This is Theory is out there, but i stand by it with confidence when considering Richard Alperts and The Others/Hostiles History. Its complicated so i'll sum it up: "The others and Richard Alpert our post apocalyptic refugees from the future finding salvation on the island and Richards their guide to the island". (I know Richard was classified as a advisor last episode, but advisor to what?) 1.Richard appears not to age as he may be immortal..well i believe he's just as human as the rest, he obviously has aging properties as in "Man behind the curtain"when we see him with long hair, and in "follow the leader" he seemed pretty anxious not to get shot by sayid and surrendered. I believe he is time traveling into different time periods of the island and bringing people from the future (others/hostiles) to these times. He needs a leader in each time period because he is never around then I.E Widmore, Ben, Locke? Richard is obviously important but to what extent. -Plus anybody notice that Richard wears the same (or close to )shirt in almost every time period, that blue button up that was in 1954 and in 2004..hmmm
2.Time travel may be to blame for the womans infertility this being said thats why amy gave birth on the island. Richard first meets Juliet he shows her mammograms that look to belong to a 70 yr old but are of a woman who's 26. A lil mess up from the time travel? 3.This is why they are hostile they can't interact with people from the past or the future would be changed, so people coming to the island could be a problem. However rues are mentioned by Dr.Chang In "Because You left" and"Dead is Dead" When Ben is saying goodbye to Widmore because he left the island harbored a child and Broke The Rules.. - Maybe these others are descendants from the original cast, maybe not? who knows', but i feel time travel is a major factor with how Richard stays the same age and where the others have come from.