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  3. One of the paradoxes of human biology is that the rich world has fewer children than the poor world. In most species, improved c

One of the paradoxes of human biology is that the rich world has fewer children than the poor world. In most species, improved c

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问题     One of the paradoxes of human biology is that the rich world has fewer children than the poor world. In most species, improved circumstances are expected to increase reproductive effort, not reduce it, yet as economic development gets going, country after country has experienced what is known as the demographic transition; fertility (defined as the number of children borne by a woman over her lifetime) drops from around eight to near one and a half. That number is so small that even with the reduced child mortality which usually accompanies development it cannot possibly sustain the population.
    This reproductive collapse is particularly worrying because it comes in combination with an increase in life expectancy which suggests that, by the middle of the century, not only will populations in the most developed countries have shrunk (unless they are propped up by historically huge levels of immigration) but also that the number of retired individuals supported by each person of working age will increase significantly. If Mikko Myrskyla of the University of Pennsylvania and his colleagues are correct, though, things might not be quite as bad as that. A study they have just published in Nature suggests that as development continues, the demographic transition goes into reverse.
    Dr. Myrskyla compared two things. One was the total fertility rate (the number of children that would be born to a woman in a particular country over the course of her life if she experienced the age-specific fertility rates observed in that country during the calendar year in question). The other was the human development index for that country. The HDI, a measure used by the United Nations, has three components; life expectancy; average income per person; and level of education. Its maximum possible value is one.
    Back in the 1970s, no country got anywhere near one. Of the 107 places the researchers looked at, the best was Canada, with an HDI of 0.89. By 2005, however, things had improved markedly. Two dozen of what were now 240 countries had HDIs above nine—and something else remarkable had happened. Back in 1975, a graph plotting fertility rate against the HDI fell as the HDI rose. By 2005, though, the line had a kink in it. Above an HDI of 0. 9 or so, it turned up, producing what is known in the jargon as a "J-shaped" curve (even though it is the mirror image of a letter J). In many countries with really high levels of development (around 0.95) fertility rates are now approaching two children per woman. There are exceptions, notably Canada and Japan, but the trend is clear.
    Why this change has come about, and why the demographic transition happens in the first place, are matters of debate. There are lots of social explanations of why fertility rates fall as countries become richer. The increasing ability of women in the developed world to control their own reproductive output is one, as is the related phenomenon of women entering the workplace in large numbers. The increasing cost of raising children in a society with more material abundance plays a part. So does the substitution of nationalised social-security systems for the support of offspring in old age. Falling rates of child mortality are also significant. Conversely, Dr. Myrskyla speculates that the introduction of female-friendly employment policies in the most developed countries allows women to have the best of both worlds, and that this may contribute to the uptick.
    No doubt all these social explanations are true as far as they go, but they do not address the deeper question of why people’s psychology should have evolved in a way that makes them want fewer children when they can afford more. There is a possible biological explanation, though.
The following statements are consistent with Dr. Myrskyla’s view about demographic transition EXCEPT that________.
选项 A、fertility rates in Canada don’t rise because of the lack of female-friendly employment policies
B、some countries experience another transition: fertility rate rises as they become more developed
C、the rising female employment does not always result in reduced reproductive output
D、HDI is an important indicator for a country’s level of development
答案A
解析 态度题。第五段末句指出，迈斯基拉博士认为最发达国家实施了有利于妇女的就业政策，可能有助于生育率的提高，但文中也强调生育率的升降可能有多方面的社会原因，甚至还可能有生物学方面的原因，因此不能逆推出加拿大等国没有出现生育率回升就是因为其缺乏有利于妇女的就业政策，因此选[A]。第四段倒数第三句显示，迈斯基拉博士的研究发现，一些国家在发展到一定程度(HDI大于0．9)时，生育率不降反升。HDI是被迈斯基拉博士用作衡量国家发展水平的指标，用于与生育率的变化相对照，研究二者的相关性。根据第五段末句可知，妇女走上工作岗位可能影响生育率，但有利于妇女的就业政策也能让妇女兼顾生育和事业，所以妇女就业并不必然导致生育率降低。所以[B]、[C]和[D]均符合迈斯基拉博士的观点，故排除。
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