   #copyright

Human

2007 Schools Wikipedia Selection. Related subjects: Mammals

            iHuman

                     Fossil range: Pleistocene - Recent

   Image of a man and a woman on Pioneer plaque, sent into space with the
   Pioneer 11 mission
   Image of a man and a woman on Pioneer plaque, sent into space with the
   Pioneer 11 mission

                             Conservation status

   Secure
                         Scientific classification

   Domain:     Eukaryota
   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Mammalia
   Order:      Primates
   Family:     Hominidae
   Genus:      Homo
   Species:    H. sapiens
   Subspecies: H. s. sapiens

                               Trinomial name

   Homo sapiens sapiens
   Linnaeus, 1758

   Humans, or human beings, are bipedal primates belonging to the
   mammalian species Homo sapiens (Latin for "wise man" or "knowing man")
   under the family Hominidae (known as the great apes). Humans have a
   highly developed brain capable of abstract reasoning, language and
   introspection. This, combined with an erect body carriage that frees
   their upper limbs for manipulating objects, has allowed humans to make
   greater use of tools than any other species. Humans or Homo sapiens as
   well as the whole Hominidae tree originated in Africa, but now inhabit
   every continent with a total population of over 6.5 billion people as
   of 2006.

   Like most primates, humans are by nature social. However, humans are
   particularly adept at utilizing systems of communication for
   self-expression and the exchange of ideas. Humans create complex social
   structures composed of co-operating and competing groups, ranging in
   scale from individual families to nations, and social interaction
   between humans has established a variety of traditions, rituals,
   ethics, values, social norms, and laws which form the basis of human
   society. Humans also have a marked appreciation for beauty and
   aesthetics which, combined with the human desire for self-expression,
   has led to cultural innovations such as art, literature and music.

   Humans are also noted for their desire to understand and influence the
   world around them, seeking to explain and manipulate natural phenomena
   through religion, science, philosophy and mythology. This natural
   curiosity has led to the development of advanced tools and skills;
   humans are the only known species to build fires, cook their food,
   clothe themselves, and use numerous other technologies.

Biology

Physiology and genetics

   An old diagram of a male human skeleton.
   Enlarge
   An old diagram of a male human skeleton.

   Human body types vary substantially. Although body size is largely
   determined by genes, it is also significantly influenced by
   environmental factors such as diet and exercise. The tallest human
   population are the Dutch people, with the average height of a Dutch
   adult female being 170 centimetres (5 feet 7 inches), while the average
   height for a male is 185 centimeters (6 feet 1 inch). The shortest
   people are the Mbuti and Baka tribes in Congo, Cameroon and Gabon who
   have an average male height of less than 150 centimeters (4 feet 11
   inches).

   Humans are capable of fully bipedal locomotion, thus leaving their arms
   available for manipulating objects using their hands, aided especially
   by opposable thumbs. Because human physiology has not fully adapted to
   bipedalism, the pelvic region and vertebral column tend to become worn,
   creating locomotion difficulties in old age.

   Although humans appear relatively hairless compared to other primates,
   with notable hair growth occurring chiefly on the top of the head,
   underarms and pubic area, the average human has more hair on his or her
   body than the average chimpanzee. The main distinction is that human
   hairs are shorter, finer, and less colored than the average
   chimpanzee's, thus making them harder to see.
   An Inuit woman, circa 1907.
   Enlarge
   An Inuit woman, circa 1907.

   The colour of human hair and skin is determined by the presence of
   pigments called melanins. Human skin colour can range from very dark
   brown to very pale pink, while human hair ranges from blond to brown to
   red, but most commonly, black. Most researchers believe that skin
   darkening was an adaptation that evolved as a defense against
   ultraviolet solar radiation: melanin is an effective sun-block. The
   skin colour of contemporary humans is geographically stratified, and in
   general correlates with the level of ultraviolet radiation. Human skin
   also has a capacity to darken ( sun tanning) in response to exposure to
   ultraviolet radiation.

   The average sleep requirement is between seven and eight hours a day
   for an adult and nine to ten hours for a child; elderly people usually
   sleep for six to seven hours. Negative effects result from restriction
   of sleep. For instance, a sustained restriction of adult sleep to four
   hours per day has been shown to correlate with changes in physiology
   and mental state, including fatigue, aggression, and bodily discomfort.
   It is common in modern societies for people to get less sleep than they
   need, leading to a state of sleep deprivation.

   Humans are a eukaryotic species. Each diploid cell has two sets of 23
   chromosomes, each set received from one parent. There are 22 pairs of
   autosomes and one pair of sex chromosomes. By present estimates, humans
   have approximately 20,000–25,000 genes and share 95% of their DNA with
   their closest living evolutionary relatives, the two species of
   chimpanzees. Genetic studies indicate that humans are more closely
   related to chimpanzees, while gorillas diverged earlier from the
   chimpanzee/human line of descent. Consequently, use of the term 'apes'
   to mean chimpanzees and gorillas is incorrect, with humans and
   chimpanzees forming one group and gorillas a second, more
   distantly-related group.

   Like other mammals, humans have an XY sex-determination system, so that
   females have the sex chromosomes XX and males have XY. The X chromosome
   is larger and carries many genes not on the Y chromosome, which means
   that recessive diseases associated with X-linked genes, such as
   hemophilia, affect men more often than women.

