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Humans (''Homo sapiens'') are the most abundant and widespread
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

species
of
primate Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...

primate
, characterized by
bipedalism Bipedalism is a form of terrestrial locomotion where an organism Motion (physics), moves by means of its two rear Limb (anatomy), limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet ...
and exceptional
cognitive Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception Perceptio ...

cognitive
skills due to a large and complex
brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...

brain
. This has enabled the development of advanced
tools A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates b ...

tools
,
culture Culture () is an umbrella term which encompasses the social behavior, institutions, and Social norm, norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the ...

culture
, and
language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...

language
. Humans are highly social and tend to live in complex
social structure In the social sciences, social structure is the aggregate of patterned social arrangements in society that are both emergence, emergent from and determinant of the Structure and agency, actions of individuals. Likewise, society is believed to b ...

social structure
s composed of many cooperating and competing groups, from
families Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

families
and
kinship In anthropology, kinship is the web of social relationships that form an important part of the lives of all humans in all societies, although its exact meanings even within this discipline are often debated. Anthropologist Robin Fox says that ...

kinship
networks to political states.
Social interaction A social relation or also described as a social interaction or social experience is the fundamental unit of analysis within the social sciences, and describes any voluntary or involuntary interpersonal relationship between two or more individuals ...
s between humans have established a wide variety of values,
social norms Social norms are shared standards of acceptance, acceptable behavior by groups. Social norms can both be informal understandings that govern the behavior of members of a society, as well as be codified into wikt:rule, rules and laws. Social normat ...
, and
ritual A ritual is a sequence of activities involving gestures, words, actions, or objects, performed according to a set sequence. Rituals may be prescribed by the traditions of a community, including a religious community. Rituals are characterized, b ...

ritual
s, which bolster human
society A society is a group of individuals involved in persistent social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same political Politics (from , ) is the set of activitie ...

society
. Its
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultura ...
and its desire to understand and influence the environment and to explain and manipulate
phenomena A phenomenon ( : phenomena) is an observable event. The term came into its modern philosophical Philosophy (from , ) is the systematized study of general and fundamental questions, such as those about existence, reason, Epistemology ...
have motivated humanity's development of
science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

science
,
philosophy Philosophy (from , ) is the systematized study of general and fundamental questions, such as those about existence, reason, knowledge, values, mind, and language. Such questions are often posed as problems to be studied or resolved. Some ...
,
mythology Myth is a folklore genre consisting of narratives that play a fundamental role in a society, such as foundational tales or origin myths. Since "myth" is widely used to imply that a story is not objectively true, the identification of a narra ...

mythology
,
religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or religious organization, organizations, that generally relates hu ...

religion
, and other
fields of study Fields may refer to: Music * Fields (band), an indie rock band formed in 2006 * Fields (progressive rock band), a progressive rock band formed in 1971 * ''Fields'' (album), an LP by Swedish-based indie rock band Junip (2010) * "Fields", a song b ...
. Although some scientists equate the term ''humans'' with all members of the genus ''
Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus ''Australopithecus'' that encompasses the extant species ''Homo sapiens'' (Human, modern humans), plus several extinct species classified as either ancestral to or closely ...

Homo
'', in common usage, it generally refers to ''Homo sapiens'', the only
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
member.
Anatomically modern human Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...
s emerged around 300,000 years ago in Africa, evolving from ''
Homo heidelbergensis ''Homo heidelbergensis'' (also ''H. sapiens heidelbergensis''), sometimes called Heidelbergs, is an extinct species or subspecies of archaic human which existed during the Middle Pleistocene. It was subsumed as a subspecies of ''H. erectus'' in 1 ...

Homo heidelbergensis
'' or a similar species and migrating out of Africa, gradually replacing or
interbreeding In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...
with local populations of
archaic humans A number of varieties of ''Homo'' are grouped into the broad category of archaic humans in the period that precedes and is contemporary to the emergence of the earliest early modern humans (''Homo sapiens'') around 300 Year#SI prefix multipliers, ...
. For most of history, humans were
nomadic A nomad is a member of a community without fixed habitation who regularly moves to and from the same areas. Such groups include hunter-gatherers, Nomadic pastoralism, pastoral nomads (owning livestock), tinkers and Merchant, trader nomads. In t ...

