Question

why do you think there is no constitution in earlier time

Answer 1

there was the constitution based on 'dharm' which was discriminate rule for poor ones and based on caste races colour and sex, but when cknstitution is formed by overviewing each and every person not based on any religion made the real constitution which is actually known as the proper constitution based on democracy. ...

hope it helps you

Answer 2

In ancient times, leadership was basically determined by who had the big muscles or who was the most powerful. in the ancient times most of the countries of the world had absolute monarchy, and where it was generally accepted that the king had absolute powers and often times it was believed that the king was some kind of a divine ruler sent by the God to rule the people. Although the rulers had some set of rules by which they ruled the people but over all they had the supreme power. Also the ancient rulers had no idea about the constitution. So, there was no constitution in early times.  
This continued for thousands of years. Later on, people eventually started to question this system of monarchy and many people demanded that the rulers respect the rights and freedom of their citizens. sometimes this happened because any particular ruler got too harsh and the people got upset. Eventually, these type of incidents started to result in formalized constitutions and more democratic governments, which over time ceded more and more powers to people.