Life cycle

   View of a human fetus in the womb. Drawing by Leonardo da Vinci.
   Enlarge
   View of a human fetus in the womb. Drawing by Leonardo da Vinci.

   The human life cycle is similar to that of other placental mammals. New
   humans develop viviparously from conception. An egg is usually
   fertilized inside the female by sperm from the male through sexual
   intercourse, though the recent technology of in vitro fertilization is
   occasionally used. The fertilized egg, called a zygote, divides inside
   the female's uterus to become an embryo, which over a period of
   thirty-eight weeks becomes a human fetus. At birth, the fully-grown
   fetus is expelled from the female's body and breathes independently as
   an infant for the first time. At this point, most modern cultures
   recognize the baby as a person entitled to the full protection of the
   law, though some jurisdictions extend personhood to human fetuses while
   they remain in the uterus.

   Compared with that of other species, human childbirth is dangerous.
   Painful labors lasting twenty-four hours or more are not uncommon, and
   may result in injury, or even death, to the child or mother. This is
   because of both the relatively large fetal head circumference (for
   housing the brain) and the mother's relatively narrow pelvis (a trait
   required for successful bipedalism), by way of natural selection. The
   chances of a successful labour increased significantly during the 20th
   century in wealthier countries with the advent of new medical
   technologies. In contrast, pregnancy and natural childbirth remains a
   relatively hazardous ordeal in developing regions of the world, with
   maternal death rates approximately 100-fold higher than developed
   countries.
   Two young human girls.
   Enlarge
   Two young human girls.

   Human children are born after a nine-month gestation period, and are
   typically 3–4 kilograms (6–9 pounds) in weight and 50–60 centimeters
   (20–24 inches) in height in developed countries. However, low birth
   weight is common in developing countries, and contributes to the high
   levels of infant mortality in these regions. Helpless at birth, they
   continue to grow for some years, typically reaching sexual maturity at
   12 to 15 years of age. Human girls continue to grow physically until
   around the age of 18, and human boys until around age 21.

   The human life span can be split into a number of stages: infancy,
   childhood, adolescence, young adulthood, maturity and old age. The
   lengths of these stages, however—particularly the later ones—are not
   fixed.

   There are striking differences in life expectancy around the world. The
   developed world is quickly getting older, with the median age around 40
   years (highest in Monaco at 45.1 years), while in the developing world,
   the median age is 15–20 years (lowest in Uganda at 14.8 years). Life
   expectancy at birth in Hong Kong, China is 84.8 years for a female and
   78.9 for a male, while in Swaziland, mostly because of AIDS, it is 31.3
   years for both sexes. One in five Europeans, but one in twenty
   Africans, is 60 years or older.

   The number of centenarians (humans of age 100 years or older) in the
   world was estimated by the United Nations at 210,000 in 2002. At least
   one person is known to have reached the age of 122 years ( Jeanne
   Calment lived for 122 years and 164 days); higher ages have been
   claimed but they are not well substantiated ( Elizabeth Israel is said
   to have been 128 years old at her death). Worldwide, there are 81 men
   aged 60 or older for every 100 women of that age group, and among the
   oldest, there are 53 men for every 100 women.

   The philosophical questions of when human personhood begins and whether
   it persists after death are the subject of considerable debate. The
   prospect of death causes unease or fear for most humans. Burial
   ceremonies are characteristic of human societies, often inspired by
   beliefs in an afterlife or immortality.

Race and ethnicity

   Humans often categorize themselves in terms of race or ethnicity,
   although the validity of human races as true biological categories is
   doubtful. Genetic studies have indicated that humans on the African
   continent are most genetically diverse, consistent with the theory that
   humans originate from Africa (see below). However, compared to other
   animals, human gene sequences are remarkably homogeneous and the
   majority of genetic variation occurs within 'racial groups', with only
   5 to 15% of total variation occurring between racial groups. Human
   racial categories are based on both ancestry and visible traits,
   especially skin colour and facial features. Ethnic groups, on the other
   hand, are more often linked by linguistic, cultural, and national or
   regional ties. Self-identification with an ethnic group is based on
   kinship and descent. Race and ethnicity can lead to variant treatment
   and impact social identity, giving rise to the theory of identity
   politics.

Evolution

   The study of human evolution encompasses the development of the genus
   Homo, but usually involves studying other hominids and hominines as
   well, such as the australopithecines. "Modern humans" are defined as
   the Homo sapiens species, of which the only extant subspecies is Homo
   sapiens sapiens; Homo sapiens idaltu (roughly translated as "elder wise
   man"), the other known subspecies, is extinct. Anatomically modern
   humans appear in the fossil record in Africa about 130,000 years ago.

   The closest living relatives of Homo sapiens are the Common Chimpanzee
   and the Bonobo. Full genome sequencing resulted in the conclusion that
   "After 6.5 [million] years of separate evolution, the differences
   between chimpanzee and human are just 10 times greater than those
   between two unrelated people and 10 times less than those between rats
   and mice." In fact, 95 per cent of the DNA sequence is identical
   between chimpanzee and human. It has been estimated that the human
   lineage diverged from that of chimpanzees about five million years ago,
   and from gorillas about eight million years ago. However, a hominid
   skull discovered in Chad in 2001, classified as Sahelanthropus
   tchadensis, is approximately seven million years old, which may
   indicate an earlier divergence.

