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Production of a sign for a new health center in the Kingdom of Tonga. Note the cultural significant motifs, or kupesi , comprising the border. Adaptive interactions in large populations often require honest signals of group membership to structure interactions. However, limitations to a simple mapping of groups onto stylistic and ethnosomatic variation suggest that new ways of measurement are needed to describe the work that objects do to facilitate social coordination. Means to measure the benefits to coordinating on specific objects, here called signaling value, would transition inquiry from general statement that signals play a role, to which signals play what roles in what contexts. This study introduces a method to measure the signaling value of specific objects using classification tasks. After mathematically showing how social coordination leads to greater associations in object classification, a statistical approach is derived to estimate the signaling value of objects from a triad classification task. The approach is then applied to a study of culturally salient motifs in the Pacific Island nation of Tonga and a comparison group in the US. The statistical estimates suggest a large role for social coordination for the full set of motifs, although there is a substantial range of signaling values among motifs. In light of the estimates, the cultural history of individual motifs is discussed as well as the future of this approach.

Quantifying the distance between cultural groups has received substantial recent interest. A key innovation, borrowed from population genetics, is the calculation of cultural F ST ( CF ST ) statistics on datasets of human culture. Measuring the variance between groups as a fraction of total variance, F ST is theoretically important in additive models of cooperation. Consistent with this, recent empirical work has confirmed that high values of pairwise CF ST (measuring cultural distance) strongly predict unwillingness to cooperate with strangers in coordination vignettes. As applications for CF ST increase, however, there is greater need to understand its meaning in naturalistic situations beyond additive cooperation. Focusing on games with both positive and negative frequency dependence and high-diversity, mixed equilibria, we derive a simple relationship between F ST and the evolution of group-beneficial traits across a broad spectrum of social interactions. Contrary to standard assumptions, this model shows why F ST can have both positive and negative marginal effects on the spread of group-beneficial traits under certain realistic conditions. These results provide broader theoretical direction for empirical applications of CF ST in the evolutionary study of culture.

Derived aspects of our human life history, such as short interbirth intervals and altricial newborns, have been attributed to male provisioning of nutrient-rich meat within monogamous relationships. However, many primatologists and anthropologists have questioned the relative importance of pair-bonding and biparental care, pointing to evidence that cooperative breeding better characterizes human reproductive and child-care relationships. We present a mathematical model with empirically-informed parameter ranges showing that natural selection favors cooperation among mothers over a wide range of conditions. In contrast, our analysis provides a far more narrow range of support for selection favoring male coalition-based monogamy over more promiscuous independent males, suggesting that provisioning within monogamous relationships may fall short of explaining the evolution of Homo life history. Rather, broader cooperative networks within and between the sexes provide the primary basis for our unique life history.

Evolutionary models broadly support a number of social learning strategies likely important in economic behavior. Using a simple model of price dynamics, I show how prestige bias, or copying of famed (and likely successful) individuals, influences price equilibria and investor disposition in a way that exacerbates or creates market bubbles. I discuss how integrating the social learning and demographic forces important in cultural evolution with economic models provides a fruitful line of inquiry into real-world behavior.

Understanding the prevalence of adaptive culture in part requires understanding the dynamics of learning. Here we explore the adaptive value of social learning in groups and how formal social groups function as effective mediums of information exchange. We discuss the education literature on Cooperative Learning Groups (CLGs), which outlines the potential of group learning for enhancing learning outcomes. Four qualities appear essential for CLGs to enhance learning: (1) extended conversations, (2) regular interactions, (3) gathering of experts, and (4) incentives for sharing knowledge. We analyze these four qualities within the context of a small-scale agricultural society using data we collected in 2010 and 2012. Through an analysis of surveys, interviews, and observations in the Tongan islands, we describe the role CLGs likely plays in facilitating individuals' learning of adaptive information. Our analysis of group affiliation, membership, and topics of conversation suggest that the first three CLG qualities reflect conditions for adaptive learning in groups. We utilize ethnographic anecdotes to suggest the fourth quality is also conducive to adaptive group learning. Using an evolutionary model, we further explore the scope for CLGs outside the Tongan socioecological context. Model analysis shows that environmental volatility and migration rates among human groups mediate the scope for CLGs. We call for wider attention to how group structure facilitates learning in informal settings, which may be key to assessing the contribution of groups to the evolution of complex, adaptive culture.

