The main argument of scientists like Ken Miller and Jerry Coyne is not that the GULOP pseudogene exists. It's that the GULOP gene and its pseudogene are at the same location in the genomes of all mammals. In the primate lineage this gene is non-functional due to a number of mutations that make it impossible to produce a functional protein. Some of the same deactivating mutations are found in related species such as humans and chimpanzees. This suggests strongly that the non-functional pseudogene was inherited from a common ancestor.
How did Moran arrive at such a conclusion? Why is the vitamin C pseudogene such strong evidence for inheritance via common descent? Unfortunately, Moran fails to explain his reasoning. He simply asserts this amazing claim.
Evolution and common descent have failed to explain how the original vitamin C gene could have arisen. In fact they fail to explain how any protein could have arisen. They have also failed to explain how all of biology could have arisen.
This is not a good start. So far this evidential claim of Moran’s seems unlikely. But let’s look at the pseudogene in particular. Perhaps there is something about this pseudogene that will make the evidence more obvious. For example, perhaps evolution made a strong, heroic prediction about this pseudogene.
In fact, evolution and common descent made no such prediction.
Well is there, at least, a powerful retrodiction? Again, no. Well perhaps evolution and common descent would absolutely be falsified if there were no such vitamin C pseudogene. Again, the answer is no.
No prediction, no retrodiction, and no falsification. Evolution and common descent do not predict the vitamin C pseudogene, and they are not harmed if there was no such thing. This in addition to the fact that evolution and common descent do not explain how the original gene could have arisen in the first place.
Moran’s assertion that the vitamin C pseudogene is powerful evidence for his unlikely idea appears to be just that, an empty assertion.