When we review the concept of evolution, we generally treat it as a single process, focused on the development of ever more complex forms. Sri Aurobindo points out that there is, rather, a double evolutionary process: the first being the evolution of the forms of Nature (mind, life and body) and the second, the inner spiritual evolution of consciousness. These two proceed with a different emphasis and speed depending on the stage of the universal development that is being viewed. Nature focuses first on the evolution of forms, in order to prepare the vessels capable of holding increasing powers of consciousness.
Sri Aurobindo describes this dual process: “But Nature’s major preoccupation must necessarily be still and for a long time the evolution of mind to its greatest possible range, height, subtlety; for noly so can be prepared the unveiling of an entirely intuitive intelligence, of Overmind, of Supermind, the difficult passage to a higher instrumentation of the Spirit.”
Sri Aurobindo points out that if the intention of Nature were simply to escape, or to leave this field for some other-worldly fulfillment, there would be no necessity for this dual evolution. The effort, focus and goal would be to achieve a revelation of the “essential spiritual Reality” realised either “here” or “elsewhere”.
It is within the framework of a transformation here that the double evolution takes on significance: “But if her intention is a comprehensive change of the being, this double evolution is intelligible and justifies itself; for it is for that purpose indispensable.”
Sri Aurobindo, The Life Divine, Book 2, Part 2, Chapter 24, “The Evolution of the Spiritual Man”
Sri Aurobindo Studies 