nomadic
hunter-gatherers. Humans began exhibiting
behavioral modernity Behavioral modernity is a suite of behavioral and cognition, cognitive traits that distinguishes current ''Homo sapiens'' from other anatomically modern humans, Hominini, hominins, and primates. Most scholars agree that modern human behavior ca ...
about 160,000–60,000 years ago. The
Neolithic Revolution The Neolithic Revolution, or the (First) Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunter-gatherer, hunting and gathering to one of agriculture and sedentism, ...
, which began in
Southwest Asia Western Asia, West Asia, or Southwest Asia, is the westernmost subregion of the larger geographical region of Asia, as defined by some academics, UN bodies and other institutions. It is almost entirely a part of the Middle East, and includes ...
around 13,000 years ago (and separately in a few other places), saw the emergence of
agriculture Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

agriculture
and permanent
human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people live. The complexity of a settlement can range from a minuscule number of dwellings grouped together to the largest of cities ...
. As populations became larger and denser, forms of governance developed within and between communities, and a number of
civilization A civilization (or civilisation) is any complex society characterized by the development of a state, social stratification, urbanization Urbanization (or urbanisation) refers to the population shift from Rural area, rural to urban are ...

civilization
s have risen and fallen. Humans have continued to expand, with a global population of over 8 billion .
Gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian inheritance#History, Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanin ...

Gene
s and the environment influence human biological variation in visible characteristics, physiology, disease susceptibility, mental abilities, body size, and life span. Though humans vary in many traits (such as genetic predispositions and physical features), any two humans are at least 99% genetically similar. Humans are sexually dimorphic: generally, males have greater body strength and females have a higher
body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four primary types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the ...
percentage. At
puberty Puberty is the process of physical changes through which a child's Human body, body matures into an adult body capable of sexual reproduction. It is initiated by hormone, hormonal signals from the brain to the gonads: the ovary, ovaries in a g ...

puberty
, humans develop
secondary sex characteristic Secondary sex characteristics are features that appear during puberty in human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism and exceptional cognitive skills due ...
s. Females are capable of
pregnancy Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...

pregnancy
, usually between puberty, at around 12 years, and
menopause Menopause, also known as the climacteric, is the time in women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause usually occurs between the age of 47 and 54. Medical professionals often ...
, around the age of 50. Humans are
omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and Dietary fiber, fiber, and metab ...
, capable of consuming a wide variety of plant and animal material, and have used fire and other forms of heat to prepare and
cook
cook
food since the time of ''H. erectus''. Humans can survive for up to eight weeks without food and three or four days without water. Humans are generally diurnal, sleeping on average seven to nine hours per day.
Childbirth Childbirth, also known as labour and delivery, is the ending of pregnancy where one or more babies exits the internal environment of the mother ] A mother is the female parent of a child. A woman may be considered a mother by virtue of h ...

Childbirth
is dangerous, with a high risk of complications and death. Often, both the mother and the father provide care for their children, who are Altricial, helpless at birth. Humans have a large and highly developed
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas Brodmann area 8, BA8, Brodmann area 9, BA9, Brodmann area 10, BA10, Brodmann area 11, BA ...

prefrontal cortex
, the region of the brain associated with higher cognition. They are highly intelligent, capable of
episodic memory Episodic memory is the memory Memory is the faculty of the mind by which data or information is Encoding (memory), encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing futur ...
, have flexible facial expressions,
self-awareness In philosophy of self, self-awareness is the experience of one's own personality or individuality. It is not to be confused with consciousness in the sense of qualia. While consciousness is being aware of one's environment and body and lifesty ...
, and a
theory of mind In psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, including feelings and thoughts. It is an academic dis ...
. The human mind is capable of
introspection Introspection is the examination of one's own conscious thoughts and feelings. In psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious m ...
, private
thought In their most common sense, the terms thought and thinking refer to conscious cognitive Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasse ...

thought
,
imagination Imagination is the production or simulation of novel objects, sensations, and ideas in the mind without any immediate input of the senses. Stefan Szczelkun characterises it as the forming of experiences in one's mind, which can be re-creations o ...

imagination
, volition, and forming views on
existence Existence is the ability of an entity to interact with reality. In philosophy Philosophy (from , ) is the systematized study of general and fundamental questions, such as those about existence, reason, knowledge, values, mind, and la ...

