Indian history
-Dravidian migration into South India
-Aryan invasion
-Hindu culture borrowed from Aryan IVC
-Caste system started
-Warring Hindu kingdoms
-Islamic invasion
-British invasion
-Caste system ended
-British left
-Caste system restarted
-Partition
-Republic of India
To start with the word Dravidian was used to designate a group of people who speak Dravidian languages, they are evidence that people in south western pakistan still speak languages related to Dravidian groups.
Aryan Invasion do not mean blood Invasion and recent studies showed that the Rigvedic was composed in Indian subcontinent and the date is also pushed back Much older than the previous date.
IVC is later period than Rigveda
In Mahabharata there is no caste system and this book was composed in B.C. To start with there are only two categories
1) Vysyas who are natives.
2) Shudras who are immigrants.
The guys who can fight and learned fighting skills are called Kshatriya's (Warrior group) and the guys who are interested in studies are called priests (you may call them Bhrahmins, Rishis or Acharya's etc).
India is a at its peak when Mauryans rules close to 400 years. During that time Buddhism became popular which opposed the Brahmanisation of Indian society which also freezed the flexible divisions in system of Indian society (there by bringing in the caste system).
Buddhism opposed this and emperors started embracing Buddhism and Jainism.
-- During the golden ages of India Shankaracharya revived the Hinduism in India by debating with Buddhist monks and defeating them. Shankaracharya also opposed the rigidity in Indian society (caste system).
-- Islamic Invasions
-- British rule
-- Partition based on religion
-- Secular republic of India
-- India's emergence on the world stage as a biggest democracy, an economic and military power.
Regarding caste system in Today's India, I oppose it and some of the twisted traditions like caste are embedded for centuries but I hope gradually these evil systems will go.