James William H
The Galton Laboratory, Department of Genetics, Evolution and Environment, University College London, Wolfson House, 4 Stephenson Way, London NW 1 2 HE, UK.
J Theor Biol. 2009 Mar 7;257(1):116-23. doi: 10.1016/j.jtbi.2008.09.028. Epub 2008 Oct 10.
Data on wartime sex ratios (proportions male at birth) are reviewed. Two sorts of variation are empirically well supported viz. (a) rises during and just after both World Wars and (b) a fall in Iran during the Iran-Iraq War. Potential explanations are offered here for these rises and fall. The fall seems plausibly explained by psychological stress causing pregnant women disproportionately to abort male fetuses. The rises may be explained by either or both of two different forms of hypothesis viz. (i) Kanazawa's "returning soldier" hypothesis and (ii) variation in coital rates. The coital rate hypothesis potentially accounts, in slightly different ways, for the rises both during, and just after, some wars. The argument that coital rate affects sex ratio just after wars seems to be supported by evidence that in some combatant countries, dizygotic (DZ) twinning rates (which also reportedly vary with coital rate) peaked after the World Wars. The suggestion that war is associated with rises in sex ratio at birth was first made more than two centuries ago. However, I have been unable to locate direct supporting sex ratio data relating to any conflict before World War One. So it would be useful if historical demographers were to search for such data relating to these earlier wars.
对战时性别比例（出生时的男性比例）的数据进行了综述。有两种变化在实证上得到了有力支持，即：（a）两次世界大战期间及战后不久的上升，以及（b）两伊战争期间伊朗的下降。本文针对这些上升和下降情况提供了可能的解释。伊朗的下降似乎可以合理地解释为心理压力导致孕妇更多地流产男性胎儿。上升情况可能由两种不同形式的假设中的一种或两种来解释，即：（i）金泽的“返乡士兵”假设，以及（ii）性交频率的变化。性交频率假设以略有不同的方式，可能解释了一些战争期间及战后不久的性别比例上升情况。战争结束后性交频率影响性别比例这一观点似乎得到了一些证据的支持，即在一些参战国，异卵双胞胎出生率（据报道也随性交频率而变化）在两次世界大战后达到峰值。战争与出生时性别比例上升相关这一观点早在两个多世纪前就首次提出。然而，我未能找到与第一次世界大战之前任何冲突相关的直接支持性别的比例数据。因此，如果历史人口统计学家能寻找与这些早期战争相关的此类数据，将很有帮助。
