Human

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Scientific classification
Domain: {{{domain}}} Superkingdom: {{{superregnum}}} Kingdom: Animalia Subkingdom: {{{subregnum}}} Superdivision: {{{superdivisio}}} Superphylum: {{{superphylum}}} Division: {{{divisio}}} Phylum: Chordata Subdivision: {{{subdivisio}}} Subphylum: {{{subphylum}}} Infraphylum: {{{infraphylum}}} Microphylum: {{{microphylum}}} Nanophylum: {{{nanophylum}}} Superclass: {{{superclassis}}} Class: Mammalia Sublass: {{{subclassis}}} Infraclass: {{{infraclassis}}} Superorder: {{{superordo}}} Order: Primates Suborder: {{{subordo}}} Infraorder: {{{infraordo}}} Superfamily: Hominoidea Family: Hominidae Subfamily: Homininae Supertribe: {{{supertribus}}} Tribe: Hominini Subtribe: {{{subtribus}}} Genus: Homo Subgenus: {{{subgenus}}} Section: {{{sectio}}} Series: {{{series}}} Species: H. sapiens Supspecies: {{{subspecies}}}
[[{{{diversity_link}}}|Diversity]]
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Binomial name
Homo sapiens Linnaeus, 1758
Trinomial name
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Type Species
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Subspecies
Homo sapiens idaltu (extinct) Homo sapiens sapiens
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Synonyms
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This article is about modern humans. For other human species, see Homo (genus). For other uses, see Human (disambiguation).

Humans or human beings define themselves in biological, social, and spiritual terms. Biologically, humans are classified as the mammalian species Homo sapiens (Latin for "wise man" or "thinking man"): a bipedal primate of the superfamily Hominoidea, together with the other apes: chimpanzees, gorillas, orangutans, and gibbons.

Humans have an erect body carriage that frees their upper limbs for manipulating objects and a highly developed brain capable of abstract reasoning, speech, language, and introspection. Bipedal locomotion appears to have evolved before the development of a large brain. The origins of bipedal locomotion and of its role in the evolution of the human brain are topics of ongoing research.

The human mind has several distinct attributes. It is responsible for complex behaviour, especially language. Curiosity and observation have led to a variety of explanations for consciousness and the relation between mind and body. Psychology attempts to study behaviour from a scientific point of view. Religious perspectives emphasise a soul, qi or atman as the essence of being, and are often characterised by the belief in and worship of God, gods, spirits, or other people. Philosophy, especially philosophy of mind, attempts to fathom the depths of each of these perspectives. Art, music and literature are often used in expressing these concepts and feelings.

Like all primates, humans are inherently social. They create complex social structures composed of co-operating and competing groups. These range from nations and states down to families. Seeking to understand and manipulate the world around them has led to the development of technology and science. Artifacts, beliefs, myths, rituals, values, and social norms have all helped to form humanity's culture.

Terminology

In general, the word "people" is a collective or plural term for any specific group of individual persons. However, when used to refer to a group of humans possessing a common ethnic, cultural or national unitary characteristic or identity, "people" is a singular count noun, and as such takes an "s" in the plural (examples: "the English-speaking peoples of the world", "the indigenous peoples of Brazil").

Inuit woman (c.1907)

Juvenile males are called boys, adult males men, juvenile females girls, and adult females women. Humans are commonly referred to as persons or people, and collectively as Man (capital M), mankind, humankind, humanity, or the human race. Until the 20th century, "human" was only used adjectivally ("pertaining to mankind"). Nominal use of "human" (plural "humans") is short for "human being", and not considered good style in traditional English grammar. As an adjective, "human" is used neutrally (as in "human race"), but "human" and especially "humane" may also emphasise positive aspects of human nature, and can be synonymous with "benevolent" (versus "inhumane"; cf. humanitarian).

