Modelling the role of environmental circumscription in the evolution of inequality.

Circumscription theory proposes that complex hierarchical societies emerged in areas surrounded by barriers to dispersal, e.g. mountains or seas.

Playing the political game: the coevolution of institutions with group size and political inequality.

All societies need to form institutional rules to regulate their social interactions. These specify what actions individuals should take in particular situations, and what sanctions will apply if individuals violate these rules. However, forming these institutional rules involves playing a political game-a process of negotiation between individuals that is costly and time-consuming.

Sequence alignment of folk song melodies reveals cross-cultural regularities of musical evolution.

Culture evolves, but the existence of cross-culturally general regularities of cultural evolution is debated. As a diverse but universal cultural phenomenon, music provides a novel domain to test for the existence of such regularities. Folk song melodies can be thought of as culturally transmitted sequences of notes that change over time under the influence of cognitive and acoustic/physical constraints.

Assessing different historical pathways in the cultural evolution of economic development.

A huge number of hypotheses have been put forward to explain the substantial diversity in economic performance we see in the present-day. There has been a growing appreciation that historical and ecological factors have contributed to social and economic development. However, it is not clear whether such factors have exerted a direct effect on modern productivity, or whether they influence economies indirectly by shaping the cultural evolution of norms and institutions.

Exploring correlations in genetic and cultural variation across language families in northeast Asia.

Culture evolves in ways that are analogous to, but distinct from, genomes. Previous studies examined similarities between cultural variation and genetic variation (population history) at small scales within language families, but few studies have empirically investigated these parallels across language families using diverse cultural data. We report an analysis comparing culture and genomes from in and around northeast Asia spanning 11 language families.

The cultural evolution and ecology of institutions.

Human societies are structured by what we refer to as 'institutions', which are socially created and culturally inherited proscriptions on behaviour that define roles and set expectations about social interactions. The study of institutions in several social science fields has provided many important insights that have not been fully appreciated in the evolutionary human sciences. However, such research has often lacked a shared understanding of general processes of change that shape institutional diversity across space and time.

Complex societies precede moralizing gods throughout world history.

The origins of religion and of complex societies represent evolutionary puzzles. 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. Although previous research has suggested an association between the presence of moralizing gods and social complexity, the relationship between the two is disputed, and attempts to establish causality have been hampered by limitations in the availability of detailed global longitudinal data.

Effects of supplementary feeding on interspecific dominance hierarchies in garden birds.

Individuals often differ in competitive ability, which can lead to the formation of a dominance hierarchy that governs differential access to resources. Previous studies of dominance have predominently focussed on within-species interactions, while the drivers of between-species competitive hierarchies are poorly understood. The increasing prevalence of predictable anthropogenic food subsidies, such as that provided by garden bird feeders, is likely to intensify between-species competition.

Analyses of ovarian activity reveal repeated evolution of post-reproductive lifespans in toothed whales.

In most species the reproductive system ages at the same rate as somatic tissue and individuals continue reproducing until death. However, females of three species - humans, killer whales and short-finned pilot whales - have been shown to display a markedly increased rate of reproductive senescence relative to somatic ageing. In these species, a significant proportion of females live beyond their reproductive lifespan: they have a post-reproductive lifespan.

Quantitative historical analysis uncovers a single dimension of complexity that structures global variation in human social organization.

Do human societies from around the world exhibit similarities in the way that they are structured, and show commonalities in the ways that they have evolved? These are long-standing questions that have proven difficult to answer. To test between competing hypotheses, we constructed a massive repository of historical and archaeological information known as "Seshat: Global History Databank." We systematically coded data on 414 societies from 30 regions around the world spanning the last 10,000 years.

Can We Deliver Better?

Human childbirth has been described as an "obstetrical dilemma". Evolution favours enlargement of the foetal brain, whilst bipedal locomotion demands a reduction in pelvic breadth for improvements in biomechanical efficiency. The result of this conflict is a human pelvis incongruous with the dynamics of childbirth.

Cultural group selection is plausible, but the predictions of its hypotheses should be tested with real-world data.

