"Render unto Caesar" isn't that old in Christian nations, either. The separation of Church and State is, as history goes, a recent phenomenon, hard-won in nations like England (which, as far as I remember, still has an "official" church, in fact if not in practice), and integrated into the founding of America.

Through much of Christian history, the Church wielded as much power as the King and government of many nations, and, as one would expect given that power, abuses were many.

Ironically, during the Dark Ages, Muslim civilization was quite advanced, and far more tolerant of other religions and new ideas than the European Christians were, or for that matter, than present-day Islamics. There's a reason that many math terms and star names have Arabic origins.