Before I get into my theories, I want to share this video.
This is an Irish children’s song, teaching the story of Noah and the Ark while adding in some folklore about the mystical horned horse. (You can read the lyrics here).
Let me begin by saying this was my favorite song as a child and, despite the Christian background, continues to make the Top 10 without blinking. Second, nearly every culture has a flood story, and I read somewhere (can’t remember where now) that there was archeological information proving significant water rise thusly proving the Noah story. They didn’t find an ark, but they found water lines. And anyone who has studied any amount of geology knows that we are currently in an Ice Age, coming out of one and the caps will melt and the waters will rise. They of course will fall again when the Earth enters its next ice age. It has happened many times before and will continue to happen many times again.
If you listen to the lyrics, the song confirms that Christians (at least the Irish) acknowledge the presence of Magick and mystical. Perhaps they brush it off as stories for children, but they still acknowledge its existence at some level which is a lot more than I can say about American Christians in the Biblebelt!
My personal theory of unicorns: they existed, but they have evolved. Again, I can’t remember where, but I have read a few articles about ocean mammals evolving from land mammals to ocean mammals because of competition for resource, or environmental changes. So yes, unicorns existed. And they still do, just in an evolved form. There was an environmental change that caused a mass migration from land to see.
The mythical Unicorn is the modern day Narwhal.