Kennedy didn't have earlobes and the back of his head was gone. Those photos are of someone else.
"The back of Kennedy's head" was not "gone".
The right parietal region of the skull was gone. The occipital bone was right where it should be.
If you look at the photo in Post 37 carefully, you can see the cavity where the right parietal bone and overlying scalp should be at the upper right hand edge of the photo.
The autopsy X-Rays confirm that the portion of the skull that was "gone" was the right parietal region and portions of the right frontal region. Radiologist Reports
On the X-Rays below, the lateral view (side view) is on your right hand side. On that lateral view, the face is towards your right hand side and the back of the skull is towards your left hand side. Black represents "air density" which represents, in layman's terms, "the part of the skull that's gone".
As to "earlobes", the photo in Post 37 is showing the superior-posterior portion of the ear.