I propose an evolutionary theory of human female sexual fluidity and argue that women may have been evolutionarily designed to be sexually fluid in order to allow them to have sex with their cowives in polygynous marriage and thus reduce conflict and tension inherent in such marriage. In addition to providing an extensive definition and operationalization of the concept of sexual fluidity and specifying its ultimate function for women, the proposed theory can potentially solve several theoretical and empirical puzzles in evolutionary psychology and sex research. Analyses of the National Longitudinal Study of Adolescent Health (Add Health) confirm the theory's predictions that: (i) women (but not men) who experience increased levels of sexual fluidity have a larger number of children (suggesting that female sexual fluidity, if heritable, may be evolutionarily selected); (ii) women (but not men) who experience marriage or parenthood early in adult life subsequently experience increased levels of sexual fluidity; and (iii) sexual fluidity is significantly positively correlated with known markers of unrestricted sexual orientation among women whereas it is significantly negatively correlated with such markers among men.

中文翻译：

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人类女性性流动的可能进化起源

我提出了人类女性性流动性的进化理论，并认为女性可能在进化上被设计为性流动性，以便允许她们在一夫多妻的婚姻中与她们的母牛发生性关系，从而减少这种婚姻中固有的冲突和紧张。除了提供性流动性概念的广泛定义和可操作化并指定其对女性的最终功能外，所提出的理论还可以潜在地解决进化心理学和性研究中的几个理论和经验难题。对全国青少年健康纵向研究 (Add Health) 的分析证实了该理论的预测：(i) 性流动性水平增加的女性（但不是男性）有更多的孩子（表明女性性流动性，如果可以遗传的话） , 可以进化选择）；(ii) 在成年早期经历婚姻或为人父母的女性（但不是男性）随后经历了更高水平的性流动；(iii) 性流动性与已知的女性不受限制的性取向标志显着正相关，而在男性中与这些标志显着负相关。