I think we see more of these interesting finds in the world of small animals because they have a much higher frequency of turnover. Therefore a higher statistical probability to produce interesting adaptations.
I'm just a layperson so I'm using my own terminology here.
Then there's the other interesting possibility, that there is some way to consciously influence the evolution of DNA. I mean it's pretty freaky that this beetle evolved an exact replica of a termite, a creature it presumably spends a lot of time around. How did its DNA "know" to evolve in that diretion? Are there thousands of beetles out there with half assed copies of termites on their backs?
This is the best argument against so far. Still, if a species co-evolved alongside us since our ancestors were small furry animals, this would be quite a few generations.
I'd bet you could tell with DNA analysis, or through other medical means such as scans since they wouldn't have had time to adjust for that. If even a single mimic was found the secret would get out, so they'd have to be very good at avoiding the medical world.
I guess you'd probably be looking at either small groups of particularly successful people who have the resources to keep their mimicry hidden and keep to themselves (nobility?), or at some societal outcasts that roam around, never getting close to anyone.
They'd somehow have to avoid their nature being discovered even after death which may be one of the harder things to believe, since presumably they could also die suddenly from accidents etc. which would often prompt careful medical examination which would then reveal the truth. Of course it's possible some individuals did discover the truth, but no one believe them, but it's hard to imagine that at scale. So if these mimics exist, we're probably talking a few hundred or thousand of them at most
I'm imagining these creatures as something we do not have defenses against, so, given that this creature would have evolved alongside our social, language and analytical abilities, these would not be defenses.
If NHI's do exist, one wonders if they could pull out such tricks as well in order to blend in and take over different biomes/planets.
The X-Files episode "Folie a Deux" featured an insect which "fit in" among humans. You might like that.
Oh, that is sad news. She was very good, and somewhat underrated, I think. I thought her books vastly better than Anne Rice or even the fun Lauren Hamilton ones, for instance. I must admit I've never even read Stephanie Meyer or E F Leonard's ones on this theme but I'm willing to go out on a limb and say SMC was better than them anyway.
Charnas was one of the last old-school s/f writers and the proof to it is that The Vampire Tapestry is what they used to call a "fix-up." She brought a certain psychological angle that was almost tender, I think, to the issue of being a predator (and worse, what appears to be a species of one!) embedded in a world of your prey.