   There are two prominent scientific theories of the origins of
   contemporary humans. They concern the relationship between modern
   humans and other hominids. The single-origin, or "out of Africa",
   hypothesis proposes that modern humans evolved in Africa and later
   migrated outwards to replace hominids in other parts of the world. The
   multiregional hypothesis, on the other hand, proposes that modern
   humans evolved, at least in part, from independent hominid populations.

   Geneticists Lynn Jorde and Henry Harpending of the University of Utah
   proposed that the variation in human DNA is minute compared to that of
   other species, and that during the Late Pleistocene, the human
   population was reduced to a small number of breeding pairs—no more than
   10,000 and possibly as few as 1,000—resulting in a very small residual
   gene pool. Various reasons for this hypothetical bottleneck have been
   postulated, the most popular being the Toba catastrophe theory.

   Human evolution is characterized by a number of important physiological
   trends, including the expansion of the brain cavity and brain itself,
   which is typically 1,400 cm³ in volume, over twice that of a chimpanzee
   or gorilla. The pattern of human postnatal brain growth differs from
   that of other apes ( heterochrony), allowing for an extended period of
   social learning in juvenile humans. Physical anthropologists argue that
   a reorganization of the structure of the brain is more important than
   cranial expansion itself. Other significant evolutionary changes
   included a reduction of the canine tooth, development of bipedal
   locomotion, and the descent of the larynx and hyoid bone, making speech
   possible. How these trends are related and what their role is in the
   evolution of complex social organization and culture are matters of
   ongoing debate in the field of physical anthropology.

Habitat and population

   Map of early human migrations according to mitochondrial population
   genetics (The arctic is at the centre of the map and the numbers are
   millennia before present).
   Enlarge
   Map of early human migrations according to mitochondrial population
   genetics (The arctic is at the centre of the map and the numbers are
   millennia before present).

   The most widely accepted view among current anthropologists is that
   Homo sapiens originated in the African savanna between 200,000 and
   250,000 years ago, descending from Homo erectus, and colonized Eurasia
   and Oceania by 40,000 years ago, and finally colonized the Americas by
   10,000 years ago. They displaced Homo neanderthalensis and other
   species descended from Homo erectus (which had colonized Eurasia as
   early as 2 million years ago) through more successful reproduction and
   competition for resources.

   The earliest humans were hunter-gatherers, a lifestyle well-suited to
   the savanna. Some later groups of humans were nomads, often to
   facilitate animal herding, and still later humans established permanent
   settlements, which was made possible by the development of agriculture.
   Permanent human settlements were dependent on proximity to water and,
   depending on the lifestyle, other natural resources, such as fertile
   land for growing crops and grazing livestock, or seasonally by hunting
   populations of prey. However, humans have a great capacity for altering
   their habitats by various methods, such as through irrigation, urban
   planning, construction, transport, and manufacturing goods, and with
   the advent of large-scale trade and transport infrastructure, proximity
   to these resources has become unnecessary, and in many places these
   factors are no longer a driving force behind the growth and decline of
   a population. Nonetheless, the manner in which a habitat is altered is
   often a major determinant in population change.

   Technology has allowed humans to colonize all of the continents and
   adapt to all climates. Within the last few decades, humans have
   explored Antarctica, the ocean depths, and space, although long-term
   habitation of these environments is not yet possible. With a population
   of over six billion, humans are among the most numerous of the large
   mammals. Most humans (61%) live in Asia. The vast majority of the
   remainder live in the Americas (14%), Africa (13%) and Europe (12%),
   with 0.5% in Oceania. (See list of countries by population and list of
   countries by population density.)

   Human habitation within closed ecological systems in hostile
   environments, such as Antarctica and outer space, is expensive,
   typically limited in duration, and restricted to scientific, military,
   or industrial expeditions. Life in space has been very sporadic, with
   no more than thirteen humans in space at any given time. Between 1969
   and 1972, two humans at a time spent brief intervals on the Moon. As of
   2006, no other celestial body has been visited by human beings,
   although there has been a continuous human presence in space since the
   launch of the initial crew to inhabit the International Space Station
   on October 31, 2000.

   From AD 1800 to 2000, the human population increased from one to six
   billion. In 2004, around 2.5 billion out of 6.3 billion people (39.7%)
   lived in urban areas, and this percentage is expected to rise
   throughout the 21st century. Problems for humans living in cities
   include various forms of pollution and crime,, especially in inner city
   and suburban slums. Benefits of urban living include increased
   literacy, access to the global canon of human knowledge and decreased
   susceptibility to rural famines.

