Originally published in Island Ad-Vantages, July 2, 2020
Opinion - Some facts about race, part 1
by Bill Haviland, Deer Isle
Now that race has become a topic of serious discussion, some facts about the concept need to be understood. Having taught about race at the college and university level for some 37 years, it is something I know about. I have also written about it in my text book Anthropology, the most widely used textbook in its field not just in the United States but worldwide. It has been translated into several different languages.
The first fact to recognize is that race is not a valid biological category when applied to humans, as is commonly thought. Human races, in the biological sense, do not exist. What we know as human races are social constructs that have little to do with biology.
We all know that humans show enormous physical variety, but those characteristics singled out as “racial” do not sort themselves out into discreet, clearly defined clusters. Skin color, for example, shows a continuous gradation over space from south to north, from dark skin to light skin, without any sharp break. By contrast, the ABO blood groups show a continuous gradation from a high incidence of Type A blood in western Europe to a high incidence of blood group B in east Asia. Some other variants have a more spotty distribution. For example, when it comes to the genetic ability to assimilate the milk sugar lactose, some west African populations have more in common with northern Europeans than most other Africans. Conversely, northern Europeans have more in common with some west Africans than eastern Europeans.
Generally, the idea of race is most commonly equated with skin color. Returning to this subject, the following is what I wrote for the eleventh edition of my textbook:
Skin color is subject to great variation, and there are at least four main factors associated with it: transparency or thickness of the skin, a copper-colored pigment called carotene, reflected color from the blood vessels (responsible for the rosy color of lightly pigmented people) and the amount of melanin found in a given area of skin. Exposure to melanin is known to protect skin against damaging solar radiation; consequently, darkly pigmented people are less susceptible to skin cancers and sunburn than are those whose skin has less melanin. They also seem less susceptible to photo-destruction of certain vitamins. Because the highest concentration of dark-skinned people tends to be found in the tropical regions of the world, it appears that natural selection has favored heavily pigmented skin as a protection against the strong solar radiation of equatorial latitudes, where ultraviolet radiation is most intense.
The inheritance of skin color involves several genes (rather than variants of a single gene), each with several alleles [variants], thus creating a continuous range of phenotypic [visible] expression for this trait. In addition, the geographical distribution or cline of skin color, with few exceptions, tends to be continuous. The exceptions have to do with the recent movement of certain populations from their original homelands to other regions, or the practice of selective mating, or both.
Because skin cancers generally do not develop until later in life, they are less likely to have interfered with the reproductive success of lightly pigmented individuals in the tropics, and so are unlikely to have been the agent of selection. [Reproductive success is what natural selection is all about.] On the other hand, severe sunburn, which is especially dangerous to infants, causes the body to overheat and interferes with its ability to sweat, by which it might rid itself of excess heat. Furthermore, it makes one susceptible to other kinds of infection. In addition to all this, decomposition of folate, an essential vitamin sensitive to heavy doses of ultraviolet radiation, can cause anemia, spontaneous abortion, and infertility.