Historical background behind the Vegetarianism - Jainism
When Mahavira revived and reorganized the Jain community in the 6th century BCE, ahimsa was already an established, strictly observed rule. Parshvanatha, a tirthankara whom modern Western historians consider a historical figure, lived in about the 8th century BCE and founded a community to which Mahavira’s parents belonged. Parshvanatha’s followers vowed to observe ahimsa; this obligation was part of their caujjama dhamma (Fourfold Restraint).
In the times of Mahavira and in the following centuries, Jains criticized Buddhists and followers of the Vedic religion or Hindus for negligence and inconsistency in the implementation of ahimsa. In particular, they strongly objected to the Vedic tradition of animal sacrifice with subsequent meat-eating, and to hunting.
According to the famous Tamil classic, Tirukkuṛaḷ, which is also considered a Jain work by some scholars:
If the world did not purchase and consume meat, no one would slaughter and offer meat for sale. (Kural 256)
Some Brahmins—Kashmiri Pandits and Bengali Brahmins—have traditionally eaten meat (primarily seafood). However, in regions with strong Jain influence such as Rajasthan and Gujarat, or strong Jain influence in the past such as Karnataka and Tamil Nadu, Brahmins are strict vegetarians. Bal Gangadhar Tilak has described Jainism as the originator of ahimsa. He wrote in a letter:
In ancient times, innumerable animals were butchered in sacrifices. Evidence in support of this is found in various poetic compositions such as the Meghaduta. But the credit for the disappearance of this terrible massacre from the Brahminical religion goes to Jainism.