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Human Temporal range: Pleistocene - Recent
Image of a man and a woman on Pioneer plaque, sent into space with the Pioneer 11 mission.
Conservation status
extinct
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, were 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 had a highly developed brain capable of abstract reasoning, language and introspection. This, combined with an erect body carriage that freed their upper limbs for manipulating objects, had 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 eventually inhabited every continent with a maximum total population of over 6.5 billion as of 2006.

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

Humans were 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 had led to the development of advanced tools and skills; humans were the only known species to build fires, cook their food, clothe themselves, and use numerous other technologies.

Biology

Physiology and genetics

Human body types varied substantially. Although body size was largely determined by genes, it was also significantly influenced by environmental factors such as diet and exercise. The tallest human population were 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 was 185 centimeters (6 feet 1 inch). The shortest people were the Mbuti and Baka tribes in Congo, Cameroon and Gabon who had an average male height of less than 150 centimeters (4 feet 11 inches).

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

Although humans appeared 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 had more hair on his or her body than the average chimpanzee. The main distinction was that human hairs were shorter, finer, and less colored than the average chimpanzee's, thus making them harder to see.

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

The average sleep requirement was 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 resulted from restriction of sleep. For instance, a sustained restriction of adult sleep to four hours per day had been shown to correlate with changes in physiology and mental state, including fatigue, aggression, and bodily discomfort. It was common in modern societies for people to get less sleep than they need, leading to a state of sleep deprivation.

Humans were a eukaryotic species. Each diploid cell had two sets of 23 chromosomes, each set received from one parent. There were 22 pairs of autosomes and one pair of sex chromosomes. By present estimates, humans had 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 indicated that humans were 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 was incorrect, with humans and chimpanzees forming one group and gorillas a second, more distantly-related group.

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

Life cycle

The human life cycle was similar to that of other placental mammals. New humans developed viviparously from conception. An egg was usually fertilised inside the female by sperm from the male through sexual intercourse, though the recent technology of in vitro fertilisation was occasionally used. The fertilised egg, called a zygote, divided inside the female's uterus to become an embryo, which over a period of thirty-eight weeks (9 months) became a human fetus. At birth, the fully-grown fetus was expelled from the female's body and breathed independently as an infant for the first time. At this point, most modern cultures recognised the baby as a person entitled to the full protection of the law, though some jurisdictions extended personhood to human fetuses while they remained in the uterus.

Compared with that of other species, human childbirth was dangerous. Painful labors lasting twenty-four hours or more were not uncommon, and might result in injury, or even death, to the child or mother. This was 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 remained a relatively hazardous ordeal in developing regions of the world, with maternal death rates approximately 100-fold higher than developed countries.

Human children were born after a nine-month gestation period, and were 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 was common in developing countries, and contributes to the high levels of infant mortality in these regions. Helpless at birth, they continued to grow for some years, typically reaching sexual maturity at 12 to 15 years of age. Human girls continued to grow physically until around the age of 18, and human boys until around age 21.

The human life span could 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—were not fixed.

There were striking differences in life expectancy around the world. The developed world was 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 was 15–20 years (lowest in Uganda at 14.8 years). Life expectancy at birth in Hong Kong, China was 84.8 years for a female and 78.9 for a male, while in Swaziland, mostly because of AIDS, it was 31.3 years for both sexes. One in five Europeans, but one in twenty Africans, was 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 was known to had reached the age of 122 years (Jeanne Calment lived for 122 years and 164 days); higher ages had been claimed but they were not well substantiated (Elizabeth Israel was said to had been 128 years old at her death). Worldwide, there were 81 men aged 60 or older for every 100 women of that age group, and among the oldest, there were 53 men for every 100 women.

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

Race and ethnicity

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

Evolution

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

The closest living relatives of Homo sapiens were the Common Chimpanzee and the Bonobo. Full genome sequencing resulted in the conclusion that "After 6.5 years of separate evolution, the differences between chimpanzee and human 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 was identical between chimpanzee and human. It had 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, was approximately seven million years old, which might indicate an earlier divergence.

