To investigate whether climate influenced the evolution of cultural transmission in the hominin lineage, we compared transmission strategies associated with archaeological innovations dated between 3.3 Ma and 6 ka with a continuous global palaeoclimate record. Transmission was assessed across three dimensions: spatial (proximity between learner and model), temporal (degree of modularity or sequencing), and social (selectivity in knowledge transfer). Results show that transmission modes correlate with long-term climatic phases, not with the rate of climatic variability. Within a long-term trend towards increasingly complex transmission, globally cooler phases favoured low-investment, observation-based strategies, whereas globally warmer phases promoted structured, explanation-based, and modular transmission. The strongest association between modes of cultural transmission and climate occurs between 500 and 200 ka, followed by progressive decoupling, particularly after 50 ka, when cultural transmission increasingly follows its own dynamics.

Whether a woman has an early or late age at first birth may be influenced by the amount of her wealth and/or its variability. Theory predicts that women tend to delay their first birth when they have high levels of material wealth, and reproduce earlier when they experience high wealth variability. However, both theoretical and empirical work have focused on the influence of these two aspects of wealth on age at first birth separately. Here, we study how current household wealth and short- and long-term wealth variability, simultaneously, influence reproductive onset. We analyse longitudinal data from Tanzanian Pimbwe women (n=495) using Bayesian logistic regression models. Our results show that Pimbwe women who experience more short-term and long-term wealth variability tend to have slightly earlier first births, whereas current wealth appears not to be linked to age at first birth. By introducing an analytical strategy tailored to disentangle the variable relationship between wealth and reproduction, our work sheds light on the mixed evidence linking resources and reproductive strategies more generally.

Variation in eye pigmentation across primate species has been proposed to serve as a cue to emotional or temperamental traits, potentially shaped by processes like domestication or selection against aggression. We tested whether pygmy marmosets (Cebuella pygmaea) respond differently to conspecific facial images that vary in peri-iridal pigmentation. Specifically, we examined whether darker peri-iridal pigmentation elicits more distress or aversive reactions, consistent with the hypothesis that eye colouration serves as a signal of underlying temperament. Contrary to predictions, subjects did not exhibit differential behavioural responses to stimuli depicting conspecifics with light, or dark peri-iridal tissue, or control stimuli. These results align with emerging evidence that challenges the presumed association between ocular pigmentation and temperament or aggression levels in primates. We discuss potential explanations, including species-specific differences in tolerance to eye contact, generalized arousal to experimental contexts, and the need for more controlled comparisons. While our findings do not support a signalling function for eye pigmentation in this context, they contribute to a broader reassessment of the proposed links between morphology and socio-emotional traits in primates.

Men and women differ in which characteristics they prioritise when choosing a romantic partner (e.g., on average, women place greater emphasis on the ability of partners to provide resources, and men place greater emphasis on physical attractiveness and youthfulness). However, researchers have disagreed over whether these gender gaps in partner preferences vary across cultures, specifically in relation to national levels of gender equality, given the inconsistencies in the previous literature. Here, using an open-access partner preference dataset (14,399 participants from 45 countries), we examined whether gender gaps in partner preferences correlate with the restrictiveness of societal gender norms, estimated via the Gender Social Norm Index. The analyses showed that the gender gap in preference for ‘good financial prospects’ was larger in countries with more restrictive gender norms, and the size of the age gap between self and partner exhibited the same pattern. These relationships were not replicated when using cultural tightness as a measure of the restrictiveness of social norms in general, which suggests that the findings specifically relate to gender norms. These results, which support the hypothesis that partner preferences are sensitive to local cultural contexts, are discussed in relation to evolutionary psychology and biosocial models of partner preferences.

Sir W. M. Flinders Petrie’s lifelong beliefs in race science and eugenics underlay his significant work as an archaeologist and Egyptologist. His detection of race in ancient art provided a basis for other scholars’ construction of racial typologies, while his commitment to colonialist paradigms of excavation moved numerous objects, and human remains, from Egypt and Palestine to Britain. In the 1930s, in two letters to The Times and The Palestine Post, the ageing Petrie came out against Nazi understandings of race, arguing that ‘foreign migration has been the making of Britain.’ Petrie’s claims reflected his understanding of civilisation, in antiquity and today, as a product of the ‘right sort’ of racial mixing through migration of the fit, hearty, and talented. This critical reflection considers the role of archaeology in constructing race, taking Petrie’s work on migration as a case study and situating it in wider intellectual trends of the time. Understanding how Petrie’s racial logic allowed him to oppose Nazism while promoting eugenic ‘weeding’, allows us to move beyond simplistic understandings of early twentieth-century race science. We can then detect the pernicious persistence of frameworks from this discipline in popular discourses about migration and culture in Britain today.

