Sexual strategies
兩性策略

I just called…
我只是来电话…

…to ask about my grandkids ……
问问我那外孙狗咋样了

Apr 21st 2012 | from the print edition

WHEN Stevie Wonder crooned “I just called to say ‘I love you’,” he was bang on when it comes to men and women in their sexual prime. Were the ballad sung by a post-menopausal matron, though, the person at the other end of the line would probably be her daughter—and the conversation would revolve around grandchildren. That, at least, is the picture which emerges from a study published in Scientific Reports by Robin Dunbar, of Oxford University, and his colleagues.
当蒂夫•汪达 [注1]吟唱着“我只是来电话说‘我爱你’”时，他拨动的是处于性成熟期的男男女女的心弦。但如果这首抒情歌曲是一位停经后的老太太唱的，而接电话的又恰好是她的女儿，那这次谈话就会围绕着她的外孙和外孙女。至少，这就是牛津大学的罗宾•邓巴（Robin Dunbar）及其同事们发表在《科学报告》（Scientific Reports）的研究报告中勾画的情景。

Evolutionary psychologists like Dr Dunbar are interested in how investment in close relationships differs between the sexes. Dr Dunbar, indeed, has just published a book on the phenomenon of sexual love, analysed from a scientific point of view (see article). These differences reflect distinct strategies that have evolved to maximise reproductive success across a lifetime. One prediction that makes intuitive sense, but which has been difficult to nail down empirically, is that when women hit the reproductive wall of the menopause they funnel their remaining energy into bolstering their children’s—especially their daughters’—odds of producing viable offspring. (Sons spend less time minding their progeny than their spouses do.)
让邓巴博士这类进化心理学家感兴趣的是：在有亲密关系的人之间，感情的投入是怎样因性别的差异而有所不同的。确实，邓巴博士刚刚出版了一本新书，书中以科学的观点分析了性爱现象（见另文），认为上述差异反映的是男性与女性的不同策略在一生中的逐步演化，而这一策略是要让生殖达到最大的成功。一个在直觉上合理但却很难用实例确证的预测是：当女性到了绝经期不再有生育能力时，她们会把自己尚存的精力汇聚到她们的孩子特别是女儿身上，提高他们养育成功后代的胜算。（儿子们花在照顾后代身上的时间不及其配偶。）

The main obstacle to testing the grandmother hypothesis, as it has come to be known, is that most studies have involved small numbers of people, making it hard to draw sweeping conclusions. Dr Dunbar leapt this hurdle by tapping a trove of 2 billion anonymised telephone calls and 500,000 text messages between customers of an unnamed European mobile-phone operator over the course of seven months. After eliminating those for which age and sex data were unavailable, they identified the people each subscriber contacted most often. Frequency of contact is a good proxy for emotional closeness, so this yielded a list of 1.2m “best friends”, and 800,000 “second-best friends”.
检测这一人称“姥姥假说”的主要障碍是，以往的绝大多数研究只有为数不多的人作为样本，因此难以得出有说服力的结论。但邓巴博士等人在7个月内监听了通话者姓名不详的电话20亿次、查看了某个未提及名称的欧洲移动电话运营商的顾客间的短信50万份 [注2]，因此得以冲破了这一藩篱。在剔除了那些无法确认年龄、性别的记录之后，他们确定了每一个用户最常联系的人群。联系的经常性是感情密切度的良好替代变量，于是他们据此制定了一份120万人的“至爱亲朋”名单和一份80万人的“次爱亲朋”名单。

For any given age, the researchers then calculated the average sex of men’s and women’s phone pals. They did this by adding 1 every time the friend was a man and subtracting 1 every time it was a woman, and dividing the result by the number of friends for the age/sex group in question. If every person in the sample had a male best friend, the average-sex index would be 1; if all the best friends were women, it would be -1. An equal number of male and female best friends would mean the index came out at precisely zero.
研究者们随之计算了各年龄组男性与女性的通话亲朋的平均性别，其方法是：为每一个男性通话者加1，女性通话者减1，最后将所得结果除以该年龄/性别组的总亲朋数。如果样本中每人有一个男性至爱亲朋，则平均性别指数为1；如果所有的至爱亲朋都是女性，则该指数为-1。如果男女至爱亲朋数相等，则该指数恰好为0。

Between the ages of 20 and 40 men and women behaved similarly (see chart). Both tended to have best friends of the opposite sex. The proclivity was slightly more pronounced among ladies, whose best-friend sex index peaked in their late 20s at 0.46 (equivalent to roughly three male best friends for every female one in the sample) and stayed more or less the same throughout their 30s. Men reached a maximum of -0.41 a bit later and remained there for less time. In both cases, these best friends tended also to be of a similar age, suggesting they were actually sexual mates. Second-best friends, meanwhile, were typically of the same sex—chums, in other words.
20与40岁之间的男性与女性表现类似（见图表），都倾向于有较多的异性至爱亲朋。女性的这一倾向表现得更为明显一些，其至爱亲朋性别指数在年近30时达到峰值0.46（大约相当于在样本中女性挚友与男性挚友之比为1：3），而且在整个30到40岁期间大致保持此值。男性稍迟一点到达其峰值-0.41，且保持此值的时间较短。无论男性女性，其挚友的年龄都与他们大致相当，说明他们与至爱亲朋其实是性伴。与此同时，次爱亲朋通常是同性，换句话说是通常意义上的好友。


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Things change markedly, though, as people enter middle age. For men, the best-friend sex index falls steadily from its peak until it levels off at the age of 50 or so, while remaining skewed towards females for the rest of their lives. However, any sexual bias for second-best friends more or less disappears when men reach their 40s, consistent with the hypothesis that these “friends” are by then no longer chums, but children (who are about as likely to be male as female) and that fathers do not favour those of any one sex.
但人到中年后情况发生了显著变化。男性的至爱亲朋性别指数从峰值持续下降，直至50岁左右才趋于稳定，但在其生命的剩余时间内还一直偏女性。男性超过40岁时，次爱亲朋原有的任何性别偏向大致消失，这符合“这些‘朋友’那时不再是好友而是子女（他们中男女比例基本为1：1），且父亲并不偏向儿子或女儿”这一假设。

Among women, by contrast, the best-friend sex index plummets around the time menopause strikes. By the age of 55, it actually turns negative, in favour of other females who are, tellingly, about half their age. At around that time, women’s second-best friends are increasingly men from their own generation. Older women, it appears, do indeed invest more time in furthering their daughters’ welfare—and reproductive success—and less in nurturing relationships with their husbands, no doubt to the latter’s chagrin. Strong evidence, then, for the grandmother hypothesis. And possibly an explanation for men’s mid-life crisis.
与此相反，女性的至爱亲朋性别指数大约在更年期开始时暴跌，且当她们年届55岁时变为负值。她们更愿意与年龄约为其一半的其他女性交谈，这很说明问题。大约在那时，女性的次爱亲朋越来越多地是她们的男性同龄人。看来，老些的女性的确把时间更多地放在增进其女儿的幸福——以及生育的成功——方面，而不那么注意培养跟丈夫的感情，这无疑很让后者恼火。这是“姥姥假说”的强有力证据。这或许也可以解释男性的中年危机。


[注1] Stevie Wonder，美国黑人盲歌手（1950-）。
[注2] 译者不清楚这种行为为什么不违法。是不是因为研究者在这样做时不知道交流者的姓名，而且完全出于科学研究的目的？请对这方面熟悉的译友指点。还有，本文未曾描述研究者监听20亿次电话的方法，译者感觉, 做到这一点简直无法思议。