Religion is a hard word to define. It seems easy, until you actually try to do it. Consider the challenges faced in the US right now regarding what should be a "protected" religious belief, versus what is a "belief" from a sham religion.
Dictionary.com provides a definition I like:
a set of beliefs concerning the cause, nature, and purpose of the
universe, especially when considered as the creation of a superhuman
agency or agencies, usually involving devotional and ritual
observances, and often containing a moral code governing the conduct
of human affairs.
Breaking this down:
- "A set of beliefs concerning the cause, nature, and purpose of the universe"
- Religions answer the tough questions about existence
- "especially when considered as the creation of a superhuman agency or agencies"
- Agency is a very particular word, implying entities which have "freewill" and can act on the universe around us
- "usually involving devotional and ritual observances"
- Doing things "because the religion says so" and "to demonstrate to others our beliefs"
- "and often containing a moral code governing the conduct of human affairs"
- Moral codes provide definition to "good" and "bad"
The creation of moral codes seems to be one of the sticking points. In fact, expanding the topic even larger than morality, religion seems to be one of the single most effective tools humanity has invented and/or been given by a deity. Methods of teaching soft skills such as "kindness" are often handled through religious channels because they're good at it.
However, I would like to focus on the first two points. It is human nature to wonder about the universe around them, and in fact, the more successful we are at building models of how nature works. Cultures that do not build models of the universe get overridden by those who do. Once you have a model of how the universe works, it is very difficult not to begin picking up the other traits of a religion.
Consider science. Science is often considered to be the alternative to religion. It explains much of the cause, nature, and purpose of the universe (though not all!), just like a religion. However, unlike religion, science does not include any superhuman agency... at least at first glance. Listen in on the musings of two Quantum Physics professors bantering back and forth, and you start to pick up words of agency used to describe quantum scale particles (these words are a side effect of our inability to see nor change some quantum values in tandem). Likewise, you will hear science weigh in on "when life begins," which is heavily entwined with human agency, and it is very difficult to go too far down that road before you wonder about superhuman agencies, such as those of mob mentalities and nations. These issues rapidly produce a moral code of their own!
The last step towards science meeting that definition would be the presence of devotional rituals. Consider the repetative practice at the scientific method in school or the act of blind faith of landing in a foreign city with nothing but a GPS and the internet (or perhaps even the blind faith of getting on an airplane in the first place). These may not qualify as rituals in your own lexicon, but you have to admit that they are on a slippery slope.
And if society's alternative to religion looks this much like a religion, that suggests that it would be remarkably difficult to handle the development of an early society without accidentally treading on it. In fact, I think it would be tricky to accomplish, even if you started the society with the expressed intent of sidestepping this particular definition of religion. Things just happen, especially when they are beneficial.