When I was in Scotland in a small village north, old people at the pub asked us where we come from, we said Greece, and they said "do you know that we here have ties with you?" And they told us the myth of Scota. It was interesting because we have never heard about it, and though I searched many of our ancient texts, myths, histories, I didnt find one to match it.
It is well-known and accepted that we reached the british islands at some time (and maybe quite early), but this is another case.

So I think that some myths just repesent the need of people to have ties with other people of the -then- known world. We have greek myths which say that Aigyptos and Danaos were brothers, their grandfather was Poseidon, their mother Lybia etc. I guess all the ancient people wanted to have links with each other.