Sculpting with clay is a fast way of getting a grasp of very, very complex and organic forms, like the skull. God likes to be a show-off, but I wouldn't like to use the word "over-engineered" because I think every single bump and ridge adds beauty and utility to the human form. It is all there for a reason. Everyone seems to follow a certain blueprint that diverges in delightful ways.
This is what I made before starting my anatomical studies on skulls.