It's like some sort of ... Man...Bear...Pig. lol I didn't think of that one, it's just a few beat stem cells away! Trey Parker and matt stone were psychic.
Your point is also astute, the technological mods we will inevitably be able to make to our selves also open that same what is it to be human thought train.
I played a cyberpunk roleplaying game a few years back (cp2020); they used a game mechanic that made you lose sanity as you made increased changes to yourself.
The idea that our ability to change ourselves physically can change who we are has been around a loong, I also fuzzily remember some IRL discussion of how simple plastic surgery could change a person's mentality.
It's an interesting game mechanic. I don't know about surgery and mental processing, I've never read on the subject to be able to discuss it.
I cant point you to any links on that; whatever I read was a while back and it appealed to my bias against people that get plastic surgery ;> vanity plastic surgery, I should say