Human Variation

1. The effects of high altitude on humans is considerable. Air is comprised of nitrogen (79.04%) and oxygen (20.93%) making up the majority of each breath we take. This composition of air remains consistent, whether we are at sea level or at altitude.  However, with altitude, the partial pressure of oxygen in this air (how many molecules of oxygen are in a given volume of air) changes. At sea-level, the partial pressure of oxygen is 159 mmHg, whereas at 8,848m above sea level (the summit of Mt Everest), the partial pressure of oxygen is only 53 mmHg. 

At high altitudes oxygen molecules are further apart because there is less pressure to push them together. This effectively means there are fewer oxygen molecules in the same volume of air as we inhale. This disturbs homeostasis and can ultimately be fatal.

2. Short Term Adaptation: acute moutainsickness (also known as acute altitude sickness) is a group of general symptoms that are brought on by climbing or walking to a higher and higher altitude (elevation) too quickly. High altitude is defined as 8,000 - 12,000 feet above sea level. Very high altitude is 12,000 - 18,000 feet, and altitudes above 18,000 feet are considered extremely high altitude. Hypoxiathen occurs because the body doesn’t have enough time to adapt to the lower air pressure and lower oxygen level in the air at high altitudes. The short term adaption occurs: increasing of the breathing rate. This then boosts the blood oxygen, but not to normal levels. The body needs to adjust to operating with less oxygen than usual. When you don’t give your body time to adjust, you will develop symptomsincludingdizziness, fatigue, shortness of breath, loss of appetite, sleep problems and a general loss of energy. These symptoms usually begin within 12 to 24 hours of arriving at a high altitude. However, these symptoms lessen within a day or two as the person gets used to the altitude.

Faculative Adaptation: High altitude pulmonary oedema (HAPE) is a dangerous build-up of fluid in the lungs that prevents the air spaces from opening up and filling with fresh air with each breath. When this happens, you become progressively more short of oxygen, which in turn worsens the build-up of fluid in the lungs. This can be fatal within hours. HAPE usually develops after 2 or 3 days at altitudes above 2500 m. Typically you will be more breathless compared to those around you, especially on exertion. You will experience the same symptoms of hypoxia, but you may also develop a cough and this may produce white or pink frothy sputum. The breathlessness will progress and soon you become breathless even when you’re resting. Heart rate may be fast, the lips may turn blue and body temperature may be elevated.

Developmental Adaptation: Groups living in the highest elevations have different developmental adaptations.  For example, Andeans exhibit a hematological developmental adaptation to the thin air by developing an ability to carry more oxygen in each red blood cell (they have higher hemoglobin concentrations in their blood). Basically, they breathe at the same rate as people who live at sea level, but the Andeans have the ability to deliver oxygen throughout their bodies more effectively than people at sea level do because having more hemoglobin allows them to carry the oxygen through the blood system.  Tibetans, as pictured below, have a respiratory developmental adaptation.  In contrast, they increase their oxygen intake by taking more breaths per minute than people who live at sea level. Additionally, theyhave a second biological adaptation, which expands their blood vessels, allowing them to deliver oxygen throughout their bodies more effectively than sea-level people do.Tibetans' lungs synthesize larger amounts of a gas called nitric oxide from the air they breathe. The nitric oxide increases the diameter of blood vessels, which suggests that Tibetans may offset low oxygen content in their blood with increased blood flow.

Cultural Adaptation: A cultural adaptation has been the control of fire and an expanded tool kit that included bone needles to make complicated clothing that protected the body in a significant way. Today, climbers also use oxygen tanks and masks when climbing the summits.  

3. In studying human variation from across environmental clines we can better understand how our environment has affected us as humans and what adaptations have resulted as a way of helping us survive. For example, it is clear that the Tibetans and Andeans have biologically adapted to high altitudes through hematological and respiratory developmental adaptations.  Wouldn’t it be of great importance to study how and perhaps find cures to different conditions in which low hemoglobin levels reduce the ability of the blood to carry oxygen like anemia?  

4. Studying environmental influences on adaptations is a better way to understand human variation than race because race does not account for human biological variation. As we learned in this weeks lesson, race has only been around for a few hundred years. Race-based interpretations of human diversity limit and obscure scientific research into the true sources, patterns, and importance of human variation. There is no clear or stable relationship between easily observable traits such as skin color. What is inside our bodies is literally millions of genetic and phenotypic traits, which are notobservable. Race is a modern idea and a social construct and frankly it cannot cause any specific adaptation. Given this information I would not use it to understand the variances of the adaptations I listed in #2.