Complications during his birth that ended up killing his mom, who also shares the same name as Locke's mom, Emily. Anyway, my guess is that Ben caused this plague to follow him to the island.

Interesting.

i like it. would love to hear some extrapolation on it

If these "hostiles" were the original inhabitants, then how did they maintain their population without reproduction? And yes, after looking at Eyeliner McGee(Alpert) one can tell that aging doesnt seem to occur for some people on the island, but they still have needs, dont they?