[2020] Are the dwarves actually from Earth, most precisely from either Europe or America's continent?

Let me explain why i thought about it :

Operator often say, when a swarm is incoming : "The radar just lit like a Christmas tree."

Meaning they either are Christians, or know about christianism's traditions, that come straight from Earth (since i don't remember the Bible stating possible intelligent life form outside of Earth).

I don't know anything about this game lore, and would to know more about it!