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Surface dweller was a common colloquial term the D'ni used for humans. It was typically used in a pejorative manner. Until the years prior to the Fall, the D'ni were unsure whether the surface had sentient inhabitants until Anna discovered them.
The genetic relationship between Humans and D'ni, if any, is uncertain. A number of D'ni were believed to have gone to live on the surface shortly after their arrival on Earth and may have interbred.
Humans in other Ages
Although biologically and historically 'human' refers exclusively to the inhabitants of Earth, it's possible that the general template of human existed in various Ages, even without being related at all; the Ages being separated since their existence).
Atrus in his Channelwood Journal refers to the ancient man of the Age as 'human', not just a humanoid. At seems that terran humans, D'ni, Rivenese (and possibly Serenians etc), although not related at all, still could belong to the same 'human' classification since not only they look identical, but can also interbreed.