existence
. This has allowed great technological advancements and complex tool development possible through complex
reasoning Reason is the capacity of Consciousness, consciously applying logic by Logical consequence, drawing conclusions from new or existing information, with the aim of seeking the truth. It is closely associated with such characteristically human activ ...

reasoning
and the transmission of knowledge to subsequent generations. Language,
art Art is a diverse range of human activity, and resulting product, that involves creative or imaginative talent expressive of technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally agreed definition of wha ...

art
, and
trade Trade involves the transfer of goods and services from one person or entity to another, often in exchange for money. Economists refer to a system or network that allows trade as a market (economics), market. An early form of trade, barter, s ...

trade
are defining characteristics of humans. Long-distance trade routes might have led to cultural explosions and resource distribution that gave humans an advantage over other similar species.


Etymology and definition

All modern humans are classified into the
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

species
''Homo sapiens'', coined by
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...

Carl Linnaeus
in his 1735 work ''
Systema Naturae ' (originally in Latin language, Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Al ...
''. The generic name "''
Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus ''Australopithecus'' that encompasses the extant species ''Homo sapiens'' (Human, modern humans), plus several extinct species classified as either ancestral to or closely ...

Homo
''" is a learned 18th-century derivation from Latin , which refers to humans of either sex. The word ''human'' can refer to all members of the ''Homo'' genus, although in common usage it generally just refers to ''Homo sapiens,'' the only extant species. The name "''Homo'' ''sapiens''" means 'wise man' or 'knowledgeable man'. There is disagreement if certain extinct members of the genus, namely
Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an Extinction, extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ag ...
s, should be included as a separate species of humans or as a
subspecies In Taxonomy (biology), biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morphology), but that ca ...
of ''H. sapiens''. ''Human'' is a
loanword A loanword (also loan word or loan-word) is a word at least partly assimilated from one language (the donor language) into another language. This is in contrast to cognates, which are words in two or more languages that are similar because the ...
of
Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of England, Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments ...
from
Old French Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intel ...
, ultimately from
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

Latin
, the adjectival form of ('man' — in the sense of humankind). The native English term '' man'' can refer to the species generally (a synonym for ''humanity'') as well as to human males. It may also refer to individuals of either sex, though this form is less common in contemporary English. Despite the fact that the word ''animal'' is colloquially used as an
antonym In lexical semantics, opposites are words lying in an inherently incompatible binary relationship. For example, something that is ''long'' entails that it is not ''short''. It is referred to as a 'binary' relationship because there are two members ...
for ''human'', and contrary to a common biological misconception, humans are animals. The word ''
person A person (plural, : people) is a being that has certain capacities or attributes such as reason, morality, consciousness or self-consciousness, and being a part of a culturally established form of social relations such as kinship, ownership of pr ...

person
'' is often used interchangeably with ''human'', but philosophical debate exists as to whether personhood applies to all humans or all sentient beings, and further if one can lose personhood (such as by going into a persistent vegetative state).


Evolution

Humans are apes ( superfamily Hominoidea). The lineage of apes that eventually gave rise to humans first split from gibbons (family
Hylobatidae Gibbons () are apes in the Family (biology), family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh ...

Hylobatidae
) and
orangutan Orangutans are Hominidae, great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in ...

orangutan
s (genus ''Pongo''), then
gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or fi ...

gorilla
s (genus ''Gorilla''), and finally,
chimpanzee The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa Although tropical Africa is mostly familiar to the Western world, West for its rainfore ...

chimpanzee
s and
bonobo The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee and less often the dwarf chimpanzee or gracile chimpanzee, is an endangered great ape and one of the two species making up the genus ''Pan (genus), Pan,'' the other be ...

bonobo
s (genus '' Pan''). The last split, between the human and chimpanzee–bonobo lineages, took place around 8–4 million years ago, in the late
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent ...
epoch. During this split,
chromosome 2 Chromosome 2 is one of the twenty-three pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 2 is the second-largest human chromosome, spanning more than 242 million base pairs and representing almost ei ...

chromosome 2
was formed from the joining of two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. Following their split with chimpanzees and bonobos, the diversified into many species and at least two distinct genera. All but one of these lineages—representing the genus ''
Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus ''Australopithecus'' that encompasses the extant species ''Homo sapiens'' (Human, modern humans), plus several extinct species classified as either ancestral to or closely ...

