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.
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.
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.
