Pandoran

Pandorans are a subrace of humanity. Eons ago a village of cro-magnons were forcibly abducted and relocated to another planet by as of yet unidentified aliens. They were used as manual labor for a few decades but eventually abandoned. As the cro-magnons adapted to life on this strange new planet they evolved in response to environmental pressures - low gravity, differing light spectrum, thinner atmosphere, etc . Pandorans today share 98% of their DNA with modern humans, but have evolved to the point where the two can no longer interbreed.