All humans are actively engaged in various levels of transhumanism, especially from a medical standpoint. We all hope that medicine will help us achieve what is, to us presently, superhuman lifespans. Many of us are mentally altered through psychotropic medicine and prefer living this way. Transhumanism as a movement is just a vocal proponent of a process of technological adoption already happening on a regular basis…
I think for a long time in human history, technology simply wasn't there to alter the physical nature of humanity. But in recent decades, we understand much more about human physiology enough to alter human body in a drastic and permanent way.
This is generating lots of contention between groups about what's acceptable to change and what's not acceptable to change. Also I think about how people think they are rational about their positions on these matters but they are more like strong cultural presumptions about what's right and wrong.
Let's consider situation we already have.
Consider sex change operation. There's one camp that's complete fine with people getting sex change operation, while there's another camp that condones and some, want to outlaw such operation. The liberal camp likes to say that a person should be able to do what they want to do with their body.
However, at the same time, the both of the camp tends to dislike male steroid usage to change one's physique (https://www.govtrack.us/congress/votes/108-2004/h226). For some reason, same reason to let people decide what they want to do with their body, doesn't apply when it comes to male physique.
It's interesting to see how technology is challenging our preconceived notion of right and wrong and sheds lights to inconsistency in our rationale.