I'd say it isn't so much from the physically perfected body as it is a state of attentiveness. To answer another post which asked for my delineation between elves and humans, I'd respond by saying that I think that certain humans can become. This is not unknown in literature, yet does not require literature to substantiate it. This gets very complex very quickly. I also think that most religious terms are metaphors, not literals.
Reincarnation is the replication of the self-concept.
Liberation is what happens when one becomes Immortal, becomes an elf, if you will, and we call it by many names. The most astounding difference between elves and humans lies within their psychology and their magick. Humans tend to need these things as structures of support. Elves tend to be less attached to the things of the world, are more contented, being immortal, with patience and kindness, and they are playful in a genuine way. Elves are also often the most empathic, due to their depth of experience, their value of those things which do not change, and their direct connection to the natural, the spontaneous, the unrestricted.