Sri Chinmoy: All the possibilities have taken place. Sometimes He has literally taken a human body and gone through birth. Other times He has projected a portion of the body. Sometimes He is eighty percent upstairs in the higher worlds and twenty percent downstairs in the earth plane, and other times He wants to be one hundred percent conscious both upstairs and downstairs. It is as if someone is living on the first floor, but has access to the whole building. Sometimes He incarnates with His whole Consciousness and sometimes with a portion of His Consciousness.
When God began His creation, higher souls occasionally took incarnation in one of four or five types of forms. Sometimes cosmic gods took a human form directly. They did not go through the animal process. Then afterwards, the gods would not take human incarnation again because they were satisfied. The cosmic gods did not care for realisation, which has to be achieved through evolution on earth; they cared only for limited power. Of course, this limited power is infinitely more powerful than the power any human being can have.
So there was no one process of evolution for the higher souls. Some began from the mineral and some from the animal kingdoms. Some took human incarnations immediately. If all spiritual Masters had started with the animal form, then God alone knows how spiritual evolution would have taken place.