Diet

   The human diet is prominently reflected in human culture, and has led
   to the development of food science. In general, humans can survive for
   two to eight weeks without food, depending on stored body fat. Survival
   without water is usually limited to three or four days. Lack of food
   remains a serious problem, with about 300,000 people starving to death
   every year. Childhood malnutrition is also common and contributes to
   the global burden of disease. However global food distribution is not
   even, and obesity among some human populations has increased to almost
   epidemic proportions, leading to health complications and increased
   mortality in some developed, and a few developing countries. The United
   States Centre for Disease Control states that 32% of American adults
   over the age of 20 are obese, while 66.5% are obese or overweight.
   Obesity is caused by consuming more calories than are expended, with
   many attributing excessive weight gain to a combination of overeating
   and insufficient exercise.

   Humans are animals who can consume both plant and animal products. Most
   biologists agree humans are omnivorous. A minority believes they are an
   anatomically carnivorous species, and have started using agriculture
   (non-animal based) foodstuffs only recently. Another minority believes
   that anatomically, they are primarily herbivorous, many members of
   which have begun consuming food of animal origin. Early Homo sapiens
   employed a "hunter-gatherer" methodology as their primary means of food
   collection, involving combining stationary plant and fungal food
   sources (such as fruits, grains, tubers, and mushrooms) with wild game
   which must be hunted and killed in order to be consumed. Some humans
   choose to be vegans or vegetarians, abstaining from eating meat for
   religious, ethical, ecological, or health reasons. It is believed that
   humans have used fire to prepare and cook food prior to eating since
   the time of their divergence from Homo erectus—possibly even earlier.
   However, a small number of individuals choose a raw foodist approach,
   consuming little to no cooked food; the raw diet may be fruitarian,
   vegetarian, or omnivorous.

   At least ten thousand years ago, humans developed agriculture, which
   has substantially altered the kind of food people eat. This has led to
   increased populations, the development of cities, and because of
   increased population density, the wider spread of infectious diseases.
   The types of food consumed, and the way in which they are prepared, has
   varied widely by time, location, and culture.

   The last century or so has produced enormous improvements in food
   production, preservation, storage and shipping. Today almost every
   locale in the world has access to not only its traditional cuisine, but
   many other world cuisines.

Brain, mind, and consciousness

   The human brain.
   Enlarge
   The human brain.

   The human brain is the centre of the central nervous system in humans,
   as well as the primary control centre for the peripheral nervous
   system. The brain controls "lower", or involuntary, autonomic
   activities such as heart rate, respiration, and digestion. The brain
   also controls "higher" order, conscious activities, such as thought,
   reasoning, and abstraction. The human brain is generally regarded as
   more capable of these higher order activities, and more " intelligent"
   in general, than any other species. While other animals are capable of
   creating structures and using simple tools—mostly as a result of
   instinct and learning through mimicry—human technology is vastly more
   complex, constantly evolving and improving with time. Even the most
   ancient human tools and structures are far more advanced than any
   structure or tool created by any other animal.

   The human ability to think abstractly may be unparalleled in the animal
   kingdom. Human beings are one of only six species to pass the mirror
   test—which tests whether an animal recognizes its reflection as an
   image of itself—along with chimpanzees, bonobos, orangutans, dolphins,
   and possibly pigeons. In October 2006, three elephants at the Bronx Zoo
   also passed this test. Human beings under the age of 2 typically fail
   this test. However, this may be a matter of degree rather than a sharp
   divide. Monkeys have been trained to apply abstract rules in tasks.

   The brain perceives the external world through the senses, and each
   individual human is influenced greatly by his or her experiences,
   leading to subjective views of existence and the passage of time.

   Humans are variously said to possess consciousness, self-awareness, and
   a mind, which correspond roughly to the mental processes of thought.
   These are said to possess qualities such as self-awareness, sentience,
   sapience, and the ability to perceive the relationship between oneself
   and one's environment. The extent to which the mind constructs or
   experiences the outer world is a matter of debate, as are the
   definitions and validity of many of the terms used above. Cognitive
   scientist Daniel Dennett, for example, argues that there is no such
   thing as a narrative centre called the "mind", but that instead there
   is simply a collection of sensory inputs and outputs: different kinds
   of "software" running in parallel.

   Humans study the more physical aspects of the mind and brain, and by
   extension of the nervous system, in the field of neurology, the more
   behavioural in the field of psychology, and a sometimes loosely-defined
   area between in the field of psychiatry, which treats mental illness
   and behavioural disorders. Psychology does not necessarily refer to the
   brain or nervous system, and can be framed purely in terms of
   phenomenological or information processing theories of the mind.
   Increasingly, however, an understanding of brain functions is being
   included in psychological theory and practice, particularly in areas
   such as artificial intelligence, neuropsychology, and cognitive
   neuroscience.

   The nature of thought is central to psychology and related fields.
   Cognitive psychology studies cognition, the mental processes underlying
   behaviour. It uses information processing as a framework for
   understanding the mind. Perception, learning, problem solving, memory,
   attention, language and emotion are all well-researched areas as well.
   Cognitive psychology is associated with a school of thought known as
   cognitivism, whose adherents argue for an information processing model
   of mental function, informed by positivism and experimental psychology.
   Techniques and models from cognitive psychology are widely applied and
   form the mainstay of psychological theories in many areas of both
   research and applied psychology. Largely focusing on the development of
   the human mind through the life span, developmental psychology seeks to
   understand how people come to perceive, understand, and act within the
   world and how these processes change as they age. This may focus on
   intellectual, cognitive, neural, social, or moral development.

