During early days of human civilization, we felt very insecure and helpless in front of natural calamities and search for food. We gradually tried to adjust, understand and sometimes overcome such problems. The main stratagy to do that was to organize people and act as a group. That gave rise to group activities like hunting, cultivation etc. It increased their chance of success and survival. During this process men gradually understood its own limitation. So they conceived the existence of supernatural power, which they thought are behind all those forces. They also started believing that such supernatural forces strike when they are not happy. They tried to keep them happy. They developed a set of rituals, “warship”, as the means to keep these “Gods” or “spirits” happy.
Each group of people tried to conceive the supernatural powers according to their own experience. If they liked particular meat or drink, they used to offer those to their “Gods”. “Gods” also started looking like them, physically. So the same “God” is not exactly the same in southern India as compared to that of northern India. Even definition of “God” varies from region to region. Ravana may be a demon in most of India but many people in Sri Lanka and southern India consider him as “God”. As most of the natural calamities used to be the same e.g. rain, flood, storm-wind, draught-sun, wild beasts etc, many of such supernatural powers had high similarities (though not identical) world over. Gradually all such activities and concepts gave rise to religion.
Basically religion was evolved mainly to make societies more organized and to involve everybody to participate in different activities or "rituals", for betterment of the society. “Religion” made implementing the rules much easier, as punishment was stipulated to be high. This gave rise to the concept of virtue and vice. Breaking the rules were equated to sin or vice while obeying those were termed as virtues. Here we should keep in mind that all such rules were made by human, most probably the pack leaders of concerned groups.
During early phase of human evolution and the initial days of “religion”, all were busy to ensure their own survival. So they all were interested to search the reason, in other words, the truth (mainly behind natural calamities, food supply and reproduction). Later life became a bit easier due to many innovations and inventions. Then the main evolution of religion started (as we see it today).
Ancient religions are more inclined to have idol worshipping and have many Gods/Goddesses to take care of natural causes like wind, rain, flood, life threatening animals, birth, death etc. Example of such religion is Hinduism, religions from ancient Egypt, Greece etc. Many tribes in India and abroad practice such type of “religion” with many Gods. More recent religions like Islam, Christianity etc are more like an "ideology". Almost all of such recent religions conceive a single "God" and the person who introduced that “ideology” became a “prophet”; as compared to many "Gods" in ancient religions. Such difference indicates the ultimate motive behind the introduction of such religions. It's like establishing an "ideology" mainly to prove one's supremacy than to motivate survival of a group of people. It’s the same psychology with which a king rules his subject. Evolution of such recent religions was possible as life became easier. Creation and spread of such recent religions also affected ancient religions. Leaders of those who were practicing “ancient” religions tried to invent some new “rituals” (which was not originally there) to strengthen their own grip over wealth and power. “Satidaha” (burning of brides), no beef eating, many marriages by men but not by women etc by Hindus are some of this type of “rituals”. As people and their leaders from different religions came in contact of each other, competition to prove ones’ supremacy became more intense.
To maintian the social order and their own supremacy, group-leaders did not encourage asking question. They started implementing their own version of “truth” in the name of religion. It became the norm. Gradually every religion started demanding un-questionable faith. “Search for truth” soon became the fight to establish one’s own version of “truth”. Now we see the fight among human beings to prove that their version of “truth” is more “true” than that of others! This deformed version of “religion” allegedly is the single most important reason for human sufferings, conflicts and death in the past and remains so even today.