Here's another good question. Are the children of a union of an elf and a man mortal or immortal? I think it says somewhere that Aragorn and Arwen's kid was mortal. It also says that Dior, son of Bren and Luthien, was mortal? Why? Is there any other referance to the children of an elf and a man? I would guess that the human genes are dominant over elven genes. Heck, Elves might not even have genes. I know this isn't what you're talking about now, but I just thought I'd mention it.
