Bangladesh is one of the most populated countries in the world with 161 million (16 crore) population. It is a common perception that Bangladesh has the lowest demographic status in the world - packed with people and it's getting worst over the years. There are only 7 countries more populated than this flood plain delta. Only 9 small city states (such as Singapore, Hong Kong, Macao, Monaco etc.) and island nations have more population density than Bangladesh (1237/sq.km.).
Modern human originated in Africa about 200,000 years ago. About 100,000 years passed when we started migrating to the other parts of the globe. At that point the population was less than 1 million, which expanded to about 170 million by 1 AD in just 10,000 years after the invention of organized agriculture.
Since then the big empires such as Roman, Han started to form. The golden age of India started at about 500 AD with highest population concentration in that region. Mayans in South America