Did People Always Talk as Dirty as They Do Now?

Okay, I know, Abby is short for Abigail, not a former monastery or convent, which is abbey.  Sorry.

If you based your judgment just on novels, you would think there has been an explosion in the use of dirty language since 1900.  But is that a matter of novel conventions and requirements for getting published, or are obscenities more commonly used in conversation today than they used to be?
Within my reading I see Norman Mailer's The Naked and the Dead (1948) as a transition novel.  That novel is filled with "fugs," as in "fug it" and "that fuggin' lieutenant."  It took, what, a couple of decades for writers to include the whole inventory of undisguised obscene terms in their fiction without thinking twice. 
Here's my sloppy sociological speculation:  in some groups there has probably always been about the same level of coarse language.  Soldiers in wartime, for one.  That's the life Mailer was describing.  The lower classes and the criminal class, for another.  The thieves' argot of Dickens was probably in actual life shot through with profanity.  The American detective-noir novelists of mid-century hadn't come to Mailer's threshold.  The crooks in Cain and Goodis talk like prudes.  In actuality the bad guys of that era probably sounded about the same as contemporary goodfellas.
Shakespeare's world?  Probably the same.  The plays include bawdy, but not obscenity.  Those plays had to pass the scrutiny of a censor, who was mostly interested in political issues, but who worked for a queen who was both pragmatically open-minded and prudish.  But the soldiers shipping off to Ireland probably had a larger catalog of obscenities than the guys in Afghanistan. 
What I think has happened is that the use of dirty language has moved up-class. 

So what do I do with adolescent city boys in 1908?  I guess you think about the intended readership for your book.  The boys would  probably be like I was at that age, reveling in a new-found freedom to talk like foul-mouthed adults.  My choice was to clean up their speech.  If you asked me to describe the tone I tried to create in the novel, I'd struggle to be very articulate.  But that's where the answer would be.