Why,” Adam cried, “these boys are not alike! They don’t look alike.”
“Of course they don’t. They’re not identical twins.”
“That one-that one looks like my brother. I just saw it. I wonder if the other looks like me.”
“Both of them do. A face has everything in it right back to the beginning.”
(John Steinbeck, East of Eden)
Is ‘back’ a predicative complement, denoting a face has the expression just like containing everything, not split, gone back to the beginning?