Modern Man———(20,000 years 0 to 1 billion)
1830 – 1 Billion
———————–(97 years 1 to 2 billion)
1927 – 2 Billion
———————–(33 years 2 to 3 billion)
1960 – 3 Billion
———————–(14 years 3 to 4 billion)
1974 – 4 Billion
———————–(13 years 4 to 5 billion)
1987 – 5 Billion
———————–(12 years 5 to 6 billion)
1999 – 6 Billion
———————–(12 years 6 to 7 billion)
2011 – 7 Billion
———————–(& on to: 8 & 9 billion)

(nearly 4 billion added: just since 1960)