I could argue that a salmon swims upstream because he likes the fresher water. You could point to science and say, but Dixie, we know they do this to spawn! And I could continue to say that isn't the case, they just happen to spawn because they are happy to be in fresh water! But when you really begin to look at the scientific evidence objectively, and with an unbiased mind, you realize the salmon don't swim upstream because the water is fresher, it doesn't matter about the water, they do it to spawn.
I give this analogy to compare what is happening in this debate. Scientific evidence is clear, mankind has a foundational connection to spirituality, and always has. In fact, it is one distinct feature we have over other species of primates. Humans are the most advanced, creative, intelligent and imaginative creatures on the planet, and the only ones to worship. That is no coincidence.
There is an inherent connection between mankind and human spirituality, regardless of the petty arguments over religion. This is not an endorsement of religious beliefs, those are a byproduct of human spirituality, trying to understand something beyond human comprehension. Since the dawn of human civilization, mankind has had a need and desire to worship something greater than self. This attribute is strong, it can't be beaten out of man, it can't be stomped out of man, through thousands of years of persecution, war, genocide, death... human spirituality still remains, and as dominant in humans as ever.
A noted psychiatrist once stated, "if God didn't exist, man would have to invent him." Which is precisely what Atheists claim man did, but that was not the shrink's point. It was to say, mankind has a hard-wired instinctual desire to worship something, and has difficulty functioning long-term without it.
Now, this fundamental human spirituality doesn't mean God exists. That is a matter of faith, and to a great number of people who pray to something every day, he certainly does exist in their minds. But what does "exist" mean? Does God physically exist? I am not aware that anyone has claimed he does. In science, to "exist" means in a physical state. The next issue would be, how to measure existence of a God? Perhaps there is a physical existence of God and we don't know how to extrapolate the information? The bottom line is, you do not have to prove existence of God to determine human spirituality plays a vitally fundamental role in the advancement of our species.