A boy or a girl? That is usually the first question asked when awoman gives birth. Remarkably, the answer varies with where the mother lives.In rich countries the chances of its being a boy are about 5% higher than inpoor ones. Equally remarkably, that figure has been falling recently. Severaltheories have been put forward to explain these observations. Some argue thatsmoking plays a role, others that diet may be important. Neither of these ideashas been supported by evidence from large studies. But new research points to adifferent factor: stress.

Strange as it might seem, the terrorist attacks of September 11th2001 shed light on the enigma. Studies noting the sex of babies conceived inNew York during the week of the attacks found a drop in the ratio of males tofemales. That is consistent with earlier studies, which revealed a similarshift in women who became pregnant during floods and earthquakes and in time ofwar. Moreover, a study carried out eight years ago by researchers at theUniversity of Aarhus, in Denmark, revealed that women who suffered the death ofa child or spouse from some catastrophic illness around the time they conceivedwere much more likely to give birth to girls than to boys.

Taken together, these results suggest that acute stress to a womanat the time of conception shifts the sex ratio towards girls. However, CarstenObel, a researcher at Aarhus who was not involved in the earlier study,wondered if the same might be true of chronic stress too. In a paper justpublished in Human Development, he shows that it is.

Dr Obel used a set of data collected between 1989 and 1992. Duringthat period 8,719 expectant mothers were asked to fill in questionnaires thatinquired, among other things, about their level of stress. Dr Obel found thatthe more stressed a mother had been, the less chance she had of having givenbirth to a boy. Only 47% of children born to women in the top quartile ofstress were males. That compared with 52% for women in the bottom quartile. DrObel suspects the immediate cause is that male pregnancies are more likely tomiscarry in response to stress than female pregnancies are, especially duringthe first three months. However, that is difficult to prove. More intriguing,though, is the ultimate cause, for he thinks it might be adaptive, rather thanpathological.

That is because the chances are that a daughter who reachesadulthood will find a mate and thus produce grandchildren. A son is a differentmatter. Healthy, strapping sons are likely to produce lots of grandchildren, byseveral women-or would have done in the hunter-gatherer societies in which mosthuman evolution took place. Weak ones would be marginalised and maybe evenkilled in the cut and thrust of male competition. If a mother’s stressadversely affects the development of her fetus then selectively aborting boys,rather than wasting time and resources on bringing them to term, would makeevolutionary sense.

That, in turn, would explain why women in rich countries, who areless likely to suffer from hunger and disease, are more likely to give birth tosons. That this likelihood is, nevertheless, falling suggests that rich women’s lives maybe more stressful than they used to be.

1. The author begins the passage by_____.

[A] presenting an argumentation

[B] explaining a phenomenon

[C] raising a question

[D] making a comparison

2. The ratio of giving birth to a boy is falling in rich countriesbecause_____.

[A] the terrorist attacks of September 11th 2001 exerted hugenegative impact

[B] women are facing greater pressure than past

[C] women are under new pressure now which they seldom faced in thepast

[D] male pregnancies are more easily to miscarry

3. Which of the following can explain Dr Obel’s opinionthat the ultimat cause is adaptive rather than pathological?

[A] 47% of children born to women in the top quartile of stress weremales while 52% in the bottom quartile.

[B] Women in rich countries are more likely to give birth to boys

[C] Women selectively abort boys rather than waste time andresources on bringing them to term for fear of male competition.

[D] Women who suffer from calamity in conception are more likely togive birth to girls.

4. Women in the hunter-gatherer societies are more likely to givebirth to daughters because_____.

[A] they agree that giving birth to daughters is beneficial in theevolutionary sense

[B] sons are likely to produce lots of grandchildren with severalwomen

[C] they think it is a better practice for a daughter to produce grandchildrenwith only one mate

[D] they think bringing sons to term is wasting time and resources.

5.From this passage, we may draw a conclusion that_____.

[A] acute stress is more likely to cause women to choose abortingboys than chronic stress.

[B] stress to a woman at the time of conception, whether acute orchronic, will shift the sex ratio towards girls.

[C] more girls will be born in the future because today’s women, inboth rich and poor countries, suffer from increasing pressure.

[D] chronic stress is more decisive in influencing the women’spregnancies.

文章剖析：

这篇文章是介绍影响婴儿出生性别原因的一个新的研究成果--压力。文章第一段提出以往人们对该问题的看法，然后引出新的研究结果;第二段用一些事例来证明突发压力对于婴儿性别的影响;第三段、第四段讲述Obel博士调查研究表明慢性压力在这方面的影响;第五段对Obel博士的研究结果作了一些论证;第六段是对第一段提到的现象用得出的结论做解释。

词汇注释：

enigma n. 谜

chronic adj. 长期的，持续的

conception n. 受精

fetus n. 胎儿

questionnarie n. 调查表

quartile n. 四分位值

miscarry v. 流产

pathological adj. 病理的

strapping adj. 伟岸的，魁梧的

难句突破：

(1) Moreover, a study carried out eight years ago by researchers atthe University of Aarhus, in Denmark, revealed that women who suffered thedeath of a child or spouse from some catastrophic illness around the time theyconceived were much more likely to give birth to girls than to boys.

