Most of the caste aspects afaik were introduced into the original texts after 400BC. These include Balakand, uttarakand (shambuka), Gita etc. This implies some

Most of the caste aspects afaik were introduced into the original texts after 400BC. These include Balakand, uttarakand (shambuka), Gita etc. This implies some form of birth based caste system existing before 400BC which was solidified via new religious texts and additions to already popular old texts culminating with the Manusmriti and rigid caste system by 200 AD. The obvious beneficiaries were the Brahmins who wrote the text. Older texts are a bit more fluid in terms of birth based caste.