As a means for both the construction and communication of social identity in diverse human groups worldwide, objects of personal adornment can help to explain some prehistoric lifeways and beliefs. This study examines the materials and manufacture traces of whole and fragmentary pendants found in association with human burials at the Early Period (c. 4200 cal BC–cal AD 250) Ortiz site in south-western Puerto Rico. Using data from microscopy, elemental analysis and petrography, the authors propose that these pendants were a tangible manifestation of group identity, rooted in a sense of localised belonging, which persisted over almost a millennium.

The blowgun is a weapon that employs the force of breath for expelling a projectile and has been traditionally used for hunting and (occasionally) war. The use of blowguns extends to ancient times and is advantageous in dense-forest areas of South America and South East Asia. A classification system of blowgun types introduced in 1948 for South America is extended here. We assembled a global database that includes collection data and ethnographic accounts of blowgun types and other related features that were linked to available linguistic information. Our analyses show that geography explains the distribution of blowgun types to some degree, but within regions of the world it is possible to identify cultural connections. Darts are by far the most used projectiles and in combination with toxins (e.g. curare), these weapons reach their highest potential. A case study on the use of blowguns in groups of Austronesian language speakers shows clade-specific preferences across the tree. Our comprehensive database provides a general overview of large-scale patterns and suggests that incorporation of other related data (e.g. sights, mouthpieces, quivers) would enhance the understanding of fine-scale cultural patterns.

How does information infrastructure shape long-term cultural evolution? Using over four centuries of professional game records from the game of Go, this study explores how strategic dynamics in opening moves reflect historical shifts in the ‘infostructure’ of skilled Go players. Drawing from recent work on how population size, AI, and information technology affect cultural evolution and innovation dynamics, I analyze over 118,000 games using measures of cultural diversity, divergence, and player network composition. The results show distinct eras of collective innovation and homogenization, including an early 20th-century explosion of novel opening strategies, a Cold-War-era die-off, and a recent increase in evolutionary tempo with the arrival of the internet and superhuman AI programmes like AlphaGo. Player population size shows an inverse-U relationship with opening move diversity, and a recent decline in strategic diversity has accompanied a shift in the player network, from many small subgroups to a few large ones. Surprisingly, the influence of AI has produced only a modest, short-lived disruption in the distribution of opening moves, suggesting convergence between humans and AI and incremental rather than revolutionary cultural change.

Humans often participate in physically harmful and demanding rituals with no apparent material benefits. Although such behaviours have traditionally been explained using the lens of costly signalling theory, we question whether the canonical theory can be applied to the case of human cooperative signals and introduce a modification of this theory based on differential benefit estimation. We propose that along with cooperative benefits, committed members also believe in supernaturally induced benefits, which motivate participation in extreme rituals and stabilize their effects on cooperative assortment. Using Thaipusam Kavadi as a prototypical costly ritual, Tamil (ingroup) and Christian (outgroup) participants in Mauritius (N = 369) assessed the cost and benefits of Kavadi participation or hiking. We found that ingroup participants estimated material costs as larger than outgroups, physical costs as lower, and benefits as larger. These findings suggest that estimated costs may vary by modality and cultural expectations (e.g. Kavadi participants are not supposed to display pain), while supernaturally induced benefits were consistently reported as larger by ingroups compared to outgroups. We conclude that differential estimation of ritual benefits, not costs, are key to the persistence of extreme rituals and their function in the assortment of committed members, underscoring the role of differential estimation in the cognitive computation of signal utility.