Multifactorial drivers of spatial variation in human body form across modern China.

Human body form reveals cumulative effects of ecological and socio-cultural factors. China provides an exceptional context for investigating these multifactorial influences, not only because of its extensive geographic and cultural diversity, but also because recent decades have been marked by rapid economic development, urbanisation, migration, and the population-level trauma of the Great Famine. Using anthropometric data from > 90,000 adults across 213 geo-referenced groups from mid-late-20th and early-21st centuries, we applied Bayesian hierarchical models to assess the roles of climate, altitude, urban-rural status, linguistic affiliation, and time in shaping stature, body mass, relative sitting height, and body breadth. Substantial secular increases in body size, particularly body mass, were associated with recent economic development and urbanisation. Males and females responded similarly across environmental and temporal gradients, indicating limited sex-based differentiation. Northern groups remained taller and heavier than their southern counterparts. Notably, maximum precipitation, not temperature, emerged as the strongest climatic correlate, likely reflecting indirect effects of subsistence and disease burden. Relative sitting height increased modestly over time, while relative body breadth showed a stable east-west gradient, potentially shaped by population history. Regional exceptions, including highland Tibetan and Sherpa populations and northeastern groups, along with widening divergence among linguistic subgroups, underscore the persistent roles of migration, developmental constraints and potential high-altitude adaptation. These findings show that recent changes in human body form in China cannot be understood as simple outcomes of modernisation alone, but instead reflect layered interactions among ecology, population history, socio-economic transformation, and cohort-specific historical experience.