This week I watched a re-run of a National Geographic documentary called "Cain and Abel: Brothers at War" (which debuted back in March). Looks like it will be airing again on Jan. 10 if you missed it. Well worth checking out.
They speculate as to the mark of Cain and his punishment, which I also took a stab at here:
Here's an interesting drawing of Naram-Sin wearing the horned hat of divinity.
General info on the significance of the horned hat:
The documentary mentioned that leprosy (rather than horns) may have been the mark of Cain.
According to the Gospel of Judas, it was not only Cain but also his descendants that bore the 'mark'. As we now know, the royal family suffered from a number of genetic disorders that were passed down from generation to generation, such as skin diseases ('leprosy'), bone problems ('lameness'), and so forth. However, it is hard to imagine that Cain would have been 'protected' by any of these things.
Cain must have been very important for the Lord to pardon him for the killing of his own son Abel. Obviously the tribe of Cain was large and powerful. The Lord must have given Cain some insignia of rule that would have made people fearful to attack him, even when he was alone or lightly guarded. Perhaps the Lord gave Cain one of his own crowns (horned or otherwise).
The horned cap was closely associated with the Mesopotamian god Bel-Marduk. He also was a famous fugitive. He is also the archetype for Biblical Moses, who not only was exiled but later suffered from a kind of leprosy (that raised 'horns' on his forehead?).
© Charles N. Pope, US Library of Congress. All rights reserved.