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Related subjects: Mammals

Background Information


Temporal range: 0.195–0Ma
Pleistocene – Recent
A man and a woman from Southeast Asia
Conservation status

Least Concern ( IUCN 3.1)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Tribe: Hominini
Genus: Homo
Species: H. sapiens
Binomial name
Homo sapiens
Linnaeus, 1758

Homo sapiens idaltu White et al., 2003
Homo sapiens sapiens

Range of Homo sapiens (green)





Etymology and definition

With the discovery and study of fossil ancestors of modern humans the meaning of the word "human" changed, as the previously clear boundary between human and ape blurred, now encompassing multiple species. Today in scientific usage "human" may refer to any member of the genus Homo. Furthermore within Homo sapiens, there is a distinction between anatomically modern Homo sapiens and Archaic Homo sapiens, the earliest fossil members of the species. Sometimes groups such as the Neanderthals are classified as a subspecies of Homo sapiens - Homo sapiens neanderthalensis. However, in everyday usage, and in this article, the word "human" generally refers to the only extant species of the genus - anatomically and behaviorally modern Homo sapiens. The open question about possible extinct subspecies will be briefly covered. Fossil humans are covered in the article " Homo", and in the articles about individual species of the genus.

The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the adjective form of homō "man". The word's use as a noun (with a plural: humans) dates to the 16th century. The native English term man can refer to the species generally (a synonym for mankind), and could formerly refer to specific individuals of either sex. The latter use is now obsolete. Generic uses of the term "man" are declining, in favour of reserving it for referring specifically to adult males. The word is from Proto-Germanic * mannaz, from a Proto-Indo-European (PIE) root *man-.

The species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae, and he himself is the lectotype specimen. The generic name Homo is a learned 18th century derivation from Latin homō "man", ultimately "earthly being" ( Old Latin hemō, a cognate to Old English guma "man", from PIE *dʰǵʰemon-, meaning 'earth' or 'ground'). The species-name sapiens means "wise" or "sapient". Note that the Latin word homo refers to humans of either gender, and that sapiens is the singular form (there is no word sapien).



Scientific study of human evolution studies the development of the genus Homo, reconstructing the evolutionary divergence of the human lineage from other hominins (shared ancestors of humans and chimpanzees), hominids (great apes) and primates. Modern humans are defined as belonging to the species Homo sapiens, specifically to the single extant subspecies Homo sapiens sapiens.

Evidence from molecular biology



Evidence from the fossil record




Anatomical adaptations






Rise of Homo sapiens

The path followed by humans in the course of history

By the beginning of the Upper Paleolithic period (50,000 BP (Before Present)), full behavioural modernity, including language, music and other cultural universals had developed. As modern humans spread out from Africa they encountered other hominids such as Homo neanderthalensis and the so-called Denisovans, who may have evolved from populations of Homo erectus that had left Africa already around 2 million years ago. The nature of interaction between early humans and these sister species has been a long standing source of controversy, the question being whether humans replaced these earlier species or whether they were in fact similar enough to interbreed, in which case these earlier populations may have contributed genetic material to modern humans. Recent studies of the Human and Neanderthal genomes suggest gene flow between archaic Homo sapiens and Neanderthals and Denisovans.


Transition to civilization







Habitat and population

The Earth, as seen from space in October 2000, showing the extent of human occupation of the planet. The bright lights are the most densely inhabited areas.



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 April 2013, no other celestial body has been visited by humans, although there has been a continuous human presence in space since the launch of the initial crew to inhabit the International Space Station on October 31, 2000. However, other celestial bodies have been visited by human-made objects.


Humans have had a dramatic effect on the environment. As humans are rarely preyed upon, except by other humans for a variety of reasons, they have been described as apex or superpredators. Currently, through land development, combustion of fossil fuels, and pollution, humans are thought to be the main contributor to global climate change. If this continues at its current rate it is predicted that climate change will wipe out half of all species over the next century.



Anatomy and physiology

Human body types vary substantially. Although body size is largely determined by genes, it is also significantly influenced by environmental factors such as diet and exercise. The average height of an adult human is 1.4 m (4 ft 7 in) to 1.9 m (6 ft 3 in) tall, although this varies significantly from place to place and depending on ethnic origin. The average mass of an adult human is 54–64 kg (120–140 lbs) for females and 76–83 kg (168–183 lbs) for males. Weight can also vary greatly (e.g. obesity).

