Monogamy

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How Monogamy Evolved? 一夫一妻制的演变
Did you know that nine percent of non-human mammals are socially monogamous?
One common explanation of social monogamy is that it’s a result of females choosing mates based on the male’s ability to provide for his offspring and protect them from being killed by hostile males or by predators. As you can imagine, females who have help from males produce more litters, and have more offspring that survive to pass on that paternal behavior.
Actually, a study suggests that maybe things happened the other way around, that monogamy evolved first and that paternal instincts evolved later and helped stabilize monogamy.
Researchers in the UK classified more than 2500 mammalian species as either solitary, socially monogamous, or as group living, which is when several breeding females live together. Then, for the socially monogamous species, they analyzed data from closely related species and discovered that, in each case, the females used to be solitary and territorial, and that infanticide was rare and therefore couldn’t have led to monogamy.

Then why did monogamy evolve? The current thinking is that monogamy evolved as a mate guarding strategy in species where females lived alone too far apart for a single male to monopolize access to more than one female at a time. So monogamy enabled males to pass on their genes more reliably. 
你知道吗，9%的非人类哺乳类动物实行“一夫一妻制”。
雌性动物需要一个能养育后代的雄性，这个雄性动物还可以保护幼崽们免于被具有敌意的其他雄性和天敌杀害。人们通常这样解释一夫一妻制的由来。你可以想象，有了雄性动物的帮助，雌性可以生产出更多幼崽，这样就有更多的后代存活，父系行为模式就可以世世代代传播下去。
事实上，一项研究表明，也许一夫一妻制形成的过程恰好相反，即，首先是一夫一妻制逐渐形成，之后才有了父性本能的介入，并最终巩固了一夫一妻制的形成。
英国的研究人员分类整理了在多个正处于孕期的雌性动物一起生活时，独居动物，实行一夫一妻制的动物，和群居动物等2500多种哺乳类动物的行为。他们分析了实行一夫一妻制动物近亲的数据，发现在各个案例中，雌性动物以前都是独居，并且地盘意识非常强，杀死幼崽的现象也几乎没有，因此不可能促使一夫一妻制的形成。
那么一夫一妻制是怎么形成的呢？目前的想法是，当雌性动物离得太远，雄性动物一次无法同时两个及两个以上的雌性动物时，出于雄性动物保卫自身繁衍的目的，出现了一夫一妻制。这种制度可以增大遗传雄性基因的可能性，于是一夫一妻制就形成了。