Theosophy, the parent of all religions by definition, teaches that what is known as human is actually a Spiritual Nature classically called the Monad (Higher Self).
This Monad has prompted wakefulness (self analyzing reflection) called the human state through myriad lives passing through the mineral, plant and animal stages during the evolution of life on earth.
However Theosophy differs from the New Age or simply shallow belief that regression is possible. Human beings cannot incarnate as animals or plants again having attained awareness of Self, or really awareness of themselves as distinct from the lower kingdoms for whom such awareness does not exist, for form follows functional mind. Conversely, people are considered only the epitome of spiritual/physical life on Earth and not the end stage of evolution, which continues for further stages.
This natural progression includes those types of beings that were men and women like ourselves, but have since become more than egocentric personalities. The Ancient Wisdom Religion considers that in reaching such levels of selfless spiritual development, a man or woman naturally partakes in a Hierarchy of Being, where concern is the welfare and highest good of all beings.
Therefore, in this sense, where religions would have men worship such Angelic types as the son of the Father (God), Theosophy teaches that all people are such beings in various stages of attainment, through the changing of their focus of life from the outer ego to the welfare of all others.
Of course this must take as many lives to occur as it took to become enmeshed in so called material life. Men and women that have accomplished this are known throughout history as the benefactors and teachers of humanity, and have taught that all people may become what they have become. They teach that it is the duty of human beings to follow this Path of self-emancipation from the bondage of selfishness and become their own saviours, vicarious atonement essentially being impossible and outside the natural order.
For although the thoughts and actions of another may be emulated, no being can be saved from foolishness through another's actions. Therefore Theosophy teaches that the immortal ethical life must be lived, and to this end teaches a Heart Doctrine of ethical thought and action as the practice by which the changes spoken of may be made.