I've always found it interesting that virtually all human societies, from the smallest band of nomads in the bush to the largest of civilizations have worshipped something or another.
The reasons for this are a subject for debate, though. It could be a biological thing, but I think it's more the fact that human beings are intelligent enough to wonder about the world around them.
Almost all religions answer some basic, universal questions: What is this place? Where did it come from? How did I get here? What happens when I die? What's that big light in the sky? That sort of thing.
It stands to reason that humans are going to ask those questions, just as our youngsters continue to ask why the sky is blue, etc.
If biology plays a part, it would be in the source for our intelligence.
But, that's just my opinion, based on a lot of reading and a lot of thinking.
I haven't seen anyone answer the actual and deep question itself, "Why is the sky blue". Except perhaps by poets and songwriters who say it is to match "your baby blue eyes" -- and that is a version of the anthropic princible. To whit that the universe is "just-so" so that we can be here to appreciate it.
However the anthropic principle has two versions. One -- the one that makes sense -- is that the universe is just-so for us for a purpose. And Two -- held when one's depth of understanding stops at some level before the full, exhausting and terrifying depth is reached -- that the universe is just-so because of nothing, That it, it just happened to be that way.
It is understandable why people -- very smart ones too -- hold the second view of the anthropic princible. But at least they DO acknowledge that there is something special about the universe being so exacted tailored for us! How do we know that they do think it is special? Because, one, they gave it a name "the anthropic principle" and, two, they wax on and on in long treatises about how it is *nothing of meaning*, but chance alone for it to be just so. One example is with the "too complex to explain" multiverse theories. (They are too complex to explain because they are not real, btw, if I may cut to the chase -- Occam's Razor and all.) For example to a anthropic mulitverser, we are in this particular universe because it is the one where we are exactly just so, yet there are a infinite number of alternative univerese where we are not, and some where we are, but different.
Such fantasies are wonderful intellectual exercises as well, a potent imagination is a wonderful gift, and all should seek to develop their own.
Yet to track down that "why?" in full one ends up never ending, so to speak, until one arrives back at the primally obvious. That we are here for a reason, that all this creation in its wonderous complexity and "just-so"-ness is for us, about us, for a purpose.
So then, even Occam, himself, looked up at the blue sky and enjoyed the beautiful and comforting expanse blue sky above.
To be an atheist, you must be able to prove a "universal negative" - you would have to be in all places, at the same time, to prove that nowhere in the entire universe something exists. Biblically, this man is a fool - Psalm 14:1 "The fool has said in his heart, 'There is no god.'"