Actually, the evidence says that the universe started about 13.5 billion years before there were any people, and the earth began about 4.6 billion years before there were any people, so I am not sure exactly what you mean when you talk about evidence that “the world didn’t start with an original couple.” I assume what you are saying is that the evidence points to the conclusion that modern humans evolved over time from a lower species of primates to become what we see today. And let me say that I agree that the evidence points in this direction. The genetic evidence points to what is known as a “bottleneck” of human population somewhere around 80,000 years ago. In other words, humans have a surprisingly narrow range of genetic material, which says that humans descend from a very small population quite recently on a geological timescale.
Nevertheless, the Bible seems to describe the initiation of human population by the special creation of just two humans. It is fair to say that, if this is what the Bible says (and I believe it is debatable that this is what the Bible “says.”), then this does not appear to correspond precisely with the data. A small bottleneck of human population does not equal only two humans.
Nevertheless, I personally have been absolutely convinced for many reasons that the entire Bible is inspired by God. Therefore, I cannot discount the Genesis account. So, what does a believer do with Genesis 1? I see three possibilities. One is to speculate that God did in fact create two humans ex-nihilo (from nothing), perhaps as much as 80,000 or more years ago and all modern humans are descended from this original couple. Another is that God took an already-evolved pair of hominids and miraculously changed them into people made in the image of God, and that their descendants also had this trait of having God’s image. Eventually, all humans came to be in God’s image. A third possibility is that God never intended us modern humans to take Genesis 1 literally at all–that it has no actual historical meaning at all–that it is metaphorical. I have a problem with option #3, as Jesus and Paul seem to accept that Adam was a real person (Romans 5, 1 Corinthians 15 and other scriptures, for example). I am open to the first two options.
Let me point out that the Bible is true in this: We are made in God’s image. We have traits that simply could not evolve by any conceivable random process. We have a soul. We are spiritual. We are moral beings. We have self-awareness. Our memories do not seem to be explainable by merely physical processes. Neither does our “conscience.” We are in the image of God. To me, exactly how and when God did this is not particularly important. The honest truth is that I have no way of definitively answering this question, so I am willing to let it go, secure in the truth of the conclusion, which is that we are fearfully and wonderfully made by an omnipotent Creator.