Fran
Post like you mean it!
Here is a theory, I don't necessarily believe it but it's just a theory.
Viera live to be very old as the game says. Maybe they don't reproduce at all.
Maybe the Viera somehow came to this world from another "world" Thousands of years ago and this is still the First and Last Generation of them.
But if that were true, they'd all be the same age.