Final answer:
Natives living at high altitudes adapt by producing more red blood cells, a process called acclimatization, facilitated by the secretion of the hormone erythropoietin that enhances the oxygen-carrying capacity of the blood.
Step-by-step explanation:
Natives who have resided at high altitude all their lives adapt to the altitude by producing more red blood cells. This physiological response is known as acclimatization and is key to surviving in environments with lower partial pressure of oxygen. The kidneys play a crucial role by secreting erythropoietin (EPO), which promotes the formation of erythrocytes, consequently increasing the oxygen-carrying capacity of the blood.
This adjustment allows individuals to maintain adequate oxygen delivery to their tissues despite the lower oxygen saturation levels at high altitudes. Over time, this enables natives of high altitude regions to engage in physical activities without experiencing acute mountain sickness (AMS) or other hypoxemic symptoms.