The impressive video Human Population Through Time that you will see below, describes the growth of the earth's population in the last thousands of years. You will notice that it took a long time to populate explosion.
To become more specific we took 200 thousands of years to get the first billion people, but only 200 years to hit the landmark of seven billion. 
Watch the video with the map that tracks world population growth. The video shows how we spread around the world and highlights the empires and historical events during duration of years.
The very interesting Human Population Through Time video you are about to watch was uploaded to YouTube from the American Museum of Natural History or American Museum of Natural History.
Watch it