The evidence compiled in the target article demonstrates that the assumptions of cultural group selection (CGS) theory are often met, and it is therefore a useful framework for generating plausible hypotheses. However, more can be said about how we can test the predictions of CGS hypotheses against competing explanations using historical, archaeological, and anthropological data.

Statistical universals reveal the structures and functions of human music.

Music has been called "the universal language of mankind." Although contemporary theories of music evolution often invoke various musical universals, the existence of such universals has been disputed for decades and has never been empirically demonstrated. Here we combine a music-classification scheme with statistical analyses, including phylogenetic comparative methods, to examine a well-sampled global set of 304 music recordings.

Broad supernatural punishment but not moralizing high gods precede the evolution of political complexity in Austronesia.

Supernatural belief presents an explanatory challenge to evolutionary theorists-it is both costly and prevalent. One influential functional explanation claims that the imagined threat of supernatural punishment can suppress selfishness and enhance cooperation. Specifically, morally concerned supreme deities or 'moralizing high gods' have been argued to reduce free-riding in large social groups, enabling believers to build the kind of complex societies that define modern humanity.

Phylogenetic reconstruction of Bantu kinship challenges Main Sequence Theory of human social evolution.

Kinship provides the fundamental structure of human society: descent determines the inheritance pattern between generations, whereas residence rules govern the location a couple moves to after they marry. In turn, descent and residence patterns determine other key relationships such as alliance, trade, and marriage partners. Hunter-gatherer kinship patterns are viewed as flexible, whereas agricultural societies are thought to have developed much more stable kinship patterns as they expanded during the Holocene.

Evolution of cultural traits occurs at similar relative rates in different world regions.

A fundamental issue in understanding human diversity is whether or not there are regular patterns and processes involved in cultural change. Theoretical and mathematical models of cultural evolution have been developed and are increasingly being used and assessed in empirical analyses. Here, we test the hypothesis that the rates of change of features of human socio-cultural organization are governed by general rules.

War, space, and the evolution of Old World complex societies.

How did human societies evolve from small groups, integrated by face-to-face cooperation, to huge anonymous societies of today, typically organized as states? Why is there so much variation in the ability of different human populations to construct viable states? Existing theories are usually formulated as verbal models and, as a result, do not yield sharply defined, quantitative predictions that could be unambiguously tested with data. Here we develop a cultural evolutionary model that predicts where and when the largest-scale complex societies arose in human history. The central premise of the model, which we test, is that costly institutions that enabled large human groups to function without splitting up evolved as a result of intense competition between societies-primarily warfare.

Cultural phylogeography of the Bantu Languages of sub-Saharan Africa.

There is disagreement about the routes taken by populations speaking Bantu languages as they expanded to cover much of sub-Saharan Africa. Here, we build phylogenetic trees of Bantu languages and map them onto geographical space in order to assess the likely pathway of expansion and test between dispersal scenarios. The results clearly support a scenario in which groups first moved south through the rainforest from a homeland somewhere near the Nigeria-Cameroon border.

Analyses do not support the parasite-stress theory of human sociality.

Re-analysis of the data provided in the target article reveals a lack of evidence for a strong, universal relationship between parasite stress and the variables relating to sociality. Furthermore, even if associations between these variables do exist, the analyses presented here do not provide evidence for Fincher & Thornhill's (F&T's) proposed causal mechanism.

Mode and tempo in the evolution of socio-political organization: reconciling 'Darwinian' and 'Spencerian' evolutionary approaches in anthropology.

Traditional investigations of the evolution of human social and political institutions trace their ancestry back to nineteenth century social scientists such as Herbert Spencer, and have concentrated on the increase in socio-political complexity over time. More recent studies of cultural evolution have been explicitly informed by Darwinian evolutionary theory and focus on the transmission of cultural traits between individuals. These two approaches to investigating cultural change are often seen as incompatible.

Is horizontal transmission really a problem for phylogenetic comparative methods? A simulation study using continuous cultural traits.

Phylogenetic comparative methods (PCMs) provide a potentially powerful toolkit for testing hypotheses about cultural evolution. Here, we build on previous simulation work to assess the effect horizontal transmission between cultures has on the ability of both phylogenetic and non-phylogenetic methods to make inferences about trait evolution. We found that the mode of horizontal transmission of traits has important consequences for both methods.