Some anxieties about evolution

This morning, while showering, I noticed a single scale on my leg. It was iridescent, primarily on the green end of the spectrum, and pulled at my skin as I inserted a fingernail under its edge. I bent over, water forced my eyes shut; I could still make out the flashing scale behind my closed lids. A little breathless, I reached to turn the water off, blinking at the sudden brightness.