Thinking about Spirit

As I was on my computer, early this AM, I also said a morning prayer.  Not the first of the morning as I try to pray continuously.(impossible for me at all times, but at every time I think of it).
Anyway, I began to wonder when Mankind first began to worship the God within, The Holy Spirit, or just Spirit.
I thought of ancient man worshiping trees and rocks and animal spirits.  I thought of Greek and Roman Gods like Zeus, etc. I thought of the Jewish un-named God, Yahweh, I thought of the Muslim God Allah. I thought of Hindu Gods like Krishna; and  Buddha.
Most, if not all of these Gods were and are worshipped externally.  They are worshiped as mountains, statues, at Holy places like Mecca and Jerusalem, and countless other places around the world which are deemed to represent the dwelling place of God.  Temples, synagogues, churches.  Countless fields( Stonehenge), mountains, waters( like the Ganges), many, many Spirit filled places.
God has appeared to men and women, and even children, in dreams, visions and prophesies, altered states and told them many things, instructions, the future, etc. 
I wondered when however, the first of humankind began to worship the God within each one of us? How and when did the external become internal as well, or was it always so? 
This is not a learned discussion.  I have done no research, not do I intend to. Far better and more educated minds than mine have most likely thought about, written about and discussed this question.My thinking tells me that we acknowledged this Spirit within as God when Jesus said

And I will send to you my Spirit of Truth.

"But when he, the Spirit of truth, comes, he will guide you into all the truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come."

John 16:12-14

I welcome your comments and feedback.  PooBah