One of the more common areas of dispute between scientific realists and Biblical literalists is of course on the topic of the origin of human life. The two groups understandably cannot agree on much at all, but on one point they tend to see eye to eye more often than not; a person must agree with evolution as the authoritative narrative for human origins or reject it completely. The ground outside of their positions is frequently seen by them as untenable, harboring a morass of horribly mismatched worldviews which are profoundly incoherent.
As someone who stands in a very sparsely inhabited portion of that ground, I would like to explain why I chose this stand. I am a devout Christian and I accept the findings of evolutionary biology, a position which is more common currently than it was previously in the United States where a literal reading of the Bible became widely popular in the last couple of centuries. I also have very uncommon reasons for holding this position, though my motivations for doing so are nothing unusual. I seek to build an increasingly evidence-based worldview that is not predicated on either the reckless a priori exclusion of the possibility of supernatural agencies or the reckless a priori assumption that everything has an immediate and simplistic supernatural cause.
When I claim that I am on a very sparsely inhabited portion of the ground between the two, it means that I have over the course of the past decade examined and rejected many different perspectives on the accounts of the origins of the earth and of humanity. So what are the options available to me, and why have I rejected the common options?
Scientific realists, as previously discussed, take the claims of scientific disciplines as generally true in an ontological sense. So when that is applied to biological evolution, they accept it as the correct narrative explanation of human origins, often to the exclusion of other narratives with different purposes and approaches. As an instrumentalist with regard to science, I don't take scientific theories to provide us with any sort of ontological truth about what things really are, but I do agree that the evidence for biological evolution having been going on for many millennia is fairly strong and the theoretical framework being used is coherent. I also agree that the geological evidence strongly suggests that we're on a very old planet rather than a very young planet.
All that said, I still have reasons to be uncertain about scientific claims made about events in the distant past. One is that we have no way to travel back in time and make sure that our dating methods remain accurate that far into the distant past, so we can't properly calibrate our measurements and ensure that our rational inferences hold true even into the distant past. The other is a sample problem; in many cases, either we have very limited samples of evidence for human evolution in the distant past or it's difficult to be sure that our samples are not contaminated (or both), which leaves me leery of drawing bold conclusions from that evidence. Does this mean that I'm open to the possibility that the earth is actually quite young? Yes, but what is the evidence for that?
Young Earth Creationism
Biblical literalists often take the Young Earth Creationist (hereinafter referred to as YEC) perspective, believing that the Genesis account of God creating the world features a week with approximately 24-hour days. Young earth creationists throughout history have tried to calculate the age of the earth based on the Torah and/or Septuagint, their results varying considerably, sometimes by many thousands of years. The first problem I have with this view is that it attempts to impose modern literary forms in the context of modern philosophical views onto an ancient text written by people with ancient philosophical views. And in the case of creationists who were doing their calculations long before the scientific revolution, they usually had an unhealthy tendency to believe that the text of the Torah or Septuagint could provide them with an accurate date for creation when neither the Torah nor the Septuagint nor their authors claim to be able to do any such thing. And the only ancient tradition of using the texts in such a way comes from a few folks who had an interest in esoteric questions and no other way to decide the question of how old our planet is than to appeal to Sacred Scripture. Apparently, just admitting we don't know and admitting that Sacred Scripture never even tries to answer the question is not good enough for them.
The second problem I have with this view is that in addition to being a product of poor literary analysis, it often gets its support from psuedo-science. The basic job of the creation scientist is to find evidence that supports Young Earth Creationism. The basic job of the geologist or biologist is to collect data or design experiments which can disprove a hypothesis or component of existing scientific theory. In essence, creation science is an exercise in confirmation bias, while science has structures in place to mitigate the effects of confirmation bias so that we don't just set out to prove whatever we want to be true. The problem with setting out to prove whatever you want to be true is that you will accept evidence that supports your conclusion and deny the validity of evidence which does not support your conclusion. This approach isn't designed to help you find truth, but it is designed to reinforce whatever you currently believe, and that's exactly what creation science does. In the end, the YEC perspective is generally a result of ignoring good practice in both literary analysis and scientific inquiry in favor of acquiring a certain and precise answer to a question that the authors of the Torah and Septuagint never bothered to answer outright.
Old Earth Creationism
Old Earth Creationists (hereinafter referred to as OECs) try to reconcile the scientific evidence from geology, archaeology, and biology for a much older earth than what the YEC view would allow with the Genesis account of the origins of the earth and of humans. Like the YEC view, the problem I have with this view is that it attempts to impose modern literary forms in the context of modern philosophical views onto an ancient text written by people with ancient philosophical views; it reads the Genesis account as a crude allegory that corresponds to contemporary scientific theory about the origins of our planet and humanity, a crude allegory of the sort that the folks who passed down the oral tradition that was eventually written down in Genesis would likely find to be baffling and missing the point because it makes assumptions quite different from the assumptions they were making.
