Explanations for the evolution of monogamy in mammals typically emphasise one of two possibilities: monogamy evolves when females are overdispersed (such that males cannot defend more than one female at a time) or when males provide a service to the female. However, the first claim has never been directly tested. I test it directly at three levels using data from primates and ungulates. First, I show that the females of monogamous genera do not have territories that are significantly larger, either absolutely or relatively, than those of polygamous genera. Second, using both the Mitani-Rodman and Lowen-Dunbar inequalities, I show that, given their typical day journey lengths, males of most monogamous species could easily defend an area large enough to allow them to monopolise as many as 5-10 females if these ranged solitarily. Finally, I use a model of male mate searching strategies to show that, unlike the males of socially-living polygamous species, the opportunity cost that monogamous males incur is typically more than five times the reproductive success they have by being obligately monogamous. This suggests that the selection pressure dissuading them from pursuing a roving male strategy must be very considerable.

中文翻译：

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女性分散对于哺乳动物一夫一妻制的进化是必要的，但不是充分的

一夫一妻制在哺乳动物中进化的解释通常强调以下两种可能性之一：一夫一妻制是在雌性过度分散时发生的（这样一来，雄性不能一次捍卫一个以上的雌性），或者当雄性为雌性提供服务时。但是，第一项索赔从未经过直接测试。我使用灵长类和有蹄类动物的数据直接在三个级别上对其进行测试。首先，我证明一夫一妻制女性的领土绝对或相对没有一夫多妻属的领土。其次，结合米塔尼-罗德曼（Mitani-Rodman）和洛文-邓巴（Lowen-Dunbar）不等式，我证明，考虑到典型的一日游时间，大多数一夫一妻制物种的雄性很容易捍卫一个足够大的区域，足以使它们垄断5-10个雌性这些范围很小。最后，我使用男性伴侣搜索策略模型来表明，与具有社交生活的一夫多妻物种的男性不同，一夫一妻制男性所获得的机会成本通常是专心一夫一妻制所获得的生殖成功的五倍以上。这表明阻止他们追求游荡男性策略的选择压力必须非常可观。