[1] http://www.politicsforum.org/forum/viewtopic.php?t=109598
"It took over 200,000 years of human history for the world's population to reach 1 billion;[2] and only 200 years more to reach 7 billion." [0]
[0]https://en.wikipedia.org/wiki/World_population
[1] http://www.politicsforum.org/forum/viewtopic.php?t=109598