>>534243263
one human race, so long as we can still compatibly breed together. Any sort of drawn out genetic isolation like on a moon/planetary colony or even something like North Korea for long enough, may lead to speciation though

Scifi homogenous empires are a meme; the moment we become physically isolated from each other with little to no genetic flow, then given enough time, humans will split off into different branches.
This hasn't happened on Earth because even the most iaolationist places still exchange enough DNA with others that we're all in the same overlapping pool of compatible building blocks

Maybe give the Sentinalese more time and we'll speciate away from each other. Afaik, they're the only truly isolated people with no gene flow