User blog comment:Jho5689/Fairy Tail 337 and onwards/@comment-11232389-20130625163146/@comment-7418318-20130625200619

They have been confirmed by people within the story suspecting it. That doesn't mean those people are necessarily true, or they might just use different terms. Often a different timeline is also called a different or parallel dimension, whether that's the correct use for the term or not (just take Star Gate or Star Trek as examples).

And if the event that split those realities had the impact to change the laws of magic, combined with the different geography (i.e. flying islands) it's hardly surprising that different species developed over time.

Also the problem with Edolas can't be the absence of Ethernano, because if it was the case neither the Exceed nor the Earthland humans could ever use magic there. Most likely people in Edolas are born without a magic container or somesuch, that's why they need external magic sources to cast spells.

If they were completely unrelated realities it's extremely unlikely that Humans races came to be in both of them, much less similar counterparts, so there has to be some kind of link. A common (very) distant past is just one possible way to link those two together.