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 to high-resolution paleoclimate records. 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 toward 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 500–200 ka, followed by progressive decoupling, particularly after 50 ka, when cultural transmission increasingly follows its own dynamics.
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 sclera pigmentation elicits more distress or aversive reactions, consistent with the hypothesis that eye coloration serves as a signal of underlying temperament. Contrary to predictions, subjects did not exhibit differential behavioural responses to light-sclera, dark-sclera, 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 signaling 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.
Abstract 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. 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 aging 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 Flinders 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.
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.
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.
Hereditarianism is a pseudoscientific view relying on the assumption that varying environmental forces selected for intelligence differentially on ancestral populations. As human groups migrated to different areas worldwide, hereditarians argue, novel ecological pressures necessitated different degrees of innovation. Hereditarians use a mixture of genome-wide association studies, intelligence quotient metrics, and arguments stemming from evolutionary psychology to defend these positions. Yet despite evidence from population genetics refuting hereditarianism, these authors also fail to engage effectively with the social sciences. Specifically, hereditarians consistently ignore or misrepresent the social brain hypothesis, which proposes that sociality – and specifically, pressures to cooperate or compete in different circumstances with conspecifics – was the primary selective pressure for cultural innovation, brain size, and different forms of human intelligence more broadly. The purpose of this article is to evaluate hereditarianism from the views of human behavioural ecology, cultural evolutionary studies, and current understanding of the relationship between forms of capital and reproductive success to show that arguments for hereditarianism are poor and wilfully ignore established research in the social sciences. The pressure to succeed socially drives innovation, and refusal to confront this reality leads hereditarians to make both wrong and unethical claims about human nature.
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.
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.
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.
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.
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 strength of 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 stronger gender norms, and men preferred larger age gaps between themselves and their partner in countries with stronger gender norms. These relationships were not replicated when using cultural tightness as a measure of the strength 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.
In this paper, we chart an emerging academic terrain: cultural evolution of the arts, which is a theory-driven exploration of artistic dynamics, often done with large datasets of music, literature, movies, paintings, or games. This field has grown at the intersection of cultural evolution theory and several academic fields: computational humanities, anthropology, network science, and others, and poses interesting challenges for each of them. What constitutes artistic transmission in the first place? Is it possible to find recurring patterns in artistic history - and how much data is needed for that? What makes the evolution of the arts different from the evolution of other forms of knowledge? We discuss all these problems in this paper. Additionally, we perform a bibliometric analysis of this field and explore a co-citation network of the works on artistic evolution. Finally, we highlight major challenges for this field in the future, as the arts are rapidly evolving in the digital age.
The menopausal transition is a pivotal period in the female reproductive lifespan with potential consequences for long-term health and quality of life. Latine adults in the US often experience menopause earlier and have more frequent vasomotor symptoms (VMS) compared to non-Latine White adults. These differences may be partly attributed to early-life adversity, such as adverse childhood experiences (ACEs), which may alter energy allocation towards faster maturation and reproductive efforts, potentially shaping variations in menopausal experiences. Using data from a sample of primarily immigrant, Mexican adults living in an agricultural region in California (N = 459), we evaluated the extent to which ACEs were associated with age at menopause and VMS (hot flashes and night sweats). In adjusted models, having ACEs (vs. none) was significantly associated with experiencing hot flashes (1-3 ACEs: odds ratio [OR] = 2.50, 95% confidence interval [CI]: 1.57-4.00; 4+ ACEs: OR = 2.51, 95% CI: 1.49-4.24) and night sweats (1-3 ACEs: OR = 1.67, 95% CI: 1.02-2.76; 4+ ACEs: OR = 2.36, 95% CI: 1.37-4.06) but not earlier menopause (e.g., 1-3 ACEs: HR = 0.85, 95% CI: 0.59-1.21). These results suggest that the sequelae of childhood adversity may influence menopausal symptom burden.
Explaining how cooperation evolves is a major research programme in the biological and social sciences. In this study, we tested evolutionary theories of human cooperation in a real-world social dilemma: joint liability microfinance, in which groups of borrowers must cooperate to successfully repay a shared loan. We used pre-registered Bayesian multilevel models to estimate meta-analytic associations between loan repayment and proxies of four evolutionary mechanisms proposed to support cooperation: relatedness, reciprocity, partner choice, and punishment. A systematic search of the microfinance literature yielded 73 effect estimates for 11 proxies of evolutionary mechanisms analysed in 11 separate meta-analyses. Punishment-based variables showed the strongest positive meta-analytic associations with loan repayment, with mixed results for other mechanisms. However, estimates varied widely in their certainty, with generally high levels of between-study heterogeneity. Our results provide some evidence for evolutionary mechanisms supporting cooperation in real-world contexts, but also indicate there are non-generalisable findings and/or reproducibility issues in the microfinance literature.
