When did Lewd Behavior Become the Norm?

It has been said that man is a rational animal. All my life I have been searching for evidence which could support this. -Bertrand Russell



Today, amid my 14 hour shift at the kissing booth, I read a couple of articles in the New York Times arts section (for the first time in weeks, I've had time to actually delve into the paper which was incredibly exciting). One of which was about the upcoming royal wedding and the media's overwhelming response to it - which I honestly hadn't noticed until this week because I just hadn't time or interest enough to watch tv.
The article about the soon to be newlyweds got me thinking a bit about etiquette and what pomp and circumstance would be seen this upcoming Friday. Somewhere in this train of thought, I became curious as to my own etiquette....I was brought up to be painstakingly proper but have been a tad more relaxed as of late. None-the-less, in my personality, passing judgement happens quite naturally even when I display the unappealing qualities that I am eager to correct in others...so I began spouting off (with my co-workers) a list of pet peeves that I believe genuinely stem from our culture's defiance of all perceived norms.
I don't know when people stopped knocking on doors - especially bathrooms - before entering. Or when it became acceptable to break wind in public without asking pardon. Or when spitting began being fashionable. Or when walking with a group of people (taking up the entire sidewalk)refusing to budge even when you see others attempting to get through. Or not cleaning up your dog's excrement in other people's yards or walkways. I thought these were mostly common sense....definitely not something, you needed a book or a visit to Miss Manners to instill, but somehow we've forgotten general politeness...and it makes me ill.
I would like to think that as humans with the ability to reason, we would be more aware of others (and our impact) than our bonobo relatives...Maybe someday we will improve mentally upon the evolutionary chain.