Sure, there is no concrete theory of how we came to be, but with rational thinking, the idea of some omnipotent, omniscient being that is everywhere and nowhere at the same time is ludicrous.
Philosophers have proven God's existence and non-existence using logic for centuries. In this case, rational thinking will not lead you to the conclusion that god exists/does not exist. Rather, rational thinking will try to find a argument that already supports what you already believe in.
jonsmth wrote...
most scientists (the well-known at least) aren't atheists you know, they're
open-minded after all
Yes. Einstein was deeply religious. Theories _hint_ at having a god that doesn't run the universe riles him up (some aspects of quantum theories pissed him off).
Stephen Hawkings, probably the most famous physicist alive, was likely a deist.
If anybody understands the nature of the universe, its them. Or maybe the smartest people who have ever lived are simply incapable of rational thought.