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Recent Human Evolution
Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within ''Homo sapiens'' populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster than ever before. It has been proposed that human culture acts as a selective force in human evolution and has accelerated it; however, this is disputed. With a sufficiently large data set and modern research methods, scientists can study the changes in the frequency of an allele occurring in a tiny subset of the population over a single lifetime, the shortest meaningful time scale in evolution. Comparing a given gene with that of other species enables geneticists to determine whether it is rapidly evolving in humans alone. For example, while human DNA is on average 98% identical to chimp DNA, the so-called Human Accelerated Region 1 (HA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recent Human Evolution
Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within ''Homo sapiens'' populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster than ever before. It has been proposed that human culture acts as a selective force in human evolution and has accelerated it; however, this is disputed. With a sufficiently large data set and modern research methods, scientists can study the changes in the frequency of an allele occurring in a tiny subset of the population over a single lifetime, the shortest meaningful time scale in evolution. Comparing a given gene with that of other species enables geneticists to determine whether it is rapidly evolving in humans alone. For example, while human DNA is on average 98% identical to chimp DNA, the so-called Human Accelerated Region 1 (HA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neolithic
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts of the world. This "Neolithic package" included the introduction of farming, domestication of animals, and change from a hunter-gatherer lifestyle to one of settlement. It began about 12,000 years ago when farming appeared in the Epipalaeolithic Near East, and later in other parts of the world. The Neolithic lasted in the Near East until the transitional period of the Chalcolithic (Copper Age) from about 6,500 years ago (4500 BC), marked by the development of metallurgy, leading up to the Bronze Age and Iron Age. In other places the Neolithic followed the Mesolithic (Middle Stone Age) and then lasted until later. In Ancient Egypt, the Neolithic lasted until the Protodynastic period, 3150 BC.Karin Sowada and Peter Grave. Egyp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Menarche
Menarche ( ; ) is the first menstrual cycle, or first menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility. Girls experience menarche at different ages. Having menarche occur between the ages of 9–16 in the west is considered normal.US National Health Statistics Report September 2020 Canadian psychological researcher Niva Piran claims that menarche or the perceived average age of puberty is used in many cultures to separate girls from activity with boys, and to begin confinement as a woman and future wife. The timing of menarche is influenced by female , as we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brain Size
The size of the brain is a frequent topic of study within the fields of anatomy, biological anthropology, animal science and evolution. Brain size is sometimes measured by weight and sometimes by volume (via MRI scans or by skull volume). Neuroimaging intelligence testing can be used to study the volumetric measurements of the brain. Regarding "intelligence testing", a question that has been frequently investigated is the relation of brain size to intelligence. This question is quite controversial and will be addressed further in the section on intelligence. The measure of brain size and cranial capacity is not just important to humans, but to all mammals. Humans In humans, the right cerebral hemisphere is typically larger than the left, whereas the cerebellar hemispheres are typically closer in size. The adult human brain weighs on average about . In men the average weight is about 1370 g and in women about 1200 g. The volume is around 1260 cm3 in men and 1130 &nbs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased appetite. If left untreated, diabetes can cause many health complications. Acute complications can include diabetic ketoacidosis, hyperosmolar hyperglycemic state, or death. Serious long-term complications include cardiovascular disease, stroke, chronic kidney disease, foot ulcers, damage to the nerves, damage to the eyes, and cognitive impairment. Diabetes is due to either the pancreas not producing enough insulin, or the cells of the body not responding properly to the insulin produced. Insulin is a hormone which is responsible for helping glucose from food get into cells to be used for energy. There are three main types of diabetes mellitus: * Type 1 diabetes results from failure of the pancreas to produce enough insulin due ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alzheimer's Disease
Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, self-neglect, and behavioral issues. As a person's condition declines, they often withdraw from family and society. Gradually, bodily functions are lost, ultimately leading to death. Although the speed of progression can vary, the typical life expectancy following diagnosis is three to nine years. The cause of Alzheimer's disease is poorly understood. There are many environmental and genetic risk factors associated with its development. The strongest genetic risk factor is from an allele of APOE. Other risk factors include a history of head injury, clinical depression, and high blood pre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cholesterol
Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell membranes. When chemically isolated, it is a yellowish crystalline solid. Cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid and vitamin D. Cholesterol is the principal sterol synthesized by all animals. In vertebrates, hepatic cells typically produce the greatest amounts. It is absent among prokaryotes (bacteria and archaea), although there are some exceptions, such as '' Mycoplasma'', which require cholesterol for growth. François Poulletier de la Salle first identified cholesterol in solid form in gallstones in 1769. However, it was not until 1815 that chemist Michel Eugène Chevreul named the compound "cholesterine". Etymology The word "cholesterol" comes from the Ancient Greek ''chole- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactase Persistence
Lactase persistence is the continued activity of the lactase enzyme in adulthood, allowing the digestion of lactose in milk. In most mammals, the activity of the enzyme is dramatically reduced after weaning. In some human populations, though, lactase persistence has recently evolved as an adaptation to the consumption of nonhuman milk and dairy products beyond infancy. Lactase persistence is very high among northern Europeans, especially Irish people. Worldwide, most people are lactase ''non''-persistent, and are affected by varying degrees of lactose intolerance as adults. However, lactase persistence and lactose intolerance do not always overlap. Global distribution of the phenotype The distribution of the lactase persistence (LP) phenotype, or the ability to digest lactose into adulthood, is not homogeneous in the world. Lactase persistence frequencies are highly variable. In Europe, the distribution of the lactase persistence phenotype is clinal, with frequencies ranging from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eye Color
Eye color is a polygenic phenotypic character determined by two distinct factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. In humans, the pigmentation of the iris varies from light brown to black, depending on the concentration of melanin in the iris pigment epithelium (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma. The appearance of blue, green, and hazel eyes results from the Tyndall scattering of light in the stroma, a phenomenon similar to that which accounts for the blueness of the sky called Rayleigh scattering. Neither blue nor green pigments are ever present in the human iris or ocular fluid. Eye color is thus an instance of structural color and varies depending on the lighting conditions, especially for lighter-colored eyes. The brightly colored eyes of many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Skin
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 devel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malaria
Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. Symptoms usually begin ten to fifteen days after being bitten by an infected mosquito. If not properly treated, people may have recurrences of the disease months later. In those who have recently survived an infection, reinfection usually causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria. Malaria is caused by single-celled microorganisms of the ''Plasmodium'' group. It is spread exclusively through bites of infected ''Anopheles'' mosquitoes. The mosquito bite introduces the parasites from the mosquito's saliva into a person's blood. The parasites travel to the liver where they mature and reproduce. Five species of ''Plasmodium'' can infect and be spread by h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection. Infections can be caused by a wide range of pathogens, most prominently bacteria and viruses. Hosts can fight infections using their immune system. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response. Specific medications used to treat infections include antibiotics, antivirals, antifungals, antiprotozoals, and antihelminthics. Infectious diseases resulted in 9.2 million deaths in 2013 (about 17% of all deaths). The branch of medicine that focuses on infections is referred to as infectious disease. Types Infections are caused by infectious agents (pathogens) including: * Bacteria (e.g. '' Mycobacterium tubercul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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