I honestly think quite a few of them were either
a) real (at one point)
b) still real
c) existed in a way that is necessarily "known" to us.

The latter answers make me sound crazy or like a fool, but I do believe there are things we can't explain and things we can't know/beyond our understanding. Humans were much more open to things/existences beyond our own in the past...

But that's just me. And yes, I do believe in science, I've studied it, I will continue to study it. I just don't believe it has all the answers.