Buddhi originates from avyakta, ahamkara from buddhi, and the five subtle mahabhutas (Tanmatras), viz. akashatanmatra etc. from ahamkara.These, along with the five gross mahabhutas (in the right sequence) and the bio-transformed five indriyas, constitute the Purusha.
Thus, with this Purusha manifested in its entirety, the body (life) with its all constituents is said to be born (living life). At the time of destruction of life, the Purusha (soul) again dissociates itself from all the manifestations meant for its enjoyment, viz. buddhi etc.
In response to the question on the signs and symptoms of a soul in the living body, as well as the proofs of existence of the soul in living animates, Lord Atreya mentions the following as proof: