"If a man is offered a fact which goes against his instincts, he will scrutinize it closely, and unless the evidence is overwhelming, he will refuse to believe it. If, on the other hand, he is offered something which affords a reason for acting in accordance to his instincts, he will accept it even on the slightest evidence. The origin of myths is explained in this way."
In short, man wants to be 'special', man believes it 'can't just be chemicals', man finds others who believe similarly, and presto: denialism (lol)
I'm emphasizing that this is just my opinion, but oh do I believe it. Life is essentially: learning how to deal. Life is a set of rules and you spend your time learning what they are and/or how to bend them.