Tolkien: Evolutionist or Creationist?

[Lotessa]

This is a very contentious subject, so I thought I’d bring it up.
I’ve read that Arda was once flat but eventually evolved into a globe.
Also, according to Tolkien the history of Arda is actually a made-up account of our own world.

From one of Tolkien’s letters:

“I have, I suppose, constructed an imaginary time, but kept my own feet on my own mother-earth for place."

Tolkien also says he created Middle-earth because there were hardly any English myths:

“I was from early days grieved by the poverty of my own beloved country: it had no stories of its own, not of the quality that I sought, and found in legend of other lands. There was Greek, and Celtic, and Romance, Germanic, Scandinavian and Finnish; but nothing English, save impoverished chap-book stuff.”

Anyway, I want to know if Tolkien was an evolutionist or a creationist.
Please tell me what you think.

~Lotessa