High Altitude and its Affect on Human Variation

          Travelling to high altitudes has a negative impact on the survival of humans that are not used to living in higher elevations.  This is because the mechanisms of homeostasis in humans evolved at low altitudes.  Some of the things that disturb homeostasis at high altitudes are hypoxia, more intense solar radiation, cold temperatures, aridity, wind, reduced nutrition, and rough terrain.  Hypoxia can be one of the more severe disturbances to homeostasis and can be life threatening.  Hypoxia is oxygen deprivation which is due to a lower concentration of oxygen at high altitudes caused by reduced barometric pressure.  This type of response is more commonly seen at elevations of at least 9,000 feet and higher, though mild symptoms can be experienced at as low as 5,000 feet.  The symptoms include a lack of appetite, vomiting, headache, distorted vision, fatigue, and difficulty with memorizing and thinking clearly.  In serious cases, pneumonia-like symptoms (pulmonary edema) due to hemorrhaging in the lungs and an abnormal accumulation of fluid around the brain (cerebral edema) develop. Pulmonary and cerebral edema usually results in death within a few days if there is not a return to normal air pressure levels.

Short term, the ears of the human body adapt to the change in pressure when going to a higher altitude by popping.  One can pop their ears if they yawn or chew.  If someone has a stuffy nose, popping of the ears may be more difficult and painful, but it is a temporary discomfort as the body adapts to being at a higher elevation.

An example of a facultative response to hypoxia would be the body’s response after a couple days in a higher elevation.  After the body begins to acclimate, a response takes place in which more red blood cells and capillaries are produced to carry and deliver more oxygen throughout the body. The lungs also increase in size and the vascular system makes changes to enhance its ability to transfer gases.  Once you return to a lower altitude again, these physiological changes revert to normal.  People with high expressions of the PD2P gene, the gene that codes for a protein that turns food into fuel, tend to have less severe symptoms of hypoxia in high altitudes and can adapt better.

 

               

An example of a developmental response to high altitudes is evident in the permanent physiological changes of peoples who live in high altitudes in Tibet and in Nepal as well as in the Quechua people who live in the Peruvian Andes Mountains.  Being born and raised in these extreme elevations caused their bodies to process glucose differently.  These native people burn glucose in a way that permits more efficient oxygen use. This suggests that their mitochondrial DNA has undergone genetic mutations because the mtDNA directs how the cells process glucose.  Another developmental response in high altitudes of native dwellers is that they’ve developed larger hearts and lungs during their growth and development to aid in the distribution of oxygen throughout their bodies.  Native high-altitude dwellers have been found to have 10 oxygen processing genes not found in people who were born and live in low altitudes.  Natives of the Andes Mountains, their bodies began producing more red blood cells to compensate for the less concentrated oxygen in the air, causing increased distribution of oxygen throughout their bodies during their growth and development.  Ninety percent of Tibetans have a single point mutation in their EPAS1 gene that causes them to produce the same amount of red blood cells as low altitude dwellers, which higher production of hemoglobin can lead to higher incidence of blood clots, heart attacks, and strokes as well as cause issues with fetal development and growth in pregnant women, explaining why natural selection has favored this mutation in their EPAS1 gene.

 

An example of a cultural response to living in high altitudes is the use of hats in Tibet.  Tibetans use wide brimmed hats as part of their cultural working dress in the summers, which helps protect them from the sun, and they wear thick, furry hats in the winter to help keep them warm. 

One of the benefits of studying human variation from the perspective of environmental clines is we’re able to see how different populations have adapted differently and can see measurable effects of natural selection.  This alone is extremely beneficial to the advancement of science and understanding our history and genetics. Another benefit of looking at human variation from an environmental perspective is that skin color is a result of environmental processes and not associated with inferiority or superiority in genetics.  Differences are explained by natural adaptations over time as opposed to being explained using elitism.  Looking at human variation across environmental clines can be helpful in a multitude of ways from identifying causes of vitamin deficiency in order to prevent them in high risk populations or to just understanding why some of us have the variations we have.  One helpful example of understanding human variation based on environmental adaptations would be understanding the risks of traveling to a high altitude and watching for the signs and symptoms of an acute onset of hypoxia.  Knowledge like that can save a life.  Another example of the helpfulness of studying adaptation across environmental clines would be prescribing a multivitamin that includes vitamin D to a darker skinned family that moves to a more northern climate, knowing that higher melanin production is associated with vitamin D deficiency in northern climates.  This could help prevent the onset of a disease like rickets. 

I honestly couldn’t use race to understand the variation of adaptations I listed in #2. No one could, because the variations listed are not based on race, but based on adaptations to environmental influences.  Scientifically, studying human variation based on environmental influences makes more sense than trying to use race, because environmental influences are responsible for our variations, including skin color. Race has no genetic basis, it is not biological, so looking at human variation from the perspective of race is unscientific.  Not only would it be unscientific to approach the subject of human variation based on race but also irresponsible.  In the past, trying to explain variation based on race has led to some ridiculous and disgusting ideas of superiority and inferiority.  People today are still haunted by the effects of racism and slavery in the past, and the unfortunate truth is, people with a skin color other than white are still not entirely treated as equal.  Science should be objective and should never be used as a tool of oppression.