I am thinking that island is the omphalos of the earth and perhaps, time/space. The Greeks thought that Delphi's power was because it was the navel of the world. Also many other cultures/religions have a similar concept of the omphalos. This would also explain the heavy religious elements of the series, especially the black and white stones (sacred?) Jack took from Adam and Eve. We know the island was formed by volcanic activity which means it is made of rock (i.e. Greek omphalos). Perhaps, the surge of power which caused the formation of the island directly taps into the energy source of our reality/space/time. This energy also allows time travel, regeneration, and telekenetic energy, which is why the island tapped into Walt by using his already existing telekenetic abilities. This energy shields the island's existence from the world, but sometimes it gets breached and/or pulls things into it. Ben, the Dharma Initiative, the plane, Desmond, and those yet to be discovered have somehow broken into the energy. The four newcomers were all chosen by Abbadon to find the island because of abilities and connections that have yet to be completely disclosed. Their objective is to stop Ben from trying to harness the islands power via the birth of a child on the island, for obviously all of the wrong reasons, and whatever else it is the Others were really up too and still are. That is why the Others' women all die in child birth; the island or whatever is stopping them. This is also the reason that the Others recruited Juliette because of her fertility and parapsychological experience. Claire and Sun are able to carry their children because they have been drawn to the island for some other reasons, and not because they wish to harness or exploit it's powers.