Transmission networks of long-term and short-term knowledge in a foraging society.

Cultural transmission across generations is key to cumulative cultural evolution. While several mechanisms-such as vertical, horizontal, and oblique transmission-have been studied for decades, how these mechanisms change across the life course, beyond childhood, remains unclear. Furthermore, it is under-explored whether different mechanisms apply to distinct learning processes: long-term learning-where individuals invest time and effort to acquire skills-and short-term learning-where individuals share information of immediate use. To investigate the network structure of these two types of knowledge transmission-long-term learning of foraging skills and short-term learning of food location information-we present social network data (1,633 nominations) collected from all inhabitants (aged 4 to 75) of a BaYaka community in the Republic of the Congo. Applying latent network models that estimate and adjust for measurement biases typical to self-reported data, we find that the demographic structure of a population-age distribution, sex, kinship, and marriage-shapes the dynamics of community-wide knowledge transmission. Foraging skills are transmitted within smaller, sparser networks with limited reciprocity, whereas food location information is exchanged more widely and reciprocally among peers. Both long-term and short-term knowledge transmission extend into adulthood, with adults learning from older adults, peers, and marital partners, and sharing knowledge with younger generations. Crucially, individuals tend to report more accurately about the partners with whom they shared knowledge than about those from whom they received knowledge. Our findings provide important empirical evidence on how community-wide cultural transmission is structured by demography and perception, and how these factors operate across different learning processes in a contemporary foraging society.