What do you think, could evolution have brought that about...?
Very possibly, but why go that far when the social standards and cumulative experience explanation is already there.
I don't think I'm following your reasoning. You suggest that social convention and experience are not a source of morality as they are frequently contravened. Then you ask if some 'inbuilt' moral restraint, which also apparently frequently fails, is evidence for the existence of a creator God.
If the contravention of moral standards are enough to dismiss highly relative and flexible sources such as social standards, etc.., how on earth can they not be even worse for something as fundamental as something created within us by God?
TTFN,
WK