The strength of [common descent] arises not from the evidence that supports it, although one can certainly build an overwhelmingly compelling case on that basis alone. The strength of the theory arises from its vast explanatory power.
Here Matheson radically misrepresents scientific evidence. The claim that the case for common descent is "overwhelmingly compelling" is an incredible over reach. Indeed, the evidence is so mixed that even evolutionists have expressed doubts in recent years. Evolution is having to be patched and repatched to fit the data.
While much evidence does fit the common descent pattern, much evidence does not. And those evidences that do not fit the pattern often are stunning departures. The picture is a muddle and to say that the idea is "overwhelmingly compelling" is simply bad science.
But this is not Matheson's main point. It gets worse from here. Matheson's main point is that common descent has great explanatory power. This claim that evolution or common descent has such great explanatory power is a code phrase amongst evolutionists for the religious belief that god wouldn't have designed it that way. In fact, evolution and common descent have essentially zero explanatory power for what we observe.
Common descent doesn't explain how genes arose, or the DNA code, the fantastic trilobite eye, or a thousand other marvels. Nor does common descent explain striking similarities in distant species or striking differences in otherwise allied species. In fact this so called "explanation" of common descent goes like this: When the data fit the expected pattern then it is due to common descent, and when the data don't fit then they are not due to common descent. Or more succinctly, common descent explains the evidence except when it doesn't.
This lack of explanatory power has never stopped evolutionists from claiming that their theory has great explanatory power. After all, they can always draw upon the contingencies of natural history. A comet hit, a mutation occurred, who knows, somehow what we observe evolved. Their great confidence does not come from their explanations of how evolution is supposed to work, but rather from how creation is supposed not to work. Enter the metaphysics.
Repeatedly in the evolution genre you will see phrases such as "while we can make sense of this under evolution, it makes no sense under creation." The bar is moved ever so low for evolution because it is the only possible answer--the metaphysics makes it the only option. Darwin first used this move at the end of his two chapters on variation where he wrote:
And we can clearly understand these analogies, if species once existed as varieties, and thus originated; whereas, these analogies are utterly inexplicable if species are independent creations.
Clearly understand? Actually there is very little understanding under common descent and evolution. But that's not the point--evolution is the only choice. As Matheson puts it:
The data that make common descent so scientifically compelling are not just the data that “support” the theory. To really understand why common descent is such a powerful theory, one must focus on data that are explained by the theory, findings that just don’t make sense without an explanatory framework of common ancestry.
The "just don’t make sense without ... common ancestry" is a metaphysical claim. It states that of all possible explanations, only common descent makes sense. If that's true then, yes, common descent becomes compelling. It is the fact that evolutionists claim it is. It is the truth that they proclaim.
Evolutionists misrepresent the evidence and smuggle metaphysics into science--even the best of them. Religion drives science and it matters.