The dependence of hunter-gatherers on local net primary production (NPP) to provide food played a major role in shaping long-term human population dynamics. Observations of contemporary hunter-gatherers have shown an overall correlation between population density and annual NPP but with a 1,000-fold variation in population density per unit NPP that remains unexplained. Here, we build a process-based hunter-gatherer population model embedded within a global terrestrial biosphere model, which explicitly addresses the extraction of NPP through dynamically allocated hunting and gathering activities. The emergent results reveal a strong, previously unrecognized effect of seasonality on population density via diet composition, whereby hunter-gatherers consume high fractions of meat in regions where growing seasons are short, leading to greatly reduced population density due to trophic inefficiency. This seasonal carnivory bottleneck largely explains the wide variation in population density per unit NPP and questions the prevailing usage of annual NPP as the proxy of carrying capacity for ancient humans. Our process-based approach has the potential to greatly refine our understanding of dynamical responses of ancient human populations to past environmental changes.

狩猎采集者对当地净初级生产 (NPP) 提供食物的依赖在塑造长期人口动态方面发挥了重要作用。对当代狩猎采集者的观察表明，人口密度和年度 NPP 之间存在总体相关性，但每单位 NPP 的人口密度变化 1,000 倍，这仍然无法解释。在这里，我们构建了一个嵌入全球陆地生物圈模型中的基于过程的狩猎采集人口模型，该模型明确解决了通过动态分配的狩猎和采集活动来提取 NPP。新出现的结果揭示了季节性通过饮食构成对人口密度的强烈的、以前未被认识到的影响，即狩猎采集者在生长季节较短的地区消耗大量肉类，由于营养效率低下，导致人口密度大大降低。这种季节性的食肉动物瓶颈在很大程度上解释了每单位 NPP 人口密度的巨大差异，并质疑每年 NPP 作为古代人类承载能力的代表的普遍使用。我们基于过程的方法有可能极大地改善我们对古代人类对过去环境变化的动态反应的理解。