Image of a man and woman,
taken from the Pioneer 11
Homo sapiens idaltu (extinct)
Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. Biologically, they are classified as Homo sapiens (Latin for knowing man), a primate species of mammal with a highly developed brain. In spiritual terms, they are described using various concepts of soul which, in religion, are understood in relation to divine powers or beings; in mythology, they are also often contrasted with other humanoid races. In cultural anthropology, they are defined by their use of language, their organisation in complex societies and their development of technology, and especially by their ability to form groups and institutions for mutual support and assistance.
Juvenile males are known as boys and adult males as men. Juvenile females are known as girls and adult females as women. Human beings are commonly referred to individually as persons or people and collectively as man, mankind, humanity, or the human race, while humans is used both for the collective and for individuals. Until the 20th century, human was only used adjectivally ("pertaining to mankind"). Nominal use of human (plural humans) is short for human being, and is 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 emphasize positive aspects of human nature, and can be synonymous with benevolent (vs. inhuman; c. f. humanitarian).
In biology, humans are usually studied as one of many known species on Earth. The biological study of humans often extends to the psychological as well as the physical, but usually not to the spiritual or the religious. Biologically, humans are defined as hominids of the species Homo sapiens, of which the only extant subspecies is Homo sapiens sapiens. They are usually considered the only surviving species in the genus Homo. Humans exhibit fully bipedal locomotion. This leaves the forelimbs available for manipulating objects using opposable thumbs.
The mean height of an American adult female is 162 cm (64 in) and the mean weight is 62 kg (137 lb). Males are typically larger: 175 cm (69 in) and 78 kilograms (172 lb). Humans vary substantially around these means, and the means themselves have varied depending on locality and historical factors. Although body size is highly heritable, it is also significantly influenced by environmental and cultural factors such as diet.
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. Helpless at birth, they continue to grow for some years, typically reaching sexual maturity at around 12-15 years of age. Boys continue growing for some time after this, often only reaching their maximum height around the age of 18.
Human skin color can range from almost black to pinkish white in different people. In general, people with ancestors from sunny regions have darker skin than people with ancestors from regions with less sunlight. (However, this is complicated by the fact that there are people whose ancestors come from both sunny and less-sunny regions; and these people may have skin colors across the spectrum.) On average, women have slightly lighter skin than men.
Human life expectancy at birth is approaching 80 years in wealthy nations, with the assistance of science and technology. The number of centenarians in the world was estimated  at about 50,000 in 2003. The maximum human life span is thought to be about 120 years.
Humans may be have been extremely successful due to their high intelligence, but they also have their share of physical complications. Humans are prone to suffer from obesity more so than other primates. This is largely due to the fact that humans are capable of producing more body fat than their primate relatives. Because humans are strictly bipedal, the pelvis region and spinal column tends to get worn, creating locomotion difficulties in advanced old age. Also, human females suffer from relatively complicated child-births (painful labors lasting up to 24 hours are not uncommon). Before the 20th century, child-birth was a dangerous ordeal for some women, and it still is in remote, underdeveloped regions of the world.
Humans consider themselves the most intelligent organism in the animal kingdom. Humans have the highest brain to bodymass ratio of all large animals (Dolphins have the second highest; sharks have the highest for a fish; and octopuses have the highest for an invertebrate). While this is not an absolute measure (inasmuch as a minimum brain-mass is necessary for certain "housekeeping" functions), the brainmass to bodymass ratio does give a good indication of relative intelligence. (Carl Sagan, The Dragons of Eden, 38)
The human ability to abstract is unparallelled in the animal kingdom. Human beings are only one of five species to have passed the mirror test of abstraction - the others being chimpanzees, orangutans, gorillas, and dolphins. Tests have shown that a full grown chimpanzee has approximately the same ability to abstract as a four-year-old human child.
Pattern recognition is another area for which human beings are mentally well-suited.
