Originally posted by Setekh
I think that was pretty much debunked, unfortunately. Would have been nice. 
http://halo.bungie.org/oldnews.html?item=11345
So is that text actually in the credits, though?
I've never liked the idea of a concrete human-forerunner relationship, as in a direct genetic relationship. It's unlikely that forerunners, IMO, could have ended up on Earth and yet left no trace(or did they?) of their technology.
Of course, there's another question - were the Halos' ever actually fired? Assuming it's valid, there's no corresponding Earth extinction event in known history. If Earth was an 'ark' world, fair enough - but there's still the Covenant races' issue. (of course, if Earth was designed / designated / built to survive, it would explain why a human was required to fire it.... maybe 'reclaimer' means not reclaiming the key, but reclaiming solitude & security over the galaxy)
And if the Halos weren't fired, then are they even for cleansing the galaxy? Does anyone beyond Guilty Spark say they were fired - because he/it is obviously gone nuts.
Of course, it's pretty much using biblical imagry anyways. The flood comes, and wipes away life. One ark (Earth? A forerunner ship?) survives to carry life until the flood subsides. Except that ark wasn't the 'ark of the covenant', was it?
IIRC it says somewhere in Halo2 (I've read spoilers) that the Flood are sort of an embodiment of sin. Which would imply that the 'ark' might contain the opposite of that... something to defeat the Flood, or to stop them? I dunno, because I don't exactly how and where the 'ark' is mentioned in the game, only that the Covies apparently want it.
EDIT; after all, didn't the Forerunners keep the Flood alive for a reason?