You can look at certain structures in one animal and show how they’re made from repurposed parts of an earlier animal (like fish gills becoming human ears). Can that be done with humans and those animals with Xenomorph double-mouths? Can you say “in humans, this particular piece of tendon in the neck is what eels reused for an additional mouth” or something along those lines?
Thanks for your time!
Do we have a common ancestor with eels that also have jaws?
Edit: you must check if this characteristic didn’t evolve after our ancestry lines diverged.
Eels are not monophyletic—can you be specific as to which eels you’re talking about?
Sorry for the vagueness of the post! In trying to find the name of the eel in question, I typed “eel two mouths” into DDG and got this Wikipedia article:
https://en.wikipedia.org/wiki/Pharyngeal_jaw
Having read through that article, it seems to be yet another example of a fish gill becoming something else haha, gills are apparently like the most plentiful LEGO brick in the box (from evolution’s perspective)!
So it’s moray eels. Very interesting! I don’t know the answer to your question but I thought this information might be useful for those who may be able to.
Generally there are many such examples of structures, but the great evolutionary distance between mammals and moray eels also means it’s possible some structures have been lost completely in the intervening time.
You might look at embryonic development to see which gill-like structures end up forming which organs in humans, then compare that to moray eel anatomy and development, if you can find such information.
