Tomkins Joseph L, Black Robert, Hazel Wade N
Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.
School of Biological Sciences, The University of Western Australia, Crawley, WA, Australia.
Arch Sex Behav. 2025 Jan;54(1):107-116. doi: 10.1007/s10508-024-03008-y. Epub 2024 Oct 24.
Seasonal variation in birth rates is a ubiquitous property of human populations. Although the general birth rate is dependent on relatively few parameters-sexual behavior, zygote survival, and the number of ova released-the quantitative influence of the effects of each is difficult to estimate. Research has been directed more towards seasonal variation in physiology and less towards behavioral effects such as preferences for birthing in particular seasons. This may be because alongside seasonal variation in birth rate there is also seasonal variation in the multiple birth rate, which necessarily depends on the same physiological factors as the birth rate, suggestive of a link. Here we use a simulation that follows females through their reproductive lives, replicating the incidence of singleton and twin births that arise from single and double ovulations. We use the simulation to quantify the impact of seasonal variation in the physiological variables that affect birth rate. We can generate the seasonal variation in twinning rates observed in European populations, but this does not generate the magnitude of the observed seasonal variation in birth rate. Our simulation shows that, despite correlations between twinning rate and general birth rate, seasonal changes in sexual behavior are necessary to explain the magnitude of the seasonal variation in the general birth rate in humans.
出生率的季节性变化是人类种群普遍存在的一个特征。尽管总体出生率取决于相对较少的几个参数——性行为、受精卵存活率以及排卵数量——但每个参数影响的定量作用却很难估计。研究更多地指向生理学上的季节性变化，而较少关注行为方面的影响，比如在特定季节分娩的偏好。这可能是因为除了出生率的季节性变化外，多胞胎出生率也存在季节性变化，而多胞胎出生率必然取决于与出生率相同的生理因素，这表明二者之间存在联系。在此，我们使用一个模拟程序，跟踪女性的整个生育历程，模拟单次排卵和双次排卵导致的单胞胎和双胞胎出生情况。我们利用该模拟程序来量化影响出生率的生理变量的季节性变化所产生的影响。我们能够模拟出欧洲人群中观察到的双胞胎出生率的季节性变化，但这并不能产生所观察到的出生率季节性变化的幅度。我们的模拟结果表明，尽管双胞胎出生率和总体出生率之间存在相关性，但性行为的季节性变化对于解释人类总体出生率季节性变化的幅度是必要的。
