Just wondering: Before the Beatles, were there any songs that sounded like them? I'm trying to go back in time and think about this. So, I think this means songs going back to 1962 and earlier.
Consider the fact that the Beatles were avid radio listeners so it wouldn't surprise me if you can hear the songs that they liked pre-fame influencing their songs somehow.
This may take a while, but I will be contemplating this topic and providing updates to this post as I think of possible songs that connect to the Beatles later compositions.