Genetic Variation
Genetic Variation is the differences in and among the human population, a situation where no two humans are genetically identical. The traits in human beings show significant variation between the population and sexes. A heritable trait may be acquired through genes that pass from parent to offspring, others through the combination of genes and environmental factors.
Hair Variation
One of the traits that vary between races and individuals is hair. It is mostly influenced by the genes than the environment (Bernard, 76). This hair can be straight or curly. Oval hair follicles make wavy hair, while round hair follicles makes straight hair, while the c-shaped hair follicles produce wavy hair. However, curly hair is a dominant trait in Caucasians, and straight hair is recessive. Curly hair is common in African, rare in Asia. This can as well be compared as 10% of people left hounded, but the number varies among cultures from about 0.5% to 24%. Chromosomes found in curly hair are a dominant trait. Thus, if one parent gives a curly hair gene and the other a straight-haired gene, the stronger haired gene wins the trait. There are three types of hereditary hair. Type CS gives wavy hair, SS gives straight hair, and CC gives curly hair. This is because a straight-haired parent can contribute an S gene while CC contributes a C gene; meaning that all children will possess CS genes thus inherits wavy hair.
Effect of Environment on Hair
The environment affects the phenotype of curly hair since any kind of hair is generally affected by humidity. Some of the devices such as hygrometers use hair as a measuring mechanism since it show change in length depending on the amount of water vapor in the air. Due to this weather factor, curly hair turns frizzy and small in high humid weather, while straight hair goes rising wavy (Pennisi, 87). Since we share a common ancestor who had curly hairs and also lived in hot and sunny places evolutionary, theorists came into agreement that human ancestry can be traced about five hundred thousand years ago in the sub-Saharan. Due to this factor, curly hair acted as protection from the sun and served as a shield from the blazing equatorial sunlight of sub-Saharan Africa. The curly hair also prevented obstruction of vision because it tightly sits more on top of the head and does not block the view. Thick curly hair was not needed to protect all races from the blazing sub-Saharan sun. Some races left the region and with time the dominant gene in and among population just faded from their DNA, thus the hair evolved to become straight.
Hair and Intersexual Selection
Hair type whether curly or straight may bring a significant effect to intersexual selection (Medland., et al 752). This selection is an evolutionary process in which it is dependent on the attractiveness of an individual's phenotypic trait. Mate choice is a component of natural selection a situation where people seek to date and marry only those who are similar to them. Therefore, mate choice introduces new gene combination into a population causing a genetic drift. Moreover, alterations in the DNA known as mutations can cause a real effect, although evolutionally these changes are likely a collection of many mutations. They are caused by the movement of genes from one population to another. Natural selection is the accelerating force behind adaptive evolution and for it to undergo this evolution, it must have some of the qualities such as increase the genes chances of surviving and reproducing in and among human population.
Works Cited
Bernard, Bruno A. "Hair shape of curly hair." Journal of the American Academy of Dermatology 48.6 (2003): S120-S126.
Medland, Sarah E., et al. "Common variants in the trichohyalin gene are associated with straight hair in Europeans." The American Journal of Human Genetics 85.5 (2009): 750-755.
Pennisi, Elizabeth. "Human genetic variation." (2007): 1842-1843.
