Good point mapman, about the Lennon/McCartney songs authorship. Once they went solo, it became rather apparent, if one couldn’t already tell, which of them wrote any particular later Beatles song. I believe by the time of Rubber Soul, they were no longer writing together. Also, as time went on, the writer of the song sang the lead vocal or melody. They even let George sing Taxman. ;-)
By the way, that song has a fantastic guitar solo (go ahead, listen to it right now!), which even a Jazz guitarist would be proud to say he played. It was, in fact, played by Paul McCartney. Anyone who says The Beatles weren’t good musicians has a very different concept of good than do I.