Alas, another of my failed attempts at concise wit.
I was trying to point out the absurdity of the hypothetical situation. I'm not sure there is such a thing as a reasonable response to an absurd situation. A voice from heaven would not be something I'd be 100% certain of (indeed, I'd be very skeptical of it) and science cannot prove anything about the past with 100% certainty. As for those who claim God speaks directly to them, well, let me suggest a good website I found recently:
http://www.the-highway.com/charismatic_index.html. 
In this life, the Bible is the only thing that can give 100% certainty, and it clearly teaches that Adam and Eve were real, the first humans, and they were not born.
But, I have no doubt there are some things we have misunderstood. In humble boldness, I'm quite certain this
isn't one of the things we've misunderstood, but if God tells me otherwise
after I die, I'm not going to argue with Him. I don't think I've opened any doors by making such statements.
Anyway, that's why I'd reject the first statement. I'd also reject the second statement, especially the last sentence. On the contrary, I believe specifically because the Bible says it.
