The fundamental to gain the knowledge is that until and unless it is not given by anybody else, it cannot be listened and cannot, therefore, be contained in mind failing which it cannot be used in action. This is why someone is badly needed to preach. For example, let a newly born baby be earmarked to live in a lonely cave in a dense jungle. 

If we take care of him by all means but do not make any verbal contact for his any type of education, thus we will find that when he will even attain age of twenty five years ,he will remain ignorant, foolish. When we will keep him out of cave in the open air, he will not know even any languages or worldly knowledge either spiritual or materialistic. 

Question arises, "Why he remained ignorant or foolish or illiterate?" The answer is very clear that he was not provided with his mother, the first teacher and he was not provided with any Rishi or Guru for spiritual/materialistic education etc. Now a days too, the races are still living in the dense jungles separated from the modern world's civilization, are still illiterate and they even do not wear the clothes. In this connection again another question arises, "Why the seven days of week, twelve months in a year the names of cow, horses, trees etc are the same at every part of the world."

Keeping aside the languages if we think unprejudiced then we will come to the conclusion that somebody has taught us to pronounce mother as mother, father as father ,brother as brother ,tree as tree ,water as water, blood as blood, man as man, woman as woman at every part of the world and somebody has definitely taught us the science and deep knowledge of Yoga, Karmas, worship etc.

The oldest several holy books and the Rishis have already invented the answer thereof. In this connection Patanjali Rishi his Yoga Darshan has also cheerfully recited his experiences towards the facts after study of Vedas,Topasya, trust in God ,hard Yoga practice and when he achieved the last and final motto of human life is SAMADHI i.e. realization of God. 

His superb words of realisation are quoted in Yoga Darshan as under :

"Sah Eshah purvesham api Guruhu kalena anavachhedat".

Meaning: -The God is the Guru of the ancient Rishis also, being beyond the limitation and calculation of time.

Comments: - God is immortal. He was before the creation. He is present from the time of creation and will remain when the time will come of destruction. He will remain after the destruction too. That is why he will continue the creation as usual, and will remain again Guru of the new creation. But open the other hand human being will not remain alive for ever, and traditional Guru knowledge will be finished in human life At the time of total destruction of the world. 

Vedas are originated by God and Yoga knowledge has been preached in Vedas. See Rishi Yagvalk Smiriti`s Shaloka.  "Hiranya Garbha Yogasya Vakta". Hiranya Garbh mean- God,Yogasya =of Yoga,Vakta=Teacher. So God is teacher of Yoga knowledge. 

So the result of deep study of vedas, Shastras, Bhagwat Geeta, Ramayana and other holy  books concludes that the first Guru of our ancient Rishis is almighty God. Thereafter, the Rishis/Munis/Acharyas/Gurus have been teaching us the spiritualism/materialistic knowledge up till now.