The conventional view of human evolution states that humans evolved in inland savanna environments in Africa. (see Human evolution, Vagina gentium, Environment of Evolutionary Adaptedness). Culturally transmitted technology has allowed humans to colonize all of the continents and adapt to all climates. Within the last few decades, humans have been able to temporarily inhabit Antarctica, the ocean depths, and space, although long-term habitation of these three environments is not yet economical. Humans, with a population of about six billion, 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 only 0.3% in Australia. See list of countries by population and list of countries by population density.
Humans' original life style is hunting/gathering, which is adapted to the savannah where they evolved. Other human life styles 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 and construction, and activities accessory to those, such as transportation 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 transportation infrastructure, immediate proximity to these resources has become less necessary, and in many places these factors are no longer the driving force behind growth and decline of population.
A sizable minority—around 2.5 of a total of 6.3 billion people—live in urban surroundings. Urbanisation is expected to rise drastically during the 21st century. Problems for humans in cities include various forms of pollution, crime and poverty, especially in inner city and suburban slums.
Humans living on Antarctica, under the ocean, or in space are part of scientific, military, or industrial expeditions, and habitation of these environments is expensive and typically limited in duration.
Life in space has thus far been sporadic, with up to ten humans in space at a given time (seven on the Space Shuttle, three on Mir) and currently around three in the International Space Station. This is a direct result of humans' vulnerability to ionizing radiation. Prior to 1961, all humans were restricted to the earth; Yuri Gagarin was the first human to travel into space. At various periods between 1969 and 1974, up to two humans spent varying amounts of time on the Moon. No other moons or planets have yet been visited or occupied by human beings.
Main article: Human evolution
The closest surviving animal to humans is the chimpanzee; the second closest the gorilla and the third the orangutan. It is important to note, however, that humans only share a common ancestor population with these and are not descended directly from them. Biologists have compared a sequence of DNA base pairs between humans and chimpanzees, and estimated an overall genetic difference of less than 5% . It has been estimated that the human lineage diverged from that of chimpanzees about 5 million years ago, and from gorillas about 8 million years ago. However, recent news reports of a hominid skull approximately 7 million years old already showing a divergence from the ape lineage strongly suggests an earlier divergence.
Human evolution is characterized by a number of important trends:
- expansion of the brain cavity and brain itself, which is typically about 1,400 cm³ in volume, well over twice that of a chimpanzee or gorilla. Some physical anthropologists argue that a reorganization of the structure of the brain is more important than cranial expansion itself.
- canine tooth reduction.
- bipedal locomotion
- descent of the larynx (which makes possible the production of the complex sound known as vocal language).
How these trends are related, in what ways they have been adaptive, and what their role is in the evolution of complex social organization and culture, are matters of ongoing debate among physical anthropologists.
Various religious groups have raised objections concerning the theory of humanity's evolution from a common ancestor with the other hominoids. This has resulted in some controversy. See creationism, argument from evolution, and intelligent design for opposing points of view.
- Jablonski, N.G. & Chaplin, G. The evolution of human skin coloration. Journal of Human Evolution 39 (2000) 57-106. 
- Robins, A.H. (1991). Biological Perspectives on Human Pigmentation. Cambridge: Cambridge University Press. 
- A Look at Modern Human Origins
- Tree of Life
- Wade, N. "Why Humans and Their Fur Parted Ways." New York Times (Science Times), 19 August 2003. Summary of clues to the saga in which humans evolved to lose their hair and had to adjust, including turning from white skin to black skin, together with an estimation of the time at which humans invented clothing.
- The Wonder of Man (a book defending a christian creationist view of human biology, by W. Gitt (PDF 9 MB))
Spirituality and Religion
Many believe that modern humans are purely physical beings that can only be defined in biological and cultural terms (see materialism). Many others believe that humans have a spirit or a soul; thus, mind is not the same as brain. This section details how human beings have been defined in spiritual terms, as well as some of the ways that this definition has been expressed through ritual and religion.
In aboriginal peoples, probably reflecting the state of early human society, ritual, mythology and religion are closely interwoven, with notions of animacy of many aspects of Nature, in many cases combined with ancestor worship. Shamans are humans gifted and trained in bridging the natural and the supernatural worlds.
