2. 外语
  3. There are about 105 males born for every 100 females, but this【B1】______ drops to near balance at the age of maturity, and among

There are about 105 males born for every 100 females, but this【B1】______ drops to near balance at the age of maturity, and among

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问题     There are about 105 males born for every 100 females, but this【B1】______ 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【B2】______ is being changed. Now, boy babies【B3】______ almost as well as girls do. Fifty years ago, the chance of a baby(particularly a boy baby)surviving depended on its weight. A kilogram too light or too heavy【B4】______ almost certain death. Today it makes almost no【B5】______ . Since much of the variation is due to genes, one more agent of evolution has gone.
    There is another way to【B6】______ evolutionary suicide: stay alive, but have fewer children. Few people are as【B7】______ as in the past. Nowadays the number of births, like the age of death, has become  【B8】______ .Again,【B9】______ .
    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.【B10】______ . 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 a savage looks at a ship, as at something wholly beyond his Comprehension." No doubt we will re- member a 20th century way of life beyond comprehension for its ugliness.【B11】______ .
【B9】
选项
答案differences between people and the opportunity for natural selection to take advantage of it have diminished
解析 differences between people and the opportunity for natural selection to take advantage of it have diminished
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