This question came to me when I saw the new Man of Steel movie. There was a scene in the movie that talked about Kryptonians being on earth 20,000 year ago. At 1st I was like this is stupid, but then I thought about it and figured actually that would make since. If DC wanted to go there if they haven't already. They could suggest that Kryptoians are the reason why metahumans like The Flash, exist.
Think about it, Kryptonians came to earth and mated with some of the 1st humans. This caused a change in DNA that added the potential for a Meta Gene to exist. Going further you can say that the Meta gene being activated by different methods caused alternate powers. Basically because of how the flashes power were activated, instead of receiving all the powers of a Kryptonians he just got one, "SPEED."
Well it's just a theory. I'd like to hear some of you Superman pros speak on this subject. What are your thoughts on this?