Although humans appear hairless compared to other primates, with notable hair growth occurring chiefly on the top of the head, underarms and pubic area, the average human has more hair follicles on his or her body than the average chimpanzee. The main distinction is that human hairs are shorter, finer, and less heavily pigmented than the average chimpanzee's, thus making them harder to see. Humans, like other primates, have sweat glands, better enabling them to conserve energy in tropical environments.

The hue of human skin and hair is determined by the presence of pigments called melanins. Human skin hues can range from dark brown to pale pink, or even nearly white or colorless, such as in cases of Albinism. Human hair ranges from white to brown to red to most commonly black. This depends on the amount of melanin (an effective sun blocking pigment) in the skin and hair, with hair melanin concentrations in hair fading with increased age, leading to grey or even white hair. Most researchers believe that skin darkening was an adaptation that evolved as a protection against ultraviolet solar radiation, which also helps balancing folate, which is destroyed by ultraviolet radiation, and vitamin D, which requires sunlight to form. The skin pigmentation of contemporary humans is clinally distributed across the planet, and in general correlates with the level of ultraviolet radiation. Human skin also has a capacity to darken ( sun tanning) in response to exposure to ultraviolet radiation. Humans tend to be physically weaker than other similarly sized primates.

The construction of the human pelvis differs from other primates, as do the toes. As a result, humans are slower for short distances than most other animals, but are among the best long-distance runners in the animal kingdom. Humans' thinner body hair and more productive sweat glands also help avoid heat exhaustion while running for long distances. A trade-off for these advantages of the modern human pelvis is that childbirth is more difficult and dangerous, especially given the larger head size of human babies compared to other primates. This means that human babies must turn around as they pass through the birth canal which other primates do not do, and it makes humans the only species in which females require help from their conspecifics to reduce the risks of birthing.





One human genome was sequenced in full in 2003, and currently efforts are being made to achieve a sample of the genetic diversity of the species (see International HapMap Project). By present estimates, humans have approximately 22,000 genes. The variation in human DNA is minute compared to that of other species, possibly suggesting a population bottleneck during the Late Pleistocene (ca. 100,000 years ago), in which the human population was reduced to a small number of breeding pairs. Nucleotide diversity is based on single mutations called single nucleotide polymorphisms (SNPs). The nucleotide diversity between humans is about 0.1%, which is 1 difference per 1,000 base pairs. A difference of 1 in 1,000 nucleotides between two humans chosen at random amounts to approximately 3 million nucleotide differences since the human genome has about 3 billion nucleotides. Most of these SNPs are neutral but some (about 3 to 5%) are functional and influence phenotypic differences between humans through alleles.



Life cycle

A 10 mm human embryo at 5 weeks
Boy and girl before puberty
Adult man and woman in the reproductive age
Elderly man and woman

As with other mammals, human reproduction takes place as internal fertilization by sexual intercourse. Upon fertilization and implantation, gestation then occurs within the female's uterus.


Compared with other species, human childbirth is dangerous. Painful labors lasting 24 hours or more are not uncommon and sometimes lead to the death of the mother, the child or both. This is because of both the relatively large fetal head circumference and the mother's relatively narrow pelvis. The chances of a successful labor increased significantly during the 20th century in wealthier countries with the advent of new medical technologies. In contrast, pregnancy and natural childbirth remain hazardous ordeals in developing regions of the world, with maternal death rates approximately 100 times greater than in developed countries.




Humans preparing a meal in Bali, Indonesia
Venus of Willensdorf statuette from the Upper Palaeolithic period
Two starved boys during the Russian famine of 1921


Until the development of agriculture approximately 10,000 years ago, Homo sapiens employed a hunter-gatherer method as their sole means of food collection. This involved combining stationary food sources (such as fruits, grains, tubers, and mushrooms, insect larvae and aquatic mollusks) with wild game, which must be hunted and killed in order to be consumed. It has been proposed that humans have used fire to prepare and cook food since the time of Homo erectus. Around ten thousand years ago, humans developed agriculture, which substantially altered their diet. This change in diet may also have altered human biology; with the spread of dairy farming providing a new and rich source of food, leading to the evolution of the ability to digest lactose in some adults. Agriculture 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.