Homo
'' and its sole extant species ''Homo sapiens''—are now extinct. The genus ''Homo'' evolved from ''
Australopithecus ''Australopithecus'' (, ; ) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genus ''Homo'' (which includes modern humans) emerged within ''Australopithecus'', as sister to e.g. ''Australopi ...

Australopithecus
''. Though
fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, Seashell, shells, exoskeletons, stone imprints of animals or microbes, objects pre ...
from the transition are scarce, the earliest members of ''Homo'' share several key traits with ''Australopithecus''. The earliest record of ''Homo'' is the 2.8 million-year-old specimen
LD 350-1 LD 350-1 is the earliest known specimen of the genus ''Homo'', dating to 2.8–2.75 million years ago (mya), found in the Ledi-Geraru site in the Afar Region of Ethiopia. The specimen was discovered in silts above the Gurumaha Tuff section of the ...
from Ethiopia, and the earliest named species are ''
Homo habilis ''Homo habilis'' ("handy man") is an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.31 million years ago to 1.65 million years ago (mya). Upon species description in 1964, ''H. habilis'' was highly c ...

Homo habilis
'' and ''
Homo rudolfensis ''Homo rudolfensis'' is an extinct species of archaic human from the Early Pleistocene of East Africa about 2 million years ago (mya). Because ''H. rudolfensis'' coexisted with several other hominins, it is debated what specimens can be confiden ...

Homo rudolfensis
'' which evolved by 2.3 million years ago. '''' (the African variant is sometimes called '''') evolved 2 million years ago and was the first
archaic human A number of varieties of ''Homo'' are grouped into the broad category of archaic humans in the period that precedes and is contemporary to the emergence of the earliest early modern humans (''Homo sapiens'') around 300 Year#SI prefix multipliers, ...
species to leave Africa and disperse across Eurasia. ''H. erectus'' also was the first to evolve a characteristically human
body plan A body plan, ( ), or ground plan is a set of morphology (biology), morphological phenotypic trait, features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many. This term, usually ap ...
. ''Homo sapiens'' emerged in Africa around 300,000 years ago from a species commonly designated as either '''' or '''', the descendants of ''H. erectus'' that remained in Africa. ''H. sapiens'' migrated out of the continent, gradually replacing or interbreeding with local populations of archaic humans. Humans began exhibiting
behavioral modernity Behavioral modernity is a suite of behavioral and cognition, cognitive traits that distinguishes current ''Homo sapiens'' from other anatomically modern humans, Hominini, hominins, and primates. Most scholars agree that modern human behavior ca ...
about 160,000-70,000 years ago, and possibly earlier. The "out of Africa" migration took place in at least two waves, the first around 130,000 to 100,000 years ago, the second (
Southern Dispersal In the context of the recent African origin of modern humans, the Southern Dispersal scenario (also the coastal migration or great coastal migration hypothesis) refers to the early migration along the southern coast of Asia, from the Arabian Pe ...
) around 70,000 to 50,000 years ago. ''H. sapiens'' proceeded to colonize all the continents and larger islands, arriving in
Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern Hemisphere, Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Ja ...

Eurasia
60,000 years ago, Australia around 65,000 years ago, the Americas around 15,000 years ago, and remote islands such as Hawaii,
Easter Island Easter Island ( rap, Rapa Nui; es, Isla de Pascua) is an island and special territory of Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, ...

Easter Island
,
Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...

Madagascar
, and
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...

New Zealand
between the years 300 and 1280 CE. Human evolution was not a simple linear or branched progression but involved interbreeding between related species. Genomic research has shown that hybridization between substantially diverged lineages was common in human evolution. evidence suggests that several genes of
Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an Extinction, extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ag ...
origin are present among all non sub-Saharan African populations, and Neanderthals and other hominins, such as
Denisovan The Denisovans or Denisova hominins ) are an extinct species or subspecies of archaic human that ranged across Asia during the Lower Paleolithic, Lower and Middle Paleolithic. Denisovans are known from few physical remains and consequently, mos ...
s, may have contributed up to 6% of their
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gene ...

genome
to present-day non sub-Saharan African humans. Human evolution is characterized by a number of morphological, developmental, human physiology, physiological, and Human behavior, behavioral changes that have taken place since the split between the chimpanzee-human last common ancestor, last common ancestor of humans and chimpanzees. The most significant of these adaptations are obligate bipedalism, increased brain size and decreased sexual dimorphism (neoteny). The relationship between all these changes is the subject of ongoing debate.


