Are Humans Still Evolving Body Paragraph 1

One example of recent modern evolution lies in the Tibetan highlands. At high altitudes oxygen availability is reduced which contributes to altitude sickness, marked by fatigue, insomnia, and nausea. People who are not acclimated or well adapted to life at high altitude suffer serious health issues. “Individuals from low-altitude populations who move to live at high altitude suffer from a number of potentially lethal diseases specifically related to the low levels of oxygen and struggle to reproduce at these altitudes. The hypoxia of altitude would thus have exerted substantial evolutionary selective pressure (Cynthia Beall et al., 2010).”  However, Tibetan highlanders can comfortably reside at elevations above 4,000m or 13,200 ft. The adaptations in tibetan populations that allow them to live at high altitude originates from the EPAS1 gene. This gene encodes for a transcription factor used in the induction of genes regulated by oxygen. The protein is induced when oxygen levels fall and controls the production of red blood cells. Tibetans actually produce fewer red blood cells than their lowland counterparts. An increase in blood cells is only beneficial to a certain point in delivering oxygen to tissues. Having too many red blood cells will make the blood too viscous to efficiently oxygenate tissues. Therefore, the changes in the EPAS1 gene ultimately make Tibetans less likely to overproduce red blood cells at high altitudes. The version of the EPAS1 gene found in tibetans varies from the versions of the gene found in any extant human population, it is unique and seems to be adapted to this specific environment.