Ethnic markers are a prominent organizing feature of human society when individuals engage in significant anonymous interactions. However, identifying markers in natural settings is nontrivial. Although ad hoc assignment of markers to groups is widely documented in the ethnographic literature, predicting the membership of individuals based on stylistic variation is less clear. We argue that a more systematic approach is required to satisfy the basic assumptions made in ethnic marker theory. To this end we introduce a three-step ethnographic method to assess the presence, recognition, and transmission of markers of group identity: (1) continual scans, (2) a utilization survey, and (3) a comparative classification task. Applying the method to a study of culturally significant motifs in the South Pacific Island nation of Tonga, we provide evidence that the motif set satisfies basic theoretical assumptions and thus the motifs are likely expressions for social coordination. We also found that the coordinating role of each motif is variable and requires further investigation.

Since despotism is a common evolutionary development in human history, we seek to understand the conditions under which it can originate, persist, and affect population trajectories. We describe a general system of population ecology equations representing the Ideal Free and Despotic Distributions for one and two habitats, one of which contains a despotic class that controls the distribution of resources. Using analytical and numerical solutions we derive the optimal concession strategy by despots with and without subordinate migration to an alternative habitat. We show that low concessions exponentially increase the time it takes for the despotic habitat to fill, and we discuss the trade-offs despots and subordinates confront at various levels of exploitation. Contrary to previous hypotheses, higher levels of despotism do not necessarily cause faster migration to alternative habitats. We further show how, during colonization, divergent population trajectories may arise if despotic systems experience Allee-type economies of scale.

Demographic effects on cultural complexity are controversial. Some view the arguments for cultural drift and similar mechanisms as overstating the importance of difficulty in learning, socially or individually. Others stress that social learning is vital, and larger social groups with active cultural transmission yield greater cultural complexity. Using ethnographic data collected among women weavers in the South Pacific, I advance the debate by estimating learning parameters directly relevant to a theoretical model of the evolution of cultural complexity. Through a sensitivity analysis of the estimated model, I show potential learning effects on the production rate of a prestigious cultural good. I advocate further ethnographic work to understand the learning process in naturalistic contexts, as vital to advancing our knowledge of the origins and persistence (or not) of cultural complexity in past and contemporary societies.

Understanding the prevalence of adaptive culture in part requires understanding the dynamics of learning. Here we explore the adaptive value of social learning in groups and how formal social groups function as effective mediums of information exchange. We discuss the education literature on Cooperative Learning Groups (CLGs), which outlines the potential of group learning for enhancing learning outcomes. Four qualities appear essential for CLGs to enhance learning: (1) extended conversations, (2) regular interactions, (3) gathering of experts, and (4) incentives for sharing knowledge. We analyze these four qualities within the context of a small-scale agricultural society using data we collected in 2010 and 2012. Through an analysis of surveys, interviews, and observations in the Tongan islands, we describe the role CLGs likely plays in facilitating individuals’ learning of adaptive information. Our analysis of group affiliation, membership, and topics of conversation suggest that the first three CLG qualities reflect conditions for adaptive learning in groups. We utilize ethnographic anecdotes to suggest the fourth quality is also conducive to adaptive group learning. Using an evolutionary model, we further explore the scope for CLGs outside the Tongan socioecological context. Model analysis shows that environmental volatility and migration rates among human groups mediate the scope for CLGs. We call for wider attention to how group structure facilitates learning in informal settings, which may be key to assessing the contribution of groups to the evolution of complex, adaptive culture.