Patterns of social organisation and gender differentiation in past societies are difficult to reconstruct from material culture data alone, are prone to modern interpretation biases, and often remain subjects of controversy. An important aspect of social organisation is patterns of post-marital residence, for example, matrilocality and patrilocality. To date, archaeological studies have recognised mostly patrilocal communities, with rare contested exceptions that were considered 'outliers' to the established rule of patrilocality. The advent of ancient DNA analysis has made it possible to evaluate past social structures from a genetic perspective as well, with the majority of ancient DNA studies identifying patrilocal communities and highlighting genetic patriline connections. Recently, three studies reported genetic evidence for matrilocality and genetic matriline connections across broad geographical and temporal scales. Here, we draw on these three studies to explore past social organisation forms in light of new evidence and reconsider preconceptions that continue to endure over time.
Indirect reciprocity is a reputation-based mechanism proposed to explain the evolution of human cooperation. Theoretical models demonstrated that the use of both first-order information (i.e., whether an evaluation target cooperated) and second-order information (i.e. the reputation of an interaction partner of the evaluation target) is critical for the evolution of cooperation. However, empirical findings on the use of second-order information have been mixed. Drawing upon the literature on group-bounded indirect reciprocity, we tested the hypothesis that individuals would be more sensitive to second-order information when evaluating ingroup interactions, compared to when evaluating outgroup interactions. We conducted a preregistered online experiment (N = 604), where we independently manipulated group membership (ingroup vs. outgroup), target behaviour (cooperation vs. defection), and recipient reputation (good vs. bad). We found that donors who defected against good recipients were rated more negatively than those who defected against bad recipients, indicating the use of second-order information. Partly consistently with our hypothesis, when individuals evaluated coopering donors, second-order information influenced reputation for ingroup donor-recipient interactions more than for outgroup donor-recipient interactions. Nevertheless, individuals readily used second-order information, whether or not they evaluated ingroup or outgroup donor-recipient interactions.
Research focusing on first impression formation based on facial stimuli lacks a conclusion on whether there is a cross-cultural agreement and how deeply it has proliferated across distant populations. Social media may play an important role in the level of cross-cultural agreement as they provide us with overwhelming numbers of visual stimuli, including faces. Sharing social media aesthetics, their users may utilise facial cues congruently. We asked participants from seven distant, ethnically variable countries from five continents to rate facial attractiveness, trustworthiness and dominance of a single ethnically invariant facial sample (N = 195, 106 women, M_Age = 23.23), also accounting for their self-reported social media use intensity and socioeconomic background. We expected the agreement between cultures to be better for participants who reported a higher intensity of social media use. Instead, we observed substantial cross-cultural agreement, especially for attractiveness and trustworthiness, regardless of the self-reported social media use intensity. However, the samples of participants from similar cultural backgrounds (same countries) agreed more. We also see substantial agreement in facial cue utilisation. In line with previous research, the distinctiveness of facial shape affects perceived attractiveness congruently across cultures. Despite the relatively small age range, age positively affects ascribed dominance.
Tooth wear constrains feeding efficiency, life history, and survival in mammals, yet its progression in wild populations remains poorly understood. We use high-resolution 3D analysis to quantify occlusal tissue loss over a 3-year period in the upper premolars and molars (P3-M3; n = 70) of wild baboons (Papio). Our sample includes olive baboons (P. anubis) and naturally occurring olive-hamadryas hybrids (P. anubis × P. hamadryas) from Awash National Park, Ethiopia. We calculate mean values for tooth types, visualize tissue loss across occlusal surfaces, and compare individuals by age, sex, and hybrid status. Molars lost tissue faster than premolars (molars: 0.13 mm3/mm2/year; premolars: 0.08 mm3/mm2/year), with the bulk of wear shifting from lingual to buccal cusps in older individuals. The rate of tissue loss did not increase with age, despite greater dentine exposure. There was no clear difference in wear patterns relating to sex or hybrid status, although subtle sex-related differences in P3 wear patterns were observed. These findings demonstrate the adaptive significance of gradual tissue loss in preserving dental function and establish comparative baselines for interpreting wear patterns in extinct primates, where dental remains often provide the primary record of diet and behaviour.
Religious service attendance is associated with better well-being, but observational associations do not establish causation. We analyse six annual waves of the New Zealand Attitudes and Values Study (N = 46,377) to estimate causal effects of monthly attendance on 24 well-being indicators using target trial emulation. Deterministic 'make everyone attend' contrasts fail positivity: only 2–3% of non-attenders initiate attendance per year. We therefore estimate supported stochastic interventions ($\delta = 5$) among baseline non-attenders (N = 38,477) using a sequentially doubly robust estimator with cross-validated machine learning. Effects are selective: small gains appear in meaning and purpose, forgiveness, and sexual satisfaction, with little movement in somatic health, psychological distress, social belonging, or perceived social support. A comparison exposure (+1 hour per week socialising with others) does not reproduce the pattern. We interpret the selective pattern through a prominent cooperative account of religion: gains concentrate in coordination-relevant domains rather than in direct health pathways.