History

Until about 12,000 years ago, all humans lived as hunter-gatherers. The
Neolithic Revolution The Neolithic Revolution, or the (First) Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunter-gatherer, hunting and gathering to one of agriculture and sedentism, ...
(the invention of
agriculture Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

agriculture
) first took place in
Southwest Asia Western Asia, West Asia, or Southwest Asia, is the westernmost subregion of the larger geographical region of Asia, as defined by some academics, UN bodies and other institutions. It is almost entirely a part of the Middle East, and includes ...
and spread through large parts of the Old World over the following millennia. It also occurred independently in Mesoamerica (about 6,000 years ago), China, Papua New Guinea, and the Sahel and Sudanian savanna, West Savanna regions of Africa. Access to food surplus led to the formation of permanent
human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people live. The complexity of a settlement can range from a minuscule number of dwellings grouped together to the largest of cities ...
s, the domestication of animals and the Chalcolithic, use of metal tools for the first time in history. Agriculture and sedentary lifestyle led to the emergence of early civilizations. An urban revolution took place in the 4th millennium BCE with the development of city-states, particularly Sumerian cities located in Mesopotamia. It was in these cities that the earliest known form of writing, cuneiform script, appeared around 3000 BCE. Other major civilizations to develop around this time were Ancient Egypt and the Indus Valley civilisation, Indus Valley Civilization. They eventually traded with each other and invented technology such as wheels, plows and sails. Astronomy and mathematics were also developed and the Great Pyramid of Giza was built. There is evidence of a 4.2-kiloyear event, severe drought lasting about a hundred years that may have caused the decline of these civilizations, with new ones appearing in the aftermath. Babylonians came to dominate Mesopotamia while others, such as Poverty Point cultures, Minoan civilization, Minoans and the Shang dynasty, rose to prominence in new areas. The Bronze Age suddenly Late Bronze Age collapse, collapsed around 1200 BCE, resulting in the disappearance of a number of civilizations and the beginning of the Greek Dark Ages. During this period iron started replacing bronze, leading to the Iron Age. In the 5th century BCE, history started being Historiography, recorded as a discipline, which provided a much clearer picture of life at the time. Between the 8th and 6th century BCE, Europe entered the classical antiquity age, a period when ancient Greece and ancient Rome flourished. Around this time other civilizations also came to prominence. The Maya civilization started to build cities and create Maya calendar, complex calendars. In Africa, the Kingdom of Aksum overtook the declining Kingdom of Kush and facilitated trade between India and the Mediterranean. In West Asia, the Achaemenid Empire's system of centralized governance became the precursor to many later empires, while the Gupta Empire in India and the Han dynasty in China have been described as golden ages in their respective regions. Following the fall of the Western Roman Empire in 476, Europe entered the Middle Ages. During this period, Christianity and the Catholic Church, Church would provide centralized authority and education. In the Middle East, Islam became the prominent religion and expanded into North Africa. It led to an Islamic Golden Age, inspiring achievements in architecture, the revival of old advances in science and technology, and the formation of a distinct way of life. The Christendom, Christian and Islamic worlds would eventually clash, with the Kingdom of England, the Kingdom of France and the Holy Roman Empire declaring a series of crusades, holy wars to regain control of the Holy Land from Muslims. In the Americas, complex Mississippian culture, Mississippian societies would arise starting around 800 CE, while further south, the Aztecs and Incas would become the dominant powers. The Mongol Empire would conquer much of
Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern Hemisphere, Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Ja ...

