I would say reasoning is a satisfying process towards secure knowledge from beliefs that might have any bases. Reasoning itself, by creative induction and strict deduction to confirm it, is a process that provides our ability to progress, and it is always open to debate as to the security of its knowledge. Consequently, if one seeeks absolutes, one may be entering spirituality, because even though nature might be an absolute and structured machanism (or might not), individual humans cannot state that is is an absolute reality because we are limited to our reasoning process, which is always provisional as to truth - its just a process towards greater satisfaction. You are welcome to read a new book I have written on this as a free download at http://home.iprimus.com.au/marcus60/1.pdf or at my site www.thehumandesign.net (it's a non-spiritual Design, just science).

So your issue might be in why people seek spiritual absolutes when we might be restricted to a process of reasoning 'towards' satisfaction. Perhaps it is over confidence, or an easy half step to say that so much is regular (as we see it) that is 'just is' that way by the hand of a creator. Perhaps it is laziness, of lack of understanding, as we do develop the ideas in my post and this site generally over time. We learn our limitations by reasoning more and more about them. So, I would not look so much to the need to believe at the most basic level, as I would not say I have ever had any particular beliefs (except beliefs as those things I subject to reasoning to raise their status to more satisfying knowledge). The evolutionary psychology rationale, like all natural selection rationales, is open to interpretation as to what benefits survival, and there might some argument that its helps us to survive to believe without confirmation, but I would probably see it as a side issue with pluses and minuses for survival, and merely a slip into error.