伦理研究: 一夫一妻是人类的天性吗

In this time of year for heart-shaped boxes of chocolate, I hope it won't seem too cynical to ask an objective scientific question: Are we humans actually monogamous by nature?

又到了一年中一盒盒心形巧克力受宠的日子，我希望这时候问一个客观的科学问题不会太煞风景：我们人类一夫一妻真的是天性吗？

Our cultural landscape doesn't help much in answering that. We praise stable, devoted relationships, yet we that are titillated and tempted by alternatives. A large percentage of marriages end in divorce, yet a far smaller percentage of married people get divorced-that is, our high divorce rate results disproportionately from serial divorcers.

我们的文化背景对于回答这个问题并没有多大帮助。我们赞许稳定和忠诚的关系，但对于相反的情况我们又会感到兴奋和受到诱惑。以离婚告终的婚姻占了婚姻总数的很大比例，但最终结过婚的人群中离婚人士所占比例却很小。这意味着我们的高离婚率主要是一些人多次离婚的结果。

Anthropology doesn't give a clear answer either. Historically, most cultures have allowed polygamy. But within such cultures, most people are monogamous. In the numerous cultures where polygamy is a function of wealth, there are no doubt many monogamous men who would be polygamous if they could buy more wives. And then, of course, there are the rare polyandrous cultures where one woman may have multiple husbands.

人类学家也没有给出明确的答案。从历史上看，很多文化都允许有一夫多妻。但在这些文化中，很多人都是一夫一妻。在那些一夫多妻与财富相关的诸多文化中，毫无疑问的是，许多只有一个妻子的男性在有能力买到更多妻子的时候会选择一夫多妻。当然，在少数文化中也有一妻多夫的现象。

Other primates offer some insights into our human nature. Among the hundreds of primate species, some are polygamous (including our close relatives, chimps and baboons), and others monogamous (such as gibbons and marmosets). Each group has a different cluster of biological and behavioral traits.

我们可以从其他灵长类动物身上了解一些人类的天性。在种类数以百计的灵长类动物中，一些是“一夫一妻”（包括人类的近亲黑猩猩和狒狒），其他一些是“一夫多妻”（例如长臂猿和狨猴）。每一种灵长类动物都有一系列不同的生物和行为特征。

Among polygamous primates, males typically spend much of their time competing for high rank in dominance hierarchies and for mating access to females. Males are far more aggressive, bigger, heavier and more muscular than females and have bigger canines-the better to slash an opponent with. Male baboons, for example, have twice the body weight and canine length of females. Such primates are often called, for good reason, 'tournament' species.

在“一夫多妻”的灵长类动物中，雄性动物通常用大量时间来争夺更高的统领地位、以及与雌性交配的机会。和雌性动物相比，雄性动物更具攻击性、体型更大、更重且肌肉更发达，并有更尖利的犬齿，这些都更有利于攻击对手。例如，雄性狒狒的体重和犬齿长度是雌性的两倍。出于这些理由，此类灵长类动物通常被归为“竞赛类”。

Males in these species have higher metabolic rates and shorter life spans than females, and they basically put zero effort into caring for kids. In other words, all a female gets from a mate are his genes, and females select for males with good genes. This has led to the evolution of conspicuous, costly displays in males that advertise good genes. These features-flamboyant facial coloration, big capes of hair, silver backs-are the primate equivalents of the peacockery of peacocks (a classic polygamous species).

和雌性相比，此类动物中的雄性新陈代谢率更高，寿命更短，它们基本上不负责照看后代。换言之，雌性动物能从雄性配偶那里获得的只是它的基因，雌性动物会选择基因好的雄性动物。这导致雄性动物进化出显著且代价高昂的特征，以表现出它们良好的基因。这些特征包括鲜艳的面部颜色、浓毛、银色的背部等，这些都是灵长类动物中类似孔雀开屏那样用来吸引雌性的特征。（孔雀是典型的“一夫多妻”动物。）

Because fertile females will mate with multiple males, male-male competition extends to sperm competition. By primate standards, polygamous male primates have large Testes (as a percentage of body weight) and high rates of sperm production. And they happily mate with anyone in the county who is ovulating.

有生育能力的雌性会同多个雄性交配，所以雄性之间的竞争从精子就开始了。按照灵长类的标准，“多配偶制”的雄性灵长类动物往往有较大的睾丸（依据睾丸占身体重量的比例来衡量）和较强的精子制造能力，它们愿意和任何能够排卵的同类交配。

Things are quite different among monogamous 'pair bonding' primates. Critically, males do much of the infant care. Thus, you don't see a male indiscriminately mating left and right (or fighting for the chance to do so), since he'll be doing a lot of work if there's a child. In these primates there isn't a high degree of 'sexual dimorphism'-sex differences in body size, musculature, metabolism and life span-and males don't have those garish secondary sexual characteristics of males of polygamous species. Testes are small, sperm count low, mating infrequent.

但在“一夫一妻”的灵长类动物中，情况截然不同。这一群体的雄性承担大部分照顾后代的工作。你看不到雄性到处留情（或为争取交配机会而争斗），因为雄性有很多事情要做（如果有孩子的话）。在这些灵长类动物中，雌雄之间在体形、肌肉、新陈代谢、寿命等方面差异并不十分明显，雄性也不像多配偶物种的雄性那样具备很多第二性征。它们的睾丸较小，精子数量少，交配也没那么频繁。

These profiles are consistent. If 10 seconds into watching a newly discovered type of primate you see that males are twice the size of females and have flashing neon noses, the issue is settled: it's a polygamous species. If you spend forever trying to tell the sexes apart, they're monogamous.

这些特征是始终如一的。对于新发现的灵长类物种，只需要看10秒钟，如果其雄性的体形是雌性的两倍，而且有发亮的红鼻子，那么毋庸置疑，这是一个多配偶的物种。如果很长时间都不能分辨雌雄，那么它就是单配偶物种。

So by these various biological measures, are humans a pair-bonding or a tournament species? Neither. Across populations, men are roughly 10% taller and 20% heavier than women, need 20% more calories and live 6% shorter-more sexually dimorphic than monogamous species, less than polygamous species. Moreover, compared with, say, monogamous gibbons, human males have bigger testes and higher sperm pale in comparison to polygamous chimps. Measure after measure, it's the same.

所以从多种多样的生物指标来判断，人类是单配偶物种还是多配偶物种呢？都不是。人类的男性身高、体重和需要的热量分别比女性多大约10%、20%和20%，寿命比女性短6%，这种性别差异要比单配偶物种明显，但不如多配偶物种。举例来说，人类男性的睾丸大小和精子数量均超过单配偶的长臂猿，但不如多配偶的黑猩猩。其他指标也是如此。

It turns out that we aren't monogamous or polygamous by nature. As everyone from poets to divorce attorneys can attest, we are by nature a profoundly confused species-somewhere in between.

所以人类本质上既非“一夫一妻”，也不是“一夫多妻”。无论是诗人还是离婚律师，都可以证明，人类本质上是一个介于中间地带的深奥复杂的物种。