Spiritual practices and experiences possibly, but not necessarily coupled with theism or religious institution have been present in all societies. Essentially mystic movements include the Vedanta, Yoga, early Buddhism (see also Human realm), the Eleusian cults, Christian mystic orders and preachers such as Meister Eckhart, and Islamic Sufism. They center on ineffable experience of, and unity with the supernatural (see enlightenment, immanence).
The concept of gods as supernatural or very powerful intelligent beings, mostly imagined as anthropomorphic or zoomorphic, that want to be worshipped and appeased by humans is present from the beginning of history, and possibly reflected in Stone Age artwork, as well. In historical times, sacrificial rites evolved into institutionalised pagan religions led by clergies (e. g. Vedic religion, continued in Hinduism, Egyptian, Greek, Roman and Germanic paganism). In these religions, humans are mainly characterised by their inferiority to the gods, sometimes reflected in a hierarchical society ruled by dynasties that claim divine descent. In religions that believe in reincarnation, most notably Hinduism, there is no impermeable barrier between animals, humans and gods, as the soul may migrate across different species without losing its identity.
The idea of a single God that either incorporates or excels all lesser gods appeared independently in several cultures, possibly first in the heresy of Akhenaten (better referred to as Henotheism, a typical stage in the emergence of Monotheism). Concepts of good and evil in a moral sense arise as a consequence of a single God as absolute authority. In Judaism, God is central for having chosen the Hebrews as a people, and in the Hebrew Bible (referred to by christians as the Old Testament) the fate of the community and its relationship with God has clear precedence over the fate of individuals. Christianity grew out of Judaism by emphasizing the fate of the individual, especially after death, and the personal intervention of God by incarnation, i.e. by temporally becoming human himself. Islam, while rejecting the christian belief in Trinity and divine incarnation, is similar to Christianity in seeing humans as the viceregents of God and the only incarnate beings capable of free will (or of sin), as well as in its expansiveness, leading to the long-standing rivalry between the two religions. Monotheistic religions have in common the belief that humanity was created by God, bound by filial duty, and cared for by paternal providence.
The human individual is the subject experiencing the human condition. It is tied into its environment by its senses and into society by its personality, its gender and its social status. During its existence, it successively passes the stages of infancy, childhood, adolescence, maturity and old age. The universal declaration of human rights undertakes to protect rights of the individual.
Psyche and Consciousness
The subjective experience of an individual centers around its consciousness, self-awareness or mind, allowing it the perception of its own existence and of the passage of time. Consciousness gives rise to the perception of free will, although some believe that perfect free will is an illusion, either limited or eliminated by predestination or social or biological determinism. The human psyche extends beyond consciousness, encompassing the total of the individual's mental and emotional aspects. The science of psychology studies the human psyche, in particular the unconscious. The practice of psychoanalysis devised by Sigmund Freud attempts to reveal portions of the unconscious. Freud structures the human self into Ego, Superego and Id. Carl Gustav Jung introduced the notion of the collective unconscious and a process of individuation, casting doubt on the exact definability of the individual.
The human individual is exposed to emotions that significantly influence its decisions and its behaviour. Pleasant emotions like love or joy contrast with unpleasant emotions like hate, envy, jealousy or pain.
Human sexuality, besides ensuring reproduction, has important social functions, creating bonds and hierarchies among individuals. Sexuality is experienced as a bodily urge, often accompanied with strong emotions both positive (such as love or ecstasy) and negative (such as jealousy or hate).
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, jewelry or similar ornaments. Hairstyles also have important cultural implications. Beauty or ugliness are strong subjective impressions of human appearance.
The individual need for regular intake of food and drink is prominently reflected in human culture (see also food science). Failure to obtain food will lead to hunger and eventually starvation (see also famine, malnutrition).
