At what point in the evolutionary line did humans develop the Image of God? At what point in time did we fall into sin? What is the eternal fate of our evolutionary ancestors? Please forgive my rusty science, but what I am asking is will there be neanderthals, cro-magnons, etc. in heaven
Humans did not “develop” the image of God. They were given the image of God at a definite point in time. That certainly seems to be the picture in Genesis. Whether God created Adam and Eve ex nihilo (out of nothing) or whether God put his image in a pre-evolved intelligent creature, I am not sure, but what I am sure of is that the human soul did not evolve. The human consciousness, his awareness of God, his eternal nature, his God-likeness (imago dei) did not evolve. We are eternal and, almost by definition, an eternal nature cannot evolve. That would make no sense. It was created and given by God. Exactly when this happened, I cannot give a date. Did this happen way back in the time of the Neanderthal? I doubt it, but because I do not have a firm date, I will have to settle for saying that I doubt it. The theory of evolution may help to explain our physical origin and nature but it does not explain at all our spiritual nature or our image-of-God nature.
When did we fall into sin? According to Genesis chapter three, we fell into sin almost immediately after we were created in the image of God. I assume that this happened within days, weeks, or, at most years of when Adam and Eve were created in the image of God.
I do not believe that dogs or cockroaches or chimpanzees or whales have eternal spirits. I do not believe that they will be resurrected or that primates who lived thousands of years ago will be in heaven. There is no biblical reason to believe that soul-less animals will be resurrected and will be in heaven. Therefore, Australopithecus and home erectus and other such fairly well evolved primates will not have eternal life. Unless I misinterpret the Bible, only creatures with an imparted soul are eternal.
I hope this helps,