Beatles songwriting?

In a couple of biographies I read, John Lennon and Paul McCartney did collaborate on their songs. One would come up with a melody and some lyrics. The other would then contribute their ideas to the song such as changes or additions to the lyrics, chord changes, intro's, endings, and harmonies, until it become something worth recording. You can pretty much tell who initially came up with the song by the Beatle who sings the lead melody. Eventually, they started to do songs on their own with some contribution by the other members but not as elaborate as how John and Paul started out in their earlier career. If you're interested in this remarkable band, I would suggest that you read The Beatles by Bob Spitz and Paul McCartney: Many Years From Now by Barry Miles. There are also some good books about the Beatles by their producer, Sir George Martin, and their second recording engineer, Geoff Emerick.

Regarding the Lennon/McCartney credits, I'm guessing that even though one Beatle authored the song, legalities in their publishing contracts, the songs were still credited as if John and Paul had written those songs together.

Why does everyone blames Yoko for everything? It's getting old.

Paul try to change it before John met Yoko.

You have it about right. The Revolver album showed the dramatic differences in their writing styles.

a little of this and a little of that in essence. you can tell if you listen enough who did what in the music as well.