Without cultural indoctrination, all of us would be atheists. Or, more specifically, while many may dream up their own gods as did our ancestors, they would certainly not be 'Christian' or 'Jewish' or 'Muslim' or any other established religion. That's because, without the texts and churches and familial instruction, there are no independent evidences that any specific religion is true. Outside of the Bible, how would one hear of Jesus? The same goes for every established religion.