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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] |
Dress (Klashorst)-cropped
A dress (also known as a frock or a gown) is a garment traditionally worn by women or girls consisting of a skirt with an attached bodice (or a matching bodice giving the effect of a one-piece garment). It consists of a top piece that covers the torso and hangs down over the legs. A dress can be any one-piece garment containing a skirt of any length, and can be formal or casual. A dress can have sleeves, straps, or be held up with elastic around the chest, leaving the shoulders bare. Dresses also vary in color. The hemlines of dresses vary depending on modesty, weather, fashion or the personal taste of the wearer. Overview Dresses are outer garments made up of a bodice and a skirt and can be made in one or more pieces. Dresses are generally suitable for both formal wear and casual wear in the West for women and girls. Historically, dresses could also include other items of clothing such as corsets, kirtles, partlets, petticoats, smocks, and stomachers. History 11th ... [...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 polybenzothiazine 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 undert ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Chimpanzee
The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative the bonobo was more commonly known as the pygmy chimpanzee, this species was often called the common chimpanzee or the robust chimpanzee. The chimpanzee and the bonobo are the only species in the genus ''Pan''. Evidence from fossils and DNA sequencing shows that ''Pan'' is a sister taxon to the human lineage and is humans' closest living relative. The chimpanzee is covered in coarse black hair, but has a bare face, fingers, toes, palms of the hands, and soles of the feet. It is larger and more robust than the bonobo, weighing for males and for females and standing . The chimpanzee lives in groups that range in size from 15 to 150 members, although individuals travel and forage in much smaller groups during the day. The species lives i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiang West Savanna
The kiang (''Equus kiang'') is the largest of the ''Asinus'' subgenus. It is native to the Tibetan Plateau, where it inhabits montane and alpine grasslands. Its current range is restricted to the plains of the Tibetan plateau; Ladakh; and northern Nepal. Other common names for this species include Tibetan wild ass, khyang and gorkhar. Travellers' accounts of the kiang are one inspiration for the unicorn. Characteristics The kiang is the largest of the wild asses, with an average height at the withers of . They range from high at the withers, with a body long, and a tail of . Kiangs have only slight sexual dimorphism, with the males weighing from , while females weigh . They have a large head, with a blunt muzzle and a convex nose. The mane is upright and relatively short. The coat is a rich chestnut colour, darker brown in winter and a sleek reddish brown in late summer, when the animal moults its woolly fur. The summer coat is 1.5 cm long and the winter coat is doubl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homo
''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' (modern humans), plus several extinct species classified as either ancestral to or closely related to modern humans (depending on the species), most notably ''Homo erectus'' and '' Homo neanderthalensis''. The genus emerged with the appearance of ''Homo habilis'' just over 2 million years ago. ''Homo'', together with the genus ''Paranthropus'', is probably sister to '' Australopithecus africanus'', which itself had previously split from the lineage of '' Pan'', the chimpanzees. ''Homo erectus'' appeared about 2 million years ago and, in several early migrations, spread throughout Africa (where it is dubbed '' Homo ergaster'') and Eurasia. It was likely that the first human species lived in a hunter-gatherer society and was able to control fire. An adaptive and successful species, ''Homo erectus'' persisted for more than a million ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skin Reflectance
In anthropology, reflectometry devices are often used to gauge 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 individu ... through the measurement of skin reflectance. These devices are typically pointed at the upper arm or forehead, with the emitted waves then interpreted at various percentages. Lower frequencies represent lower skin reflectance and thus darker pigmentation, whereas higher frequencies represent greater skin reflectance and therefore lighter pigmentation. Below are global estimates of skin reflectance frequencies in various countries, populations and areas as observed and predicted by Jablonski and Chaplin. References {{reflist Skin pigmentation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet
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 contac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recent African Origin Of Modern Humans
In paleoanthropology, the recent African origin of modern humans, also called the "Out of Africa" theory (OOA), recent single-origin hypothesis (RSOH), replacement hypothesis, or recent African origin model (RAO), is the dominant model of the geographic origin and early migration of anatomically modern humans (''Homo sapiens''). It follows the early expansions of hominins out of Africa, accomplished by ''Homo erectus'' and then '' Homo neanderthalensis''. The model proposes a "single origin" of ''Homo sapiens'' in the taxonomic sense, precluding parallel evolution in other regions of traits considered anatomically modern, but not precluding multiple admixture between ''H. sapiens'' and archaic humans in Europe and Asia. ''H. sapiens'' most likely developed in the Horn of Africa between 300,000 and 200,000 years ago, although an alternative hypothesis argues that diverse morphological features of ''H. sapiens'' appeared locally in different parts of Africa and converged du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone). In terms of climate, the tropics receive sunlight that is more direct than the rest of Earth and are generally hotter and wetter as they aren't affected as much by the Season, solar seasons. The word "tropical" sometimes refers to this sort of climate in the zone rather than to the geographical zone itself. The tropical zone includes deserts and snow-capped mountains, which are not tropical in the climatic sense. The tropics are distinguished from the other climatic and biomatic regions of Earth, which are the middle latitudes and the polar regions of Earth, polar regions on either side of the equatorial zone. The tropics constitute 40% of Earth's surface area and contain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aboriginal Tasmanians
The Aboriginal Tasmanians ( Palawa kani: ''Palawa'' or ''Pakana'') are the Aboriginal people of the Australian island of Tasmania, located south of the mainland. For much of the 20th century, the Tasmanian Aboriginal people were widely, and erroneously, thought of as being an extinct cultural and ethnic group that had been intentionally exterminated by white settlers. Contemporary figures (2016) for the number of people of Tasmanian Aboriginal descent vary according to the criteria used to determine this identity, ranging from 6,000 to over 23,000. First arriving in Tasmania (then a peninsula of Australia) around 40,000 years ago, the ancestors of the Aboriginal Tasmanians were cut off from the Australian mainland by rising sea levels c. 6000 BC. They were entirely isolated from the outside world for 8,000 years until European contact. Before British colonisation of Tasmania in 1803, there were an estimated 3,000–15,000 Palawa. The Palawa population suffered a dra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rickets
Rickets is a condition that results in weak or soft bones in children, and is caused by either dietary deficiency or genetic causes. Symptoms include bowed legs, stunted growth, bone pain, large forehead, and trouble sleeping. Complications may include bone deformities, bone pseudofractures and fractures, muscle spasms, or an abnormally curved spine. The most common cause of rickets is a vitamin D deficiency, although hereditary genetic forms also exist. This can result from eating a diet without enough vitamin D, dark skin, too little sun exposure, exclusive breastfeeding without vitamin D supplementation, celiac disease, and certain genetic conditions. Other factors may include not enough calcium or phosphorus. The underlying mechanism involves insufficient calcification of the growth plate. Diagnosis is generally based on blood tests finding a low calcium, low phosphorus, and a high alkaline phosphatase together with X-rays. Prevention for exclusively breastfed babi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
-cropped.jpg "Click for more on -> Dark Skin")
_from_the_book_entitled%2C_The_great_and_small_game_of_India%2C_Burma%2C_and_Tibet_(1900)_(cropped).jpg "Click for more on -> Kiang West Savanna")
