I suspect that if you were completely isolated from the influence of other thinking minds from birth many questions wouldn't arise...there would be a natural instinct to do the things necessary to survive but there would also be a deep connection to the immediate environment; I would venture to say that you wouldn't feel any separation from the environment at all, and ideas of god wouldn't be necessary because the immediate experience of god would be a tangible reality even though there may not be a claim/thought that that experience had the label god. Things would just be seen as they are because that's what they are to that individual. This wouldn't be the same as just being an animal, however, because the human species seems, at least, to be endowed with a thinking mind. The mind in this case, however, would only be used as a tool and not as something to construct an identity out of.
I tend to feel that many concepts wouldn't even be entertained because the person would be so in tune with what's immediately in front of him that the mind wouldn't generate questions. Would there be pain? of course. Would there be suffering? I tend to think not, for suffering is generated by a mind which resists what is, and there would be an inherent acceptance of what is (IMO).
I would guess the mind would operate when needed to deal with an immediate situation but would "turn off" when no longer needed. Why bother with something that isn't immediately in front of one? I suspect that the concept of time wouldn't be created - it would always be now (which of course it is anyway, but it would be one's reality) and without such a concept problems aren't created. Just think to yourself how the concept of time generates so many problems in your own life.
Since there would be no societal/religious/educational institutions telling one how things are "supposed" to be, there would be no struggle to change things from what they already are. In other words, there would be a natural surrender to what is. And in that is found a deep and abiding peace.