In general, humans can survive for two to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days. About 36 million humans die every year from causes directly or indirectly related to hunger. Childhood malnutrition is also common and contributes to the global burden of disease. However global food distribution is not even, and obesity among some human populations has increased rapidly, leading to health complications and increased mortality in some developed, and a few developing countries. Worldwide over one billion people are obese, while in the United States 35% of people are obese, leading to this being described as an " obesity epidemic". Obesity is caused by consuming more calories than are expended, so excessive weight gain is usually caused by a combination of an energy-dense high fat diet and insufficient exercise.

Biological variation


Most current genetic and archaeological evidence supports a recent single origin of modern humans in East Africa with first migrations placed at 60,000 years ago. Current genetic studies have demonstrated that humans on the African continent are the most genetically diverse. However, compared to the other great apes, human gene sequences are remarkably homogeneous.

Nonetheless, there is important biological variation in the human species — with traits such as skin color, eye color, hair colour and texture, height and build, and cranial features varying clinally across the globe. Those aspects of genetic variation that gives clue to human evolutionary history, or which are relevant for medical research have received particular attention. For example the genes that cause adult humans to be able to digest lactose are present in high frequencies in population that have long histories of cattle domestication, suggesting natural selection having favored that gene in populations that depend on cow milk. Some hereditary diseases such as Sickle cell anaemia are frequent in populations from areas in which Malaria has been endemic throughout history — it is believed that the same gene causes increased resistance to Malaria among those who are unaffected carriers. Similarly populations that have inhabited specific climates such as arctic or tropical regions or high altitudes, tend to have developed specific phenotypes that are beneficial for conserving energy in those environments — short stature and stocky build in cold regions, tall and lanky in hot regions, and with high lung capacities in high altitudes. Similarly variation in skin colour varies clinally with darker colors around the equator where the added protection from the sun is thought to give an evolutionary advantage, and lighter skin tones closer to the poles where there is less sunlight and the lighter colored skin improves Vitamin D synthesis.

Today it is possible to determine, by genetic analysis, the geographic ancestry of a person and the degree of ancestry from each region. Such analyses can pinpoint the migrational history of a person's ancestors with a high degree of accuracy. Often, due to practices of group endogamy, allele frequencies cluster locally around kin groups and lineages, or by national, cultural or linguistic boundaries, giving a detailed degree of correlation between genetic clusters and population groups when considering many alleles simultaneously.



There is considerable biological variation in between human populations across the globe, resulting in fairly variable phenotypes. Traditionally human phenotypical variation has been described as breaking down into large continental races, characterized by easily definable traits. Humans were then classified into one of four or five phenotypical groups often based on skin colour, hair texture, and facial anatomy, and which were matched to a continent with which each group were associated. Often racial classification of humans was described in terms of essential characteristics, and came to serve as a way of naturalizing social and cultural stereotypes about racial groups, in turn justifying or motivating different forms of racism. As the study of human biological variation advanced it became clear that most variation is clinally distributed and blends gradually from one area to the next, with no clear boundaries between continents, additionally different traits have different clinal distributions. This realization made many anthropologists and biologists abandon the idea of major human races, instead describing biological variation in terms of populations and clinally distributed traits.

Today there is no scientific consensus on the biological relevance of race. While biological characteristics of an individual can give many clues about the geographical origin of their ancestors, anthropologists generally reject the notion of human "race" as a biological classification scheme. Instead they see it as a set of social constructions that map onto, but partly obscures, biological variation. Most anthropologists also maintain that the term "race" tacitly assumes that races are clearly bounded groups with essential characteristics, often ordered hierarchically and used to justify social inequality. An opposing view has it that it is possible to talk about "races" without making essentialist or hierarchical assumptions, and some biologists and many forensic scientists use the word race to describe biological variation associated with continental ancestry. It is generally agreed upon that certain genetic traits, including some common illnesses, correlate with genetic ancestry from specific regions, and genetic ancestry as determined by racial identification is becoming an increasingly common tool for risk assessment in medicine.