Despite growing recognition of racial and ethnic exclusion in the life sciences, mechanisms for achieving structural change remain underdeveloped. Grassroots organisations have emerged as key drivers of equity within the life sciences, yet their sustainability is regularly constrained by voluntary labour, financial precarity, and omission from institutional decision-making. Using the REED (Racial & Ethnic Equality & Diversity) Ecological Network as a case study, this paper examines how grassroots initiatives can advance racial and ethnic inclusion in academic and professional institutions. Founded in 2020, REED has grown into a UK-based, community-led network supporting ecologists from underrepresented racial and ethnic backgrounds through training, mentorship, advocacy, and institutional partnership. Drawing on evidence from qualitative testimonies, self-report survey data (n = 20), and organisational records, we extract key principles and propose a four-pillar framework for institutional allyship: (1) dedicated funding streams, (2) structured mentorship programmes, (3) peer-led training for retention, and (4) equitable representation in decision-making spaces. We argue that institutions adopting this partnership-based model, centred on grassroots expertise, create a viable pathway to racial and ethnic equity across the life sciences, which can build more diverse research cultures and strengthen the epistemic foundations of science.

Analogies are a fundamental part of our cognition and communication. Humans are also a social species with shared cultural repertoires learnt throughout our lifetimes. As such, we expect analogies to enable the learning of complex, novel information by communication that takes advantage of shared cultural information. Here, we demonstrate the plausibility of this proposal and clarify its scope through computational modelling. We first model the individual-level process of learning via analogy with access to a shared repertoire of cultural information, using NK landscapes to represent high-dimensional solution spaces for complex problems. We then analyse a model of population dynamics to consider the conditions under which analogical communication will evolve and be maintained when costly. Our analyses suggest that even when analogy use is costly in terms of both search time and memory constraints, it can nevertheless be advantageous by allowing learners to obtain high-quality solutions more efficiently and more often than those who do not learn via analogy.

Compliance with epidemic prevention norms has been found to be higher in developing regions than in developed regions; however, the nature and underlying mechanisms remain unclear. We propose that socioeconomic development of environments changes the adaptive benefits of fundamental social motives, especially disease avoidance and familial motives, which shape variations in compliance during pandemics. To examine the effects of these motives on the relationship between socioeconomic environments and compliance, we conducted three studies measuring environmental socioeconomic development with the Human Development Index (HDI). Study 1 (with two datasets: N = 43,244, 53 countries; N = 94,657, 71 countries) revealed a stable negative correlation between country-level HDI and compliance, even after controlling disease severity, government responses, and individualism. Studies 2 (an analysis of social media text data; N = 22,588, 31 provinces) and 3 (a large-sample survey; N = 6,122, 31 cities) replicated this correlation in China at the provincial and city levels, and identified disease avoidance and familial motives as mediators. These findings provide evidence for how socioeconomic environments shape compliance during pandemics, highlight the importance of familial motives alongside disease avoidance, and offer insights into tailoring public health strategies across diverse environments.

Inclusive fitness theory predicts that to maximize fitness, individuals should invest in kin, but relatives can also compete for resources. These opposing forces can have opposite effects on fertility, which was further constrained by marital and inheritance norms in traditional Western societies. How available resources influence this balance between helping and competing remains poorly understood. To investigate whether kin help or harm fertility, we used genealogical records from a population registry to study how relatives alive at age 15 were associated with marriage and lifetime number of children in Finnish people born 1752–1879, comparing landowning and landless individuals. Our results show that for focals born to landowning families, both older and younger siblings were associated with a higher age at first marriage, but the maternal grandmother and younger sisters were positively associated with fertility. These associations also differed by the focal’s sex. Among the landless, siblings were also relatively weakly associated with poor marital outcomes, but not with the lifetime number of children. Relatives were not associated with lifetime childlessness. These results suggest that a high level of resources may intensify both positive and negative associations between kin and fertility, possibly through inheritance patterns, competition for resources and childcare help.

