Today, around 30 million people live at altitudes of over 10,000 feet, with the highest permanent human settlements at 17,500 feet in the Peruvian Andes. The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg. As altitude increases, the concentration remains the same but the number of oxygen molecules per breath is reduced. At 12,000 feet (3,658 meters) the barometric pressure is only 483 mmHg, so there are roughly 40% fewer oxygen molecules per breath. In order to properly oygenate the body, your breathing rate (even while at rest) has to increase. This extra ventilation increases the oxygen content in the blood, but not to seal level concentrations. Since the amount of oxygen required for activitiy is the same, the body must adjust to having less oxygen. Studies have shown that some humands living at these high altitudes exhibit the following anatomical and physiological differences relative to populations at sea level:

1. 30% higher red blood cell counts.

2. Larger right ventricles of the heart

3. Lower birth weights, but larger placentas.

4. Delayed sexual maturity.

5. Higher infant mortality rates, mainly resulting from respiratory infections.

 

 

Question: What evolutionary forces would you hypothesize have been at work on these populations?

 

 

Question 2: Is it possible that these anatomical and physiological changes are not the result of changes in allele frequencies, but are environmental effects on phenotype? Explain.

 

 

 

 

 

This was presented to us in my biology 102. Of course I'm not looking for the answer, but I'm having trouble with the question.

What about the question, specifically, don't you understand?

Well I do not think there are any changes in allele frequencies at work, but I do not know how to know for sure

Well, what does evolution require in order to work? Which of those assumptions may be violated by this example?

 

Hint: think about athletes who train at high altitude and why they do so.