What’s the highest place on Earth that humans live?
Live Science: Cynthia Beall, Distinguished University Professor Emerita and the Sarah Idell Pyle Professor of Anthropology at the College of Arts and Sciences, said that at higher altitudes, humans’ percentage of hemoglobin—the protein within red blood cells that carries oxygen—in the blood decreases. “By the time you’re at about 4,500 meters (14,763 feet), the same breath of air that you take at sea level has about 60% of the oxygen molecules, so that’s a big stress,” she said.