Humans haven't always existed, the Earth hasn't always existed, the universe hasn't even always existed, but god has always existed. There is no chicken and egg question. God didn't have to come first, as god has always been.
OR... not.
That's simply an opinion. God is a faith. It is not a proven. And while we can prove many things scientifically and follow patterns from and grow from the additional knowledge we acquire we cannot prove a God nor has a "God" presented himself to provide proof.
It is the ultimate chicken or the egg question. And as such leaves us each free to believe in either a glorified Aesop's Fable or science.
Heathens Greetings!