有一种理论认为，两足动物的进化与核心家庭有关：一夫一妻制的父母合作照顾他们的后代。
One theory is that bipedality evolved in conjunction with the nuclear family: monogamous parents cooperating to care for their offspring.
但是一夫一妻制的家庭又有不同种类。
Within the monogamic family there are, however, many varieties.
我们对一夫一妻制的理解主要来自鸟类而非哺乳类。
Our understanding of monogamy draws heavily on birds rather than mammals.
当一个男人说他不遵循一夫一妻制的时候，你应该相信他。
When a man says he can't be monogamous, you should believe him.
根据我们对古代最文明﹑最发达的民族所能作的考察，一夫一妻制的起源就是如此。
This is the origin of monogamy as far as we can trace it back among the most civilized and highly developed people of antiquity.
这就是为什么，他们通常不会意识到自己喜欢某个人，直到那个人离开了），女人的幻想就是一夫一妻制的关系。
That's why they often don't realize they feel something for someone until that person is gone.) Women's fantasies are about a monogamous relationship.
火烈鸟的男性都爱丈夫和细心的父亲。他们聚集的群体可以人数在数十万，但红鹳一般保持一夫一妻制的生活。
They congregate in flocks that can number in the hundreds of thousands, but flamingos generally remain monogamous for life.
垂体后叶加压素，一种抗利尿激素，又是一种与一夫一妻制的长久关系形成有关的化学物质（见“钟情者只有我们吗？”）
Vasopressin, an antidiuretic hormone, is another chemical that has been associated with the formation of long-term, monogamous relationships (see "Are We Alone in Love?").
同时它们是一夫一妻制的，父母双方都需要花费大量的时间用来寻找食物，这就使得它们没时间去进行花哨的求爱行为。
They're monogamous, and both parents need to spend most of their time foraging. This means less time for elaborate courtship behavior.
试着放下背包，有些动物生来就要相互背负，以求生存，共生共栖，匆匆一世，好像灾星下相爱的恋人，一夫一妻制的天鹅。
Why don't you set that bag down? Some animals were meant to carry each other, to live symbiotically of a lifetime. star-crossed lovers, monogamous swans.
和研究人员怀疑的一样，在其他条件相同的情况下，一夫一妻制的家庭育有更多的儿子：平均每生出100个女儿，就会生出101个儿子。
As the researchers suspected, when all other things were equal mothers in monogamous marriages had most sons: 101 for every 100 daughters.
据PeggyVaughan所说，他是《一夫一妻制的秘密》的作者，书上的数据显示40%的女人和60%的男人在他们的婚姻生活里起码有一次出轨。
According to Peggy Vaughan, author of the Monogamy Myth, statistics show that 40 percent of women and 60 percent of men have affairs at least once in their marriages.
虽然现在的世界无论在哪里都不是象慕雷·伊斯梅尔的王国那样多夫妻制的，但也不是完全类似于现代的一夫一妻制的社会，一夫一妻制使的妇女比较广泛的分布。
Though the world in which humanity evolved was nowhere near as polygamous as Moulay Ismail's, neither did it resemble the modern one of monogamous marriage, which distributes women widely.
不像其他的鱼类，它们是一夫一妻制并终生厮守。
Unlike most other fish, they are monogamous and mate for life.
我知道忠实的非一夫一妻制夫妻，他们有些结婚了不住在一起。
And I know committed nonmonogamous couples, some of whom are married, who don’t live together.
因此，如果你想研究一夫一妻制，法律又不允许你拿人类的爱情生活做实验时，你就可以找田鼠。
So if you want to study monogamy - and the government won't let you manipulate human love lives - you play God with the voles.
草原田鼠作为一种社会性生物，它是仅存3%的“一夫一妻制”哺乳动物中的一类。
The prairie vole is a sociable creature, one of the only 3% of mammal species that appear to form monogamous relationships.
一夫一妻制不仅是可能的，而且是必要的。孩子们必须有所依靠；你也必须有所依靠。
Monogamy is a possibility - and a necessity. Kids have got to have something they can rely on. You have got to have something you rely on.
一夫一妻制一般是指即将要结婚的两个人六个月的相处时间，经过了一年的约会后，订婚是比较现实的下一个步骤。
Monogamy usually comes within six months for those who will marry, and after a year of exclusive dating, engagement is a realistic next step.
这些类似老鼠的生物是哺乳动物中少数（不到5%）有人类一般的一夫一妻制倾向的动物之一。
These mouselike creatures are among the small minority of mammals — less than 5 percent — who share humans’ propensity for monogamy.
这些类似老鼠的生物是哺乳动物中少数(不到5%)有人类一般的一夫一妻制倾向的动物之一。
These mouselike creatures are among the small minority of mammals - less than 5 percent - who share humans' propensity for monogamy.
不过社会提倡的是婚姻和一夫一妻制，那么为什么采取行动来改变现状呢？
Society values marriage and monogamy, though, so why isn't it doing anything about it?
在哺乳动物中，它的与众不同之处在于它既是群居性的，也实行一夫一妻制。
What makes it unusual among mammals is that it is both sociable and monogamous.
她的求爱故事反映了她那个时代的社会规范：一夫一妻制和婚姻对于人们来说并不是必须的，却直到死为止都是我们必须遵守的原则。
Her courtship story reflects the social norms of her time: monogamy and matrimony, not necessarily in that order, but certainly till death do us part.
她的求爱故事反映了她那个时代的社会规范：一夫一妻制和婚姻对于人们来说并不是必须的，却直到死为止都是我们必须遵守的原则。
Her courtship story reflects the social norms of her time: monogamy and matrimony, not necessarily in that order, but certainly till death do us part.
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