I think it is the Egyptian King Tut who shows the apparent and disgusting results of inbreeding
The talk I mentioned earlier had to do with ordinary Egyptians at a later period (either Ptolemaic or Roman, don't recall)--I don't know how soon the common people began to imitate the pharaohs in this regard.
Athens allowed half-sibling marriages. The Roman emperor Claudius married his niece and Romans at the time professed to be shocked.