Just wanna ask a biology-related question relating to elves in an original fic I'm thinking of, and I figured you were the person to ask; since they're effectively allergic to iron, presumably they don't have iron-based blood, so I'm going to steal an idea from Pratchett (whose elves bled green in "Lords and Ladies", IIRC) and give them hemocyanin-based blood. If they have this, would they still be genetically close enough to humans to crossbreed with them, or would they have to be so vastly genetically different that they couldn't?