How do you claim sexual practices are "similar" today as a generation ago? Christianity has been prescribing missionary sex position for a long time now, and even Islam has guidelines on sexual activity (that covers the first two largest religions of the world). (Remember the line in catholic influenced Godfather where someone says that he can't have oral sex with his wife because she also kisses their kids with the same mouth, and hence his need for prostitutes for oral sex?). Pornography is the next biggest influencer. And if you look at that, oral sex were heavily promoted in the past, and now anal sex is heavily promoted. Now, even movies and television have normalised oral sex in the last 2 decades or so.