Why the others live on the island??

I think they prefer to be on the island. They were there before the Dharma Initiative got there and they seem to be there to protect the island ou something.
I don't know how they got there though. It also seems like they never really age, because Richard has looked the same forever. Charles and Eloise got older once they left the island (why and how they left hasn't really been explained yet).
Richard must be special somehow though because Ben came to the island as a child and he grew up..
now I'm just rambling and thinking up plus questions.
Richard is pretty interesting though, I can't wait to find out all the secrets about him.