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Light-skinned
Light skin is a human skin color that has a base level of eumelanin pigmentation that has adapted to environments of low UV radiation. Light skin is most commonly found amongst the native populations of Europe and East Asia as measured through skin reflectance. People with light skin pigmentation are often referred to as "white" or "fair", although these usages can be ambiguous in some countries where they are used to refer specifically to certain ethnic groups or populations. As populations migrated away from the tropics into areas of low UV radiation, they developed light skin pigmentation as an evolutionary selection acting against vitamin D depletion. Humans with light skin pigmentation have skin with low amounts of eumelanin, and possess fewer melanosomes than humans with dark skin pigmentation. Light skin provides better absorption qualities of ultraviolet radiation. This helps the body to synthesize higher amounts of vitamin D for bodily processes such as calcium developm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Skin
Dark skin is a type of human skin color that is rich in melanin pigments. People with very dark skin are often referred to as "black people", although this usage can be ambiguous in some countries where it is also used to specifically refer to different ethnic groups or populations. The evolution of dark skin is believed to have begun around 1.2 million years ago, in light-skinned early hominid species after they moved from the equatorial rainforest to the sunny savannas. In the heat of the savannas, better cooling mechanisms were required, which were achieved through the loss of body hair and development of more efficient perspiration. The loss of body hair led to the development of dark skin pigmentation, which acted as a mechanism of natural selection against folate (vitamin B9) depletion, and to a lesser extent, DNA damage. The primary factor contributing to the evolution of dark skin pigmentation was the breakdown of folate in reaction to ultraviolet radiation; the rel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Skin
Dark skin is a type of human skin color that is rich in melanin pigments. People with very dark skin are often referred to as "black people", although this usage can be ambiguous in some countries where it is also used to specifically refer to different ethnic groups or populations. The evolution of dark skin is believed to have begun around 1.2 million years ago, in light-skinned early hominid species after they moved from the equatorial rainforest to the sunny savannas. In the heat of the savannas, better cooling mechanisms were required, which were achieved through the loss of body hair and development of more efficient perspiration. The loss of body hair led to the development of dark skin pigmentation, which acted as a mechanism of natural selection against folate (vitamin B9) depletion, and to a lesser extent, DNA damage. The primary factor contributing to the evolution of dark skin pigmentation was the breakdown of folate in reaction to ultraviolet radiation; the rel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Skin Color
Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics (inherited from one's biological parents and or individual gene alleles), exposure to the sun, natural and sexual selection, or all of these. Differences across populations evolved through natural or sexual selection, because of social norms and differences in environment, as well as regulations of the biochemical effects of ultraviolet radiation penetrating the skin. The actual skin color of different humans is affected by many substances, although the single most important substance is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skin humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White People
White is a racialized classification of people and a skin color specifier, generally used for people of European origin, although the definition can vary depending on context, nationality, and point of view. Description of populations as "White" in reference to their skin color predates this notion and is occasionally found in Greco-Roman ethnography and other ancient or medieval sources, but these societies did not have any notion of a White or pan-European race. The term "White race" or "White people", defined by their light skin among other physical characteristics, entered the major European languages in the later seventeenth century, when the concept of a "unified White" achieve universal acceptance in Europe, in the context of racialized slavery and unequal social status in the European colonies. Scholarship on race distinguishes the modern concept from pre-modern descriptions, which focused on physical complexion rather than race. Prior to the modern era, no Europe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eumelanin
Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization. The melanin pigments are produced in a specialized group of cells known as melanocytes. Functionally, eumelanin serves as protection against UV radiation. There are five basic types of melanin: eumelanin, pheomelanin, neuromelanin, allomelanin and pyomelanin. The most common type is eumelanin, of which there are two types— brown eumelanin and black eumelanin. Pheomelanin, which is produced when melanocytes are malfunctioning due to derivation of the gene to its recessive format is a cysteine-derivative that contains poly benzothiazine portions that are largely responsible for the of red yellow tint given to some skin or hair colors. Neuromelanin is found in the brain. Research has been u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Folate Deficiency
Folate deficiency, also known as vitamin B9 deficiency, is a low level of folate and derivatives in the body. Signs of folate deficiency are often subtle. A low number of red blood cells (anemia) is a late finding in folate deficiency and folate deficiency anemia is the term given for this medical condition. It is characterized by the appearance of large-sized, abnormal red blood cells (megaloblasts), which form when there are inadequate stores of folic acid within the body. Signs and symptoms Loss of appetite and weight loss can occur. Additional signs are weakness, sore tongue, headaches, heart palpitations, irritability, and behavioral disorders. In adults, anemia (macrocytic, megaloblastic anemia) can be a sign of advanced folate deficiency. Women with folate deficiency who become pregnant are more likely to give birth to low birth weight premature infants, and infants with neural tube defects and even spina bifida. In infants and children, folate deficiency can lead to f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pole, with 0° at the Equator. Lines of constant latitude, or ''parallels'', run east–west as circles parallel to the equator. Latitude and ''longitude'' are used together as a coordinate pair to specify a location on the surface of the Earth. On its own, the term "latitude" normally refers to the ''geodetic latitude'' as defined below. Briefly, the geodetic latitude of a point is the angle formed between the vector perpendicular (or ''normal'') to the ellipsoidal surface from the point, and the plane of the equator. Background Two levels of abstraction are employed in the definitions of latitude and longitude. In the first step the physical surface is modeled by the geoid, a surface which approximates the mean sea level over the ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeogenetic Analysis Of Human Skin Pigmentation In Europe
Archaeogenetics is the study of ancient DNA using various molecular genetic methods and DNA resources. This form of genetic analysis can be applied to human, animal, and plant specimens. Ancient DNA can be extracted from various fossilized specimens including bones, eggshells, and artificially preserved tissues in human and animal specimens. In plants, Ancient DNA can be extracted from seeds and tissue. Archaeogenetics provides us with genetic evidence of ancient population group migrations, domestication events, and plant and animal evolution. The ancient DNA cross referenced with the DNA of relative modern genetic populations allows researchers to run comparison studies that provide a more complete analysis when ancient DNA is compromised. Archaeogenetics receives its name from the Greek word ''arkhaios'', meaning "ancient", and the term ''genetics'', meaning "the study of heredity". The term archaeogenetics was conceived by archaeologist Colin Renfrew. In February 2021, scientis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UV Radiation
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Journal Of Clinical Nutrition
''The American Journal of Clinical Nutrition'' (''AJCN'') is a monthly peer-reviewed biomedical journal in the fields of dietetics and clinical nutrition. The journal was established in 1952 as the ''Journal of Clinical Nutrition'', edited by S.O. Waife and published by the Nutrition Press. It was continued in series under the present title from 1954 and was published by the American Society for Clinical Nutrition (ASCN).Catalog entry at the . It is now published by the .< ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skin Cancer
Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC), squamous-cell skin cancer (SCC) and melanoma. The first two, along with a number of less common skin cancers, are known as nonmelanoma skin cancer (NMSC). Basal-cell cancer grows slowly and can damage the tissue around it but is unlikely to spread to distant areas or result in death. It often appears as a painless raised area of skin that may be shiny with small blood vessels running over it or may present as a raised area with an ulcer. Squamous-cell skin cancer is more likely to spread. It usually presents as a hard lump with a scaly top but may also form an ulcer. Melanomas are the most aggressive. Signs include a mole that has changed in size, shape, color, has irregular edges, has more than one color, is itchy or bleeds. More than ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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