What would the average skin tone and facial features look like after 300 years if every partner relationship was interracial until there were no other ethnicities? Just a hodgepodge of DNA. What would the average human look like having a little bit of everything in them?
I just think the idea is neat is all.
I think having a 300 year life span would tend to select for darker skin and possibly other traits that would better survive 300 years of exposure - enough to distinguish it from any existing ethnicity.