Here's one for those writing "deep" historical fiction.
Genetic sequencing of skeletons found in Ireland have discovered something quite interesting. 5,000 years ago the inhabitants of Ireland were dark haired, dark eyed and mostly Middle Eastern (possibly even Semitic) and didn't use metal.
4,000 years ago they were blue eyed, fair haired people from the steppes of Eastern Europe who did.
This sort of fits some Irish fairy stories, doesn't it. (And also explains the minority of dark haired Irish sometimes called "black Irish" by people who aren't Irish and don't think it's completely silly much better than "survivors from the Spanish armada).
Now, who wants to write a novel about the conflict between the two groups when they met? I already have TMIS...