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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.
What does the word " uptick" at the end of the 5th paragraph refer to?
选项 A、Longer life expectancy.
B、Rising survivability of children.
C、More and more women pursuing their own career.
D、Increasing fertility rates in countries with HDI above 0.9.
答案D
解析 语义题。第五段解释了发生“人口转变”(即国家越发达生育率越低)的原因，该段最后一句的“Conversely”显示此处行文发生转折，转而解释另一个现象，即第四段介绍的“J形”分布：一些国家在发展到当HDI超过0．9时，生育率不降反升。按照迈斯基拉博士的观点，一些最发达国家实施了有利于妇女的就业政策，使得妇女可以多生孩子而无后顾之忧。因此选[D]。
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