According to Timperely (2023), ectoparasites such as lice could have played a role in the natural selection of human beings. Hominids may have struggled with the spread of diseases caused by insects. The possibility is that entire tribes of prehistoric humans died from the fatal bacterial effects caused by different types of ectoparasites, such as typhus, trench fever, and relapsing fever. These types of diseases could have killed thousands of humans, contributing to the process of natural selection and the diminishing genetic traits of the thick-haired human. This could have presented an adaptation against ectoparasites according to the theory of Darwin (1859). protein is present in all mammalian species, suggesting the HR gene contributed a crucial role in human hair evolution throughout mammalian history. Traces of the gene do not exist in nonmammals. Wen et al. (2023) shared a discovered mutation in Homo sapiens’ DNA clusters, called the human type 1 hair keratin (KRTHAP1), consisting of nonfunctional genes called pseudogenes (phihHaA). Scientific evidence suggests an inactivation of the human gene (hHaA) by pseudogenes only 240,000 years ago, which altered the similarity of great apes’ DNA code to humans. Evolutionary molecular mutations substituted the gHaA of apes for the phihHaA of humans, resulting in the pan-Homo divergence over 5 million years ago. The phihHaA gene is also helpful and effective in supporting the beliefs of the human population, beginning in Africa (Wen et al., 2023). Research on the human type 1 hair keratin has provided scientific evidence explaining a unique genetic makeup of keratin in various types of human hair. The data reveals individuals’ current diversity of hair textures (sizes of hair strands). The large strands of hair (coarse hair) present among people of ethnic backgrounds result from the human type 1 keratin (Wen et al., 2023).
Most theories of human metamorphosis can be explained according to Darwin’s theory of evolution (Darwin, 1859), describing how living organisms can change over long periods. This transforming ability resulted in heritable physical changes caused by behavioral traits, allowing prehistoric humans to adapt to environmental conditions and survive. Timperely (2023) introduced assumptions on how humans gained the look of hairlessness compared to other hairy mammals. Genetic alterations and adaptation against ectoparasites are the reasons for the change in hair strands among humans. Genetic metamorphosis On the scientific level, Kowalczyk et al. (2022) documented that the human genetic metamorphosis of human hair involves a molecular evolution of the HR gene. The HR gene is a protein contributing to hairlessness, known as the hairless protein. The hairless protein regulates the hair follicles’ growth cycles and variations in pigmentation produced by human cells. During hair regeneration, the HR protein facilitates the growth cycles of hair (transitions of the telogen to anagen phase). Kowalczyk et al. (2022) argued that the HR protein regulates the processes within the hair follicle through over-expressions of the HR mutants, establishing a Wnt signaling inhibito r. The Wnt signaling prevents the follicle from facilitating new hair growth. Once the hair reaches the final growth stage, the old strand detaches from the bulb, and the derma papilla does not produce new hair. This finding provided evidence of the control of the HR gene in regulating the hair growth cycle. The mutation of the hairless human protein is associated with premature hair loss cases, such as alopecia universalis congenital (AUC). The molecular evolution of the HR gene is the reason for the drastic change in hair growth among prehistoric humans compared to modern humans (Kowalczyk et al., 2022). Ortiz-Ramírez et al. (2023) explained that the hairless
CHAPTER 3: CHEMICAL COMPOSITION, STRUCTURE, AND CHARACTERISTICS OF HAIR
Throughout human history, hair has served as a form of protection, a signifier of social status, an approach toward representations of authority, power, conformity, nonconformity, culture, and ways to communicate individual uniqueness (Sherrow, 2023). Much research supports hair The chemical composition of hair According to Milady (2023), hair is a component of the skin, a complex structure created by cells within the hair follicle. The thin threadlike structure, called the hair shaft, is the visible part of the hair, projecting outside the skin’s top layer. The hair shaft is composed of 90% protein. Chemical units called amino acids build up the proteins that produce hair strands. Lopez and Mohiuldin (2023) defined amino acids as chemical elements and protein building blocks existing in every body cell. All living organisms have protein- building items (amino acids) within their cells. Scientists have discovered 50 amino acids within the cells of living organisms. Of those 50, 20 make up proteins for human bodies. Only nine of the 20 proteins are necessary elements for life. Milady (2023) documented only five elements (amino acids) essential to hair production. Individual hair strands comprise carbon, oxygen, hydrogen, nitrogen, and sulfur. COHNS is the acronym describing the hair-building elements. See Figure 1.
as an adorn for creating specific looks and demonstrating personal expressions. Hair care is a part of human lives, contributing greatly to personal hygiene, grooming, and health practices. But what is hair?
Figure 1: The Amino Acids Referred to as Cohns, Essential in Human Hair Production The COHNS Elements (Amino Acids) Elements Amount in Healthy Hair Carbon 51% Oxygen 21% Hydrogen 6% Nitrogen 17% Sulfur 5%
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