   Social psychology links sociology with psychology in their shared study
   of the nature and causes of human social behavior, with an emphasis on
   how people think towards each other and how they relate to each other.
   The behaviour and mental processes of animals, both human and
   non-human, can be described through animal cognition, ethology,
   evolutionary psychology, and comparative psychology as well. Human
   ecology is an academic discipline that investigates how humans and
   human societies interact with both their natural environment and the
   human social environment.

Complete scientific classification

   The complete scientific classification of the modern human consists of
   many sub- and super- sections to the basic chart:

   Eukaryota (Domain)
   Animalia (Kingdom)
   Eumetazoa (Subregnum)
   Bilateria [having bilateral symmetry]
   Deuterostomia (Superphylum)
   Chordata (Phylum)
   Craniata [animals with skulls]
   Vertebrata (Subphylum) [...and backbones]
   Gnathostomata (Infraphylum) [...and jaws]
   Teleostomi [advanced fish and descendants]
   Tetrapoda (Superclass) [...and four limbs]
   Amniota (Series) [...and amniotic eggs]
   Synapsida [mammal-like reptiles]
   Mammaliaformes / Mammalia (Class) [all mammals]
   Eutheria (Subclass)
   Euarchontoglires (Superorder)
   Euarchonta (Superorder)
   Primates (Order)
   Haplorrhini (Suborder)
   Simiiformes (Infraorder)
   Catarrhini (Parvorder)
   Hominoidea (Superfamily)
   Hominidae (Family)
   Homininae (Subfamily)
   Hominini (Tribe)
   Hominina (Subtribe)
   Homo (Genus)
   Homo sapiens (Species)
   Homo sapiens sapiens (Subspecies)

Society and culture

   CAPTION:

   Human society statistics
   World population 6,637,070,000 (August 2006)
   Population density 12.7 per km² (by total area)
   43.6 per km² (by land area)
   Largest agglomerations Tokyo, Mexico City, Shanghai, New York City,
   Seoul, Bombay
   Most widespread languages (2000 est.) Mandarin Chinese 14.37 %
   Hindi 6.02 %
   English 5.61 %
   Spanish 5.59 %
   Bengali 4.9 %
   Arabic 4.59 %
   Largest religions
   (2002 est.) Christianity 32.71 %
   Islam 21.67 %
   ( No religion 14.84 %)
   Hinduism 13.28 %
   Buddhism 5.84 %
   Most widespread currencies United States dollar, Euro, Japanese yen,
   Pound sterling
   GDP ( nominal) $36,356,240 million USD
   ($5,797 USD per capita)
   GDP ( PPP) $51,656,251 million IND
   ($8,236 per capita)

   Society is here defined as the organizations and institutions arising
   from interaction between humans, while culture is defined here as a set
   of distinctive material, intellectual, emotional, and spiritual
   features of a social group, including art, literature, lifestyles,
   value systems, traditions, rituals, and beliefs. The link between human
   biology and human behaviour and culture is often very close, making it
   difficult to clearly divide topics into one area or the other; as such,
   the placement of some subjects may be based on convention more than
   reality.

   Culture and society consist of values, social norms, and artifacts. A
   culture's values define what it holds to be important or ethical.
   Closely linked are norms, expectations of how people ought to behave,
   bound by tradition. Artifacts, or " material culture", are objects
   derived from the culture's values, norms, and understanding of the
   world.

Language

   Some of the areas of the brain involved in language processing: Broca's
   area, Wernicke's area, Supramarginal gyrus, Angular gyrus, Primary
   Auditory Cortex
   Enlarge
   Some of the areas of the brain involved in language processing: Broca's
   area, Wernicke's area, Supramarginal gyrus, Angular gyrus, Primary
   Auditory Cortex

   The capacity humans have to transfer concepts, ideas and notions
   through speech and writing is unrivaled in known species. The faculty
   of speech is a defining feature of humanity, possibly predating
   phylogenetic separation of the modern population (see origin of
   language). Language is central to the communication between humans, as
   well as being central to the sense of identity that unites nations,
   cultures and ethnic groups.

   The invention of writing systems around 5000 years ago allowed the
   preservation of language on material objects, and was a major step in
   cultural evolution. Language is closely tied to ritual and religion
   (c.f. mantra, sacred text).

   The science of linguistics describes the structure of language and the
   relationship between languages. There are approximately 6,000 different
   languages currently in use, including sign languages, and many
   thousands more that are considered extinct.

Art, music and literature

   Joseph. Detail from Caravaggio's Rest on Flight to Egypt (ca. 1594)
   Enlarge
   Joseph. Detail from Caravaggio's Rest on Flight to Egypt (ca. 1594)

   Artistic works have existed for almost as long as humankind, from early
   pre-historic art to contemporary art. Art is one of the most unusual
   aspects of human behaviour and a key distinguishing feature of humans
   from other species.

   As a form of cultural expression by humans, art may be defined by the
   pursuit of diversity and the usage of narratives of liberation and
   exploration (i.e. art history, art criticism, and art theory) to
   mediate its boundaries. This distinction may be applied to objects or
   performances, current or historical, and its prestige extends to those
   who made, found, exhibit, or own them.

