Got Oxygen?

Almost my entire life I have lived at over 2800 m above sea level as have three generations preceding me in the San Juan Mountains of southwest Colorado. I have also always been curious as to how long-term exposure to higher altitudes affects the human body. 

In general, many factors contribute to the acute human physiological response to high altitudes.  In short, the lower ambient and arterial P-O2 stimulate chemoreceptors in the body that then incite decreased blood oxygenation or hypoxemia (Marriot & Newberry, 1996). It is also interesting that chemoreceptor sensitivity and tolerance for high altitudes varies from person to person and there are most likely genetic components involved (Marriot & Newberry, 1996; Virues-Ortega et al., 2006). While the immediate response is increased ventilation to compensate for the decrease in ambient P-O2, the body also experiences lower hemoglobin saturation and lower arterial P-O2 causing respiratory compensation in the form of hyperventilation, which then restricts increased ventilation (Marriot & Newberry, 1996). Over a few days the kidneys release bicarbonate to counteract the respiratory alkalosis while the body’s ventilation rate slowly rises (acclimatization), improving cellular respiration at the new higher altitude (Marriot & Newberry, 1996). 

I am doubtful there are any genetic abnormalities in my or my family’s physiology pertaining to the high altitude in which we live, but there are some interesting physiological differences in generational highlanders across the world. In this article, Virues-Ortega et al. (2006) discuss the differences in indigenous populations who traditionally live at extreme altitudes (3500m and higher). These adaptions vary physiologically in different indigenous populations even though the stressor of higher altitude remains the same (Virues-Ortega et al., 2006). Larger chest size and higher pulmonary pressure have been observed in Amerindian populations leading to enlarged hearts, while blood-related adaptions have been observed in Andean highlanders through increased levels of red blood cells (Virues-Ortega et al., 2006).

Independent evolutionary adaptions to the same ecological obstacles have been observed over the course of millennia around the world, just as history repeats itself so too does evolution. However, finding examples of independent evolution to high altitudes in the present day and in Humans no less is absolutely fascinating! It makes me wonder how a growing global population and increased global travel will affect patterns like this in the future. 

Marriott, B. M., & Newberry, S. J. (1996). Nutritional needs in cold and in high-altitude environments: Applications for military personnel in field operations. Washington, D.C.: National Academy Press.

Virues-Ortega, J., Garrido, E., Javierre, C., & Kloezeman, K. C. (2006). Human Behavior and Development under High-Altitude Conditions. Developmental Science, 9(4), 400–410.