The critical underlying issue is the apparent incompatibility of current scientific theory regarding genetic diversity and the prevalent Christian doctrines regarding original sin and the fall. In very simplified terms for those not so familiar with each, genetic theory says that in addition to mutations that are a clear benefit or detriment, there are also those that don't make a lot of difference (e.g. blue eyes vs. green eyes) that slowly accumulate in a population over many generations; by measuring how much diversity there is now and making some reasonable assumptions about the rate of accumulation of variation, one can estimate the minimum number of genetically distinct individuals that existed a certain number of years ago. Original sin says that the first couple sinned in disobeying God, and as a result have passed that sin nature onto all of their descendents, something that took the perfect obedience of Jesus Christ in life and death to break its power. One couple vs. many clearly forms conflicting claims, and they both can't be right.
As I am neither a theologian nor a geneticist, I do not seek to resolve the conflict here. Rather, I'd like to discuss the related but not identical concepts of evidence, theory, doctrine and Truth. I believe productive discussions of controversial topics like this require a healthy understanding of the differences. First, capital-T Truth is not something any human being or organization has a lock on. Complete understanding of the universe we live it is simply beyond any one or group of human beings. In the physical realm, it is simply far too complex for anyone to really know more that a small slice, and there are limits on knowledge, from the quantum mechanical uncertainty principle that says one can't have perfect knowledge of a particle, the speed of light that limits how fast information can travel, to limits on our ability to gather information-my astronomy colleagues tell us that 96% of the mass/energy in the universe is of some form that almost none of the current detection methods can see. In the spiritual realm we have only the limited amount of revelation that God has chosen to provide, which comes to us in the language of ancient human authors, which can be sometimes ambiguous and cultural dependent. This is not to say we can't know anything, but neither a scientific theory nor a Christian doctrine are the same thing as Truth. Both are human constructs that correspond to a greater or lesser extent to the Truth that we can't know completely. The actually serve similar functions in their respective disciplines, providing us a framework for making since of the myriad of related facts and encapsulating the best understandings for passing on to the next generation. The theories and doctrines that are widely taught today are the ones that won out over others because they provided a better fit to the evidence. The type and nature of the evidence they utilize tend to be quite different; science relies heavily on observations and experimental results to establish theories, while doctrines rely more on scriptural interpretation, tradition and individual impressions. I do not believe that either theories or doctrine are intrinsically more reliable than the other; consulting a physics text on how to treat my wife and the Bible on how to build an airplane are equally foolish. Some theories are far more established than others with much stronger evidence, and the same goes for doctrines. There is good evidence for them, so they are not to be lightly tossed aside because we don't like them or a few pieces of evidence seems to conflict. But even the most established theories and doctrines are not the same as the Truth, so we must not conflate the two and be prepared to rethink even the most cherished theory or doctrine if the evidence warrants it. The goal should not be to prove my theory or doctrine is right, but to better approach the Truth.
