The following is lifted from the Wiki discussion on Culture.

Religion and other belief systems are often integral to a culture. Religion, from the Latin religare, meaning "to bind fast", is a feature of cultures throughout human history. The Dictionary of Philosophy and Religion defines religion in the following way:
... an institution with a recognized body of communicants who gather together regularly for worship, and accept a set of doctrines offering some means of relating the individual to what is taken to be the ultimate nature of reality.

I would go further and say that religion also always includes some means of relating individuals to other individuals, and to the social group.

I will also say, as did Don Firth, that I think it unlikely that human beings have the native capability to ever discover the "ultimate nature of reality."   

Janie