HOW MANY PEOPLE ON EARTH? — DESMOND 547 



tion in the rate of population growth during the past century. Now, 

 public health programs reach even the world's most remote villages, 

 and death rates in the less developed areas are falling rapidly. But 

 the traditionally high birth rates — so essential to offset the high death 

 rates of even the very recent past — remain high. Thus, population 

 growth soars. 



Therefore, over the long span of history, the rate of population 

 growth has tended to accelerate — almost imperceptibly at first ; then 

 slowly; and recently, at a rapid clip. By the beginning of the Chris- 

 tian Era, 200 to 300 million people are believed to have lived on earth. 

 Tliat number had grown to some 500 million by 1650. Then the 

 growth curve took a sharp upward trend. By 1850, world population 

 was more than 1 billion. Today, it is over 3 billion. 



The quickening tempo of growth is even more dramatically 

 expressed in doubling time. It took hundreds of thousands of years 

 for world population to reach the quarter-billion mark, at about the 

 beginning of the Christian Era. Over 16 centuries more passed before 

 that number reached an estimated half-billion. It took only 200 addi- 

 tional years to reach 1 billion, and only 80 more years — to about 1930 

 — to reach 2 billion. Population growth rates are still going up. Dur- 

 ing all of the eons of time — perhaps as long as 2 million years — the 

 human race grew to its present total of 3 billion. But it will take only 

 40 years to add the next 3 billion, according to United Nations esti- 

 mates. In certain nations and larger areas, populations will double 

 in 25 years or even less, if growth rates remain unchanged. 



This historical review traces the proliferation of the human species 

 through three very broad time-spans : Period I extends from 600,000 

 B.C. to 6000 B.C.; Period II extends to A.D. 1650; and Period III, 

 to 1962. These time periods are chosen because the dates mark impor- 

 tant epochs in man's cultural development. 



It should be emphasized, however, that not all portions of the globe 

 experienced simultaneously the cultural and technological advances 

 which mark these different stages of man's history. When the first 

 European settlement was established in Australia in 1788, the 

 aborigines there were in the Stone Age. Even today, some tribes liv- 

 ing in New Guinea and elsewhere still remain at that level. 



PERIOD I— THE OLD STONE AGE 



Period I extends from 600,000 to 6000 B.C. It begins early in the 

 Paleolithic or Old Stone Age and continues to the beginning of the 

 Neolithic or New Stone Age. It is estimated that during this period 

 numbers grew to about 5 million, that man's birth rate was close to 

 50 per thousand, and that there was an approximate total of 12 

 billion births. 