Eurasia
in the 13th and 14th centuries. Over this same time period, the Mali Empire in Africa grew to be the largest empire on the continent, stretching from Senegambia to Ivory Coast. Oceania would see the rise of the Tuʻi Tonga Empire which expanded across many islands in the South Pacific. The early modern period in Europe and the Near East (c.1450–1800) began with the Fall_of_Constantinople, final defeat of the Byzantine Empire, and the Ottoman Empire, rise of the Ottoman Empire. Meanwhile, Japan entered the Edo period, the Qing dynasty rose in China and the Mughal Empire ruled much of India. Europe underwent the Renaissance, starting in the 15th century, and the Age of Discovery began with the exploring and Colonialism, colonizing of new regions. This includes the British Empire expanding to become the Largest empire, world's largest empire and European colonization of the Americas, the colonization of the Americas. This expansion led to the Atlantic slave trade and the Genocide of indigenous peoples#Native American Genocide, genocide of Native American peoples. This period also marked the Scientific Revolution, with great advances in mathematics, mechanics, astronomy and physiology. The late modern period (1800–present) saw the Technological Revolution, Technological and Industrial Revolution bring such discoveries as imaging technology, major innovations in transport and energy development. The United States, United States of America underwent great change, going from a Thirteen Colonies, small group of colonies to one of the global superpowers. The Napoleonic Wars raged through Europe in the early 1800s, Spain lost most of its colonies in the New World, while Europeans continued Scramble for Africa, expansion into Africa—where European control went from 10% to almost 90% in less than 50 years—and Oceania. A tenuous Balance of power (international relations), balance of power among European nations collapsed in 1914 with the outbreak of the World War I, First World War, one of the deadliest conflicts in history. In the 1930s, Great Depression, a worldwide economic crisis led to the rise of authoritarian regimes and a World War II, Second World War, involving World War II by country, almost all of the world's countries. Following its conclusion in 1945, the Cold War between the USSR and the United States saw a struggle for global influence, including a nuclear arms race and a Space Race, space race. The current Information Age sees the world becoming increasingly Globalization, globalized and interconnected.


Habitat and population

Early human settlements were dependent on proximity to water resources, water and—depending on the lifestyle—other natural resources used for subsistence, such as populations of animal prey for hunting and arable land for growing crops and grazing livestock. Modern humans, however, have a great capacity for altering their habitat (ecology), habitats by means of technology, irrigation, urban planning, construction, deforestation and desertification. Human settlements continue to be vulnerability, vulnerable to natural disasters, especially those placed in hazardous locations and with low quality of construction. Grouping and deliberate habitat alteration is often done with the goals of providing protection, accumulating comforts or material wealth, expanding the available food, improving aesthetics, increasing knowledge or enhancing the exchange of resources. Humans are one of the most Adaptation, adaptable species, despite having a low or narrow tolerance for many of the earth's extreme environments. Through advanced tools, humans have been able to extend their tolerance to a wide variety of temperatures, humidity, and altitudes. As a result, humans are a Cosmopolitan distribution, cosmopolitan species found in almost all regions of the world, including tropical rainforest, desert, arid desert, extremely cold arctic regions, and heavily polluted cities; in comparison, most other species are confined to a few geographical areas by their limited adaptability. The human population is not, however, uniformly distributed on the Earth's surface, because the population density varies from one region to another, and large stretches of surface are almost completely uninhabited, like Antarctica and vast swathes of the ocean. Most humans (61%) live in Asia; the remainder live in the Americas (14%), Africa (14%), Europe (11%), and Oceania (0.5%). Within the last century, humans have explored challenging environments such as Antarctica, the deep sea, and outer space. Human habitation within these hostile environments is restrictive and expensive, typically limited in duration, and restricted to Science, scientific, military, or Industry (economics), industrial expeditions. Humans have briefly visited the exploration of the Moon, Moon and made their presence felt on other celestial bodies through human-made robotic spacecraft. Since the early 20th century, there has been continuous human presence in Antarctica through Research stations in Antarctica, research stations and, since 2000, human presence in space, in space through habitation on the International Space Station. Estimates of the population at the time agriculture emerged in around 10,000 BC have ranged between 1 million and 15 million. Around 50–60 million people lived in the combined eastern and western Roman Empire in the 4th century AD. Bubonic plagues, first recorded in the 6th century AD, reduced the population by 50%, with the Black Death killing 75–200 million people in
Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern Hemisphere, Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Ja ...

