale societies in which we live today. The study of the human past has been compartmentalised, each compartment using different analytical vocabularies, so that their accounts are written in mutually incompatible languages. In recent years social, cognitive and cultural evolutionary theories, building on a growing body of archaeological evidence, have made substantial sense of the social and cultural evolution of the genus Homo. However, specialists in this field of studies have found it difficult to extend their kind of analysis into the Holocene human world. Within southwest Asia the three or four millennia of the Neolithic period at the beginning of the Holocene represents a pivotal point, which saw the transformation of human society in the emergence of the first large-scale, permanent communities, the domestication of plants and animals, and the establishment of effective farming economies. Following the Neolithic, the pace of human social, economic and cultural evolution continued to increase. By 5000 years ago, in parts of southwest Asia and northeast Africa there were very large-scale urban societies, and the first large-scale states (kingdoms). An extension of cultural niche construction theory enables us to extend the evolutionary narrative of the Pleistocene into the Holocene, opening the way to developing a single, long-term, evolutionary account of human history.

Adult sex ratios and partner scarcity among hunter-gatherers: implications for dispersal patterns and the evolution of human sociality.

Small populations are susceptible to high genetic loads and random fluctuations in birth and death rates. While these selective forces can adversely affect their viability, small populations persist across taxa. Here, we investigate the resilience of small groups to demographic uncertainty, and specifically to fluctuations in adult sex ratio (ASR), partner availability and dispersal patterns. Using 25 years of demographic data for two Savannah Pumé groups of South American hunter-gatherers, we show that in small human populations: (i) ASRs fluctuate substantially from year to year, but do not consistently trend in a sex-biased direction; (ii) the primary driver of local variation in partner availability is stochasticity in the sex ratio at maturity; and (iii) dispersal outside of the group is an important behavioural means to mediate locally constrained mating options. To then simulate conditions under which dispersal outside of the local group may have evolved, we develop two mathematical models. Model results predict that if the ASR is biased, the globally rarer sex should disperse. The model's utility is then evaluated by applying our empirical data to this central prediction. The results are consistent with the observed hunter-gatherer pattern of variation in the sex that disperses. Together, these findings offer an alternative explanation to resource provisioning for the evolution of traits central to human sociality (e.g. flexible dispersal, bilocal post-marital residence and cooperation across local groups). We argue that in small populations, looking outside of one's local group is necessary to find a mate and that, motivated by ASR imbalance, the alliances formed to facilitate the movement of partners are an important foundation for the human-typical pattern of network formation across local groups.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

The psychology of deterrence explains why group membership matters for third-party punishment

Abstract Humans regularly intervene in others' conflicts as third-parties. This has been studied using the third-party punishment game: A third-party can pay a cost to punish another player (the dictator) who treated someone else poorly. Because the game is anonymous and one-shot, punishers are thought to have no strategic reasons to intervene. Nonetheless, punishers often punish dictators who treat others poorly. This result is central to a controversy over human social evolution: Did third-party punishment evolve to maintain group norms or to deter others from acting against one's interests? This paper provides a critical test. We manipulate the ingroup/outgroup composition of the players while simultaneously measuring the inferences punishers make about how the dictator would treat them personally. The group norm predictions were falsified, as outgroup defectors were punished most harshly, not ingroup defectors (as predicted by ingroup fairness norms) and not outgroup members generally (as predicted by norms of parochialism). The deterrence predictions were validated: Punishers punished the most when they inferred that they would be treated the worst by dictators, especially when better treatment would be expected given ingroup/outgroup composition.

BICA: a binary imperialist competitive algorithm and its application in CBIR systems

Imperialist Competitive Algorithm (ICA), which is a mathematical model and the computer simulation of human social evolution, works as a successful algorithm in many optimization problems. In this paper a new binary version of imperialist competitive algorithm, namely BICA is proposed using a well appropriated transfer function and optimal parameter setting. These allow the algorithm to explore a larger number of possible solutions and avoid the stagnation. To assess the performance of the proposed method the 0–1 knapsack problem, the feature selection problem and the Content-Based Image Retrieval (CBIR) systems are experienced; and the effectiveness of this method is compared with the state-of-the-art algorithms. Comparative results confirm the performance of the proposed BICA in all three applications.

