That's a good answer. I should have qualified my question (“…short of modifying the source code of humans itself?”).
Reminds me of #DavidPearce's “Hedonistic Imperative”.
@Pat
That in turn reminds me of “philosophical zombies”, eg https://80000hours.org/podcast/episodes/david-chalmers-nature-ethics-consciousness/
@tripu
I meant to say, "I recently pondered whether consciousness could ever evolve *without* pain."
Yeah, philosophical zombies are an interesting thought experiment. I haven't really thought about it too much, but my unconsidered impression is that they could not exist. Certainly machines could be made that mimic human responses, but if something (someone) was an exact duplicate of a human, they'd have consciousness, I think.
We can now look into a working brain and see whats going on with fMRI and other tech, and going forward that will improve, so I think sometime this century we'll have some kind of an answer to the hard problem.
I think we will find that consciousness is much more pervasive, beyond just human consciousness.