Morality Stumper

One of the claims of slavery proponents was that the African race was inherently inferior to the white man, giving them a sort of moral obligation to give them good work and happy living. This argument, of course, holds no water, in part because the underlying assumption, that the African race is inherently inferior, does not stand up to scrutiny. But what if it did?

So my question to ponder is this: What if there was a missing link species (or a closely related dead end branch species, like the Neanderthals) that was still in existence with a significant population? Suppose this species almost never surpassed the intellectual ability of a 10 year old homo sapien, but could develop basic speech abilities. They also have similiar physical capabilities as a homo sapien. Would we be morally obligated to help them survive? Would it be moral to employ them to do menial tasks for less pay? What would be the role in modern society of these people? Would they vote? Would it be acceptable to give them a fractional vote? And as a side note, how might have historical events proceeded given this population?

Just something to ponder, I don't have good answers, yet.