Final answer:
The third group that has adapted to living at high altitudes is from the Ethiopian highlands. Unlike Tibetans and Andean peoples, whose adaptations are understood, the adaptation strategies of Ethiopians are still a mystery.
Step-by-step explanation:
The third human population that has biologically adapted to high altitudes, in addition to Tibetans and Andean peoples, is the group from the Ethiopian highlands. While Tibetans have adapted by taking more breaths per minute and Andean individuals have higher concentrations of hemoglobin in their blood, the adaptation strategies of the Ethiopians living at altitudes between 9,800 to 11,580 feet remain less understood. Unlike the Tibetans and Andeans, Ethiopians do not share these specific physiological adaptations, but they are still capable of thriving in low-oxygen environments, indicating a different form of adaptation that has yet to be fully explained.