The use of the term "race" to mean something like " subspecies" among humans is obsolete; Homo sapiens has no existing subspecies (with the exception of Homo sapiens sapiens, the subspecies which includes all existing humans). In its modern scientific connotation, the term is not applicable to a species as genetically homogeneous as the human one, as stated in the declaration on race (UNESCO 1950, re-ratified 1978). Genetic studies have substantiated the absence of clear biological borders; thus the term "race" is rarely used in scientific terminology, either in biological anthropology and in human genetics. What in the past had been defined as "races"—whites, blacks, or Asians—are now defined as "ethnic groups" or "populations", in correlation with the field (sociology, anthropology, genetics) in which they are considered.


Drawing of the human brain, showing several important structures



Sleep and dreaming


Consciousness and thought

Humans are one of the relatively few species to have sufficient self-awareness to recognize themselves in a mirror. Already at 18 months, most human children are aware that the mirror image is not another person.

Lecture at the Faculty of Biomedical Engineering, CTU in Prague.





Motivation and emotion

Illustration of grief from Charles Darwin's book The Expression of the Emotions in Man and Animals.



Emotion has a significant influence on, or can even be said to control, human behaviour, though historically many cultures and philosophers have for various reasons discouraged allowing this influence to go unchecked. Emotional experiences perceived as pleasant, such as love, admiration, or joy, contrast with those perceived as unpleasant, like hate, envy, or sorrow. There is often a distinction made between refined emotions that are socially learned and survival oriented emotions, which are thought to be innate. Human exploration of emotions as separate from other neurological phenomena is worthy of note, particularly in cultures where emotion is considered separate from physiological state. In some cultural medical theories emotion is considered so synonymous with certain forms of physical health that no difference is thought to exist. The Stoics believed excessive emotion was harmful, while some Sufi teachers felt certain extreme emotions could yield a conceptual perfection, what is often translated as ecstasy.



Human society statistics
World population 7.1 billion
43.6 per km² (16.8 mi²) by land area
Most popular religions Christianity, Islam, Hinduism, Buddhism, Sikhism, Judaism, Baha'i
GDP ( nominal) $36,356,240 million USD
($5,797 USD per capita)
GDP ( PPP) $51,656,251 million IND
($8,236 per capita)


Culture is defined here as patterns of complex symbolic behavior, i.e. all behaviour that is not innate but which has to be learned through social interaction with others; such as the use of distinctive material and symbolic systems, including language, ritual, social organization, traditions, beliefs and technology.


The human capacity to exchange information and ideas through speech (and recently, writing) is unparalleled in other species. Unlike the closed sign systems of other primates in which sounds are unique and mutually exclusive, human language is open — an infinite number of meanings can be produced by combining a limited number of sounds and words. Human language also has the capacity of displacement, using words to represent things and happenings that are not presently or locally occurring, but reside in the shared imagination of interlocutors. Basic displacement may occur in other species, but is uniquely elaborated in humans, allowing symbols and language to refer to abstract or even purely imaginary states, and underpinning the complex symbolic culture of the species. Humans are the only species able to ask questions. Unlike chimpanzees and bonobos, who are able to answer complex questions but can not formulate and ask questions themselves, humans ask questions from a very early age. Human language is also unique in being a modality independent sign system, the same meanings can be conveyed through different media, auditively in speech, visually by gestural signs or writing and even through tactile media such as braille. The faculty of language is a defining feature of humanity, and a cultural universal. Language is central to the communication between humans, and to the sense of identity that unites nations, cultures and ethnic groups. The invention of writing systems at least five thousand years ago allowed the preservation of language on material objects, and was a major technological advancement. The science of linguistics describes the structure and function of language and the relationship between languages. There are approximately six thousand different languages currently in use, including sign languages, and many thousands more that are extinct.

Gender roles



Humans often live in family-based social structures.




Society, government, and politics




Trade and economics

Buyers and sellers bargaining in a market




Japanese samurai attacking a Mongol ship in the 13th century. Warfare has been an integral aspect of all human societies since before the rise of civilization.



Material culture and technology




Body culture

Throughout their history humans have altered their appearance by wearing clothing and adornments, by trimming or shaving hair or by means of body modifications.


Religion and spirituality




Philosophy and self-reflection

Statue of Confucius on Chongming Island in Shanghai


Science and mathematics


Art, music, and literature




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