The Evolution of Myelin: Theories and Application to Human Disease

Myelin, once thought of as a simple insulating sheath, is now known to be a complex, dynamic structure. It has multiple functions in addition to increasing conduction velocity, including reducing the energetic cost of action potentials, saving space, and metabolic functions. Myelin is also notable for likely having arisen independently at least three times over the course of evolutionary history. This article reviews the available evidence about the evolution of myelin and proposes a hypothesis of how it arose in vertebrates. It then discusses the evolutionary trade-offs associated with myelination and suggests a possible animal model for further study of this phenomenon. Finally, it briefly covers the neural regulation of myelination before discussing possible roles of myelin in human social cognition and evolution, and the relevance of this to human disease.

Charting the neglected West: The social system of Guinea baboons.

ObjectivesPrimate social systems are remarkably diverse, and thus play a central role in understanding social evolution, including the biological origin of human societies. Although baboons have been prominently featured in this context, historically little was known about the westernmost member of the genus, the Guinea baboon (Papio papio).Material and MethodsHere, we summarize the findings from the first years of observations at the field site CRP Simenti in the Niokolo Koba National Park in Senegal.ResultsGuinea baboons reveal a nested multi‐level social organization, with reproductive units comprising one “primary” male, one to several females, young, and occasionally “secondary” males at the base of the society. Three to five units form “parties,” which team up with other parties to form a “gang.” Different gangs have largely overlapping home ranges and agonistic interactions between different parties or gangs are rare. Some but not all strongly socially bonded males are highly related, and population genetic and behavioral evidence indicate female‐biased dispersal. Females play an important role in intersexual bond formation and maintenance, and female tenure length varies between a few weeks to several years.DiscussionWhile the social organization resembles that of hamadryas baboons (P. hamadryas), the social structure differs considerably, specifically in terms of low male aggressiveness and female freedom. Despite substantial differences in social organization and social structure, the acoustic structure of Guinea baboon vocalizations does not differ substantially from that of other baboon taxa. With its multi‐level organization, stable bonds between males and females, as well as a high‐degree of male‐male cooperation and tolerance, Guinea baboons constitute an intriguing model for reconstructing human social evolution.

The Invention of Stone Tools

This paper was written to study the development of stone tool technology throughout the stone age. It finds the technology developed with the simplest discoveries being made first and more complex discoveries being made later. The chemical structure and properties of the raw materials determined that stone tools could be useful to humans and overtime people learnt to make better and better stone tools. The improvements occurred in an order that was necessary and inevitable with later improvements building upon earlier improvements and is an illustration of how ever increasing human knowledge drives technology and human social and cultural evolution forward.

A critical review of Dunbar’s social brain hypothesis

Dunbar’s social brain hypothesis constitutes an influential position among those that relate the evolution of human cognition and sociality. In this work, we first present the essentials of the theory and discuss the paleoanthropological and social evidence claimed to support it. We also point out its shortcomings, which have to do with the general strategy of finding linear relations among different traits, the lack of attention to the mental capacities that make human social life possible, and the diversity of social relations and structures that take place. We put forward our way of complementing Dunbar’s approach by focusing on the role of trust in cementing society and explaining diversity.

Are Humans Too Generous and Too Punitive? Using Psychological Principles to Further Debates about Human Social Evolution.

Are humans too generous and too punitive? Many researchers have concluded that classic theories of social evolution (e.g., direct reciprocity, reputation) are not sufficient to explain human cooperation; instead, group selection theories are needed. We think such a move is premature. The leap to these models has been made by moving directly from thinking about selection pressures to predicting patterns of behavior and ignoring the intervening layer of evolved psychology that must mediate this connection. In real world environments, information processing is a non-trivial problem and details of the ecology can dramatically constrain potential solutions, often enabling particular heuristics to be efficient and effective. We argue that making the intervening layer of psychology explicit resolves decades-old mysteries in the evolution of cooperation and punishment.

