[Right Wing Professor]

The conclusion of common descent is built into the bare assumption that the lack of the L-gulano-g-lactone oxidase gene is a "defect", or "nonfunctional" version of a gene that was purportedly functional at some point in human histor

That's not an assumption. The purpose of the gene is well established.

It simply cannot be said definitively at this point that these types of genes have no function.

That is true. It can however be said definitively that they have lost the function they previously had, and as a result that humans and the great apes lack the ability to make vitamin C, but still carry the relic gene. It is not inconceivable that the pseudogene was coopted for some function yet to be discovered, and it's unlikely we'll be doing knockout experiments on humans or great apes to rule out that contingency, not because we can't, but because there are ethical issues.

However, the ID explanation is unfalsifiable; an inscrutable deity could have done whatever he wanted for whatever ineffable reason he liked.

[Diamond]

That's not an assumption. The purpose of the gene is well established...

How is it not an assumption, if as in Darwinism

It is not inconceivable that the pseudogene was coopted for some function yet to be discovered...

and in Darwinism there is no "purpose" in the strict sense of the term in the first place?

Cordially,

[Senator Bedfellow]

That is true. It can however be said definitively that they have lost the function they previously had, and as a result that humans and the great apes lack the ability to make vitamin C, but still carry the relic gene.

Well said. I would also point out that, IIRC, L-GLO is merely the last of a series of necessary steps to synthesizing ascorbic acid - in humans and other primates, all the other steps and ingredients necessary are still present, despite the fact that the process is broken due to the missing ingredient. So it's not as though we only have this one broken gene, held in isolation, which may or may not be related to functional genes in other organisms - in addition to the broken homolog in humans, we also have a set of other genes that are homologous to ascorbic acid-producing genes in other organisms.

It's not as though Alice simply has a bag of rotten flour, and we don't know how to begin interpreting that one odd ingredient. Alice also has eggs and butter and sugar and chocolate and shortening, and everything you need for the recipe. Except the flour, of course. Bob and Carol have all those things, plus functional flour, and they're happily baking away - why should we not infer that Alice was once capable of baking a cake too?