Mountain goat

A mountain goat was a particular kind of goat, whose sure-footedness made it particularly adept at climbing mountains. When having to climb an incline in India with Gandhi and the Tenth Doctor, Donna Noble struggled in comparison and claimed, "We're not all descended from mountain goats, you know." As it turned out, the inhabitants of the planet Istervaal were descended from mountain goats. (PROSE: Ghosts of India)