What is meant by psycho-social evolution? From the living cell up to man, biological evolution was motivated by organic satisfactions, numerical increase, and organic survival. But with the appearance of man, these become, says modern biology secondary and not primary; the primary motivation becomes fulfilment; and evolution itself becomes, at the stage of man, conscious and deliberate and goal-oriented, unlike the blind processes at the pre-human stages.
This revolutionary change is the result of the fully developed cerebral system in man, in virtue of which the evolutionary process itself undergoes a revolutionary change; what was organic evolution becomes psycho-social evolution. Organic evolution has no primary significance in the case of man endowed by nature with the versatile cerebral organ, with the aid of which he can invent any organs he may need more efficiently and quickly than what nature can do for him through her slow and wasteful evolutionary processes. Accordingly, evolution has risen from its organic to the psycho-social level in man, says biology.
In a self-centred man, as in all pre-human species, the psyche or mind or soul is limited and confined to the physical organism. In a moral or ethical man, it expands, goes beyond the limitations of his physical organism and enters, and is entered into by, other psyches of the social milieu. This is the fruit of psycho- social evolution.
What biology calls psycho-social evolution is what the science of religion calls ethical awareness and social feeling, the by-product of the early phase of the spiritual growth of man.
With the onset of this psycho-social evolution, men develop the capacity to dig affections into each other as a matter of conscious choice, thus revealing a higher dimension to the human individuality than what is revealed by his physical individuality with its appetites and choices. All ethical theories presuppose a distinction between a lower self and a higher self in man; and the liberation of the higher self is what man achieves through psycho-social evolution or spiritual growth; it is renunciation of the lower self and manifestation of the higher self.
The subject of the spiritual growth of man, of evolution as psycho-social, is a pregnant theme to man in the modern age. It points out to him the way to rescue himself from the tyranny of the sensate and the quantitative and from the prevailing stagnation of worldliness and helps him to continue his evolutionary march of qualitative richness and fulfilment, individually and collectively.