One more tidbit - not from last nights ep. - and some speculation:
Locke stated that the Black Rock was likely a slave ship. I've been able to verify that Portsmouth, England ( the BR is registered to a Portsmouth ) was the first port used by convict ships sailing to Australia. These ships sailed from 1787 - 1868.
Passenger manifests show both men and women sent out on the same ships.
Given the good/bad/redemption theme of this show, I think it is more likely that this was a convict ship, and I wonder if their descendants are the people saying "This is our island".