Ana Maria ? If I were to answer your question , I would rather timidly say that no true answer may ever be found to your excellent query.
The main principles of Christianity were laid down by Jesus Christ before His Crucifixion in 33 AD. Roman Emperor Constantine gathered together all the decentralized Christian sects of Roman Empire at ( Council of ) Nicaea and with the help of savants of various Christian denominations arrived at what we may call THIS IS WHAT WE BELIEVE IN in 325 AD. Between Christ's Crucifixion and adoption of centralized Christianity at Nicaea in 325 AD , three hundred years had elapsed within which period original Christian doctrines may have undergone various changes and impurities could have seeped in . ( Why, didn't we incorporate confraria principles in Goa ? ) As for your queries on this belief and that belief, let me say that it is possible that a Pope here and there could have converted some superstitious beliefs into dogmas on the ground that he is not only omniscient but infallible as well.