For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
I try to avoid using the term "religion", when referencing salvation or Jesus Christ. To my way of thinking religion is simply doing something (ANYTHING) repeatedly. You can be religious about brushing your teeth 3 times a day, washing your hands for 30 seconds, letting your car warm up before driving, etc. etc. Obviously these actions have nothing, whatsoever, to do with God, Jesus, salvation or anything spiritual.
The "spiritual" religions are all worthless. This includes all of the ways people try to do things, thinking that it is making "points" for them with God.
It seems to me that spiritual "religions" are used by people trying to do something to gain salvation, or favor with God. True spiritual salvation is a gift. If you have to work, in order to get something, it is not a gift.
I am, therefore, NOT religious, but God loves me anyway, and I love Him because He loved me first!
I don't think the question here is about how people got started brushing their teeth at a certain time each day. Many people are religious about where they sit in worship service.
The question isn't about being religious; it's about "religion." Someone is curious about how belief in deities and traditions got started. That's the generally accepted meaning of the idea of "religion."
The Bible tells a story of the God Jehovah, who is reputed to have created the world and all that's in it, including mankind. The man and woman to which He gave life, had physical fellowship with God. They sinned; then they had only spiritual fellowship with Him (they were evicted from Eden). Then sin began to abound. One of their sons, Cain, killed his brother, Abel.
Then Cain went out from the presence of the LORD... (Genesis 4:16) (This, I believe, is a clue of the beginning of how men began to lose spiritual contact with God).
To Adam and Eve, another son was born and they named him Seth. To Seth was born a son and he named him Enosh. (Here's the next clue) "Then men began to call on the name of the LORD" (Genesis 4:26).
There was a flood, the survivors built a tower, God confused their language and they were scattered (Genesis 11). The people are scattered, God is silent, the different tribes begin speaking different languages. Ideologies naturally broadened. Various religions were born.
God's salvation plan precedes these religions. Grace supersedes our sinful weaknesses..