Williams G C
Proc R Soc Lond B Biol Sci. 1979 Sep 21;205(1161):567-80. doi: 10.1098/rspb.1979.0085.
Of various published theories of adaptive control of progeny sex ratio only two are plausible, a physiological theory by Trivers & Willard, and a demographic theory by Verner. The first applies to species in which sons and daughters impose different costs on parents, and in which only one or very few young are produced at once. They ought to show positive correlations in the sex of successive offspring and high sex-ratio variance among progenies. Verner's theory postulates a minimization of competition for mates in neighbourhoods subject to random fluctuation in sex ratio. Optimal progenies would exactly match the population's evolutionary equilibrium sex ratio. There would be little variance among progenies. Evidence from vertebrates is unfavourable to either theory and supports, instead, a non-adaptive model, the purely random (Mendelian) determination of sex. The apparent absence of parental control of progeny sex ratio is a serious theoretical difficulty.
在已发表的各种关于后代性别比例适应性控制的理论中，只有两种看似合理，一种是特里弗斯和威拉德提出的生理学理论，另一种是弗纳提出的人口统计学理论。第一种理论适用于后代性别对父母造成不同成本，且每次只生育一个或极少数后代的物种。这些物种的连续后代性别之间应呈现正相关，且后代之间的性别比例差异较大。弗纳的理论假定，在性别比例随机波动的邻域中，配偶竞争应降至最低。最优后代将与种群的进化平衡性别比例完全匹配。后代之间的差异将很小。脊椎动物的证据对这两种理论都不利，反而支持一种非适应性模型，即性别由纯粹随机（孟德尔式）决定。亲代对后代性别比例明显缺乏控制是一个严重的理论难题。
