Cliff-edge model of obstetric selection in humans
Cliff-edge model of obstetric selection in humans
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DOI：
10.1073/pnas.1612410113
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发表时间：
2016-12-20
影响因子：
11.1
通讯作者：
Pavlicev, Mihaela
中科院分区：
文献类型：
--
作者：
Mitteroecker, Philipp;Huttegger, Simon M.;Pavlicev, Mihaela
由于胎儿大小和母亲骨盆尺寸的不比例导致的难产发生率高得惊人，这让进化科学家困惑了几十年。在这里，我们提出，这些高比率是人类产科选择的鲜明特征的直接后果。新生儿的体型相对于与出生相关的母亲的体型是高度可变的，并且与生殖成功呈正相关，直到达到一个临界值，超过这个临界值自然分娩就不可能了。因此，对称的表型分布不能很好地匹配高度不对称的、悬崖边缘的适合度分布：使种群平均适合度最大化的最优表型分布需要一小部分个体超出“适合度边缘”（即那些具有胎盆腔不比例的个体）。使用一个简单的数学模型，我们表明，弱的方向选择对于一个大的新生儿，一个狭窄的骨盆管，或两者都足以说明相当大的发生率胎盆腔不平衡。基于这个模型，我们预测，在过去的几十年里，经常使用剖腹产导致胎盆腔不比例的进化增加了10%到20%。
The strikingly high incidence of obstructed labor due to the disproportion of fetal size and the mother's pelvic dimensions has puzzled evolutionary scientists for decades. Here we propose that these high rates are a direct consequence of the distinct characteristics of human obstetric selection. Neonatal size relative to the birth-relevant maternal dimensions is highly variable and positively associated with reproductive success until it reaches a critical value, beyond which natural delivery becomes impossible. As a consequence, the symmetric phenotype distribution cannot match the highly asymmetric, cliff-edged fitness distribution well: The optimal phenotype distribution that maximizes population mean fitness entails a fraction of individuals falling beyond the "fitness edge" (i.e., those with fetopelvic disproportion). Using a simple mathematical model, we show that weak directional selection for a large neonate, a narrow pelvic canal, or both is sufficient to account for the considerable incidence of fetopelvic disproportion. Based on this model, we predict that the regular use of Caesarean sections throughout the last decades has led to an evolutionary increase of fetopelvic disproportion rates by 10 to 20%.