Hi @John_Harshman. I’d simply say that scripture is silent on the existence of people outside the Garden. It neither confirms nor denies since its not essential to the message of salvation. For instance, it doesn’t say where the sons of Adam got their wives etc., which gives rise in some quarters that they married their sisters. So, that’s one idea based on the presupposition that all human life came from one couple. I find the concept of genealogical descent offered by @swamidass is quite interesting on this matter you could find with an easy search on this site.
The difference for me is not in image lost as much as image restored, which we see in Christ. “He is the image of the invisible God”. And those brought into His body have that image restored through “Christ in you the hope of glory”.
Now, to the idea of Human Rights, I don’t think therefore that the Imago Dei can be used to ground it. These things may inform a Christian ethic of human rights in that we have equal standing before God. But not everyone believes God exists. And those that do don’t agree on what is the basis for human rights. So I think it’s not equal standing before the Gospel but rather equal standing before the Law that forms the “grounding” for human rights. In a sense it is as @T_aquaticus said it. We define it, whatever our believes personally are, from a human standpoint we agree on and actively support those rights with our actions.
Only by defining it in that way can we reach common understanding as to what constitutes our rights and on what basis they can be denied.
That said, I think things like the UN declaration on human rights fall short of Christian ideals because it uses the terms “born with” and “reason” as the basis for those inherent rights. But some would say, “What about the unborn?”. Others might say, “What about those with limited or no reason?” “What about those in a persistent vegetative state like Terri Shiavo? or those with severe Downs syndrome? Or those with dementia?” On what basis may their rights be denied? These are the areas where I think it moves from the academic and theoretical to the practical things that are really important.