In his History of the World Roberts (1990:908), commenting on a world population exceeding 5 billion persons, writes: ‘Though it had taken at least 50000 years for Homo sapiens to increase to 1000 millions (a figure reached in 1840 or so) the last 1000 million of his species took only 15 years to be added to a total growing more and more rapidly’. More recently it is estimated that the world population reached 6 billion in October 1999 and that the increase from 5 to 6 billion, huge army of the world’s desires, took place in a mere 12 years (Schoon 1999)
