2006年VOA标准英语-Study: Boys Born During Social Upheaval Li

By Jessica Berman
Washington
25 January 2006

Researchers have long observed that during times of social stress, there are fewer male births than female births.  Now, a new study has found that boys born during tough times live longer than those born during periods of social stability.

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Drops in male-to-female sex ratios are nothing new.

"During the Kobe earthquake in Japan, sex ratio drops," said Ralph Catalano, a professor public health at the University of California at Berkeley.  "The collapse¹ of the east German economy, sex ratio drops.  The major smog in London in 1952, sex ratio dropped.  Variation in the economy such that you get very bad economic times in Sweden over a century and a half, sex ratio drops."

Then, when environmental factors return to normal, experts say sex ratios even out.

Most scientists believe the dip in sex ratios is a stark² example of evolution at work:  through a process of natural selection, the theory goes, daughters are better able to propagate the species than weaker sons. 

The mothers' bodies seem to spontaneously abort³ weak male fetuses⁴ more often by exposing them to high levels of the stress hormone⁵ cortisol in utero, while sparing the females.

Professor Catalano says cortisol acts as an evolutionary⁶ "testing mechanism⁷" to weed out weaker male fetuses.

"And what we're interested in is whether the mechanism itself, the testing mechanism, of the fetuses actually damages those that survive, because the presumption⁸ has been that if you've been subjected to this kind of regimen of cortisol production in utero, that it has health consequences that affect you in life if you've made it to birth," he said.

That's one theory.  Professor Catalano and colleague Tim Bruckner also wanted to explore another notion, that sons who survive end up living longer and healthier lives than males born during less stressful times. 

They decided⁹ to look at cohort data in Sweden of babies born between 1751, the first year the Swedes began keeping birth records, and 1912. 

Up until the mid-1800s, Sweden's history was marked by royal coups¹⁰, wars, farming reform and religious intolerance.

Based on the male-to-female birth ratios over the 160-year period, the investigators¹¹ found that the fewer males that survived the cortisol challenge in utero lived slightly longer than sons born during periods of relative calm. 

"Our work suggests that at least historically, smaller cohorts of males than you would expect from the number of females does not mean that that cohort is a relatively¹² fragile cohort," said Professor Catalano.  "In fact, quite the contrary, those cohorts may be relatively hardy¹³ even though they may be smaller because the weakest of them are no longer there."

Professor Catalano doesn't think the findings are likely to have any impact on the way a doctor interacts with an expectant mother.

The study on sex ratios and lifespan were published in Proceedings¹⁴ of the National Academy of Sciences.

1 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

2 stark   

adj.荒凉的；严酷的；完全的；adv.完全地

参考例句：

• The young man is faced with a stark choice.这位年轻人面临严峻的抉择。
• He gave a stark denial to the rumor.他对谣言加以完全的否认。

3 abort   

v.使流产，堕胎；中止；中止(工作、计划等)

参考例句：

• The captain instructed them to abort the mission.上尉指示他们中止执行任务。
• With this button the user can abort the audio sequence.用户可以用该按钮终止音频序列。

4 fetuses   

n.胎，胎儿( fetus的名词复数 )

参考例句：

• DNA was extracted from fetuses at mid-gestation, about 10 days past conception. DNA从受孕大约10天后的中期妊娠胚胎中提取。 来自互联网
• Brucellosis is a disease that causes fetuses to abort in cattle. 普鲁士菌病是一种可以导致牲畜胎儿夭折的疾病。 来自互联网

5 hormone   

n.荷尔蒙，激素，内分泌

参考例句：

• Hormone implants are used as growth boosters.激素植入物被用作生长辅助剂。
• This hormone interacts closely with other hormones in the body.这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。

6 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

7 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

8 presumption   

n.推测，可能性，冒昧，放肆，[法律]推定

参考例句：

• Please pardon my presumption in writing to you.请原谅我很冒昧地写信给你。
• I don't think that's a false presumption.我认为那并不是错误的推测。

9 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

10 coups   

n.意外而成功的行动( coup的名词复数 )；政变；努力办到难办的事

参考例句：

• China has seen many political coups within the ruling class. 中国统治阶级内部发生过很多政变。 来自互联网
• Thailand has had eighteen coups or coup attendance since nineteen thirty-two. 泰国1932年以来有18次政变或参加政变。 来自互联网

11 investigators   

n.调查者，审查者( investigator的名词复数 )

参考例句：

• This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
• The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》

12 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

13 hardy   

adj.勇敢的，果断的，吃苦的；耐寒的

参考例句：

• The kind of plant is a hardy annual.这种植物是耐寒的一年生植物。
• He is a hardy person.他是一个能吃苦耐劳的人。

14 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