The subjective life of the individual begins at its birth, or in the preceding phase of pregnancy during which the fetus develops within the mother. It ends with the individual's death. Both birth and death as singular events delimiting a human life can have great influence on the subjective individual. Complications during birth may result in a trauma and the prospect of death may cause unease or fear (see also near death experience). Burial ceremonies are a typical characteristic of human societies, often inspired by beliefs in an afterlife. Institutions of inheritance or ancestor worship may extend an individual's presence over its physical lifespan (see immortality).
Although many species are social, forming groups based on genetic ties, self-protection, or shared food gathering and distribution, humans are distinguished by the variety and complexity of the institutions that they form both for individual and group survival and for the preservation and development of technology, knowledge, and belief. Group identity and acceptance can exert powerful influence on individual behaviour, yet humans are also unique in their ability to form and adapt to new groups.
Sociology is the science that describes the interaction of human beings.
The faculty of speech is 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. The Hebrew word for "animal" (behemah) means "mute", defining humans as the "speaking animal" (animal loquens). Language is central to the feeling of identity of any culture or ethnicity and is often thought to have supernatural status or powers (see Magic, Mantra, Vac). The invention of writing systems some 5000 years ago, allowing the preservation of utterances, was a major step in cultural evolution. The science of Linguistics describes the structure of language, and the relation between different languages. There are estimated to be some 6000 different languages spoken today.
In every human culture, spirituality and ritual find expression in some form. These elements can combine essentially personal experience with uniting, communal experience, sometimes evoking very strong, even ecstatic emotions. The strong bonding power of such experiences may sometimes also lead to fanatism or aggression towards humans not belonging to the own group, resulting in schisms or even war. Theocracies are societies that are dominantly structured by religion, governed by a sacral king or by a clergy. Religion can also serve as a means of influencing and transmitting cultural norms of world-view and acceptable behaviour.
Families and Peer Groups
A similarly strong attachment may be forged with a small group of equals, resulting in peer groups of individuals of similar age, typically of the size of ten to twenty individuals, possibly related to the optimal size of a hunting party. Group dynamics and peer pressure may substantially influence the behaviour of group members (see also Asch conformity experiments).
Larger groups of humans can be unified by notions of common ancestry (tribes, ethnicities) or common cultural or material interests (nations or states), often further divided into social classes and hiearchical structures. A tribe may consist of a few hundred individuals, while the largest modern states contain more than a billion. Violent conflicts between such larger groups are wars. Loyalty to a larger group of this type is called nationalism or patriotism. In the extreme, feelings of loyalty towards an institution or an authority can reach pathological extremes, leading to mass hysteria or fascism (see also Milgram experiment, Stanford prison experiment).
Cultural anthropology describes the different human societies, and History records their interactions and acheivements. The organization and government of modern states are described by Political Science and Economics.
Culture and Civilization
A civilization is a society that has reached a certain level of complexity, usually including cities and institutionalized government, religion, science, literature and philosophy. The earliest cities were founded near important trade routes some 10.000 years ago (Jericho, Çatalhöyük). Human culture and artistic expression predates civilization and can be traced to the palaeolithic (cave paintings, Venus figurines, pottery). The development of agriculture allowed the transition from hunter-gatherer or nomadic societies to permanent settlements from the 9th millennium BC. The domestication of animals becomes an important part of human culture (dog, sheep, goat, cattle). In historical times science and technology have progressed ever faster (see History of science and technology).
Humanity has always taken great interest in itself. The human faculty of introspection, the urge of an individual to discover more about its essence, invariably leads to the inquiry about the human condition and the essence of the human kind as a whole. Such self-reflection is the basis of philosophy and is present from the earliest historical records. This very article, since it is written by humans, is itself unavoidably an example of such self-reflection.
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 Western culture, and is derived in part from the biblical creation story in which Adam is explicitly given dominion over the Earth and all of its creatures.
Prehistoric notions about the status of humanity may be guessed by the etymology of ancient words for man. Latin homo (PIE *kþonyon) means "of the earth, earthling", probably in opposition to "celestial" beings. Greek ανθρωπος (mycenaean *anthrokwos) means "low-eyed", again probably contrasting with a divine perspective.
