Most people have some kind of spiritual beliefs- because of their culture and upbringing.
Virtually no one is raised without some exposure to culture and upbringing- but like i said- this is a thought experiment.
You believe that is someone was raised without any exposure to religion or religious faith they would somehow automatically and inevitably invent some spiritual beliefs.
I don't.
Understood, but disagreed. If a bunch of babies were placed on an island and raised by machines, I believe they'd not only invent their own culture, but as they went through pubescence, would do what came natural. Similarly, since spirituality not only seems to be a natural part of ourselves, including genetically (a dicey subject for some!), I think they'd become spiritual.
Sure, some would become "religious" just like B.F. Skinner's "religious pigeons", but the smart ones would contemplate existence itself thus exploring the same questions countless philosophers and spiritual-seekers have done throughout history.