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.

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 2007, no other celestial body has been visited by human beings, although there has been a continuous human presence in outer 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.

Humans have had a dramatic effect on the environment. It has been hypothesized that in the past, human predation has contributed to the extinction of a number of species; as humans are not generally preyed on themselves, humans have been described as the ultimate superpredators. Currently, through land development and pollution, humans are causing significant climate change, including global warming. This is believed to be a major contributor to the ongoing Holocene extinction event, a mass extinction which, if it continues at its current rate, is predicted to wipe out half of all species over the next century.

Humans are animals who can consume both plant and animal products. Most biologists agree humans are omnivorous. A minority believes that anatomically, they are primarily frugivorous, many members of which avoid 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.

History

Evolution

The scientific study of human evolution encompasses the development of the genus Homo, but usually involves studying other hominids and hominines as well, such as Australopithecus. "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 200,000 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% 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 and language acquisition 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.

Rise of civilization

The most widely accepted view among current anthropologists is that Homo sapiens originated in the African savanna around 200,000 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. They generally lived in small, nomadic groups. Around 10,000 years ago, the advent of agriculture prompted the Neolithic Revolution. Access to a stable food source led to the formation of permanent human settlements, the domestication of animals, and the use of metal tools. Agriculture also encouraged trade and cooperation, leading to complex societies. Villages developed into thriving civilizations in regions such as the Middle East's Fertile Crescent.

Around 6,000 years ago, the first states developed in Mesopotamia, Egypt and the Indus Valley. Military forces were formed for protection, and government bureaucracies for administration. States cooperated and competed for resources, in some cases waging wars. Around 2,000–3,000 years ago, some states, such as Persia, China, and Rome, developed through conquest into the first expansive empires. Influential religions, such as the Abrahamic and Dharmic religions, also rose to prominence at this time.

The late Middle Ages saw the rise of revolutionary ideas and technologies. In China, an advanced and urbanized economy promoted innovations such as printing and the compass, while the Islamic Golden Age saw major scientific advancements in Muslim empires. In Europe, the rediscovery of classical learning and inventions such as the printing press led to the Renaissance in the 14th century. Over the next 500 years, exploration and imperialistic conquest brought much of the Americas, Asia, and Africa under European control, leading to later struggles for independence. The Scientific Revolution in the 17th century and the Industrial Revolution in the 18th–19th centuries promoted major innovations in transport, such as the railway and automobile, energy development, such as coal and electricity, and government, such as democracy and communism.

As a result of such changes, modern humans live in a world that has become increasingly globalized and interconnected. Although this has encouraged the growth of science, art, and technology, it has also led to culture clashes, the development and use of weapons of mass destruction, and increased environmental destruction and pollution.

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 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 primarily on convention.

Culture consists 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

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

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 behavior 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.

Spirituality and religion

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.

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 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.

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.

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 expansion 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.

Humans often categorize themselves in terms of race or ethnicity, although the validity of human races as true biological categories is questionable. Genetic studies have demonstrated that humans on the African continent are most genetically diverse (Y-chromosome and MtDNA lineages), consistent with the theory that humans originated in Africa. However, compared to other animals, human gene sequences are remarkably homogeneous. 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 color and facial features.Ethnic groups, on the other hand, are more often linked by linguistic, cultural, ancestral, 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 racism and the theory of identity politics.

Society is the system of organizations and institutions arising from interaction between humans.

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 behavior 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 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 use 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 armoured fighting vehicles are used to control the land, warships the sea, and air power the sky. Outer space has recently become an important factor in warfare as well, although no actual warfare is currently carried out in space. War is a strong catalyst in politics, history and technology. Important inventions such as medicine, navigation, metallurgy, mass production, nuclear power and computers having been completely or partially driven by war.

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

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.