From the 3rd millennium Old Kingdom of Egypt, belief in the eternal afterlife of the human Ka is documented. From the earliest times, we make out a claim of dominance of humanity alongside radical pessimism because of the frailty and brevity of human life (In the Old Testament, for example, dominion of man is promised in Genesis 1:28, but the author of Ecclesiastes bewails the vanity of all human effort).
Protagoras has made the famous claim that "Man is the measure of all things; of what is, that it is; of what is not, that it is not". Socrates gave the (doubtlessly tongue-in-cheek) definition of humans as "featherless bipeds" (Plato, Politicus). More serious is Aristotle's description of man as the "communal animal" (ζωον πολιτικον), i. e. emphasizing society-building as a central trait of human nature, and "animal with sapience" (ζωον λογον εχων, animal rationale), a term that also inspired the species' taxonomy, Homo sapiens.
The dominant world-view of medieval Europe, as dictated by the Catholic Church, was that human existence is characterized by sin, and that its aim should be to prepare for divine judgement after death. The 13th century pope Innocent III wrote about the essential misery of earthly existence in his "On the misery of the human condition" – a view that was disputed by, for example, Gianozzo Manetti in his treatise "On human dignity".
See Renaissance humanism.
- What a piece of work is a man! How noble in reason! how infinite in faculties! in form and moving, how express and admirable! in action how like an angel! in apprehension, how like a god! the beauty of the world! the paragon of animals! And yet, to me, what is this quintessence of dust?
The Enlightenment was driven by a renewed conviction, that, in the words of Immanuel Kant, "Man is distinguished above all animals by his self-consciousness, by which he is a 'rational animal'". In the 19th century, Karl Marx defined man as "labouring animal" (animal laborans) in conscious opposition to this tradition. In the early 20th century, Sigmund Freud dealt a serious blow to positivism by postulating that human behaviour is to a large part controlled by the unconscious mind.
Comparison to other Species
From a scientific viewpoint, Homo sapiens certainly is among the most generalized species on Earth. Smaller and simpler organisms such as bacteria and insects greatly surpass humans in population size and diversity of species, but few single species occupy as many diverse environments as humans. Many other species are adapted to specific environments, whereas humans use fire, clothing and manufactured shelter for protection against averse environmental conditions.
Various attempts have been made to identify a single behavioral characteristic that distinguishes humans from all other animals, e.g. the ability to make and use tools, the ability to alter the environment, language and the development of complex social structures. Considered in isolation, however, these differences are not absolute, as ethologists have recorded such behaviors in many species. Apes and even birds, for example, are known to "fish" for insects using blades of grass or twigs, and even to shape the tools for that purpose. For these reasons, the idea that making and using tools is a defining characteristic of humans is often considered outdated. Similarly, other animals often have methods of communication, but the degree to which humans create and use complex grammar and abstract concepts in language has not been seen in any other species (see also Universal Grammar).
Some anthropologists think that these readily observable characteristics (tool-making and language) are based on less easily observable mental processes that might be unique among humans: the ability to think symbolically, in the abstract or logically, although several species have demonstrated some abilities in these areas. Nor is it clear at what point exactly in human evolution these traits became prevalent. They are probably not restricted to the species Homo sapiens, seeing that the extinct species of the Homo genus (e.g. Homo neanderthalensis, Homo erectus) were also adept tool makers and may also have had linguistic skills.
The existence of other species that shape tools or use sign language may shed light on human evolution, but from the biological viewpoint the question "What single characteristic distinguishes humans from all other animals?" is peculiar: while superlatives are often also used for the description of other species (e. g. Whale, Cheetah, Hummingbird), the wish to find unique human characteristics is a matter of human self-reflection more than one of zoology.
- homo, humanoid
- human behaviour
- human biology, human ecology
- human evolution, human variability
- space and survival
- world population, world hunger
- human rights
- human condition
- human nature
- humanism, humanitarian
- man & woman, child & baby
- personal life