Eurasia
and North Africa alone. Human population was believed to have reached one billion in 1800. It has since then increased exponentially, reaching two billion in 1930 and three billion in 1960, four in 1975, five in 1987 and six billion in 1999. It passed seven billion in 2011 and was expected to pass eight billion in November 2022. It took over two million years of prehistory, human prehistory and human history, history for the human population to reach one billion and only 207 years more to grow to 7 billion. The combined Biomass (ecology), biomass of the carbon of all the humans on Earth in 2018 was estimated at 60 million tons, about 10 times larger than that of all non-domesticated mammals. In 2018, 4.2 billion humans (55%) lived in urban areas, up from 751 million in 1950. The most urbanized regions are Northern America (82%), Latin America (81%), Europe (74%) and Oceania (68%), with Africa and Asia having nearly 90% of the world's 3.4 billion rural population. Problems for humans living in cities include various forms of pollution and crime, especially in inner city and suburban slums. Humans have had a dramatic Human impact on the environment, effect on the environment. They are apex predators, being rarely preyed upon by other species. Human population growth, industrialization, land development, overconsumption and combustion of fossil fuels have led to Environmental degradation, environmental destruction and pollution that significantly contributes to the ongoing mass extinction of other forms of life. They are the main contributor to global climate change, which may accelerate the Holocene extinction.


Biology


Anatomy and physiology

Most aspects of human physiology are closely Homology (biology), homologous to corresponding aspects of animal physiology. The human body consists of the legs, the torso, the arms, the neck, and the head. An adult human body consists of about 100 trillion (1014) cell (biology), cells. The most commonly defined body systems in humans are the Human nervous system, nervous, the Cardiovascular system, cardiovascular, the Human digestive system, digestive, the Endocrine system, endocrine, the Human immune system, immune, the Integumentary system, integumentary, the Lymphatic system, lymphatic, the Human musculoskeletal system, musculoskeletal, the Human reproductive system, reproductive, the Respiratory system, respiratory, and the urinary system. The dental formula of humans is: . Humans have proportionately shorter palates and much smaller Human tooth, teeth than other primates. They are the only primates to have short, relatively flush canine teeth. Humans have characteristically crowded teeth, with gaps from lost teeth usually closing up quickly in young individuals. Humans are gradually losing their wisdom teeth, third molars, with some individuals having them congenitally absent. Humans share with chimpanzees a Vestigiality, vestigial tail, Appendix (anatomy), appendix, flexible shoulder joints, grasping fingers and opposable thumbs. Apart from bipedalism and brain size, humans differ from chimpanzees mostly in smelling, hearing and Digestion#Protein digestion, digesting proteins. While humans have a density of hair follicles comparable to other apes, it is predominantly vellus hair, most of which is so short and wispy as to be practically invisible. Humans have about 2 million sweat glands spread over their entire bodies, many more than chimpanzees, whose sweat glands are scarce and are mainly located on the palm of the hand and on the soles of the feet. It is estimated that the worldwide average Human height, height for an adult human male is about , while the worldwide average height for adult human females is about . Shrinkage of stature may begin in middle age in some individuals but tends to be typical in the extremely Old age, aged. Throughout history, human populations have universally become taller, probably as a consequence of better nutrition, healthcare, and living conditions. The average Body weight, mass of an adult human is for females and for males. Like many other conditions, body weight and body type are influenced by both genetic susceptibility and environment and varies greatly among individuals. Humans have a far faster and more accurate throw than other animals. Humans are also among the best long-distance runners in the animal kingdom, but slower over short distances. Humans' thinner body hair and more productive sweat glands help avoid heat exhaustion while running for long distances.


Genetics

Like most animals, humans are a ploidy, diploid and eukaryote, eukaryotic species. Each somatic cell has two sets of 23 chromosomes, each set received from one parent; gametes have only one set of chromosomes, which is a mixture of the two parental sets. Among the 23 pairs of chromosomes, there are 22 pairs of autosomes and one pair of sex-determination system, sex chromosomes. Like other mammals, humans have an XY sex-determination system, so that females have the sex chromosomes XX and males have XY.
Gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian inheritance#History, Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanin ...

