I don't know where I heard or read this, wearing sunglasses tricks your body into thinking it is dark (no surprise). In response to that, your thymus (?) which

I don't know where I heard or read this, wearing sunglasses tricks your body into thinking it is dark (no surprise). In response to that, your thymus (?) which is influenced by light levels now diminished because you covered your eyes with dark glass, releases less melanin which makes your skin more susceptible to UV light. It's weird, your skin is more likely to burn because you are wearing sunglasses. I believe it was CBC Radio quirks and Quarks where I heard it. Also, (I mentioned over at Reddit) another interesting thing is the ability of the majority (95%) of adult northern Europeans to be able to digest milk. the next closest group are people from India where 50% of adults are able to digest milk.