Cecilia Padilla-Iglesias

Through a hunting and gathering lifestyle, humans have managed to thrive across all terrestrial ecosystems. A key adaptive feature enabling this ecological success is the ability of hunter-gatherer societies to maintain high levels of genetic diversity despite ecological and demographic shocks, but the mechanisms underlying this resilience are poorly understood. Here, we integrate genomic, demographic, mobility, and ethnographic data from two Central African hunter-gatherer populations to show that genetic diversity emerges from interacting effects of population size, mobility, and cultural norms governing marriage. We first demonstrate direct selection against background homozygosity: Even modest increases in runs of homozygosity, in the near absence of close-kin marriages, are associated with reduced reproductive success. Despite regional differences in effective population size, clustering of relatives, sedentism, and exogamy rules, overall levels of homozygosity are similarly low in both populations. These shared genetic outcomes are achieved through distinct strategies: In one region, strict exogamy combined with high lifetime mobility limits local relatedness, whereas in the other, more relaxed exogamy norms are offset by increased male mate-search distances that reduce offspring homozygosity. Together, our results show that human populations flexibly adjust mobility and social norms to demographic constraints to preserve genetic diversity and avoid fitness costs, revealing culture as a central component of human adaptation.

Measuring technological complexity across species, as well as across temporal and spatial scales, is an ongoing challenge among authors who work on primatological, archaeological, and/or ethnographic questions. Researchers in these individual fields have developed a number of innovative ways of approaching this issue that reflect the specific affordances of their data with a known set of limitations. However, comparability between these approaches is often difficult. One such field-specific approach is the techno-unit method of Oswalt et al. (1976), which has had a massive impact on our interpretation of ethnographic technology over the fifty years since its publication. Nevertheless, this method has issues with its compression of variability and the different pathways to “complexity”. Here, we review a number of different ways technological complexity has been measured in non-human primates, the archaeological record, and modern human foragers, in order to identify the relative strengths and weaknesses of each. We suggest that the approach deployed in any given study should continue to follow the data and research questions under consideration, but that we lack an easily-applicable method that allows explicit comparisons between fields of study. In this context, we introduce the Tool Systems Approach as one possible way of doing so, which decomposes tool manufacture into its constituent steps ( i.e. , Tool Systems Total) and discrete forms of action ( i.e. , Total Discrete Actions). We apply the approach to a number of different technologies across the three fields, to explore the practicalities of its application, as well as its limitations. Plotting these different technologies with regards to their maximum complexity through time reveals trends that may map onto important changes in cognitive evolution, which are also reflected in ever-growing variability in the complexity of individual artefacts. The ramifications for the study of technological complexity as a whole are discussed.

Through a hunting and gathering lifestyle, humans have managed to thrive across all terrestrial ecosystems. A key adaptive feature enabling this ecological success is the ability of hunter-gatherer societies to maintain high levels of genetic diversity despite ecological and demographic shocks, but the mechanisms underlying this resilience are poorly understood. Here we integrate genomic, demographic, mobility and ethnographic data from two Central African hunter-gatherer populations to show that genetic diversity emerges from interacting effects of population size, mobility and cultural norms governing marriage. We first demonstrate direct selection against background homozygosity: even modest increases in runs of homozygosity, in the near absence of close-kin marriage, are associated with reduced reproductive success. Despite regional differences in effective population size, clustering of relatives, sedentism and exogamy rules, overall levels of homozygosity are similarly low in both populations. These shared genetic outcomes are achieved through distinct strategies: in one region, strict exogamy combined with high lifetime mobility limits local relatedness, whereas in the other, more relaxed exogamy norms are offset by increased male mate-search distances that reduce offspring homozygosity. Together, our results show that human populations flexibly adjust mobility and social norms to demographic constraints to preserve genetic diversity and avoid fitness costs, revealing culture as a central component of human adaptation.

This study investigates how different types of social interactions are reflected in the archaeological record, specifically analyzing the extent to which artifacts can serve as proxies for past human interactions. Utilizing the ArchMatNet agent-based model (ABM), we simulate the social behaviors of small-scale communities and their material culture production, enabling a comparative analysis of social and material culture networks. The networks were compared using graph correlation and the quadratic assignment procedure (QAP), the effects of model parameters on correlation strength were analyzed using generalized additive models (GAMs), and underlying network structures were compared using Exponential Random Graph Models (ERGMs). Our results demonstrate strong correlations between social interaction networks and material culture networks, particularly when significant variation is present in material culture traits. The study also demonstrates that some circumstances, such as low material culture variation, can present poor correlations. Thus, there is some caution for the application of network methods to archaeological data. Key factors influencing these correlations include the frequency of interaction, learning strategies, and the visibility of cultural traits. The study underscores the complexity of using material culture as a proxy for social networks, emphasizing the importance of empirical validation and careful consideration of network structures. The findings highlight the potential of ABMs as a methodological tool in archaeology to explore and validate methodological tools.

