Sex-specific division of labour and the associated use of different subsistence techniques by males (e.g., hunting) and females (e.g., gathering) has played an important role in shaping human societies. Skills needed in adulthood are practiced in play during childhood and object play has been proposed to foster tool-use skills necessary for adult subsistence techniques. Here, we investigated sex differences in the ontogeny of object play in Tsimane children in Bolivia to understand its potential role in shaping gender-specific adult roles. We used observational data (>80,000 scan samples) from nine Tsimane communities collected between 2002 and 2007. We analysed age and sex differences in general play, object play and object types. Our results show that both general play and object play peaked in early to middle childhood (3.5-7.5 years of age), with boys spending more time playing. Moreover, boys engaged more with objects related to male-specific roles (e.g., hunting tools), while girls played more with objects related to female-specific roles (e.g., cooking tools). Our findings suggest that object play serves as an adaptive, culturally-embedded pathway to develop gender-specific adult skills. Studying developmental patterns of object play across human cultures enriches our understanding of the evolutionary contexts shaping divisions of labour.

Recent years have seen growing interest in applying the Evolutionary Transitions in Individuality (ETI) framework to human sociocultural evolution. Proponents argue that human societies exhibit features—such as multilevel organisation, cooperation, and division of labour—sufficiently analogous to biological ETIs to warrant theoretical extension. This paper critically assesses such claims and argues that they rest on a fundamental misapplication of the ETI framework. Drawing on recent work in cultural evolution, I show that sociocultural systems typically lack the core conditions required for an ETI, including autonomous reproduction at the group level and the operation of natural selection in the reproductive mode. Attempts to relax these criteria risk undermining the coherence of the framework itself. I conclude that while the broader MET framework may still have value for understanding sociocultural change, the specific explanatory structure of ETI theory does not transfer.

The manosphere is a collection of online antifeminist men’s groups whose ideologies often invoke Darwinian principles and evolutionary psychological research. In the present study, we reveal that the manosphere generates its own untested and speculative evolutionary hypotheses, or “just-so stories”, about men, women, and society. This is a unique phenomenon, where lay (i.e., non-expert) individuals creatively employ evolutionary reasoning to explain phenomena in accordance with their particular worldview. We thus assembled the first dataset of lay evolutionary just-so stories extracted from manosphere content (n = 102). Through qualitative analysis, we highlight the particularity of the manosphere’s lay evolutionism. It is a collective bottom-up endeavor, which often leads to practical advice and exhibits a male gender bias. We further show that 83.3% of manosphere just-so stories pertain to sex differences, and that only 36.3% explicitly signal that they are speculative. Given this evidence that lay communities collectively engage in evolutionary hypothesizing, we reflect on implications for evolutionary scholars and for the field as a whole, in terms of ethics and public image. Lastly, we issue a call for renewed discussion and reflection on evolutionary hypothesizing, a central yet somewhat neglected feature of evolutionary behavioral science.

We investigate and compare the evolution of two aspects of culture, languages and weaving technologies, amongst the Kra-Dai (Tai-Kadai) peoples of southwest China and southeast Asia, using Bayesian Markov-Chain Monte Carlo methods to uncover phylogenies. The results show that languages and looms evolved in related but different ways, and bring some new insights into the diaspora of the Kra-Dai speakers across southeast Asia. We found that the languages and looms used by Hlai speakers of Hainan are outgroups in both linguistic and loom phylogenies, and that the looms used by speakers of closely related languages tend to belong to similar types. However, we also found discrepancies at a deep level between linguistic subgroups and loom types, in particular among widely dispersed South-Western Tai speakers, and we discuss possible reasons for this.