   In the modern use of the word, art is commonly understood to be the
   process or result of making material works which, from concept to
   creation, adhere to the "creative impulse"—that is, art is
   distinguished from other works by being in large part unprompted by
   necessity, by biological drive, or by any undisciplined pursuit of
   recreation.

   Music is a natural intuitive phenomenon based on the three distinct and
   interrelated organization structures of rhythm, harmony, and melody.
   Listening to music is perhaps the most common and universal form of
   entertainment for humans, while learning and understanding it are
   popular disciplines. There are a wide variety of music genres and
   ethnic musics.

   Literature, the body of written—and possibly oral—works, especially
   creative ones, includes prose, poetry and drama, both fiction and
   non-fiction. Literature includes such genres as epic, legend, myth,
   ballad, and folklore.

Motivation and emotion

   Motivation is the driving force of desire behind all actions of any
   organism. Motivation is based on emotion—specifically, on the search
   for satisfaction (positive emotional experiences), and the avoidance of
   conflict; positive and negative are defined by the individual brain
   state, not by social norms: a person may be driven to self-injury or
   violence because their brain is conditioned to create a positive
   response to these actions. Motivation is important because it is
   involved in the performance of all learned responses.

   Within psychology, conflict avoidance and the libido are seen to be
   primary motivators. Within economics motivation is often seen to be
   based on financial incentives, moral incentives, or coercive
   incentives. Religions generally posit Godly or demonic influences.
   Goya's Tio Paquete, Thyssen-Bornemisza museum, Madrid (1820)
   Enlarge
   Goya's Tio Paquete, Thyssen-Bornemisza museum, Madrid (1820)

   Happiness, or being happy, is a human emotional condition. The
   definition of happiness is a common philosophical topic. Some people
   might define it as the best condition which a human can have—a
   condition of mental and physical health. Others may define it as
   freedom from want and distress; consciousness of the good order of
   things; assurance of one's place in the universe or society, inner
   peace, and so forth.

   Human emotion has a significant influence on, or can even be said to
   control, human behaviour. Emotional experiences perceived as pleasant,
   like love, admiration, or joy, contrast with those perceived as
   unpleasant, like hate, envy, or sorrow. There is often a distinction
   seen between refined emotions, which are socially learned, and survival
   oriented emotions, which are thought to be innate.

   Human exploration of emotions as separate from other neurological
   phenomena is worthy of note, particularly in those cultures where
   emotion is considered separate from physiological state. In some
   cultural medical theories, to provide an example, emotion is considered
   so synonymous with certain forms of physical health that no difference
   is thought to exist. The Stoics believed excessive emotion was harmful,
   while some Sufi teachers (in particular, the poet and astronomer Omar
   Khayyám) felt certain extreme emotions could yield a conceptual
   perfection, what is often translated as ecstasy.

   In modern scientific thought, certain refined emotions are considered
   to be a complex neural trait of many domesticated and a few
   non-domesticated mammals, developed commonly in reaction to superior
   survival mechanisms and intelligent interaction with each other and the
   environment; as such, refined emotion is not in all cases as discrete
   and separate from natural neural function as was once assumed. Still,
   when humans function in civilized tandem, it has been noted that
   uninhibited acting on extreme emotion can lead to social disorder and
   crime.

Love and sexuality

   Rodin's "The Kiss"
   Enlarge
   Rodin's " The Kiss"

   Human sexuality, besides ensuring biological reproduction, has
   important social functions: it creates physical intimacy, bonds and
   hierarchies among individuals; may be directed to spiritual
   transcendence; and in a hedonistic sense to the enjoyment of activity
   involving sexual gratification. Sexual desire, or libido, is
   experienced as a bodily urge, often accompanied by strong emotions such
   as love, ecstasy and jealousy.

   As with other human self-descriptions, humans propose that it is high
   intelligence and complex societies of humans that have produced the
   most complex sexual behaviors of any animal, including a great many
   behaviors that are not directly connected with reproduction.

   Human sexual choices are usually made in reference to cultural norms,
   which vary widely. Restrictions are sometimes determined by religious
   beliefs or social customs.

   Many sexologists believe that the majority of homo sapiens have the
   inherent capacity to be attracted to both males and females (a kind of
   universal potential bisexuality). In a variation of this, pioneering
   researcher Sigmund Freud believed that humans are born polymorphously
   perverse, which means that any number of objects could be a source of
   pleasure. According to Freud, we then pass through five stages of
   psychosexual development (and can fixate on any stage because of
   various traumas during the process). For Alfred Kinsey, another
   influential sex researcher, people can fall anywhere along a continuous
   scale of sexual orientation (with only small minorities fully
   heterosexual or homosexual). Recent studies of neurology and genetics
   may suggest people may be born with one sexual orientation or another,
   so there is not currently a clear consensus among sex researchers.

Spirituality and religion

   Sculpture of a man meditating.
   Enlarge
   Sculpture of a man meditating.

   Spirituality, belief or involvement in matters of the soul or spirit,
   is one of the many different approaches humans take in trying to answer
   fundamental questions about mankind's place in the universe, the
   meaning of life, and the ideal way to live one's life. Though these
   topics have also been addressed by philosophy, and to some extent by
   science, spirituality is unique in that it focuses on mystical or
   supernatural concepts such as karma and God. However, critics would
   argue that spirituality does not actually answer any questions, and
   complicates the issues further by raising more questions.

