Human Variations in High Altitude Populations

Jessyca Caumo
26 november 1996

Thesis:The purpose of this paper is to describe the high altitude stresses and
the general adaptations made by the Tibetan population in the Himalayas and the
Quechua in the Andes.

I Introduction
II Background
A Quechua People
B Tibetan People
III General Adaptations
A Physical
1 Growth
2 Development
3 Core temperature
4 Extremity temperature
B Non- Physical
1 Clothing
2 Houses
3 Schedule
V Conclusion

“Some ten to twenty-five million people (that is less than 1% of the
earth’s population) currently make it[high altitude zones] their
home(Moran,143).” The adjustment high altitude populations must make are firstly
physical and secondly cultural. Although most people adapt culturally to their
surroundings, in a high altitude environment these cultural changes alone aren’t
enough. Many physical adaptations that reflect “the genetic plasticity common to
all of mankind(Molinar,219)” have to be made to survive and even more than that
thrive in this type of environment.
In this paper I will describe the high altitude stresses. Along with
adaptations made by the populations living in them. The two high altitude
populations which I will examine in this paper are the Tibetan people of the
Asian Himalayas and the Quechua of the South American Andes.
The Quechua are an Indian people who inhabit the highlands of Peru and
Bolivia. They speak Quechua, which is a branch of the Andean-Equitorial stock.
They show many remnants of Inca heritage by their houses, music, and religion
which has pagan rites under the Roman-Catholic surface. Their villages consist
of kin groups . Their marriage partners are taken from within each village.
Agriculture is the dominant subsistence pattern in the central Andean
region but the Nunoa region where the Quechua reside can only support a few
frost-resistant crops. Which include bitter potato, sweet potato, and a few
grain crops of quinoa and canihua. The rest of the fruits and vegetables of the
Quechua come from the eastern mountains on it’s way to the markets. The most
important subsistence pattern for the Quechua is stock raising. Which is limited
to the few animals that do well in the high altitudes. Their stock include
alpacas,llamas and sheep.
In the Himalayas only “5% of the geographical area(Baker,36)” can be
used for agriculture. The main crops are barley, wheat and buckwheat. The crops
are grown between 3,500 and 4,300 meters. These few crops are threatened by
drought, hail, frost, snow and erosion. The Himalayas also have extensive
pasture areas which are used by the nomadic and sedentary peoples. The higher
regions have pastures where yak, sheep, and goats are the main animals used.
In the high altitude there are many environmental stresses that the
people must endure. They include hypoxia, intense ultraviolet radiation, cold,
aridity, and a limited nutritional base. The people adapt to these stresses in
many ways.
Hypoxia, or low oxygen pressure, is the most prominent stress which
populations living at high altitudes must deal with. “Hypoxia results whenever
either physiological,pathological, or environmental conditions cannot deliver
adequate supply of oxygen to the tissues. Since air is compressible, air at high
altitudes is less concentrated and under less pressure. At 4500 meters the
partial pressure of oxygen is decreased by as much as 40%, in comparison to
pressure at sea level. This reduces the amount of oxygen finally available to
the tissue(Moran,147-148).” The adaptations to hypoxia are all geared towards
increasing the oxygen to the tissues.
One adaptation to hypoxia is an increase of red blood cells in
circulation. A person living in high altitude conditions is likely to have “30%
more red blood cells(Molinar,218)” than a person living at sea level. “This
greater number of red blood cells increases the hemoglobin concentration, which
in turn increases the oxygen -carrying capacity per unit volume of
blood(Molinar,219).” This then increases the oxygen sent to the tissues.
Respiration and cardiac output are also increased. There is an increase in the
capillary network to aid diffusion of oxygen to the tissues. There have also
been cellular changes that increase the resistance to the tissues to low oxygen.
Many other effects are felt from hypoxia. Growth and development are one
of the many areas affected. Kruger and Arias-Stella compared two populations at
4,570 meters and at 200 meters and found the mean placental weight of the high
population to be 561 grams as compared to the low-land population weight to be
500 grams. Placenta volumes did not differ showing that the placenta at the high
altitude was denser. The denser placenta offers the fetus more protection and
greater oxygen. The birth weights at high altitudes are uniformly lower than
that of low altitude. This is probably due to hypoxia but the