[主体句式] A study revealed that...

[结构分析]这是一个复合句，主语后面是一个过去分词短语做定语;revealed后面的宾语从句比较复杂，从句的主体句式为women or spouse were likely to ...，状语中that 引导的定语从句用来修饰time,第一个主语women后有一个以who引导的定语从句。

[句子译文] 。而且，八年前奥尔胡斯大学研究者们做的一项研究也表明经过了第一个孩子死亡的妇女或在怀孕期间经历过一些灾难性疾病的夫妇更有可能生女孩。

(2) If a mother’s stress adversely affects the development of her fetus thenselectively aborting boys, rather than wasting time and resources on bringingthem to term, would make evolutionary sense.

[主体句式] If... then selectively aborting boys...would make sense.

[结构分析] 这是一个带有条件状语从句的复合句，主语由现在分词短语构成。

[句子译文]如果母亲的压力对胎儿的发展起了相反的影响，选择性地将男孩流产，而不是浪费时间和资源将他们养足月，那么就能说明进化的问题了。

题目分析:

1. The author begins the passage by_____.1. 作者展开这篇文章一开始_____。

[A] presenting an argumentation[A] 提出一个论点

[B] explaining a phenomenon[B] 解释一个现象

[C] raising a question[C] 提出一个问题

[D] making a comparison[D] 做了一个比较

[答案]A

[难度系数] ☆

[分析]推理题。作者在文章一开始就指出在富裕国家中妇女生男孩的比率比贫穷国家高出5%，但目前这个比率在下降，有许多人给出自己的解释，但都不能被大型的研究所证明，而现在又有新的论点，就是压力的作用。接下来的几段就是对这个论点的证实。可见，作者是以提出一个论点的形式来开始这篇文章的。

2. The ratio of giving birth to a boy isfalling in rich countries because_____.2.在富裕国家中男孩的出生率下降了是因为_____。

[A] the terrorist attacks of September 11th 2001 exerted hugenegative impact[A] 2001年9月11日恐怖主义袭击带来了巨大的负面影响

[B] women are facing greater pressure than past[B] 妇女现在面临的压力比以前大

[C] women are under new pressure now which they seldom faced in thepast[C] 妇女现在要面临新的压力，这是她们以前没有遇到过的

[D] male pregnancies are more easily to miscarry[D] 怀了男孩的女性更加容易流产

[答案]B

[难度系数] ☆☆☆

[分析]推理题。首先A选项明显是错误的，因为这个影响只限于美国，并不包括所有的富裕国家。D也是错误选项，因为文章第四段中提到了这一点，但是选项中却丢掉了一个重要前提，也就是在较大的压力下，怀了男孩的女性才更加容易流产。题干要求找出富裕国家目前男孩出生率下降的原因，文章整篇都在讨论压力对于婴儿性别的作用，而最后一段的最后一句话作者指出，目前这个比率下降可能是因为富裕国家妇女现在承受的压力要比以前多，但是没有说明有新的压力。因此，答案为B。

3. Which of the following can explain Dr Obel’s opinionthat the ultimat cause is adaptive rather than pathological?3.以下那一项可以解释Obel博士认为最根本的原因是适应性的而不是生理性的这个观点?

[A] 47% of children born to women in the top quartile of stress weremales while 52% in the bottom quartile.[A]压力最大的四成妇女47%生育的是男孩，而压力最小的四成妇女52%生育的是男孩。

[B] Women in rich countries are more likely to give birth to boysbecause they are more stressful[B]富裕国家的妇女生育男孩的几率更大，因为她们所承受的压力更大。

[C] Women selectively abort boys rather than waste time andresources on bringing them to term for fear of male competition.[C]妇女因为害怕男性竞争而选择将男婴流产，而不是浪费时间和养料将他们发育完整。

[D] Women who suffer from calamity in conception are more likely togive birth to girls.[D]受精期经历了灾难的妇女生育女孩的比率更大。

[答案]C

[难度系数] ☆☆☆

[分析]细节题。第四段中提到，Obel博士认为导致女性在面临压力时生女孩的几率更大，其根本原因应该是适应性的原因而不是生理性原因。第四段提到，Obel怀疑是其直接原因是面临压力时如果怀孕的是男孩那么就更容易流产。紧接着第五段就给出了解释，那就是在资源紧缺的男性竞争社会中，弱小的男性更容易被边缘化，被淘汰，而女性则不存在这个问题，所以面对这种压力，妇女生育孩子时会选择将男婴流产，这是一种适应环境的做法。因此，答案中C是可以说明他的这个观点的，ABD只是一些表象。

4. Women in the hunter-gatherer societies are more likely to givebirth to daughters because_____.4.在原始狩猎社会中，妇女生育女儿的比率更大是因为_____。

[A] they agree that giving birth to daughters is beneficial in theevolutionary sense[A] 他们一致认为在进化的意义上，生女儿在有利的。