   A more organized, but related, concept is religion—sometimes used
   interchangeably with " faith"—which is commonly defined as a belief
   system concerning the supernatural, sacred, or divine, and the moral
   codes, practices, values, institutions and rituals associated with such
   belief. In the course of its development, religion has taken on many
   forms that vary by culture and individual perspective.
   The largest religious gathering of humans in history. Around 70 million
   people from around the world participated in Kumbh Mela at the Hindu
   holy city of Prayaga, India.
   Enlarge
   The largest religious gathering of humans in history. Around 70 million
   people from around the world participated in Kumbh Mela at the Hindu
   holy city of Prayaga, India.

   Some of the chief questions and issues religions are concerned with
   include life after death (commonly involving belief in an afterlife),
   the origin of life (the source of a variety of origin beliefs), the
   nature of the universe ( religious cosmology) and its ultimate fate (
   eschatology), and what is moral or immoral. A common source in
   religions for answers to these questions are transcendent divine beings
   such as deities or a singular God, although not all religions are
   theistic—many are nontheistic or ambiguous on the topic, particularly
   among the Eastern religions.

   Although a majority of humans profess some variety of spiritual or
   religious belief, some are irreligious, lacking or rejecting belief in
   the supernatural or spiritual. Additionally, although most religions
   and spiritual beliefs are clearly distinct from science on both a
   philosophical and methodological level, the two are not generally
   considered to be mutually exclusive; a majority of humans hold a mix of
   both scientific and religious views. The distinction between philosophy
   and religion, on the other hand, is at times less clear, and the two
   are linked in such fields as the philosophy of religion and theology.

Philosophy and self-reflection

   Plato and Aristotle in a detail from The School of Athens by Raphael.
   Enlarge
   Plato and Aristotle in a detail from The School of Athens by Raphael.

   Philosophy is a discipline or field of study involving the
   investigation, analysis, and development of ideas at a general,
   abstract, or fundamental level. It is the discipline searching for a
   general understanding of values and reality by chiefly speculative
   means.

   The core philosophical disciplines are logic, ontology or metaphysics,
   epistemology, and axiology, which includes the branches of ethics and
   aesthetics. Philosophy covers a very wide range of approaches, and is
   also used to refer to a worldview, to a perspective on an issue, or to
   the positions argued for by a particular philosopher or school of
   philosophy.

   Metaphysics is a branch of philosophy concerned with the study of first
   principles, being and existence ( ontology). In between the doctrines
   of religion and science, stands the philosophical perspective of
   metaphysical cosmology. This ancient field of study seeks to draw
   logical conclusions about the nature of the universe, humanity, god,
   and/or their connections based on the extension of some set of presumed
   facts borrowed from religion and/or observation.

   Humans often consider themselves to be the dominant species on Earth,
   and the most advanced in intelligence and ability to manage their
   environment. This belief is especially strong in modern Western
   culture. Alongside such claims of dominance is often found radical
   pessimism because of the frailty and brevity of human life.
   The Thinker, Artist's rendering of the sculpture by Auguste Rodin.
   Enlarge
   The Thinker, Artist's rendering of the sculpture by Auguste Rodin.

   Humanism is a philosophy which defines a socio-political doctrine the
   bounds of which are not constrained by those of locally developed
   cultures, but which seeks to include all of humanity and all issues
   common to human beings. Because spiritual beliefs of a community often
   manifests as religious doctrine, the history of which is as factious as
   it is unitive, secular humanism grew as an answer to the need for a
   common philosophy that transcended the cultural boundaries of local
   moral codes and religions. Many humanists are religious, however, and
   see humanism as simply a mature expression of a common truth present in
   most religions. Humanists affirm the possibility of an objective truth
   and accept that human perception of that truth is imperfect. The most
   basic tenets of humanism are that humans matter and can solve human
   problems, and that science, freedom of speech, rational thought,
   democracy, and freedom in the arts are worthy pursuits or goals for all
   peoples. Humanism depends chiefly on reason and logic without
   consideration for the supernatural.

Science and technology

   In the mid- to late 20th century, humans achieved a level of
   technological mastery sufficient to leave the atmosphere of Earth for
   the first time and explore space.
   Enlarge
   In the mid- to late 20th century, humans achieved a level of
   technological mastery sufficient to leave the atmosphere of Earth for
   the first time and explore space.

   Science is the discovery of knowledge about the world by verifiable
   means. Technology is the objects humans make to serve their purposes.

   Human cultures are both characterized and differentiated by the objects
   that they make and use. Archaeology attempts to tell the story of past
   or lost cultures in part by close examination of the artifacts they
   produced. Early humans left stone tools, pottery and jewelry that are
   particular to various regions and times.

   Improvements in technology are passed from one culture to another. For
   instance, the cultivation of crops arose in several different
   locations, but quickly spread to be an almost ubiquitous feature of
   human life. Similarly, advances in weapons, architecture and metallurgy
   are quickly disseminated.

