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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-old there are twice as many women as men. But the great universal of male mortality is being changed. Now, boy 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 have 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 a savage 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. What used to be the danger in being a man according to the first paragraph
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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-old there are twice as many women as men. But the great universal of male mortality is being changed. Now, boy 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 have 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 a savage 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. The author argues that our bodies have stopped evolving because__________.
One of the questions that is coming into focus as we face growing scarcity of resources of many kinds in the world is how to divide limited resources among countries. In the international development community, the conventional wisdom has been that the 2 billion people living in poor countries could never expect to reach the standard of living that most of us in North America enjoy, simply because the world does not contain enough iron ore, protein, petroleum, and so on. At the same time, we in the United States have continued to pursue superaffluence as though there were no limits on how much we could consume. We make up 6 percent of the world’’s people; yet we consume one-third of the world’’s resources. As long as the resources we consumed each year came primarily from within our own boundaries, this was largely an internal matter. But as our resources come more and more from the outside world, "outsiders’’’ are going to have some say over the rate at which and terms under which we consume. We will no longer be able to think in terms of "our" resources and "their" resources, but only of common resources. As Americans consuming such a disproportionate share of the world’’s resources, we have to question whether or not we can continue our pursuit of superaffluence in a world of scarcity. We are now reaching the point where we must carefully examine the presumed link between our level of well-being and the level of material goods consumed. If you have only one crust of bread and get another crust of bread, your well-being is greatly enhanced. But if you have a loaf of bread, then an additional crust of bread doesn’’t make that much difference. In the eyes of most of the world today, Americans have their loaf of bread and are asking for still more. People elsewhere are beginning to ask why. This is the question we’’re going to have to answer, whether we’’re trying to persuade countries to step up their exports of oil to us or trying to convince them that we ought to be permitted to maintain our share of the world fish catch. The prospect of a scarcity of, and competition for, the world’’s resources requires that we reexamine the way in which we relate to the rest of the world. It means we find ways of cutting back on resource consumption that is dependent on the resources and cooperation of other countries. We cannot expect people in these countries to concern themselves with our worsening energy and food shortages unless we demonstrate some concern for the hunger, illiteracy and disease that are diminishing life for them. . It can be concluded from the text that
能使运动部件实现往复直线运动，且往复速度不一样的是______液压缸。
To avoid the various foolish opinions to which mankind is liable, no superhuman genius is required. A few simple rules will keep you, not from all errors, but from silly errors. If the matter is one that can be settled by observation, make the observation yourself. Aristotle could have avoided the mistake of thinking that women have fewer teeth than men, by the simple device of asking Mrs. Aristotle to keep her mouth open while he counted. He did not do so because he thought he knew. Thinking that you know when in fact you don’’t is a fatal mistake, to which we are all liable. Many matters, however, are less easily brought to the test of experience. If, like most of mankind, you have strong convictions on many such matters, there are ways in which you can make yourself aware of your own prejudice. If an opinion contrary to your own makes you angry, that is a sign that you subconsciously are aware of having no good reason for thinking as you do. If someone maintains that two and two are five, or that Iceland is on the equator, you feel pity rather than anger, unless you know so little of arithmetic or geography that his opinion shakes your own contrary conviction. The most savage controversies are those about matters as to which there is no good evidence either way. So whenever you find yourself getting angry about a difference of opinion, be on your guard; you will probably find, on examination, that your belief is going beyond what the evidence justifies. For those who have enough psychological imagination, it is a good plan to imagine an argument with a person having a different opinion. This has one advantage, and only one, ascompared with actual conversation with opponents; this one advantage is that the method is not subject to the same limitations of time and space. Mahatma Gandhi (圣雄甘地) considered it unfortunate to have railways and steamboats and machinery; he would have liked to undo the whole of the industrial revolution. You may never have an opportunity of actually meeting anyone who holds this opinion, because in Western countries most people take the advantage of modern technology for granted. But if you want to make sure that you are right in agreeing with the prevailing opinion, you will find it a good plan to test the arguments that occur to you by considering what Gandhi might have said in refutation of them. I have sometimes been led actually to change my mind as a result of this kind of imaginary dialogue. Furthermore, I have frequently found myself growing more agreeable through realizing the possible reasonableness of a hypothetical opponent. According to the text, it is true that
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