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第九篇： We can begin our discussion of population as global issue with what most persons mean when they discuss the population problem： too many people on earth and a too rapid increase in the number added each year. The facts are not in dispute， It was quite right to employ the analogy that likened demographic growth to a long， thin powder fuse that burns steadily and haltingly until it finally reaches the charge and explodes. To understand the current situation， which is characterized by rapid increases in population， it is necessary to understand the history of population trends. Rapid growth is a comparatively recent phenomenon. Looking back at the 8，000 years of demographic history， we find that populations have been virtually stable or growing very slightly for most of human history. For most of our ancestors， life was hard， often nasty， and very short. There was high fertility in most places， but this was usually balanced by high mortality. For most of human history， it was seldom the case that one in ten persons would live past forty， while infancy and childhood were especially risky periods. Often， societies were in clear danger of extinction because death rates could exceed their birthrates. Thus， the population problem throughout most of history was how to prevent extinction of the human race. This pattern is important to notice. Not only does it put the current problems of demographic growth into a historical perspective， but it suggests that the cause of rapid increase in population in recent years is not a sudden enthusiasm for more children， but an improvement in the conditions that traditionally have caused high mortality. Demographic history can be divided into two major periods： a time of long， slow growth which extended from about 8，000 BC.till approximately AD. 1650. In the first period of some 9600 years， the population increased from some 8 million to 500 million in 1650. Between 1650 and the present， the population has increased from 500 million to more than 4 billion. And it is estimated that by the year 2000 there will be 6.2 billion people throughout the world. One way to appreciate this dramatic difference in such abstract numbers is to reduce the time frame to something that is more manageable. Between 8000BC and 1650， an average of only 50，000 persons was being added annually to the worlds population each year. At present， this number is added every six hours. The increase is about 80，000，000 persons annually. | 