There were two prominent scientific theories of the origins of contemporary humans. They concerned the relationship between modern humans and other hominids. The single-origin, or "out of Africa", hypothesis proposed 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, proposed 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 was 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 had been postulated, the most popular being the Toba catastrophe theory.

Human evolution was characterised by a number of important physiological trends, including the expansion of the brain cavity and brain itself, which was typically 1,400 cm³ in volume, over twice that of a chimpanzee or gorilla. The pattern of human postnatal brain growth differed from that of other apes (heterochrony), allowing for an extended period of social learning in juvenile humans. Physical anthropologists argued that a reorganisation of the structure of the brain was 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 were related and what their role was in the evolution of complex social organisation and culture were matters of ongoing debate in the field of physical anthropology.

Habitat and population

The most widely accepted view among current anthropologists was that Homo sapiens originated in the African savanna between 100,000 and 250,000 years ago, descending from Homo erectus, and colonised Eurasia and Oceania by 40,000 years ago, and finally colonised the Americas by 10,000 years ago. They displaced Homo neanderthalensis and other species descended from Homo erectus (which had colonised 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 had 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 had become unnecessary, and in many places these factors were no longer a driving force behind the growth and decline of a population. Nonetheless, the manner in which a habitat was altered was often a major determinant in population change.

Technology had allowed humans to colonise all of the continents and adapt to all climates. Within the last few decades, humans had explored Antarctica, the ocean depths, and space, although long-term habitation of these environments was not yet possible. With a population of over six billion, humans were 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, was expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space had 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 had been visited by human beings, although there had 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 was expected to rise throughout the 21st century. Problems for humans living in cities included various forms of pollution and crime,, especially in inner city and suburban slums. Benefits of urban living included increased literacy, access to the global canon of human knowledge and decreased susceptibility to rural famines.

Diet

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

Humans were animals who could consume both plant and animal products. Most biologists agreed humans were omnivorous. A minority believed they were an anatomically carnivorous species, and had started using agriculture (non-animal based) foodstuffs only recently. Another minority believed that anatomically, they were primarily herbivorous, many members of which had 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 chose to be vegans or vegetarians, abstaining from eating meat for religious, ethical, ecological, or health reasons. It was believed that humans had 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 chose a raw foodist approach, consuming little to no cooked food; the raw diet might be fruitarian, vegetarian, or omnivorous.

At least ten thousand years ago, humans developed agriculture, which had substantially altered the kind of food people eat. This had 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 were prepared, had varied widely by time, location, and culture.

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

Brain, mind, and consciousness

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

The human ability to think abstractly may have been be unparalleled in the animal kingdom. Human beings were one of only six species to pass the mirror test—which tests whether an animal recognises 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 failed this test. However, this may have been be a matter of degree rather than a sharp divide. Monkeys had been trained to apply abstract rules in tasks.

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

Humans were variously said to possess consciousness, self-awareness, and a mind, which corresponded roughly to the mental processes of thought. These were 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 constructed or experienced the outer world was a matter of debate, as were the definitions and validity of many of the terms used above. Cognitive scientist Daniel Dennett, for example, argued that there was no such thing as a narrative centre called the "mind", but that instead there was simply a collection of sensory inputs and outputs: different kinds of "software" running in parallel.

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

The nature of thought was central to psychology and related fields. Cognitive psychology studied cognition, the mental processes underlying behavior. It used information processing as a framework for understanding the mind. Perception, learning, problem solving, memory, attention, language and emotion were all well-researched areas as well. Cognitive psychology was associated with a school of thought known as cognitivism, whose adherents argued for an information processing model of mental function, informed by positivism and experimental psychology. Techniques and models from cognitive psychology were 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 sought to understand how people come to perceive, understand, and act within the world and how these processes changed as they age. This might focus on intellectual, cognitive, neural, social, or moral development.

