To add to the mix.....
High altitude natives such as true genetically adapted pure Tibetans (not just acclimatized) have much lower hemoglobin levels than lowlanders who come to altitude and acclimatize. So it is not just the red cells. They have metabolic changes in their cellular oxygen transport to and at the mitochondria level. This is not available, at least nowhere to the same degree, to those who stay a week or a month. I am surprised the article did not mention this as it is receiving lots of research attention these days.
Furthermore. Andean populations have runaway polycythemia (way TOO MUCH red blood production) and as a result get Chronic mountain sickness( monge's disease) and die young often age 25-35 from right ventricular heart failure. They are genetically different from Tibetans and something like four times as likely to get this. Totally different disorder than AMS, HACE, HAPE.
