We usually describe the smell [of blood] as "metallic" because it's similar to the smell left on our fingers when we handle coins, or in the air when we scrub a bare metal pan or sink. ... Our hominid ancestors would have known that molecule [epoxy decenal] and smell long before they paid much attention to rocks and ores, so for much of our prehistory, they may well have experienced metals as bloody-smelling.

— Nose Dive by Harold Mcgee