A distinction is maintained in philosophy and law between the notions "human being", or "man", and "person". The former refers to the species, while the latter refers to a rational agent (see, for example, John Locke's Essay concerning Human Understanding II 27 and Immanuel Kant's Introduction to the Metaphysic of Morals). The term "person" is thus used of non-human animals, and could be used of a mythical being, an artificial intelligence, or an extraterrestrial. An important question in theology and the philosophy of religion concerns whether God is a person.

In Latin, "humanus" is the adjectival form of the noun "homo", translated as "man" (to include males and females). The Old English word "man" could also have this generic meaning, as demonstrated by such compounds as "wifman" ("female person") → "wiman" → "woman". For the etymology of "man" see mannaz.

Biology

Anatomy and physiology

An old diagram of a male human skeleton

Main articles: Human anatomy, Human physical appearance & Human height

Humans exhibit fully bipedal locomotion. This leaves the forelimbs available for manipulating objects using opposable thumbs.

Humans vary substantially around the mean height and mean weight. Some of this variation is explained by locality and historical factors. Although body size is largely determined by genes, it is also significantly influenced by diet and exercise. The mean height of a North American adult female is 162 centimetres (5 feet 4 inches) and the mean weight is 62 kilograms (137 pounds). North American adult males are typically larger: 175 centimetres (5 feet 9 inches) and 78 kilograms (172 pounds).

Human skin appears to be relatively hairless in comparison to other primates; however, most humans have a larger number of hairs on their body than a chimpanzee. The main difference is that human hairs are shorter, finer, and less coloured then the average chimpanzee's, thus rendering them harder to see.

The colour of human hair and skin is determined by the presence of coloured pigments called melanins. Most researchers believe that skin darkening was an adaptation that evolved as a defence against UV solar radiation; melanin is an effective sunblock. The skin colour of contemporary humans can range from very dark brown to very pale pink. It is geographically stratified and in general correlates with the environmental level of UV. Human skin and hair colour is controlled in part by the MC1R gene. For example, the red hair and pale skin of some Europeans is the result of mutations in MC1R. Human skin has a capacity to darken (sun tanning) in response to UV exposure. Variation in the ability to sun tan is also controlled in part by MC1R.

Anatomical-Astrological Man, Musée Condé, Chantilly

Because humans are bipedal, the pelvic region and spinal column tend to become worn, creating locomotion difficulties in old age.

The individual need for regular intake of food and drink is prominently reflected in human culture, and has led to the development of food science. Failure to obtain food leads to hunger and eventually starvation, while failure to obtain water leads to dehydration and thirst. Both starvation and dehydration cause death if not alleviated. In modern times, obesity amongst humans has increased to almost epidemic proportions, leading to health complications and increased mortality in some developed countries, and is becoming problematic elsewhere.

It is sometimes said that the average sleep requirement is between seven and eight hours a day for an adult and nine to ten hours for a child. More accurately, 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 variables, including tiredness-fatigue, anger-aggression, and bodily discomfort. Normative data suggests elderly people usually sleep for six to seven hours, although such normative data varies depending upon the sociocultural characteristics of the population. It is common in modern societies for people to get less sleep than they need to avoid adverse effects, leading to a state of sleep deprivation.

The human body is subject to an ageing process and to illness. Medicine is the science that explores methods of preserving bodily health.

Life cycle

Human fetus

The human life cycle is similar to that of other placental mammals. New human life develops from conception. An egg is usually fertilised inside the female by sperm from the male through sexual intercourse, though in vitro fertilisation methods are also used. The fertilised egg is called a zygote. The zygote divides inside the female's uterus to become an embryo which over a period of thirty-eight weeks becomes the fetus. At birth, the fully grown fetus is expelled from the female's body and breathes independently as a baby for the first time. At this point, most modern cultures recognise 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 relatively complicated. Painful labours lasting twenty-four hours or more are not uncommon, and may result in injury to the child or the death of the mother, although the chances of a successful labour increased significantly during the twentieth century in wealthier countries. Natural childbirth remains an arguably more dangerous ordeal in remote, underdeveloped regions of the world, though the women who live in these regions have argued that their natural childbirth methods are safer and less traumatic for mother and child.

