Well, the evidence of fusion is just like every evidence of missing link, purely speculative but required by an assumptive narrative. When reviewed as a whole, that (evolutionary) narrative assumes abiogenesis. Christianity also assumes abiogenesis, and proposes that it happened 10,000 times instead of once. The mathematical fact is that both theories are more improbable than all the 10^140 events in the known universe, for which mathematicians use the words "absurd" and "impossible". Therefore both theories involve some containing function that resolves the impossibility, such as anthropic principle, directed panspermia, deity, multiverse, math universe, etc. This observation removes the objection that evolution and Christianity are not on the same scientific level.

That is, the argument that 48 became 46 and the argument that 46 and 48 have a common origin are both tenable without further context. And, interestingly, neither one explains why 46 is special and 48 lacks evidence of the sentience we're interested in. So I'm not sure that that line actually helps the immediate inquiry I have, but it's certainly an interesting sidebar.

So if we ask whether that line of sentience was ever crossed with some other species, e.g. reptilian, we have two views, it arose from a nonsentient species, or it arose from an independent origin from some containing function (like the math universe) capable of originating sentience without mediation through other species. Clearly in both theories it's a separate genesis from sentience in primates, which indicates the arising of sentience is a more common event than we suspected. Now we don't need any of the interesting observation I just made to speak to that, because either way the origin is a bit of a mystery. The issue is evidence. The fine-tuning argument suggests that I, who recognize many incredible math marvels, ought to be more open to there being more out there; and in fact others who recognize the same and give different attribution also are open to there being more than the observed. But with cryptids we have this interesting kind of barrier that observation appears "blocked" in ways that observation of Komodo dragons isn't. That leads to speculation about this blocking mechanism, which neatly aligns with the Christian theory of Spirit, and can be aligned also with the M-theory of warped p-branes. So that's about as far as I've gotten, because the hypothesized cryptid would require some extradimensional protection for its existence that presupposes a background narrative and I don't have immediate inspiration on that. But having gotten inspired to start looking my experience is that the search is always rewarded. So my next steps are to look for evidence of humanoid reptilians (although evidence of sentient saurians or dragons generally would be connected!) and to review my cosmology for places to insert sentience besides humanity.