A person's skin color is determined primarily by the proportion of eumelanin to pheomelanin, the overall amount of melanin produced, and the number and size of melanosomes and how they are distributed. People with naturally darkly pigmented skin have melanosomes that are large and filled with eumelanin.
Differences in skin and hair color are principally genetically determined and are due to variation in the amount, type, and packaging of melanin polymers produced by melanocytes secreted into keratinocytes. Pigmentary phenotype is genetically complex and at a physiological level complicated.
The type and amount of melanin in hair is determined by many genes, although little is known about most of them. The best-studied hair-color gene in humans is called MC1R. This gene provides instructions for making a protein called the melanocortin 1 receptor, which is involved in the pathway that produces melanin.
The MC1R gene provides instructions for making a protein called the melanocortin 1 receptor. This receptor plays an important role in normal pigmentation. The receptor is primarily located on the surface of melanocytes, which are specialized cells that produce a pigment called melanin.
IT is not uncommon for two dark skinned persons to have a light skinned baby. Skin colour is a physical characteristic that is determined by genes inherited from one’s parents.
For example, a gene called MFSD12 has variants that are linked to darker skin; these are common in dark-skinned people from East Africa, but rare among the lighter-skinned San. MFSD12 also shows how the search for pigmentation genes can reveal new insights about the basic biology of our skin.
The most lightly pigmented (European, Chinese and Mexican) skin types have approximately half as much epidermal melanin as the most darkly pigmented (African and Indian) skin types.
Dark skin. All modern humans share a common ancestor who lived around 200,000 years ago in Africa. Comparisons between known skin pigmentation genes in chimpanzees and modern Africans show that dark skin evolved along with the loss of body hair about 1.2 million years ago and that this common ancestor had dark skin.
Vitamin D is known to enhance the rate of melanin synthesis; and this may concurrently regulate the expression of furin expression. In silico analyses have revealed that the intermediates of melanin are capable of binding strongly with the active site of furin protease.
Skin color varies considerably from individual to individual and is generally determined by the presence of melanocytes, carotene, oxygenated hemoglobin, and local blood flow.
Human skin pigmentation is the product of two clines produced by natural selection to adjust levels of constitutive pigmentation to levels of UV radiation (UVR). One cline was generated by high UVR near the equator and led to the evolution of dark, photoprotective, eumelanin-rich pigmentation.
Skin, hair and eye coloration in humans is variable, and has been influenced by different combinations of evolutionary forces. Skin coloration has been strongly influenced by natural selection, globally and throughout human prehistory, because of the importance of melanin as a natural sunscreen on naked skin.
Skin pigmentation, i.e., melanin, absorbs the UVR that initiates vitamin D synthesis, and hence decreases the vitamin D that is made for a given exposure compared to less pigmented skin. This has been observed in UVR intervention studies [7] and more generally.
Vitamin D synthesis is highly dependent on the concentration of melanin in the skin as melanin absorbs and scatters UVR-B, resulting in a less efficient conversion of 7-dehydrocholesterol to previtamin D3[3]. Therefore, dark-skinned individuals will experience slower vitamin D synthesis than light-skinned ones.
While it's well known that Black people have the highest rates of vitamin D deficiency the United States, the reasons why may be complex and warrant more study, says Meltzer. Melanin is the pigment that provides skin color, and individuals with darker skin have more of it than those with lighter skin.
The rarest skin color in the world is believed to be the white from albinism, a genetic mutation that causes a lack of melanin production in the human body. Albinism affects 1 in every 3,000 to 20,000 people. What is this? People with albinism usually have very pale or colorless skin, hair, and eyes.
Researchers agree that our early australopithecine ancestors in Africa probably had light skin beneath hairy pelts.
Theory held that darker skin had evolved in order to afford early humans—who had recently lost the cover of fur—a protection against skin cancer under the tropical sun. But skin cancers, Jablonski knew, almost always arise later in life, when an individual is past reproductive age.
Caucasians, for example, tend to have a lower amount of melanin, which leads to a lighter skin tone. This can make Caucasians more susceptible to pronounced photoageing, the premature appearance of ageing due to damage caused ultraviolet (UV) rays.
Asian skin has a thicker dermis than white skin, meaning it contains more collagen.
Asian skin has an increased amount of melanin (or dark brown pigment) as well as the melanin-producing cells known as melanocytes. Asians in general have more melanin and more numerous melanocytes in the skin compared to Caucasian skin. Even fair-skinned Asians have more melanocytes than most Caucasians.
Humans first evolved in Africa, and much of human evolution occurred on that continent. The fossils of early humans who lived between 6 and 2 million years ago come entirely from Africa. Most scientists currently recognize some 15 to 20 different species of early humans.
Two genes are SLC24A5 and SLC45A2 that lead to skin depigmentation and, therefore, Europeans' pale skin today. The third gene, HERC2/OCA2, causes blue eyes, and it contributes to light skin color and the blonde hair.
Evolution. Due to natural selection, people who lived in areas of intense sunlight developed dark skin colouration to protect against ultraviolet (UV) light, mainly to protect their body from folate depletion. Evolutionary pigmentation of the skin was caused by ultraviolet radiation of the sun.