Two young girls

Human children are born after a nine-month gestation period, with typically 3–4 kilograms (6–9 pounds) in weight and 50–60 centimetres (20–24 inches) in height in developed countries. [1] Helpless at birth, they continue to grow for some years, typically reaching sexual maturity at twelve to fifteen years of age. Boys continue growing for some time after this, reaching their maximum height around the age of eighteen. These values vary too, depending on genes and environment.

The human lifespan can be split into a number of stages: infancy, childhood, adolescence, young adulthood, maturity and old age, though the lengths of these stages, especially 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 (the lowest in Uganda at 14.8 years). Life expectancy at birth is 77.2 years in the U.S. as of 2001. [2] The expected life span at birth in Singapore is 84.29 years for a female and 78.96 years for a male, while in Botswana, due largely to AIDS, it is 30.99 years for a male and 30.53 years for a female. One in five Europeans, but one in twenty Africans, is 60 years or older, according to The World Factbook. [3]

A man with a full beard.

The number of centenarians in the world was estimated by the United Nations [4] at 210,000 in 2002. The maximum life span for humans is thought to be over 120 years. Worldwide, there are 81 men aged 60 or over for every 100 women, 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 may cause unease or fear. People who are near death sometimes have a near-death experience, in which they have visions. Burial ceremonies are characteristic of human societies, often inspired by beliefs in an afterlife. Institutions of inheritance or ancestor worship may extend an individual's presence beyond his physical lifespan (see immortality).

Genetics

Main article: Genetics of humans

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. At present estimate, 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. [5] 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 affect men more often than women. For example, genes that control the clotting of blood reside on the X chromosome. Women have a blood-clotting gene on each X chromosome so that one normal blood-clotting gene can compensate for a flaw in the gene on the other X chromosome. But men are hemizygous for the blood-clotting gene, since there is no gene on the Y chromosome to control blood clotting. As a result, men will suffer from haemophilia more often than women.

Race and ethnicity

Main articles: Race & Ethnic group

The FBI identifies fugitives by sex, physical features, occupation, nationality, and race. From left to right, the FBI identifies the above as belonging to the following races: White, Black, White (Hispanic), and Asian. Top row males, bottom row females.

Humans often categorise themselves and others in terms of race or ethnicity, although the validity of human races is disputed. In the United States, racial categories are primarily based on language and ethnicity, although biological qualities, such as skin colour, blood type, facial features, ancestry, and other genetic variances are also key factors. Self identification with an ethnic group is usually based on kinship and descent, as well as presumed advantage. When race and ethnicity lead to variant treatment it is thought to impact social identity, giving rise to the theory of identity politics.

Although most humans recognise that variances occur within a species, it is often a point of dispute as to what these differences entail, and if discrimination based on race (racism) is acceptable in the early twenty-first century. Race and intelligence, scientific racism, xenophobia and ethnocentrism are just a few of the many bases for such practices.

Habitat

The view most widely accepted by the anthropological community is that the human species originated in the African savanna between 100 and 200 thousand years BCE, colonised the rest of the Old World and Oceania by 40,000 years BCE, and finally colonised the Americas by 10,000 years BCE. Homo sapiens displaced groups such as Neanderthals and Homo floresiensis through more successful reproduction and competition for resources, and/or extermination. (See Human evolution, Vagina gentium, and Environment of Evolutionary Adaptedness.) Technology has allowed humans to colonise all of the continents and adapt to all climates. Within the last few decades, humans have been able to explore Antarctica, the ocean depths, and space, although long-term habitation of these environments are not yet possible. Humans, with a population of about six thousand million, are one of the most numerous mammals on Earth.

Most humans (61%) live in the Asian region. The vast majority of the remainder live in the Americas (14%), Africa (13%) and Europe (12%), with 5% in Oceania. (See list of countries by population and list of countries by population density.)

