倫理研究: 一夫一妻是人類的天性嗎

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寵的日子，我希望這時候問一個客觀的科學問題不會太煞風景：我們人類一夫一妻真的是天性嗎？

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.

我們的文化背景對於回答這個問題並沒有多大幫助。我們讚許穩定和忠誠的關係，但對於相反的情況我們又會感到興奮和受到誘惑。以離婚告終的婚姻佔了婚姻總數的很大比例，但最終結過婚的人羣中離婚人士所佔比例卻很小。這意味着我們的高離婚率主要是一些人多次離婚的結果。

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.

人類學家也沒有給出明確的答案。從歷史上看，很多文化都允許有一夫多妻。但在這些文化中，很多人都是一夫一妻。在那些一夫多妻與財富相關的諸多文化中，毫無疑問的是，許多隻有一個妻子的男性在有能力買到更多妻子的時候會選擇一夫多妻。當然，在少數文化中也有一妻多夫的現象。

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.

我們可以從其他靈長類動物身上了解一些人類的天性。在種類數以百計的靈長類動物中，一些是“一夫一妻”（包括人類的近親黑猩猩和狒狒），其他一些是“一夫多妻”（例如長臂猿和狨猴）。每一種靈長類動物都有一系列不同的生物和行爲特徵。

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”的靈長類動物中，雄性動物通常用大量時間來爭奪更高的統領地位、以及與雌性交配的機會。和雌性動物相比，雄性動物更具攻擊性、體型更大、更重且肌肉更發達，並有更尖利的犬齒，這些都更有利於攻擊對手。例如，雄性狒狒的體重和犬齒長度是雌性的兩倍。出於這些理由，此類靈長類動物通常被歸爲“競賽類”。

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，此類動物中的雄性新陳代謝率更高，壽命更短，它們基本上不負責照看後代。換言之，雌性動物能從雄性配偶那裏獲得的只是它的基因，雌性動物會選擇基因好的雄性動物。這導致雄性動物進化出顯著且代價高昂的特徵，以表現出它們良好的基因。這些特徵包括鮮豔的面部顏色、濃毛、銀色的背部等，這些都是靈長類動物中類似孔雀開屏那樣用來吸引雌性的特徵。（孔雀是典型的“一夫多妻”動物。）

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.

有生育能力的雌性會同多個雄性交配，所以雄性之間的競爭從精子就開始了。按照靈長類的標準，“多配偶制”的雄性靈長類動物往往有較大的睾丸（依據睾丸占身體重量的比例來衡量）和較強的精子製造能力，它們願意和任何能夠排卵的同類交配。

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”的靈長類動物中，情況截然不同。這一羣體的雄性承擔大部分照顧後代的工作。你看不到雄性到處留情（或爲爭取交配機會而爭鬥），因爲雄性有很多事情要做（如果有孩子的話）。在這些靈長類動物中，雌雄之間在體形、肌肉、新陳代謝、壽命等方面差異並不十分明顯，雄性也不像多配偶物種的雄性那樣具備很多第二性徵。它們的睾丸較小，精子數量少，交配也沒那麼頻繁。

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.

這些特徵是始終如一的。對於新發現的靈長類物種，只需要看10秒鐘，如果其雄性的體形是雌性的兩倍，而且有發亮的紅鼻子，那麼毋庸置疑，這是一個多配偶的物種。如果很長時間都不能分辨雌雄，那麼它就是單配偶物種。

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.

所以從多種多樣的生物指標來判斷，人類是單配偶物種還是多配偶物種呢？都不是。人類的男性身高、體重和需要的熱量分別比女性多大約10%、20%和20%，壽命比女性短6%，這種性別差異要比單配偶物種明顯，但不如多配偶物種。舉例來說，人類男性的睾丸大小和精子數量均超過單配偶的長臂猿，但不如多配偶的黑猩猩。其他指標也是如此。

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.

所以人類本質上既非“一夫一妻”，也不是“一夫多妻”。無論是詩人還是離婚律師，都可以證明，人類本質上是一個介於中間地帶的深奧複雜的物種。