Sunday, March 14, 2010

The Basis of Race

On page 212, Coyne briefly discusses races as "populations of a species that are both geographically seperated and differ genetically in one or more traits". If this is true, what led to the evolution of difference races that we see today around the world ? How has sexual selection also driven the evolution of races? If races merely represent species living in different areas of the globe, should the characterisitics of different races be varied? Connect to natural seleciton and selective advantage in your response.


  1. Although races arise in a plethora of organisms, no example is more striking than humans. There are various driving forces behind the evolution of human race. The most obvious are abiotic factors. Skin, hair, and eye color vary due to amounts of melanin. Those living closest to the equator have the darkest skin which protects them from damaging sun rays. Move away from the equator, and skin color begins to gradually lighten. Since there is less frequent and less intense sunlight furthest from the equator, it is a waste of energy to produce immense amounts of melanin. Thus, organisms that had more energy to delegate to other processes had a selective advantage and were more likely to survive and reproduce. Another selective advantage of northern species is a larger body to provide warmth for essential internal organs. This reveals that the relationship between structure and function can serve as an evolutionary explanation for race.

    Another less obvious force behind evolution is sexual selection. This proposes that physical appearances differ among races merely because certain traits are deemed more attractive. This phenomenon explains the purpose of traits that seemed to have no function. The peacock is an archetype of sexual selection with its flashy feather display. These feathers serve no purpose in protection or hunting. In fact, the feathers would be a large waste of energy to produce had they aided in mate selection. Jerry Coyne provides a human example of the Japanese, whose straight hair and almond shaped eyes have no selective advantage in the environment. Coyne suggests "[an] empress in Asia...might have a penchant for men with straight black hair and almond shaped eyes...lo and behold, over time the curly-haired and round-eyed individuals will be largely replaced" (215).

    It is obvious that abiotic factors and sexual selection have been working together throughout the history of man to create races. However, it is important to remember that races are not sub-species. Races evolve through geographic separation that eventually leads to genetic diversity. This leads to certain alleles occurring at certain frequencies within close populations. The genetic differences between races is extremely small. In fact, there are no concrete distinctions. Race is more of a continuum than a dividing line. Thus, the evolution of race is a prime example of continuity and change of species.


  2. The most important thing to remember about race is that it is not a scientific term. It is a social classification used by a group in power to classify people of its appearance as "superior" and those of a different appearance as "inferior". The term first appeared in the Age of Discovery, when Europeans used physical appearance to discriminate between the white Europeans and the darker-skinned Africans and Americans whom they were attempting to subjugate. They associated dark skin with inferiority, and used this inferiority as justification for slavery (Wikipedia). The unfortunate consequences of racial distinction continue to dog society even today; although the United States achieved racial equality in the 1960s, racist undertones still exist in parts of the country. South Africa was governed by a white oligarchy under the system of apartheid all the way until 1993. With such distinctions being made, one might ask what the original reasons for the differences in appearance between races were.
    As explained above, skin color differences can be easily explained by the need for (or lack of need for) melanin due to the strength of the sun. While melanin is useful in protection against UV rays, too much of it can inhibit creation of Vitamin D in the skin; Vitamin D helps prevent rickets and tuberculosis (215). However, one aspect of the creation of races that was not discussed above was the similarities in appearance between different races, such as Austronesians and Africans or Mongolians and Amerindians. This can be traced to human migration over the years. One might expect that natives of tropical South America would have skin as dark as that of tropical Africans, but this is not the case. The reason is that the Americas were populated by humans only 25,000 years ago, and South America would have been populated even later than this due to its distance from the Bering land bridge (Wikipedia). These migrants came from northeast Asia (Mongolia), a cold climate where melanin would inhibit Vitamin D production. 25,000 years is not enough to change the skin color of native South Americans to a very dark color by natural selection; the result has been more of a medium to pale brown color. Thus, the migratory roots of South American Indians cause them to have lighter skin than Africans.
    Sexual selection was also explained well above. However, I would like to bring up the point of intermarriage between races, which has become more socially acceptable in recent years. Currently, 2.4% of Americans are mixed race (Wikipedia), and this number will probably continue to rise. As the races mingle and sexual selection of race becomes less of a determining factor, we will most likely see decreased differences between the races as their genetic traits mingle and are passed down through the generations.