Evolutionary models of social inequality suggest that status differentiation can emerge within cooperative networks through sustained asymmetric exchanges between high- and low-value resources, giving rise to patron–client relationships. From a network perspective, such asymmetric relationships take the form of multilayered reciprocity, where different types of resources are exchanged across domains. By analysing multilayered support networks in Matlab, Bangladesh, a region undergoing rapid market integration, we examine how multilayered reciprocity is differently leveraged depending on socioeconomic status and how these exchange patterns reflect an emerging patron–client system in an increasingly market-integrated community. Evidence of multilayered reciprocity is found for salaried households who provide cash and receive household items and/or labour services, but similar patterns are not found for landowners or local political leaders. Further, observed asymmetries in exchange patterns suggest that salaried households may be emerging as new patrons providing sought-after resources (especially cash) to clients with limited access to such resources, replacing a traditional patron–client system based on land ownership and political leadership. Our findings highlight a mechanism by which human cooperation can give rise to new forms of social inequality, offering a framework for extending evolutionary models to explain cooperation and inequality in changing socioeconomic contexts.

Demographic transition, characterised by declines in fertility and mortality, is a global phenomenon associated with modernisation. While typical patterns of fertility decline have been described mainly in Western countries, their applicability to other regions and the underlying mechanisms remain unclear. Using data spanning 1800–2020 from 237 countries and territories, this study identifies two universal pathways in the change in the crude birth rate (births per 1,000 person-years, λ) and period life expectancy at birth (e0). Most countries’ demographic trajectories follow one of these two pathways or shift between them. These pathways define phases governed by different mechanisms. Phase I, conserving λe0, dominated until the mid-20th century and was characterised by high child mortality and steady population growth. By contrast, Phase II, conserving λexp(e0/17), has prevailed since 1950 and is marked by low child mortality and steady growth in GDP per capita. A theoretical model considering the trade-off between reproduction and education elucidates the transition between these phases. The transition to Phase II is accelerated by declining educational costs, rising social mobility, and cultural transmission linked to modernisation and Westernisation. This study demonstrates quantitative regularities between fertility and longevity during demographic transition and provides a theoretical lens for their underlying mechanisms.

This article examines how racialised memes circulating on X revive scientific racism, demonstrating that hybrid formats reconfigure biological essentialisation within contemporary digital culture. Using a corpus of 68 viral items and 4 case studies, our analysis applies Shifman’s content–form–stance model, informed by cognitive psychology. We show that these memes adopt common scientific conventions while relying on visual polarisation, whereby rapid perceptual contrasts stand in for arguments. Familiar templates, reinforced by selective algorithmic amplification, create a sense of perceptual legitimacy through fast categorisation and pre-attentive processing. We also trace how these cognitive shortcuts provide the basis for a regime of racialisation tailored to digitally immersed male audiences, producing gendered behavioural stereotypes and disappearance anxieties. A further pattern is the recoding of older racial hierarchies into neutral-sounding language of competence, allowing these ideas to travel across racialist, masculinist, techno-elitist, and anti-DEI (Diversity, Equity, Inclusion) communities. In this environment, memes work as micro-infrastructures of classification that align claims to objectivity with affect and platform incentives, making inequality appear natural and necessary. We conclude that effective critique must meet these images on their own terrain, with a pedagogy of the gaze that teaches publics how to recognise and challenge persuasion in meme-driven spaces.

Humans selected hundreds of dog breeds, which show different levels of dependence on human-provided cues. While robust grouping factors, such as genetic relatedness-based ancestry and function-based cooperativeness, denote useful frameworks to analyse behavioural differences in dogs, they may lack fine enough resolution for a more detail-oriented understanding of human-oriented behaviours. Here, we focused on behaviour-based analysis of the characteristic reliance of dog breeds on human behaviour. We utilized N = 187 adult purebred dogs’ performance in a social learning task. Dogs observed a human demonstrator performing a detour around a transparent obstacle. With Principal Component Analysis, we established two behavioural dimensions: detour latency improvement and watching the demonstrator. Then, with K-means cluster analysis, we found six categories, based on different combinations of lower/higher values of the two dimensions. The clusters showed significant differences in both behavioural dimensions, highlighting attention combined with improvement types among purebred working dogs. Some extremes showed excellent improvement with only minimal attention to the human demonstrator, while others watched the human without improving their performance. We conclude that by finer analysis, it is possible to set up a dependence-based framework for the understanding of behavioural differences among dogs that go beyond functional breed-selection and ancestry.

