Which was the era when caste system was not found in India?

Before 1500 BCE the caste system was not found in India. 

Who started caste system in India?

Aryans

According to one long-held theory about the origins of South Asia's caste system, Aryans from central Asia invaded South Asia and introduced the caste system as a means of controlling the local populations. The Aryans defined key roles in society, then assigned groups of people to them.

https://www.ushistory.org › civ

The Caste System [ushistory.org]

When did caste system start?

1500 BC

Historically, however, it is believed that the caste system began with the arrival of the Aryans in India around 1500 BC (Daniel). Of the many cultures that flourished in India, the literary records of the Indo-Aryan culture are not the earliest.

digitalcommons.calpoly.edu › cgi

Caste System - DigitalCommons@CalPoly