Religion is a set of simple principles on the basis of which an individual should lead one’s life.
Here, I have attempted an explanation.
Humans were hunter-gatherers to begin with. They moved in groups from place to place in search of food as animals do. When the flora & fauna of a particular place was not enough to sustain them, they moved on. So, essentially, they did not stay at one place for too long. When such groups came to places like river valleys/deltas, where there was abundant vegetation & animal life, they stayed a little longer than the usual few days/weeks. The flora & fauna around these river valleys lasted long, really long. When their stay extended for more than a year, these humans experienced all the seasons at one place. During their extended stay, they saw the vegetation change, they saw the lifecycle of various plants. They saw the germination cycle, they saw that the fruits ripening & bursting & the seeds falling on the ground & germinating into new plants. Probably, this is where ancient humans discovered the art & science of cultivation. So they began cultivation & that enabled them to stay longer at these valleys/deltas. More & more humans, who accidentally chanced upon such locations stayed longer & began bringing more of the land under cultivation. Populations at such places began increasing- Obvious reason why history shows civilizations taking root at various river valleys & deltas (the Indus Valley along the Indus, The Aztec civilization in the valley of Mexico around Lake Texcoco, The Egyptian civilization along the Nile, The Mayan civilization along the Maya lowlands etc.)
All these places attracted more & more humans, the same way cities experience migration today. With a multitude of people coming & crowding the places, conflict arose. Conflicts over rights to cultivate tracts of land must have erupted on a large scale then. Humans devised newer weapons to kill each other & gain possession of each others’ lands. This resulted in mayhem in these places. The wiser souls (the people who we refer to as rishis, munis or saints) in these locales realized that if this mayhem continued, humanity would be destroyed. So they formulated some, simple tenets to be followed for conflictavoidance which later got evolved into religion…..So modern religions have their origin in Contracts & Agreements. Essentially, these tenets talked about how to lead a life of co-existence (sharing, caring …… Yama, Niyama etc…from Patanjali’s Yogasutras too probably originate from these ancient laws of coexistence).
The wise old women/men (rushis/munis/saints call them what you want) put forth these tenets to people to enable & ensure peaceful co-existence, as universal laws of righteousness/ Dharma. Most humans heeded these laws, the hedonistic ones or the rebels did not. Conflicts reduced…. but the hedonistic ones kept wanting to grab more power. In those days, power meant more land & more people under control, i.e. have more progeny, hence women became possessions more than partners. The wise old people were now in a fix as to how do we keep these rebels under control, because if they were to have their way, humans in these locales would be destroyed. So they thought, “let us introduce some unknown fear in them”…what kind of fear was the question. So they said to all around, “If you don’t follow the tenets laid down by us, there’s a power above all of us (above literally means the sky, which took the form of heaven in most religious literatures), which is watching you at all times, i.e. if you are selfish, carry on your wanton ways, don’t share/care etc… that power will punish you & if you share/care etc. the same power will reward you” & they cited instances of such things happening within the community to reinforce such beliefs. This POWER is the genesis of the concept of GOD (invisible… objective & unbiased (Nirguna)… formless & shapeless (Nirakar)). The inhabitants heeded the teachings of these wise old people & peace prevailed for a while (maybe a few years/decades or centuries). As time went by, some humans (more so the rebel/hedonist variety) started rationalizing on these tenets & looking around for instances of supposed misfortune/ fortune befalling folks around. Over a period of time, they might have concluded, “Well, fortune or misfortune is not really linked with the tenets (which had evolved into transactional ethics by then) laid down earlier”. They asked questions, such as, “Who is up there who has the power to punish us or reward us? We can’t see it”. So they began to go back to their old ways of violence, land-grabbing etc…. unleashing waves of terror.
Once again, the wise old people realized that it was time to intervene. They thought, “The concept of an invisible power above in heaven is too esoteric for the common man to relate to & visualize as being real. So what do we do now?” They did the simplest thing possible, gave that power a form that the common man could identify with. That’s where idol worship must have arisen. They, then gave different human forms to the concept of GOD. The human forms were conceptualized so that the common man could relate with the till-then-esoteric concept of GOD. Different rituals originated….Yagnya is one such..burning up of waste & purifying the surroundings must have been the original thought, which over the centuries should have evolved to managing our carbon footprint 
.Fasting on certain days/ months is a good way to clean up our digestive system, but over the millennia, it has degenerated into a superstition. Many such logical tenets degenerated into more superstitions. Selfish/corrupt individuals, all along history, have taken advantage of this ignorance about the scientific & logical basis of religion & have cornered power.
The Hindu religion has 33 crore Gods listed. Interestingly, each of these Gods has one faculty that is extremely strong & supreme, better than anyone else in the universe, but in other things, he or she is just like another human being: e.g. Indra is extremely intelligent but succeptible to bouts of selfishness, insecurity etc., So that brings me to a question…… “Are there 33 crore faculties in the universe that a human can develop?” think about it & let me know your thoughts.
