This is quite obvious considering the small population size of Hyrule in any given Zelda game. Inbreeding is essential for the hylians survival as a species.
Those who did not leave Skyloft must have bred with birds and devolved into the oocca over time.
I needed to post a picture of the postman from TP in a thread today and it struck me how much he resembled an older less musclebound Groose with a leaner face. I thought this deserved its own thread and for everyone to learn the TRUTH!
We can't see under the postman's hat but the pointed...