In the context of this discussion and skissane’s comment, religion is the tapestry of traditions/“beliefs” that bind a tribal group together.
I write “beliefs” in quotes because there are beliefs (i.e. assumptions) that people might have philosophically on how they model the world, and there are “beliefs” that people espouse they have as a means to bond with other members of the tribe.
Everybody who gets up in the morning and behaves in the ways they honestly believe are right has religion, including the non-spiritual.