Imagination in human social cognition, autism, and psychotic-affective conditions

Complex human social cognition has evolved in concert with risks for psychiatric disorders. Recently, autism and psychotic-affective conditions (mainly schizophrenia, bipolar disorder, and depression) have been posited as psychological ‘opposites’ with regard to social-cognitive phenotypes. Imagination, considered as ‘forming new ideas, mental images, or concepts’, represents a central facet of human social evolution and cognition. Previous studies have documented reduced imagination in autism, and increased imagination in association with psychotic-affective conditions, yet these sets of findings have yet to be considered together, or evaluated in the context of the diametric model. We first review studies of the components, manifestations, and neural correlates of imagination in autism and psychotic-affective conditions. Next, we use data on dimensional autism in healthy populations to test the hypotheses that: (1) imagination represents the facet of autism that best accounts for its strongly male-biased sex ratio, and (2) higher genetic risk of schizophrenia is associated with higher imagination, in accordance with the predictions of the diametric model. The first hypothesis was supported by a systematic review and meta-analysis showing that Imagination exhibits the strongest male bias of all Autism Quotient (AQ) subscales, in non-clinical populations. The second hypothesis was supported, for males, by associations between schizophrenia genetic risk scores, derived from a set of single-nucleotide polymorphisms, and the AQ Imagination subscale. Considered together, these findings indicate that imagination, especially social imagination as embodied in the default mode human brain network, mediates risk and diametric dimensional phenotypes of autism and psychotic-affective conditions.

Mechanisms of Progress in Organic and Cultural Evolution

Due to the randomly changing environmental conditions in which natural selection is acting, it is hard to see how this process could give evolution the steady direction of a large-scale incessant progress. In the present article I propose a solution to this dilemma by the application of the concept of complexity as a measure of evolutionary progress, a notion that I have developed in a descriptive way in previous works. By means of the concept of complexity one can conceive of the evolutionary process as having a stable direction towards ever-increasing complexity. The explanatory mechanism behind this trend is in the present work suggested to be found in the combined actions of natural selection, competition, feedback, arms race, and sexual selection. These mechanisms are discussed at length, being applicable not only in organic evolution but in human cultural and social evolution as well.

The burden of proof for a cultural group selection account.

Richerson et al. establish cultural group selection as a plausible force in human social evolution. However, they do not demonstrate its causal precedence for any trait, let alone its "essentialness." To do so, they must show that a particular group trait was caused by cultural transmission, and directly caused differences in group fitness.

Social insects, merely a "fun house" mirror of human social evolution.

Social insects show us very little about the evolution of complex human society. As more relevant literature demonstrates, ultrasociality is a cause rather than an effect of human social evolution.

A Cultural Algorithm for Optimal Design of Truss Structures

A cultural algorithm was utilized in this study to solve optimal design of truss structures problem achieving minimum weight objective under stress and deflection constraints. The algorithm is inspired by principles of human social evolution. It simulates the social interaction between the peoples and their beliefs in a belief space. Cultural Algorithm (CA) utilizes the belief space and population space which affects each other based on acceptance and influence functions. The belief space of CA consists of different knowledge components. In this paper, only situational and normative knowledge components are used within the belief space. The performance of the method is demonstrated through four benchmark design examples. Comparison of the obtained results with those of some previous studies demonstrates the efficiency of this algorithm.