Background: Population structure analysis is crucial for evolutionary research and medical genomics. Clustering methods, broadly categorized as model-based (e.g. ADMIXTURE) or non-model-based (e.g. SCOPE), differ in their methodology and computational efficiency. Recently, fastmixture , a model-based approach, has improved scalability and performance, while replicate alignment tools, such as Clumppling, extend previous methods by also aligning the modes across K values. However, all the existing tools are standalone and generate numerous untracked text files, as well as offering limited plot customisability. Results: We introduce an R package, tidygenclust , which brings the functionalities of the original ADMIXTURE, fastmixture and Clumppling software into R, enabling a streamlined and integrated workflow. By integrating with tidypopgen , a package designed to handle large SNP datasets, these new tools maintain metadata, simplify data handling, and produce results as customisable ggplot2 objects for flexible visualisation. Conclusions: The R package tidygenclust advances population genetic analysis by combining computational efficiency with reproducible workflows and user-friendly plotting. The source code and instructions can be accessed on https://github.com/EvolEcolGroup/tidygenclust .

Summary: The mechanisms driving the spatial organisation of early human societies in Africa are typically addressed through climate variables ^1-3 . However, genetic and archaeological studies have also suggested diseases as a major source of selection in the Pleistocene. Here, we explore whether P. falciparum -induced malaria, a major world disease, drove habitat choice in human societies between 74 and 5 thousand years ago (kya). Using species distribution models of three main mosquito complexes with palaeoclimatic reconstructions and combining the results with epidemiological information, we estimated an index of malaria transmission risk in sub-Saharan Africa through time. We then correlated it with an independent reconstruction of the human niche over the same time period and region. Our results show that humans strongly avoided or were unsuccessful in potential malaria hotspots. The effects of these choices shaped human demography for the last 74 kya, and likely much earlier, by fragmenting human societies over time and contributing to the formation of modern population structure. Our results highlight the importance of considering disease distributions when modelling estimates of past human demography, demonstrating that factors beyond climate underlay patterns of human habitat choice, exchange, and dispersal. Sentence summary: Malaria shaped human habitat choice, exchange, and dispersal since the late Pleistocene in sub-Saharan Africa.

Summary: A growing body of evidence has challenged the traditional assumption of a single-region origin for Homo sapiens , suggesting instead that our species originated from multiple geographically distinct populations in Africa, which intermittently exchanged genes and culture. However, our understanding of how this Pan-African metapopulation would have evolved through time is still limited. Furthermore, the drivers of such changes are uncertain, and quantitative models of the respective contributions of different African regions are lacking. Here we provide a complete reconstruction of the meta-population dynamics over the last 200,000 years by quantitatively integrating an ecological niche model, informed by archaeological sites, within a spatially explicit population genetic framework. The inferred metapopulation dynamics account for the divergence among all available contemporary and ancient genomes of African hunter-gatherers used to calibrate the model. In addition, it also accurately predicts the patterns of craniometric diversification across the continent from the Late Middle Pleistocene to the present. Finally, we show how the climate-driven changes in population sizes and connectivity are congruent with major patterns of archaeological and phenotypic diversification over the last 200,000 years across the African continent.

Gunnink et al. have stated that our study fails to provide evidence of a deep history of cultural and linguistic evolution among Central African hunter-gatherers (CAHGs). Whilst in our original study we discussed in detail the evolutionary processes possibly accounting for the distribution of musical instruments and related terms among CAHG, perhaps we were not explicit enough in the results section addressing lexicon. This appears to have led Gunnink et al. to misinterpret our aims, methodology, and results. Furthermore, they offer a highly unparsimonious alternative to our views that requires several unlikely and independent events simultaneously, and perhaps most importantly, they fail to acknowledge that all farming populations and their languages shared a hunter-gatherer ancestor with extant CAHGs only a few thousand years ago.

Mobility lies at the adaptive core of the hunter-gatherer foraging niche, and has shaped the cultural and genetic evolution of our species. Yet, the specific drivers and consequences of mobility are still debated. Here we analyse the lifetime mobility patterns of 776 Mbendjele BaYaka hunter-gatherers from five regions in the northern Republic of Congo, revealing pronounced gender differences in spatial behaviour. While men expand their spatial ranges from adolescence to adulthood, women’s ranges remain stable. We find evidence for a sexual division of labour underpinning these patterns, with men’s greater mobility driven by subsistence activities such as hunting or exploratory trips away from camps, and women’s mobility mostly driven by gathering closer to their residential location. Our findings challenge traditional assumptions of patrilocality, suggesting that men travel further due to their spatial separation from kin. Larger spatial ranges are associated with increased reproductive success for both genders, suggesting adaptive benefits of mobility in accessing resources, social networks, and potential mates. By linking individual behaviors to broader movement dynamics, our study deepens our understanding of gendered mobility in humans and highlights its significance to social structuring in our species and its evolutionary consequences.

Although cumulative culture is a hallmark of hominin evolution, its origins can be traced back to our common ancestor with chimpanzees. Here, we investigated the evolutionary origins of chimpanzee cumulative culture and why it remained incipient. To trace cultural transmission among the four chimpanzee subspecies, we compared population networks based on genetic markers of recent migration and shared cultural traits. We show that limited levels of group connectivity favored the emergence of a few instances of cumulative culture in chimpanzees. As in humans, cultural complexification likely happened in steps, with transmission between populations, incremental changes, and repurposing of technologies. We propose that divergence in social patterns led to increased mobility between groups in the genus Homo , resulting in irreversible dependence on cultural exchange and complexification.