The question of whether there is an individual soul that can grow, develop and evolve, or whether there is a universal soul of which each individual is simply a “data-point” is the next issue to be resolved before looking at the question of rebirth. Rebirth has no essential meaning if there is no individual soul to benefit from it.
If we overview the development of the physical and vital life, we can see the role of a process which scientists have identified as evolution. The physical characteristics are carried forward by the process called heredity and there has been established a well-developed framework for understanding this physical evolution. This does not preclude the action of some other motivating factor that uses the process, of course.
Where the processes of physical evolution seem not to be able to explain things as well is in the development of the higher mental, and spiritual, processes and capabilities. There is in fact a debate in the West about the varying impact of “nature” versus “nurture” (heredity vs. environment) as a shaping factor in the development of the individual personality and its characteristics including the higher mental, emotional and psychical responses.
This brings us then to the question Sri Aurobindo addresses at this point. The combination of the physical heredity with the environmental influences and pressures could represent the development of a “universal soul” as the central premise of existence. “…we may say that they are a phase of the universal soul, a part of the process of its evolution by selection; the race, not the individual, is the continuous factor and all our individual effort and acquisition, only in appearance, not really independent, ceases with death, except so much of our gain as is chosen to be carried on in the race by some secret will or conscious necessity in the universal being or the persistent becoming.”
If this is the ultimate truth of our existence, then, of course, there is no necessity of rebirth, as the forward development momentum is taking place in the universal being and each individual life is simply a cog or grain in a larger mechanism or existence.