   Such techniques can be passed on by oral tradition. The development of
   writing, itself a kind of technology, made it possible to pass
   information from generation to generation and from region to region
   with greater accuracy.

   Together, these developments made possible the commencement of
   civilization and urbanization, with their inherently complex social
   arrangements. Eventually this led to the institutionalization of the
   development of new technology, and the associated understanding of the
   way the world functions. This science now forms a central part of human
   culture.

   In recent times, physics and astrophysics have come to play a central
   role in shaping what is now known as physical cosmology, that is, the
   understanding of the universe through scientific observation and
   experiment. This discipline, which focuses on the universe as it exists
   on the largest scales and at the earliest times, begins by arguing for
   the big bang, a sort of cosmic explosion from which the universe itself
   is said to have erupted ~13.7 ± 0.2 billion (10^9) years ago. After its
   violent beginnings and until its very end, scientists then propose that
   the entire history of the universe has been an orderly progression
   governed by physical laws.

Government and politics

   The United Nations building in New York City, which houses one of the
   largest human political organizations in the world.
   Enlarge
   The United Nations building in New York City, which houses one of the
   largest human political organizations in the world.

   A state is an organized political community occupying a definite
   territory, having an organized government, and possessing internal and
   external sovereignty. Recognition of the state's claim to independence
   by other states, enabling it to enter into international agreements, is
   often important to the establishment of its statehood. The "state" can
   also be defined in terms of domestic conditions, specifically, as
   conceptualized by Max Weber, "a state is a human community that
   (successfully) claims the monopoly of the 'legitimate' use of physical
   force within a given territory."

   Government can be defined as the political means of creating and
   enforcing laws; typically via a bureaucratic hierarchy.

   Politics is the process by which decisions are made within groups.
   Although the term is generally applied to behaviour within governments,
   politics is also observed in all human group interactions, including
   corporate, academic, and religious institutions. Many different
   political systems exist, as do many different ways of understanding
   them, and many definitions overlap. The most common form of government
   worldwide is a republic, however other examples include monarchy,
   social democracy, military dictatorship and theocracy.

   All of these issues have a direct relationship with economics.

War

   The atomic bombings of Hiroshima and Nagasaki effectively ended World
   War II and immediately killed over 120,000 humans.
   Enlarge
   The atomic bombings of Hiroshima and Nagasaki effectively ended World
   War II and immediately killed over 120,000 humans.

   War is a state of widespread conflict between states, organizations, or
   relatively large groups of people, which is characterized by the use of
   lethal violence between combatants or upon civilians. It is estimated
   that during the 20th Century between 167 and 188 million humans died as
   a result of war.

   A common perception of war is a series of military campaigns between at
   least two opposing sides involving a dispute over sovereignty,
   territory, resources, religion or other issues. A war said to liberate
   an occupied country is sometimes characterized as a " war of
   liberation", while a war between internal elements of a state is a
   civil war.

   There have been a wide variety of rapidly advancing tactics throughout
   the history of war, ranging from conventional war to asymmetric warfare
   to total war and unconventional warfare. Techniques have nearly always
   included hand to hand combat, the usage of ranged weapons, propaganda,
   Shock and Awe, and ethnic cleansing. Military intelligence has always
   played a key role in determining victory and defeat. In modern warfare,
   soldiers and armored fighting vehicles are used to control the land,
   warships the seas, and air power the skies. Outer space has recently
   become an important factor in warfare as well, although no actual
   warfare is currently carried out within space.

   Throughout history there has been a constant struggle between defense
   and offense, armor, and the weapons designed to breach it. Modern
   examples include the bunker buster bomb, and the bunkers which they are
   designed to destroy.

Trade and economics

   Buyers bargain for good prices while sellers put forth their best front
   in Chichicastenango Market, Guatemala.
   Enlarge
   Buyers bargain for good prices while sellers put forth their best front
   in Chichicastenango Market, Guatemala.

   Trade is the voluntary exchange of goods, services, or both, and a form
   of economics. A mechanism that allows trade is called a market. The
   original form of trade was barter, the direct exchange of goods and
   services. Modern traders instead generally negotiate through a medium
   of exchange, such as money. As a result, buying can be separated from
   selling, or earning. The invention of money (and later credit, paper
   money and non-physical money) greatly simplified and promoted trade.

   Trade exists for many reasons. Because of specialization and division
   of labor, most people concentrate on a small aspect of manufacturing or
   service, trading their labour for products. Trade exists between
   regions because different regions have an absolute or comparative
   advantage in the production of some tradable commodity, or because
   different regions' size allows for the benefits of mass production. As
   such, trade between locations benefits both locations.

   Economics is a social science that studies the production,
   distribution, trade and consumption of goods and services.

   Economics, which focuses on measurable variables, is broadly divided
   into two main branches: microeconomics, which deals with individual
   agents, such as households and businesses, and macroeconomics, which
   considers the economy as a whole, in which case it considers aggregate
   supply and demand for money, capital and commodities. Aspects receiving
   particular attention in economics are resource allocation, production,
   distribution, trade, and competition. Economic logic is increasingly
   applied to any problem that involves choice under scarcity or
   determining economic value. Mainstream economics focuses on how prices
   reflect supply and demand, and uses equations to predict consequences
   of decisions.

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