Settlement and Resettlement in Asia: Migration vs. Empire in History

At its simplest, this essay provides a narrative of migration in Asia since the arrival of Homo sapiens some 70,000 years ago. More fully, it presents the case for conducting long-term, world-historical interpretation for Asia with attention to multiple perspectives, which has become increasingly central to global historical analysis. Following an introductory articulation of the benefits of long-term interpretation, the second section presents a balance of three perspectives-empire, exchange, and migration-as frameworks for interpreting the Asian past. The third section presents further detail on migration in long-term Asian history. The concluding section identifies four changes in patterns of migration during the past two centuries and emphasizes the underlying importance of cross-community migration in long-term human biological and social evolution.

Agricultural productivity in past societies: Toward an empirically informed model for testing cultural evolutionary hypotheses

Agricultural productivity, and its variation in space and time, plays a fundamental role in many theories of human social evolution. However, we often lack systematic information about the productivity of past agricultural systems on a large enough scale in order to be able to test these theories properly. The effect of climate on crop yields has received a great deal of attention resulting in a range of empirical and process-based models, yet the focus has primarily been on current or future conditions. In this paper, we argue for a “bottom-up” approach that estimates productivity, or potential productivity based on information about the agricultural practices and technologies used in past societies. Of key theoretical interest is using this information to estimate the carrying capacity of a given region, independently of estimates of population size. We outline how explicit crop yield models can be combined with high quality historical and archaeological information about past societies, in order to infer the temporal and geographic patterns of change in agricultural productivity and potential. We discuss the kinds of information we need to collect about agricultural techniques and practices in the past, and introduce a new databank initiative we have developed for collating the best available historical and archaeological evidence. A key benefit of our approach lies in making explicit the steps in the process of estimating past productivities and carrying capacities, and in being able to assess the effects of different modelling assumptions. This is undoubtedly an ambitious task, yet promises to provide important insights into fundamental aspects of past societies, and will enable us to test more rigorously key hypotheses about human socio-cultural evolution.

The effects of collaboration and minimal-group membership on children’s prosocial behavior, liking, affiliation, and trust

Recent theoretical work has highlighted potential links between interpersonal collaboration and group membership in the evolution of human sociality. Here we compared the effects of collaboration and minimal-group membership on young children’s prosocial behavior (i.e., helping and resource allocation), liking, affiliation, and trust. In a design that matched as closely as possible these two ways of connecting with others, we showed that 5-year-olds’ behavior was affected similarly by collaboration and minimal-group membership; both increased children’s preference for their partners on multiple dimensions and produced overall effects of a similar magnitude. In contrast, 3.5-year-olds did not have a strong preference for either collaborators or minimal in-group members. Thus, both collaboration and minimal-group membership are similarly effective in their influence on children’s prosocial behavior and social preferences.

Deacon’s Challenge: From Calls to Words

A Darwinian theory of the evolution of language must be incremental: to explain the transition from a hominin baseline with great ape grade communicative capacities to language-equipped hominins as a series of small steps. This paper takes up that project for the special case of words, giving an incremental model of the call to word transition. The model is embedded in a general conception of human social evolution with independent empirical support, but it also depends on some more specific assumptions about language and about the earlier forms of hominin communication. Given these assumptions, the paper can be no more than a working draft of a more complete theory.

The Social Roots of Contemporary Prejudice

Background: Evolutionary theory suggests prejudice may be a result of the evolution of human sociality. In this study, we investigate this claim by integrating theoretical insights of evolutionary theory with the well-established social psychological research on prejudice centering on Right Wing Authoritarianism (RWA) and Social Dominance Orientation (SDO) as the main predictors of prejudice. Method: First, we developed two different signaling scales, probing respondents’ propensity to signal group commitment in a genuine or deceptive way. We administered a questionnaire consisting of the two signaling measures, RWA, SDO and prejudice measures to 1380 students. Analysis of the data was done using structural equation modeling. Results: Our results indicate that genuine signaling of one’s commitment to the in-group is positively associated with RWA, and that deceptively signaling one’s commitment to the in-group is positively associated with SDO. Both RWA and SDO are positively related to prejudice. Conclusion: Our study is the first to empirically reveal the pro-social roots of prejudice using classical measurement instruments. The findings give rise to a new array of research questions.