It took over "2 million years" for the human population to reach 1 billion, but once it went past the 1 billion mark, it only took another 200 years for it to reach "7 billion".
In the late 1960s, the "human population growth rate" had reached its peak where the population growth rate had gone above 2.5% a year in the developing countries.
The population growth rate of the entire world had reached a little above 2% a year back then.
