Hair and adaptation by-products!

In light of our recent conversation on Wednesday about "putative-adaptations", here's a great example of an explicit adaptation by-product: iridescent hair in the blind golden mole. Iridescence is fairly rare in mammals, so researchers were interested in characterizing the hair of four golden mole species that have a purple/green iridescent sheen. Thorough analyses revealed that the hairs are broader and flatter than usual allowing for increased surface area to react with light. "Scales" on the hairs were also quite small, and iridescence was likely a product of light traveling through multiple layers of hairs, hitting these scales, and producing green-purple colors (a phenomenon called thin-film interference). The authors explicitly stated that iridescence was likely a by-product of some other adaptation such as "durable, low-friction pelts" (rather than a sexually selected trait...you know, because moles are blind...).