Oxygen shaped the world as we know it. It’s why we hiccup and why frogs croak. It’s so good that some turtles have learned to suck it in using not just their nose and mouth, but also… another orifice.

Hair loss isn’t always dramatic. It can be incremental. You start noticing a bit more scalp in harsh bathroom lighting; a tiny bald spot when you tie your hair up in a ponytail. The shower drain is ...