Human Variation

I chose to do my blog on high altitude and how humans adapt to compensate for the thinner air.  High altitudes itself has about the same percentage of oxygen in the air as sea level air does.  However, the air pressure at higher altitudes makes it harder for the oxygen to pass through selective permeable membranes in the lungs.  This causes the body to go into a state of hypoxia which is a term for lack of oxygen.

Short term adaptations

An initial response to higher altitudes is the body begins to start breathing faster and the heart starts working faster as well. This adaptation is to try and pump the oxygen throughout the bloodstream. At the same time, the body doesn't digest food as fast either to allow for the body to work harder on pumping oxygen rich blood throughout the body.

Facultative adaptations

Over a longer period of time, the body will begin to acclimatize to the higher altitude.  More capillaries and red blood cells are created to compensate for the smaller amounts of oxygen in the body.  This allows for the oxygen to spread faster throughout the body.  The lungs also expand in response to the lesser air pressure in the higher altitudes.

Developmental Adaptations

South Americans and Tibetans are two cultures that live and have lived in high altitudes for thousands of years.  The South Americans that inhabit the Andes Mountains produce more hemoglobin to carry oxygen in their blood.  The Tibetans breather faster and have larger arteries to allow for more blood flow.

Cultural Adaptations

It is believed that humans first started inhabiting higher altitudes roughtly 10,000 years ago.  These people were hunter gatherers and it is thought they settled here due to the warming climate after the Ice Age. After the ice sheets melted away in the high altitudes, vast regions were found where vegetation could be grown.  The early human populations also were able to keep warm with fire and and warmer clothing created from the fur of various animals that lived in the mountain.

In the case of studying human variation of environmental stresses, it was interesting to read that the Andean people and Tibetan people were able to adapt in different ways to the higher altitudes. A third population, the people of Ethiopia that live in higher plateaus, offer no difference than to the people of lower and yet are able to live there perfectly fine.  This helps in the evolution in regards to how humans adapt.  Why is it that one culture adapted to the same stress and another culture was able to do it completely different? Why is there another population that has no significant difference in genetic makeup or phenotypic expression that would explain why they are able to live at higher elevations.  These are all questions that have scientists exploring how and when the effects of evolution took place in these populations.

I'm not sure how you would use race to explain human variation.  Race includes a specific group of people that do not all live in the same way.  At least with environmental stress studies, the populations involved all live their life in a similar fashion.  It is easier to understand why people that live in hotter climates survive better where they are located than if they were in a colder climate.  Mountain people are better suited to live in mountains than your coastal populations would be.  Race isn't specific enough to determine a lifestyle from them.