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 original human lifestyle is hunting-gathering, which is adapted to the savanna. Other human lifestyles are nomadism (often linked to animal herding) and permanent settlements made possible by the development of agriculture. Humans have a great capacity for altering their habitats by various methods, such as agriculture, irrigation, urban planning, construction, transport, and manufacturing goods.

Permanent human settlements are 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 populations of prey. With the advent of large-scale trade and transport infrastructure, immediate proximity to these resources has become unnecessary, and in many places these factors are no longer the driving force behind growth and decline of population.

Human habitation within closed ecological systems in hostile environments (Antarctica, outer space) is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with a maximum of thirteen humans in space at any given time, starting with Yuri Gagarin's space flight in 1961. Between 1969 and 1974, up to two humans at a time spent brief intervals on the Moon. As of 2005, 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.

Population

City lights from space.

From 1800 to 2000, the human population increased from one to six billion. It is expected to crest at around ten billion during the 21st century. In 2004, around 2.5 billion out of 6.3 billion people lived in urban centres, and this is expected to rise during the 21st century. Problems for humans living in cities include various forms of pollution, crime, and poverty, especially in inner city and suburban slums.

Geneticists Lynn Jorde and Henry Harpending of the University of Utah have concluded that the variation in the total stock of human DNA is minute compared to that of other species; and that around 74,000 years ago, human population was reduced to a small number of breeding pairs, possibly as small as 1000, resulting in a very small residual gene pool. Various reasons for this bottleneck have been postulated, the most popular, called the Toba catastrophe theory, being the eruption of a volcano at Lake Toba.

Human evolution

Main articles: Human evolution & Human migration

The study of human evolution encompasses many scientific disciplines, but most notably physical anthropology and genetics. The term "human", in the context of human evolution, refers to the genus Homo, but studies of human evolution usually include other hominids and hominines, such as the australopithecines.

Biologically, humans are defined as hominids of the species Homo sapiens, of which the only extant subspecies is Homo sapiens sapiens (Latin for "very wise man"); Homo sapiens idaltu (roughly translated as "elderly wise man") is the extinct subspecies. Modern humans are usually considered the only surviving species in the genus Homo, although some argue that the two species of chimpanzees should be reclassified from Pan troglodytes (Common Chimpanzee) and Pan paniscus (Bonobo/Pygmy Chimpanzee) to Homo troglodytes and Homo paniscus respectively, given that they share a recent ancestor with man. [6]

Full genome sequencing resulted in these conclusions: "After 6 [million] years of separate evolution, the differences between chimp and human are just 10 times greater than those between two unrelated people and 10 times less than those between rats and mice." Chimp and human DNA is 96% identical

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, in 2001 a hominine skull approximately seven million years old, classified as Sahelanthropus tchadensis, was discovered in Chad and seems to indicate an earlier divergence.

Two prominent scientific theories of the origins of contemporary humans exist. 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 replaced hominids in other parts of the world.

The multiregional hypothesis proposes that modern humans evolved at least in part from independent hominid populations.

Human evolution is characterised by a number of important physiological trends:

• 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 reorganisation of the structure of the brain is more important than cranial expansion itself;
• canine tooth reduction;
• bipedal locomotion;
• descent of the larynx, which makes speech possible.

Humans are classified as Homo sapiens sapiens. A camp of physical anthropologists see neanderthalensis as a subspecies and classify the neanderthals as Homo sapiens neanderthalensis. A second camp of physical anthropologists see the neanderthals as a distinct species diverging from the modern human lineage over 500,000 years ago. Under this classification, neaderthals are Homo neanderthalensis. Recent DNA analysis suggests that neanderthalensis were not a subspecies.

How these trends are related and what their role is in the evolution of complex social organisation and culture are matters of ongoing debate.

