why south India is more developed than north India?

Hi friends ,today we are going to discuss a very important topic , why south Indian states are more developed than north Indian few states . You may have your own view , so i am requesting you to please share with me . Before going to start talking we need to understand few facts . Thousands years ago Gaga river give birth to a civilisation. A very large population grew up on the bank of Ganga river because of fertility of Ganga river, At the time people used to believed that if more the people will be there more earnings. On the other hand in south they mostly dependent on Trade and their land was not that much of fertile , these factors does not encourage them for bigger population. I am not telling south is more developed , even in north many state like Haryana ,Punjab , Maharastra are developed , But state like UP , Bihar , Jharkhand are not developed . But still population is not the actual cause ,  if we see literacy rate in south Indian states like Kerala 93.9%, Andhra 91.1%..compared to national avg 75%) means more people are educated and hence these peoples better understand democracy .In south India local political party are very strong ,so there are no mess of multiple political party .They have likes of CPI-M in Kerala; AIADMK ,DMK in Tamil Nadu, TDP in Andhra and these party are very strong and well connected with their peoples.If we see things from historic point of view ,them most of foreign attacks happens on north Indian states and repeatedly destroyed by many foreign powers . One of the last but most powerful reason is , most of research centre of India are developed in Southern and Gujrat and Maharastra of India ,even after 1990 there are many industrialisation done by government of India in selective states .Let me tell you one thing, suppose you have 100 cow in your area and some one want to set up a factory for cow meals , he must start his factory near to these 100 cows . Same things happens , initially government developed few area and more development started on those places only