Primate eyes vary strikingly in pigmentation, yet the drivers of said variation are strongly debated. Recent revisions of the cooperative eye hypothesis propose that the human eye’s sclera evolved to enhance gaze communication specifically under challenging conditions of visibility. We tested this idea under ecologically realistic conditions by presenting observers with a live model wearing contact lenses that simulated either a human-like or a chimpanzee-like eye. At a university lab, observers judged gaze direction at different viewing distances and lighting levels. We found no overall difference in efficacy of different eye types. Contrary to expectations, chimpanzee-like eyes outperformed human-like eyes in dim lighting and close-viewing conditions. Human-like eyes yielded the highest accuracy under bright, far-viewing conditions, consistent with a long-distance signalling advantage. Our results demonstrate that ecological visual constraints shape the potential informativeness of distinct ocular configurations. We hypothesize that species-typical eye appearances may be tuned to their species-typical visual ecology.

Most research on social media considers them as supports for information transmission, explaining online success (and pathologies) by focusing on consumers’ biases and interests. This article takes a different perspective, applying ideas from an ecological approach to culture. Success online depends both on the intrinsic appeal of content to receivers and on how well content serves producers’ strategic goals within the constraints and affordances of specific platforms. These goals include reputation management, coalition building and identity management, and coordination or participation in shared activities. Transmission is often a by-product of these motivations, and replication fidelity plays a limited role compared with transformations that adapt content to local incentives. Finally, the article suggests that platforms and communities can be understood as distinct niches, each characterised by different audience structures, affordances, metrics, and algorithmic pressures. This perspective reframes persistent debates on social media dynamics, including misinformation, radicalisation and polarisation, and the reasons behind online success.

This article analyses the evolutionary genesis of the aldehyde dehydrogenase 2 mutation in East Asia through the lenses of institutional economics. While biology typically frames the absence of alcohol tolerance as a metabolic defect, this paper proposes the concept of functional redundancy. We argue that the specific social organization of rice societies – characterized by deep material interdependence – rendered alcohol consumption superfluous as an instrument for trust-building and social cohesion. The resulting genetic path dependency illustrates how historical institutional frameworks continue to shape the biological constitution of modern populations.

Two research branches in evolutionary psychology can make similar predictions about treatment expectations in contexts of conflict of interest, where, for those involved, costs and benefits are at stake. Recalibrational Theory of Anger suggests that evolved psychological mechanisms operate at the cognitive level and regulate human behaviour. The Dark Triad Personality posits that traits of Machiavellianism, Narcissism, and Psychopathy confer adaptive advantages, leading individuals to prioritize their interests over those of others. This study aimed to conduct a direct replication of a previously experimental study on anger in conflict-of-interest situations in a Brazilian sample (Replication Analysis) and investigated whether dark triad traits predict the magnitude of anger in conflict-of-interest situations (Extension Analysis). The Replication Analysis consistently replicated previous findings, with effect sizes from moderate to large magnitudes. The Extension Analysis revealed that only Narcissism was a significant predictor when victims were intentionally targeted by offenders. While the Recalibrational Theory of Anger predictions were largely confirmed, the dark triad personality traits, except for Narcissism, were generally poor predictors of anger magnitude. The results suggest that the universality of the information processing is robust and is little influenced by antisocial personality characteristics.

Current debates concerning the use of digital technology often focus on privacy, yet privacy attitudes and behaviour are remarkably under-theorized, and relatively little empirical research has investigated privacy beyond the realm of digital communications. Building on evolutionary scholarship on information exchange, we outline a theoretical model in which cultural concepts of privacy reflect the workings of evolved psychological mechanisms that aim to regulate others’ access to fitness-relevant information towards adaptive ends. Results of two initial U.S. vignette studies distributed via Prolific (n = 425, 120) support the core predictions of this model, suggesting that people may have implicit and unstated assumptions regarding how information spreads in social environments. Specifically, participants’ privacy evaluations were predicted by whether information was intentionally acquired, the extent to which information was transmitted, and an individual’s position in an information transfer event. Importantly, how information was acquired and the nature of its transmission constituted independent but interacting influences on privacy perceptions. Additionally, results suggest the location within shared social networks of the individual to whom information is transmitted is used as a proxy for the potential costs of dissemination.