Leonardo da Vinci's Vitruvian Man

Intelligence

Main article: Intelligence (trait)

Most humans consider their species to be the most intelligent in the animal kingdom. Certainly, humans are the only technologically advanced animal. Along with the brain's internal complexity, the brain to body mass ratio is generally assumed to be a good indicator of relative intelligence. Humans have the second highest ratio, with the tree shrew having the highest [7], and the bottlenose dolphin very similar to humans.

Ronald Wright outlined in his book A Short History of Progress that humans do not possess long term thought. Ronald Wright and many other anthropologists believe it to have descended from human origins of trying to survive day to day in a warmer African climate, more concerned for the day’s food and escape from predators then the long term consequences of their actions, when compared to other cousins in northern areas like Neanderthals, who worked towards the coming winter season, preparing for it. These anthropologists state that in the several thousand years since the dawn of civilization, humans still have difficult thinking in the extreme long term. Individuals have shown to think in the long term, and some believe this might possibly be an evolutionary step in the direction in changing the way humans think. This is purely theoretical though it is carrying weight in the modern anthropology community.

The human ability to abstract may be unparalleled in the animal kingdom. Human beings are one of five species to pass the mirror test — which tests whether an animal recognises its reflection as an image of itself — along with chimpanzees or bonobos, orangutans, and dolphins. Human beings under the age of four usually fail the test.

Culture

Main articles: Culture of human beings & Culture

Cave art - Lascaux, France

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.

Culture consists of at least three elements: values, social norms, and artifacts. A culture's values define what it holds to be important. Norms are expectations of how people ought to behave. Artifacts — things, or material culture — derive from the culture's values and norms together with its understanding of the way the world functions.

Origins

Main articles: Origin belief & Creationism

Essentially every culture has its characteristic origin beliefs. Creationism or creation theology is the belief that humans, the Earth, the universe and the multiverse were created by a supreme being or deity. The event itself may be seen either as an act of creation (ex nihilo) or the emergence of order from preexisting chaos (demiurge). Many who hold "creation" beliefs consider such belief to be a part of religious faith, and hence compatible with, or otherwise unaffected by scientific views while others maintain the scientific data is compatible with creationism. Proponents of evolutionary creationism may claim that understood scientific mechanisms are simply aspects of supreme creation. Otherwise, science-oriented believers may consider the scriptural account of creation as simply a metaphor.

Language

Main articles: Language & Philosophy of language

From top-left, "human" in English, Japanese, Chinese, Korean, Hebrew and Greek

Values, norms and technology are dependent on the capacity for humans to share ideas. The faculty of speech may be a defining feature of humanity, probably predating phylogenetic separation of the modern population. (See Proto-World language, Origins of language.) Language is central to the communication between humans. Some scientists argue that non-human animals are able to use some form of language too, and that non-human primates are able to learn human sign language [8] [9] (pdf). Language is central to the sense of identity that unites cultures and ethnicities.

The invention of writing systems some 5000 years ago, allowing the preservation of speech, was a major step in cultural evolution. Language, especially written language, is sometimes thought to have supernatural status or powers. (See Magic, Mantra, Vac.)

The science of linguistics describes the structure of language and the relationship between languages. There are estimated to be some 6,000 different languages, including sign languages, used today.

Music

Music is a natural intuitive phenomenon operating in the three worlds of time, pitch, and energy, and under the three distinct and interrelated organisation structures of rhythm, harmony, and melody.

Composing, improvising and performing music are all art forms. Listening to music is perhaps the most common form of entertainment, while learning and understanding it are popular disciplines. There are a wide variety of music genres and ethnic musics.

Emotion and sexuality

Rodin's "The Kiss"

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 worth 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 civilised tandem, it has been noted that uninhibited acting on extreme emotion can lead to social disorder and crime.

Human sexuality, besides ensuring reproduction, has important social functions, creating physical intimacy, bonds and hierarchies among individuals, and that may be directed to spiritual transcendence, and/or to the enjoyment of activity involving sexual gratification. Sexual desire, libido, is experienced as a bodily urge, often accompanied by strong emotions, both positive (such as love or ecstasy) and negative (such as jealousy).

