Could the soul that inhabits a human body have inhabited an animal body or a plant in previous times?I am sure you are well acquainted with the theory of evolution. Charles Darwin, in the modern world, discovered the process of the evolution of species, that is, the change from a lower form to a higher form. But long before Darwin, a thousand years before the advent of the Christ, the great Indian sage, Kapila, had discovered the theory of spiritual evolution. The Eternal, Unchangeable and Imperishable at every moment evolves: this was his unique philosophy. Nothing came from nothing. The Indian sage discovered this truth and offered it to the world at large.
The total process of evolution on earth includes the soul as well as the physical form. In the march of evolution, each soul has to go through the plant life and the animal life before it can launch into the human life.