Greg M. about sums it up nicely over at unconditioned response:
Every once in a while, some bored scientist or art historian comes up with another theory about who the model for the famous painting the Mona Lisa (La Gioconda, or La Joconde) was. I have seen a few of these hypotheses laid out in shows on the Discovery channel, the National Geographic channel (or “Nat Geo”, as they have taken to pejoratively referring to themselves in a miserably failed attempt to seem cool), et. al., and they’re almost as varied and contradictory as the numerous programs these very same networks rotate around their schedules about the Shroud of Turin (Oh, and they’re just as boring, too; with tons of cliffhanger ad break segues that collapse into anticlimaxes after the programs recommence!). Some claim that it’s actually a self-portrait by da Vinci of himself as a woman, and they point to other self-portraits he made and compare it to the x-ray pictures of the original sketches on the canvas beneath the painting, and they say that the smile on the woman’s face is like that because he’s sort of slyly winking at us about it; blah, blah. Whatever. There are a bunch of other theories too, but I won’t bore you with them here. I’ll wait until I see you at a party and then corner you and talk at you endlessly about them when I’m really drunk. What’s that? You’d rather read about them here? Well too bad! (Sorry about that…)
Except there are now some pretty good shows about the Shroud of Turin like The Real Face of Jesus? on History. And check out David Rolfe and his Latest Shroud of Turin Films. Of course that is all in the eye of the viewer. The full unconditioned response: Mona Lisa Skull.