One cannot predict with accuracy, the exact period of emergence of 'Yog'. in Indian scriptures. Hence it is better not debate of over the matter but discuss so that we can overcome the problems of human life.
The meaning of 'Yog' is to connect. To connect one with himself, to connect the soul (atma) with soul, to connect the soul with self, which would finally result to the union of the soul with the Eternal / Cosmic soul ( Paramatma ). The process by which we can perfectly but easily complete this union is known as 'Yogkala'. The base of 'Yogkala' is knowledge. Without true knowledge, nothing is possible, not even the cosmic connection or 'Yog'. But on the other hand to get immersed in the sea of knowledge needs the support of 'Yog'.
The period when the philosophy of 'Yog' came into existence, humans started to improve their life with a particular rhythm. In this period only emerged the unparallel way of life known as 'Chatur ashram'. At this point of time the Aryan man divided his life into four stages. If a man passes through all the four stages as prescribed he will certainly be able to enjoy his life fully. Therefore he can truly experience his life and the world connected with it.
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