As with other human self-descriptions, humans propose it is high intelligence and complex societies of humans that have produced the most complex sexual behaviors of any animal. Human sexual choices are usually made in reference to cultural norms, which vary widely. Restrictions are largely determined by religious beliefs.

Body image

Women dressed as apprentice geisha in Kyoto, Japan

The physical appearance of the human body is central to culture and art. In every human culture, people adorn their bodies with tattoos, cosmetics, clothing, and jewellery. Hairstyles and hair colour also have important cultural implications. The perception of an individual as physically beautiful or ugly can have profound implications for their lives. This is particularly true of women, whose external appearance is highly valued in most, if not all, human societies. Anthropologists believe this to be an important factor in the development of personality and social relations in particular physical attractiveness.

There is a relatively low sexual dimorphism between human males and females in comparison with other mammals.

Trade and economics

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. Due to specialisation 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.

Artifacts, technology, and science

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

Main articles: Archaeology, Technology, Science & Civilisation

Human cultures are both characterised 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 jewellery 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 type of artifact, 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 civilisation and urbanisation, with their inherently complex social arrangements. Eventually this led to the institutionalisation 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 (10⁹) 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.

Mind

Main articles: Mind & Consciousness

Human head with lines connecting the senses of taste, hearing, sight, and smell to areas of the brain. (d.1525)

Consciousness is a state of mind, said to possess qualities such as, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment.

The way in which the world is experienced is the subject of much debate and research in philosophy of mind, psychology, brain biology, neurology, and cognitive science.

Humans, often mentioned with other species, are variously said to possess consciousness, self-awareness, and a mind, the fruition of which are senses and perceptions. Each human has a subjective view of existence, the passage of time, and free will.

There are many debates about the extent to which the mind constructs or experiences the outer world, and regarding 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 mind, but that instead there is simply a collection of sensory inputs and outputs: different kinds of software running in parallel (Dennett, 1991) .

Psychology and human ethology

Main articles: Psychology & Ethology

Psychoanalysis, the examination of the subconscious was, devised by Sigmund Freud and expanded and refined by the Swiss psychiatrist Carl Gustav Jung (initially one of Freud's followers and friends) and others. Freud's influence is, however, often misunderstood, though the principal theory of modern psychology. Behaviorism, as formulated by John B. Watson and popularised by B. F. Skinner, lead to a widespread rejection of psychoanalysis by psychologists due to a desire for empiricism. Behaviourism, however, rejects any study of the "mind" (or cognition), and so during the last decade of the 20th century, the study of cognitive processes within the field of psychology have begun to re-emerge, the field of cognitive science appearing as an independent field. A cognitive revolution is often stated to be occuring within modern psychology.

Sigmund Freud

Freud divided the mind into the id (an individual's basic needs and instincts), the superego (personal and cultural values and norms), and the ego (the central, organising self, whose job it is to satisfy the id but not upset the superego). [10]

C. G. Jung founded the school of analytical psychology and introduced the notion of the collective unconscious, a term taken from philosophy and used by Jung to describe symbols or archetypes that he believed might be common to all cultures.

There are also the Conscious, Subconscious, and Superconsciousness, a related but not identical set of categories.

The behaviour and mental processes of animals (human and non-human) can be described through animal cognition, ethology, and comparative psychology as well.

Human ecology is an academic discipline that investigates how humans and human societies interact with their environment, nature and the human social environment.

Philosophy

Main articles: Philosophy, Philosophy of mind & mind

Plato and Aristotle in detail from Raphael's School of Athens

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 rather than observational means comprising as its core logic, ontology or metaphysics, epistemology, and axiology which includes the branches of ethics and aesthetics. The term 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" and "being" (ontology). Problems that were not originally considered metaphysical have been added to metaphysics. Other problems that were considered metaphysical problems for centuries are now typically relegated to their own separate subheadings in philosophy, such as