In the year 0, the Earth was populated by around 300 million people; 1000 years later, the world’s population had grown by 10 million, but after the Middle Ages, growth accelerated. In 1500, the number was 500 million and in 1800 it was one billion. In 2007, there were approximately 5.8 billion people on earth and in 2009 we had reached 6.5 billion.