Our spirit is not dependent on the brain or body. It is eternal, and no one has one sentence worth of hard evidence that it isn't.
Not a single piece of material culture - not a single object - has been found at Giza that can be interpreted to come from a lost civilization.
I would rather live my life as if there is a God and die to find out there isn't, than live my life as if there isn't and die to find out there is.