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  3. Being a man has always been dangerous. There are about 105 males born for every 100 females, but this ratio drops to near balanc

Being a man has always been dangerous. There are about 105 males born for every 100 females, but this ratio drops to near balanc

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问题     Being a man has always been dangerous. There are about 105 males born for every 100 females, but this ratio drops to near balance at the age of maturity, and among 70-year-olds there are twice as many women as men. But the great universal of male mortality is being changed now, by babies survive almost as well as girls do. This means that, for the first time, there will be an excess of boys in those crucial years when they are searching for a mate. More important, another chance for natural selection has been removed. Fifty years ago, the chance of a baby (particularly a boy baby) surviving depended on its weight. A kilogram too light or too heavy meant almost certain death. Today it makes almost no difference. Since much of the variation is due to genes one more agent of evolution has gone.
    There is another way to commit evolutionary suicide: stay alive, but have fewer children. Few people are as fertile as in the past. Except in some religious communities, very few women has 15 children. Nowadays, the number of births, like the age of death, has become average. Most of us have roughly the same number of offspring. Again, differences between people and the opportunity for natural selection to take advantage of it have diminished. India shows what is happening. The country offers wealth for a few in the great cities and poverty for the remaining tribal peoples. The grand mediocrity of today everyone being the same in survival and number of offspring means that natural selection has lost 80% of its power in upper-middle-class India compared to the tribes.
    For us, this means that evolution is over; the biological Utopia has arrived. Strangely, it has involved little physical change. No other species fills so many places in nature. But in the past 100,000 years—even the past 100 years our lives have been transformed but our bodies have not. We did not evolve, because machines and society did it for us. Darwin had a phrase to describe those ignorant of evolution: they "look at an organic being as average looks at a ship, as at something wholly beyond his comprehension". No doubt we will remember a 20th century way of life beyond comprehension for its ugliness. But however amazed our descendants may be at how far from Utopia we were, they will look just like us.
Which of the following would be the best title for the passage?
选项 A、Sex Ration Changes in Human Evolution
B、Ways of Continuing Man’s Evolution
C、The Evolutionary Future of Nature
D、Human Evolution Going Nowhere
答案D
解析 从文章第l段的内容可知，如今的男婴和女婴的存活率几乎一样；这就意味着，自然选择的另一个偶然性已经被消除了；因为大部分的变异是由基因引起的，所以进化的又一个因素不存在了；从第2段的内容可知，如今，几乎没有人像过去那样能生育了；现在，出生的人数已经平均化；我们大多数人所生的子女数量几乎一样多；人与人之间的差别以及利用这种差别进行自然选择的机会都已经减少；每个人的寿命差不多，所生的子女数量也一样；从文章最后一段的内容可知，对于我们来说，这意味着进化已经结束；生物学上的理想境界已经来临；过去10万年——甚至过去100年，我们的生活发生了变化，但我们的身体却没有改变；我们没有进化，因为机器和社会代替我们进化了；无论我们的后代感到多么惊奇，他们还是会看起来跟我们一样。据此可知，本文主要讲的是：由于一些进化因素的消失，人类的进化已经结束。D项与文章的意思相符，因此D项为正确答案。
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