[B] sons are likely to produce lots of grandchildren with severalwomen[B] 儿子会和几位女性一起生育许多后代

[C] they think it is a better practice for a daughter to producegrandchildren with only one mate[C]他们认为女儿只和一个配偶生儿育女是一个更好的做法

[D] they think bringing sons to term is wasting time andresources.[D]他们认为将男婴养至足月是浪费时间和资源的。

[答案]D

[难度系数] ☆☆☆

[分析]推理题。文章第五段指出在原始狩猎社会中，健康、强壮的男性可以和几位女性一起繁殖许多后代，而弱小的则会被边缘化甚至在男性竞争中被杀死。妇女在生育孩子时就会面临这样的压力，她更情愿将男婴流产，也不愿意花费了如此多的时间和精力后将男婴生出来，却面临被淘汰的压力。因此，在原始狩猎社会中，女孩出生率较高的原因是因为妇女生育时面临的这种压力。答案中，D为正确答案。A选项显然是错误的，原始人不会以进化的观点去思考问题。B选项的说法只是一个现象，并不是题干的原因。C选项的说法与原文相反。

5.From this passage, we may draw a conclusion that_____.5.从这篇文章我们可以得出一个结论____。

[A] acute stress is more likely to cause women to choose abortingboys than chronic stress.[A]突发的压力比持续的压力更能导致妇女选择将男婴流产。

[B] stress to a woman at the time of conception, whether acute orchronic, will shift the sex ratio towards girls.[B]妇女怀孕期间经受压力，无论是突发的还是持续的，都会导致婴儿性别比例偏向女孩。

[C] more girls will be born in the future because today’s women, inboth rich and poor countries, suffer from increasing pressure.[C] 未来会有更多的女孩出生，因为现在不论是在富裕国家还是在贫穷国家，女性都面临着越来越大的压力。

[D] chronic stress is more decisive in influencing the women’spregnancies.[D]在影响女性怀孕方面慢性的压力更具有决定性的作用。

[答案]B

[难度系数] ☆☆☆

[分析] 推理题。题干要求根据整篇文章推导出一个结论，本文主要讲述了压力对于婴儿出生性别的影响，分别用一些数据和事实证明突发压力和慢性压力都有一定的影响，从中可以得出结论，就是突发与急性压力都会使得女孩出生率高一些。答案A、D文中并没有进行比较、缺少证据，C的内容也文中也没有提到。因此，正确答案为 B。

参考译文：

男孩还是女孩?这通常是一个妇女生完孩子后问的第一个问题。很显然的，因为这位母亲所在的地方不同答案也就不同。在富裕国家中生男孩的比率要比贫穷国家高 5%。同样引人注目的是，最近这个数字却降低了。人们提出了几个理论来解释这些现象。有人认为吸烟可能是原因所在，也有人认为节食在影响较大。但较大的研究的证据却都不支持这两个观点，新的研究指出了另外一个因素：压力。

虽然看起来很奇怪，但2001年911恐怖袭击将这个谜显示了出来。在恐怖袭击的那一周在纽约进行的婴儿性别研究发现男女性别比例下降了，这与早期的研究相一致。早期研究表明洪水、地震和战争期间怀孕妇女生育男女的比例也有相似的变化。而且，八年前奥尔胡斯大学研究者们做的一项研究也表明经过了第一个孩子死亡的妇女或在怀孕期间有一些灾难性疾病的夫妇更有可能生女孩。

结合这些研究来看，这些结果表明女性在受精时如果有突然的压力，那么生女孩的比例就会增大。但是，奥尔胡斯的一位研究者CarstenObel并没有参与早期的研究，他在怀疑持续的压力是否也会有同样的影响。他刚刚在《人类发展》上发表的一篇论文中他表明事实确实如此。

Obel博士使用了1989年至1992年间的一组数字。在这个时期，8791名妇女被邀填写了问卷调查，调查其中一项就是她们压力的程度。Obel博士发现一个妇女承受的压力越重，她生男孩的概率就越小。压力最大的四成妇女只有47%生育的是男孩，而最小的四成妇女其比例为52%。Obel博士怀疑直接原因是有压力的情况下怀孕的是男婴的比怀孕女婴的更容易流产，尤其是在前三个月。但是，这一点很难证实。更让人迷惑的是最根本的原因，因为他认为是适应性的而不是生理性的。

因为可能的情况时女孩成年后就要找一位男性，然后生育后代。而男孩则不一样。健康、魁梧的男性更有可能和几位女性生育很多后代，或是在原始狩猎族社会中是这样的，大多数人类进化是这样进行的。弱小的将会被边缘化，甚至有可能在男性的打杀竞争中被杀死。如果母亲的压力对胎儿的发展起了相反的影响，选择性地将男孩流产，而不是浪费时间和资源将他们养足月，那么就能说明进化的问题了。

这反过来也可以解释为什么在富裕国家中女性很少受到饥饿和疾病的威胁，更容易生育男孩。尽管这种可能存在，但是数据的下降说明富裕女性的生活目前所受的压力要比以前多得多。