Proponents of Gap Theory suggest that there is an indeterminate gap of time between the events of the first and second verse of Genesis.
"1 In the beginning God created the heavens and the earth. 2 Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters."
While they do, like YECs, agree that the earth was created in 24-hour days, YECs strongly disagree with the Gap Theory. I also disagree with it, though for essentially the same reason that I disagree with the YEC perspective: it's a product of ignoring good practice in literary analysis. It's certainly not so easily falsifiable as the YEC perspective because it takes into account the extensive evidence for an old earth, but a lack of falsifiability doesn't gain a proposition much credence. Russell's teapot demonstrates that quite nicely.
The Omphalos hypothesis is one of the more interesting attempts to reconcile the evidence of an old earth with the Genesis account. On this view, the earth was created very recently, but it was created to appear as if it were very old. This resolves the apparent disjunction between the evidence of an old earth and a Biblical literalist account of creation. Setting aside the aforementioned problem of not using a good approach to literary analysis, there are two problems faced by those who take this view.
The first is a problem related to science. Assuming this view is correct, then we have no reason to think that natural science leads to correct conclusions about the world. And if it's the case that natural science cannot help us determine the age of the earth, then why do we need a hypothesis to help us reconcile the evidence of natural science with the Genesis account? If it's true, then we really don't need to worry about what natural science concludes on the subject at all. If it's true, then it's useless as a means of resolving the difficulty of reconciling the Genesis account with scientific evidence.
The second problem is a theological problem. If it's the case that God created an earth such that all the evidence pointed to it being an old planet, and then gave us the rational faculties necessary for natural scientific inquiry, then why on earth did God do that? Is God lying to us?
Theistic evolution is a view taken by some folks who, like OECs, want to reconcile the scientific evidence with Biblical theology. In this view, biological evolution was a process used by God to bring about the existence of humanity and many other parts of creation. It is not uncommon for folks who subscribe to theistic evolution to take also the OEC perspective on geology and archaeology (or at least something similar). Beyond potentially facing the difficulties faced by OECs with regard to understanding the Bible, the theistic evolution perspective runs headlong into a thorny theological problem. If it's the case that God guided evolution, then why is an omnibenevolent, omniscient, and omnipotent God guiding the process in such a way as to be full of so much death and suffering? Evolution is extremely messy in dealing with anyone who can't survive on their own under harsh circumstances; what's happening to those people dying and being maimed all the time? Why would God cause that? Is God hateful?
Where does all this leave me?
I could take a theistic evolution position on the subject of human origins because I have a coherent solution to the Problem of Evil, but I would not be able to take the OEC, Gap Theory, or Omphalos hypothesis positions along with it to reconcile geological and archaeological science with the Genesis account because I am not willing to do what I see as abusing Scripture to contort it into an unnatural shape which would fit with contemporary views.
I face essentially the same difficulty if I embrace the theological perspective of Christos Yannaras regarding the Fall and its relationship to the human experience of death and suffering. It resolves the Problem of Evil and allows me to embrace theistic evolution, but does not touch the question of the age of the earth.
There is a way I might solve that problem, specifically by observing that the Genesis account does not posit an age for the earth, and thus there is no particular conflict between the claims of Sacred Scripture and the claims of modern science. Obviously, there is a tension between the two accounts because they are completely different approaches to understanding human origins. Modern science attempts to discern how we arrived at the current state of affairs while staying within the limits of its methodology. The creation narratives in Genesis are fairly obviously attempting to discern the meaning of the human experience within a universe inhabited by a God who created us while reaffirming their belief in God as creator and taking into account commonly understood events like the Great Flood.
In the end, my answer to the questions about the age of the earth and the veracity of evolutionary theory is: I don't know. Which is to say that on these topics, as with many topics, I do not believe we have certainty about our conclusions on the matter. But what I do believe is that the evidence for an old earth and evolutionary theory are fairly strong. I am content to accept the scientific evidence as it is and accept the theology of the Catholic Church as it is without engaging in a futile attempt to revise the scientific evidence to suit my theology or revise my theology to suit the scientific evidence.
I understand the appeal of trying to find a neat and tidy way to resolve the tension between the creation narratives in Genesis and the scientific evidence of an old earth and human evolution. Perhaps some day such a neat and tidy solution will be found, and that would be wonderful if it is. That said, I do not need to follow the path of my contemporaries and create a Christian evolution or evolve Sacred Scripture into Scientific Scripture.