I figured out this fairy allergy to iron thing. You know this deal in Northern Europe and the British Isles where fairies could not touch iron because it burned them or Some other effect.

Fairies had a Bronze Age level of technology. They had a preference for because they were a primarily ocean going people and their descendants saw no need for improvement.

Then comes humans. We start to mix with fairy kind the same way we mixed with Neanderthals, Denisovans, and maybe four or five other hominid species. Fairies started losing numbers to humans and then humans started to learn how to make iron.

Where does this come from?

All the bronze age civilizations collapsed at about the same time the land bridge between Europe and the British Isles was swept away by the Scandinavian tsunami. This was about the same time the arise of the Bicameral mind and increased color perception (humans couldn't see blue, and red and green were grey).

What a day it's been.