There are those who try to understand the unique and powerful development of the human mind and spirit within the physical body by stating that the mental/spiritual personality waits for the development of the human being and then descends to occupy that formed instrument for its development and action from that point forward. That implies that the prior development that leads up to the human body, the physical and vital evolution, did not necessarily include a soul evolution. That evolution is said to begin with the descent once the human instrument has been prepared.
Sri Aurobindo inquires as to the mechanism and significance of this concept: “…what is it that brings about this connection of a spiritual being and higher mental nature and a physical being and lower animal nature? what necessitates this taking up of the lower life by the spirit which here becomes man? It would seem surely that there must have been some previous connection; the possessing mental or spiritual being must all the time have been preparing this lower life it thus occupies for a human manifestation. The whole evolution would then be an ordered continuity from the beginning and the intervention of mind and spirit would be no sudden inexplicable miracle, but a coming forward of that which was always there behind, an open taking up of the manifested life by a power which was always secretly presiding over the life evolution.”
In essence, then, if we were to adopt this concept, there would not be any essential difference other than the locus occupied by the mental or spiritual being while the physical being was being developed. Whether that is here on the earth, or in some mental or spiritual plane, the mechanism is relatively the same for the evolutionary process to take place.
Sri Aurobindo,
Sri Aurobindo Studies 