Social psychology linked sociology with psychology in their shared study of the nature and causes of human social behavior, with an emphasis on how people thought towards each other and how they related to each other. The behavior and mental processes of animals, both human and non-human, could be described through animal cognition, ethology, evolutionary psychology, and comparative psychology as well. Human ecology was an academic discipline that investigated how humans and human societies interacted with both their natural environment and the human social environment.

Complete scientific classification

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

Eukaryota (Domain)
Animalia (Kingdom)
Eumetazoa (Subregnum)
Bilateria
Deuterostomia (Superphylum)
Chordata (Phylum)
Craniata
Vertebrata (Subphylum)
Gnathostomata (Infraphylum)
Teleostomi
Tetrapoda (Superclass)
Amniota (Series)
Synapsida
Mammaliaformes / Mammalia (Class)
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

Template:Social Infobox/Human

Society is here defined as the organisations 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 behavior and culture was often very close, making it difficult to clearly divide topics into one area or the other; as such, the placement of some subjects might be based on convention more than reality.

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

Language

The capacity humans had to transfer concepts, ideas and notions through speech and writing was unrivaled in known species. The faculty of speech was a defining feature of humanity, possibly predating phylogenetic separation of the modern population (see origin of language). Language was 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 was closely tied to ritual and religion (c.f. mantra, sacred text).

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

Art, music and literature

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

As a form of cultural expression by humans, art might 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 might 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 was 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 was distinguished from other works by being in large part unprompted by necessity, by biological drive, or by any undisciplined pursuit of recreation.

Music was a natural intuitive phenomenon based on the three distinct and interrelated organisation structures of rhythm, harmony, and melody. Listening to music was perhaps the most common and universal form of entertainment for humans, while learning and understanding it were popular disciplines. There were 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 was the driving force of desire behind all actions of any organism. Motivation was based on emotion—specifically, on the search for satisfaction (positive emotional experiences), and the avoidance of conflict; positive and negative were defined by the individual brain state, not by social norms: a person might be driven to self-injury or violence because their brain was conditioned to create a positive response to these actions. Motivation was important because it was involved in the performance of all learned responses.

Within psychology, conflict avoidance and the libido were seen to be primary motivators. Within economics motivation was often seen to be based on financial incentives, moral incentives, or coercive incentives. Religions generally posited Godly or demonic influences.

Happiness, or being happy, was a human emotional condition. The definition of happiness was a common philosophical topic. Some people might define it as the best condition which a human could have—a condition of mental and physical health. Others might 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 had a significant influence on, or could even be said to control, human behavior. Emotional experiences perceived as pleasant, like love, admiration, or joy, contrasted with those perceived as unpleasant, like hate, envy, or sorrow. There was often a distinction seen between refined emotions, which were socially learned, and survival oriented emotions, which were thought to be innate.

Human exploration of emotions as separate from other neurological phenomena is worthy of note, particularly in those cultures where emotion was considered separate from physiological state. In some cultural medical theories, to provide an example, emotion was considered so synonymous with certain forms of physical health that no difference was 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 was often translated as ecstasy.

In modern scientific thought, certain refined emotions were 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 was not in all cases as discrete and separate from natural neural function as was once assumed. Still, when humans functioned in civilised tandem, it had been noted that uninhibited acting on extreme emotion could lead to social disorder and crime.

Love and sexuality

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

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

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

Many sexologists believed that the majority of homo sapiens had 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 were born polymorphously perverse, which means that any number of objects could be a source of pleasure. According to Freud, humans then passed through five stages of psychosexual development (and could fixate on any stage because of various traumas during the process). For Alfred Kinsey, another influential sex researcher, people could fall anywhere along a continuous scale of sexual orientation (with only small minorities fully heterosexual or homosexual). Recent studies of neurology and genetics might suggest people might be born with one sexual orientation or another, so there was not currently a clear consensus among sex researchers.

Spirituality and religion

Spirituality, belief or involvement in matters of the soul or spirit, was 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 had also been addressed by philosophy, and to some extent by science, spirituality was unique in that it focused on mystical or supernatural concepts such as karma and God. However, critics argued that spirituality did not actually answer any questions, and complicated the issues further by raising more questions.

