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During the first 2 million or so years of it's history, the human population was a minor element in the world ecosystem, with at most 10 million members. In the New Stone Age, less than 10,000 years ago, the number of humans began to increase more rapidly. The rough equilibrium maintained before Neolithic times gave way when the human population developed agriculture and animal husbandry and no longer had to spread out in search of game. With the abandonment of a hunting-gathering way of life and the rise of permanent settlements and eventually cities, the human population underwent dramatic growth. By the beginning of the Christian era it had reached 250 million and by 1960, half a billion (Fraser, pg.4-6). Many ancient societies, including the Roman Empire, were Natalist-that is, they encouraged marriage and high fertility. They believed that large populations equaled power and success (Stefoff, pg.33). Growth of population during the 20th century was very rapid. In 1994 the total world population was estimated at about 5.6 billion people. It increased nearly by 4 billions of people during the past 100 years. The world's current (overall as well as natural) growth rate is about 1.3%, representing a doubling time of 54 years. We can expect the world's population of 6 billion to become 12 billion by 2054 if current growth continues. The world's growth rate peaked in the 1960's at 2% and a doubling time of 35 years (Population Reference Bureau, pg.1). Krivan, 2 The most significant world trend is that death rates are currently falling in poor and rich countries alike, while birth rates remain high in most poor countries and low in most rich ones. Exceptions are the generally higher death rates of Africa and the high birth rates of the rich oil producing countries. The most populous countries, in descending order, are China, India, the United States, Indonesia, Brazil, and Russia. The U.S population totaled about 260.8 million in 1994. In the 1990's about 4.1 million children were born annually in the United States, and more than 2.1 million people died yearly. The greater number of births is due in part to a fertility rate that has increased by nearly 20 percent since the mid 1980's. International immigration, both legal and illegal, is another major element in U.S population growth.
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