The Argument ~
Shenk suggests that Kenyans who can
athletically perform better, especially with running, than their Caucasian
athletes in the Olympics come from the “Kalenjin tribe in the Great Rift Vally
region of western Kenya, where they have a centuries-old tradition of long-distance
running.” This tradition of running and cattle raiding was continued because it
directly linked to survival since “the better a young man was at raiding
[cattle]- in large part a function of his speed and endurance- the more cattle he
accumulated […and] since cattle were what a prospective husband needed to pay
for a bride[..., such] a reproductive advantage might
cause a significant shift in a group’s genetic makeup over the course of a few
centuries”(103). Relate how natural selection and adaption/evolution ("survival and reproduction") play
into the development of the differing performances due to changes in the lungs.
In addition, compare and contrast the vital capacity, tidal volume, and
residual volume of the lungs of an American athlete to a Kenyan athlete, or an
average European Caucasian’s to a Kenyan athlete. Would a Kenyan athlete
experience a Bohr shift, and what causes this shift? Would this
shift be more significant than a shift in a Caucasian athlete in training from
America?
Relate back to the Respiratory System, the biological theme of
homeostasis, and the concept of evolution/natural selection.
Lea Nowack (lea.nowack123@gmail.com)
While Kenya is considered by some to be a long-distance runner factory, the truth is: “Ninety percent of top performing Kenyans come from the Kalenjin tribe in the Great Rift Valley region of Western Kenya” (103). This concentration of talent demonstrates that, contrary to what some may believe, not all Kenyans are natural born runners. The excellent runners we witness smashing records at the Olympics come from only a small portion of the Kenyan population in a specific region. This phenomenon is hardly coincidently and is the result of many generations of natural selection and evolution in response to cultural demands.
ReplyDeleteIn the Kalenjin tribe, the wealth of a man was determined by the size of his herd of cattle. Like in any society, wealth enhances a man’s ability to court women; a skill critical to survival and reproduction. Therefore, over centuries of male competition for cows, certain traits such as running speed and endurance have emerged as selective advantages. Since being the fastest in the tribe promises the most cows and the most opportunity to mate with females, it is the usually fastest young men that have sex the most. Conversely, the slow, lethargic men may not have the chance to reproduce at all and would possibly die without having passed on their genetics. Under this system, the fastest, most capable men go on and produce offspring while those who are not have drastically reduced contributions to the gene pool. After generations of this survival of the fittest genetic culling, the resulting Kalenjin population will naturally feature a large number of genetically “gifted” runners whose fathers were some of the fastest of the previous generation. In comparison with a different population in a region such as the United States, Kalenjin Kenyans’ would appear to possess super-human running abilities as no place in the U.S values running like the Kalenjin tribe. Therefore, nowhere would you find a genetic pool that has undergone similar natural selection to produce a comparable array of running talent like that found in the Kalenjin tribe.
An important part of any cardiovascular exercise, such as running, is the efficiency of the respiratory system. Without a well-functioning respiratory system, oxygen, a crucial component of cellular respiration, would not be delivered to cells along with glucose to produce ATP to drive the muscular activity of the body. An exercise such as long-distance running requires an extraordinary amount of ATP to operate constantly contracting muscles that perpetuate the constant motion long distance runners such as those of the Kalenjin tribe must maintain. This environmental pressure for efficient oxygen delivery would, over generations of natural selection, produce noticeable differences in the Kalenjin population’s lungs when compared to the rest of the world. Greater lung capacity would be an adaptation in response to the Kalenjin population’s constant high demand for oxygen when running. Lung capacity cannot be immediately increased by exercise (http://www.scientificamerican.com/article.cfm?id=if-a-persons-lung-size-ca); however, over generations of natural selection producing offspring of only the most active runners, greater lung capacity, and thus greater tidal volume, vital capacity, and residual volume will likely appear within the Kalenjin tribe. The Bohr effect is the result of hemoglobin proteins releasing their loads of oxygen in the presence of high carbon dioxide and hemoglobin picking up more oxygen in the presence of low carbon dioxide and thus high oxygen. A Kenyan runner would have relatively very acidic blood during low periods of running due to high consumption of oxygen and thus high levels of carbon dioxide dissolved as acidic carbonic acid in the blood. Therefore the Kenyan runner’s hemoglobin will likely be adapted to model a leftward Bohr shift by holding oxygen more tightly due being adapted to operate under acidic environments during exercise. This Bohr shift would be much greater than that of a normal Caucasian who has not undergone the natural selection process of the Kalenjin tribe because the Caucasian would not have generations of high performance runners’ genetics in his DNA.
ReplyDeletebowenjin2004@yahoo.com (Bowen Jin)