Sexual selection, or competition among members of one sex for reproductive access to the other, is one of the strongest and fastest evolutionary processes. Comparative studies support the prediction that sexual selection is stronger in polygamous than in monogamous species. We report the first study of the effect on sexual selection of a change in mating system, from polygyny to monogamy, within a historical human population. Here we show that over the reproductive lifetimes of Utahns born between 1830 and 1894, socially induced reductions in the rate and degree of polygamy correspond to a 58% reduction in the strength of sexual selection. Polygyny conferred a strong advantage to male fitness as well as a weak disadvantage to female fitness. In contrast, mating with multiple males provided little benefit to females in this population. Polygamy benefitted males by increasing reproductive rates and by lengthening reproductive tenure. Each advantage contributed to roughly half of the increased total lifetime reproductive success. This study illustrates both the potency of sexual selection in polygynous human populations and the dramatic influence that short-term societal changes can have on evolutionary processes.

中文翻译：

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交配系统的改变降低了19世纪美国边境人口的性选择强度。

性选择或一种性别成员之间在竞争性获取另一种性别方面的竞争，是最强大和最快的进化过程之一。比较研究支持这样的预测：一夫多妻制中的性选择比一夫一妻制中的更强。我们报道了在历史人口中从一夫多妻制到一夫一妻制的交配系统的变化对性别选择的影响的首次研究。在这里，我们表明，在1830年至1894年间出生的犹他州人的生殖寿命中，社会上一夫多妻制的发生率和程度的降低对应于性选择强度的降低58％。一夫多妻制对男性健身具有明显的优势，而对女性健身则具有较弱的劣势。相反，与多头雄性交配对该种群中的雌性几乎没有好处。一夫多妻制通过提高生殖率和延长生殖寿命而使男性受益。每种优势约占一生总生殖成功率的一半。这项研究说明了多性恋人群中性选择的效力以及短期社会变化对进化过程的巨大影响。