ABSTRACT

Birth seasonality is a phenomenon whereby populations can be characterized by a single month or season in which births peak. While non-human animal research suggests that seasonal birth-pulses are related to variation in climate and local energy availability, social scientists debate the mechanisms responsible for it in humans. Here we investigate the role of precipitation, temperature, and energy availability on seasonal conception and birth pulses using a historical dataset from the Baja California peninsula – a hot, arid desert that experiences seasonal climatic fluctuations associated with the North American Monsoon. Analyses suggest that 1) local energy availability had a negative relationship with conception pulses; and 2) birth pulses had a positive relationship with local energy availability and a negative relationship with temperature. Taken together, our analyses suggest that women timed conceptions when local energy availability was lowest (challenging expectations of conception rates as simply reflecting ecological influences on female fecundity), so that children were born during the seasonal “green-up” associated with the North American Monsoon. Given our results, we speculate that birth seasonality represents a form of traditional ecological knowledge to improve neonate health and wellbeing.

摘要

出生季节性是一种现象，其中人口可以通过出生高峰的单个月份或季节来表征。虽然非人类动物研究表明，季节性出生脉搏与气候和当地能源供应的变化有关，但社会科学家仍在争论人类产生这种现象的机制。在这里，我们使用来自下加利福尼亚半岛的历史数据集调查降水、温度和能源可用性对季节性受孕和出生脉冲的作用 - 一个炎热、干旱的沙漠，经历与北美季风相关的季节性气候波动。分析表明：1) 局部能量可用性与受孕脉冲呈负相关；2) 出生脉搏与当地能量供应呈正相关，与温度呈负相关。综上所述，我们的分析表明，女性在当地能源可用性最低时定时受孕（挑战受孕率的预期，因为它仅仅反映了对女性生育力的生态影响），因此孩子们在与北美相关的季节性“绿化”期间出生季风。鉴于我们的结果，我们推测出生季节性代表了一种改善新生儿健康和福祉的传统生态知识形式。