A more organised, but related, concept was religion—sometimes used interchangeably with "faith"—which was 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 had taken on many forms that vary by culture and individual perspective.

Some of the chief questions and issues religions were concerned with included 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 was moral or immoral. A common source in religions for answers to these questions were transcendent divine beings such as deities or a singular God, although not all religions were theistic—many were nontheistic or ambiguous on the topic, particularly among the Eastern religions.

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

Philosophy and self-reflection

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

The core philosophical disciplines were logic, ontology or metaphysics, epistemology, and axiology, which includes the branches of ethics and aesthetics. Philosophy covered a very wide range of approaches, and was 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 was a branch of philosophy concerned with the study of first principles, being and existence (ontology). In between the doctrines of religion and science, stood the philosophical perspective of metaphysical cosmology. This ancient field of study sought 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 considered themselves to be the dominant species on Earth, and the most advanced in intelligence and ability to manage their environment. This belief was especially strong in modern Western culture. Alongside such claims of dominance was often found radical pessimism because of the frailty and brevity of human life.

Humanism was a philosophy which defined a socio-political doctrine the bounds of which were not constrained by those of locally developed cultures, but which sought to include all of humanity and all issues common to human beings. Because spiritual beliefs of a community often manifested as religious doctrine, the history of which was as factious as it was 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 were religious, however, and saw humanism as simply a mature expression of a common truth present in most religions. Humanists affirmed the possibility of an objective truth and accepted that human perception of that truth was imperfect. The most basic tenets of humanism were that humans mattered and could solve human problems, and that science, freedom of speech, rational thought, democracy, and freedom in the arts were worthy pursuits or goals for all peoples. Humanism depended chiefly on reason and logic without consideration for the supernatural.

Science and technology

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

Human cultures were both characterised and differentiated by the objects that they make and use. Archaeology attempted 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 were particular to various regions and times.

Improvements in technology were 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 were quickly disseminated.

Such techniques could 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 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 formed a central part of human culture.

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

Government and politics

A state was an organised political community occupying a definite territory, having an organised 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, was often important to the establishment of its statehood. The "state" could also be defined in terms of domestic conditions, specifically, as conceptualised by Max Weber, "a state a human community that (successfully) the monopoly of the 'legitimate' use of physical force within a given territory."

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

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

All of these issues had a direct relationship with economics.

War

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

A common perception of war was 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 was sometimes characterised as a "war of liberation", while a war between internal elements of a state was a civil war.

There had 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 had nearly always included hand to hand combat, the usage of ranged weapons, propaganda, Shock and Awe, and ethnic cleansing. Military intelligence had always played a key role in determining victory and defeat. In modern warfare, soldiers and armored fighting vehicles were used to control the land, warships the seas, and air power the skies. Outer space had recently become an important factor in warfare as well, although no actual warfare was currently carried out within space. War was a strong catalyst in politics, history and technology. Important inventions such as medicine, navigation, metallurgy, mass production, nuclear power and computers had been completely or partially driven by war.

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

Trade and economics

Trade was the voluntary exchange of goods, services, or both, and a form of economics. A mechanism that allowed trade was called a market. The original form of trade was barter, the direct exchange of goods and services. Modern traders instead generally negotiated through a medium of exchange, such as money. As a result, buying could 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 existed for many reasons. Because of specialisation and division of labor, most people concentrated on a small aspect of manufacturing or service, trading their labour for products. Trade existed between regions because different regions had an absolute or comparative advantage in the production of some tradable commodity, or because different regions' size allowed for the benefits of mass production. As such, trade between locations benefited both locations.

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

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

Extinction

On December 17, 2006, a meteorite of unknown origin measuring approximately 45 kilometres in diameter crashed into Earth near Elephant Island in the Southern Ocean, causing earthquakes and tsunamis of unimaginable scale and the almost immediate death of most of the organisms on the planet. The effects of this event, or of Earth being knocked out of its orbit, have yet to be determined.

See also

• List of human time periods

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External links

• MNSU
• Archaeology Info

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• Apes
• Humans