The Assertion (A) is false, while the Reason (R) is true.

Jainism was not adopted exclusively by the high caste Kshatriya communities in the beginning. Rather, Jainism was open to people from all castes and communities, and many people from diverse backgrounds, including merchants, traders, and artisans, adopted Jainism in its early years. Therefore, the statement in Assertion (A) is false.

On the other hand, the statement in Reason (R) is true. Vardhaman Mahavira, the founder of Jainism, was born into a well-known Kshatriya community in ancient India. Mahavira`s teachings emphasized the importance of non-violence and asceticism, and his philosophy attracted many followers from diverse backgrounds. Therefore, while Assertion (A) is false, the Reason (R) is true.