We can observe and understand the process of genetic reproduction of specific types of beings, along with the natural selection and mutation process, all of which was documented by Charles Darwin in his book The Origin of Species. We recognize that a specific life-form, whether plant-life, microscopic life, animal life or human life reproduces itself from generation to generation through a process of seed, cell-division, cloning or live-birth. The genetic encoding is thereby passed on sequentially through time and the existence of that particular species or type continues as long as external factors do not render a particular species extinct. Under this schema, however, everything revolves around the “type”, the “species” the “race”, and there is no provision here for any individual fulfillment or destiny other than to simply be an example of the “type”.
If we recognize an individual evolutionary potential and destiny, there must be some mechanism in place to further the evolutionary cycle for the individual consciousness, and this brings in the necessity for some kind of rebirth process, whereby the individual consciousness, we may call it soul or psychic entity, is able to continue its development across a series of births and deaths, and thereby bring about not just the cosmic fulfillment for the species, but also the individual fulfillment for the individual soul.
In The Life Divine, Sri Aurobindo explores these questions: “This terrestrial evolutionary working of Nature from Matter to Mind and beyond it has a double process: there is an outward visible process of physical evolution with birth as its machinery, — for each evolved form of body housing its own evolved power of consciousness is maintained and kept in continuity by heredity; there is, at the same time, an invisible process of soul evolution with rebirth into ascending grades of form and consciousness as its machinery. The first by itself would mean only a cosmic evolution; for the individual would be a quickly perishing instrument, and the race, a more abiding collective formulation, would be the real step in the progressive manifestation of the cosmic Inhabitant, the universal Spirit: rebirth is an indispensable condition for any long duration and evolution of the individual being in the earth-existence. Each grade of cosmic manifestation, each type of form that can house the indwelling Spirit, is turned by rebirth into a means for the individual soul, the psychic entity, to manifest more and more of its concealed consciousness; each life becomes a step in a victory over Matter by a greater progression of consciousness in it which shall make eventually Matter itself a means for the full manifestation of the Spirit.”