Jack is shown on the cover art with wings. In the movie, he has no wings but scars on his back show us where the wings might have been. Biblical stories aside, the mythology that Cain (Jack) may be a child of a fallen angel and Eve might explain the vestigial wings. Since Cain was doomed to walk the earth until whenever ("I like to walk.") taking away his wings as part of the curse makes sense.
Henry Rollins' character Cain (also known as Jack) killed his brother Abel in the bible and was doomed to walk the earth for it. He also starred in the hit show Sons of Anarchy in which there is a baby called Abel.