Gene
s and environment influence human biological variation in visible characteristics, physiology, disease susceptibility and mental abilities. The exact influence of Environment (biophysical), genes and environment on certain traits is not well understood. While no humans—not even monozygotic twins—are genetically identical, two humans on average will have a genetic similarity of 99.5%-99.9%. This makes them more Human genetic variation, homogeneous than other great apes, including chimpanzees. This small variation in human DNA compared to many other species suggests a population bottleneck during the Late Pleistocene (around 100,000 years ago), in which the human population was reduced to a small number of breeding pairs. The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gene ...

genome
display directional selection in the past 15,000 years. The human genome was first sequenced in 2001 and by 2020 hundreds of thousands of genomes had been sequenced. In 2012 the International HapMap Project had compared the genomes of 1,184 individuals from 11 populations and identified 1.6 million single nucleotide polymorphisms. African populations harbor the highest number of private genetic variants. While many of the common variants found in populations outside of Africa are also found on the African continent, there are still large numbers that are private to these regions, especially Oceania and the Americas. By 2010 estimates, humans have approximately 22,000 genes. By comparing mtDNA, mitochondrial DNA, which is inherited only from the mother, geneticists have concluded that the last female common ancestor whose genetic marker is found in all modern humans, the so-called mitochondrial Eve, must have lived around 90,000 to 200,000 years ago.


Life cycle

Most human reproduction takes place by internal fertilization via human sexual intercourse, sexual intercourse, but can also occur through assisted reproductive technology procedures. The average gestation period is 38 weeks, but a normal pregnancy can vary by up to 37 days. Embryonic development in the human covers the first eight weeks of development; at the beginning of the ninth week the embryo is termed a fetus. Humans are able to Labor induction, induce early labor or perform a caesarean section if the child needs to be born earlier for medical reasons. In developed countries, infants are typically in weight and in height at birth. However, low birth weight is common in developing countries, and contributes to the high levels of infant mortality in these regions. Compared with other species, human childbirth is dangerous, with a much higher risk of complications and death. The size of the fetus's head is more closely matched to the pelvis than other primates. The reason for this is not completely understood, but it contributes to a painful labor that can last 24 hours or more. 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. Both the mother and the father provide care for human offspring, in contrast to other primates, where parental care is mostly done by the mother. Altricial, Helpless at birth, humans continue to grow for some years, typically reaching sexual maturity at 15 to 17 years of age. The human life span has been split into various stages ranging from three to twelve. Common stages include Infant, infancy, childhood, adolescence, adulthood and old age. The lengths of these stages have varied across cultures and time periods but is typified by an unusually rapid growth spurt during adolescence. Human females undergo
menopause Menopause, also known as the climacteric, is the time in women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause usually occurs between the age of 47 and 54. Medical professionals often ...
and become Infertility, infertile at around the age of 50. It has been proposed that menopause increases a woman's overall reproductive success by allowing her to invest more time and resources in her existing offspring, and in turn their children (the grandmother hypothesis), rather than by continuing to bear children into old age. The life span of an individual depends on two major factors, genetics and lifestyle choices. For various reasons, including biological/genetic causes, women live on average about four years longer than men. , the global average life expectancy at birth of a girl is estimated to be 74.9 years compared to 70.4 for a boy. There are significant geographical variations in human life expectancy, mostly correlated with economic development—for example, life expectancy at birth in Hong Kong is 87.6 years for girls and 81.8 for boys, while in the Central African Republic, it is 55.0 years for girls and 50.6 for boys. The developed world is generally aging, with the median age around 40 years. In the third world, developing world, the median age is between 15 and 20 years. While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older. In 2012, the United Nations estimated that there were 316,600 living centenarians (humans of age 100 or older) worldwide.


Diet

Humans are
omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and Dietary fiber, fiber, and metab ...
, capable of consuming a wide variety of plant and animal material. Human groups have adopted a range of diets from purely vegan to primarily carnivorous. In some cases, dietary restrictions in humans can lead to deficiency diseases; however, stable human groups have adapted to many dietary patterns through both genetic specialization and cultural conventions to use nutritionally balanced food sources. The human diet is prominently reflected in human culture and has led to the development of food science. 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 Game (food), wild game, which must be hunted and captured in order to be consumed. It has been proposed that humans have used fire to prepare and food since the time of ''Homo erectus''. Around ten thousand years ago, History of agriculture, 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. The types of food consumed, and how they are prepared, have varied widely by time, location, and culture. In general, humans can survive for up to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days, with a maximum of one week. In 2020 it is estimated 9 million humans die every year from causes directly or indirectly related to starvation. Childhood malnutrition is also common and contributes to the Disease burden, 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 country, 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 "Epidemiology of obesity, obesity epidemic." Obesity is caused by consuming more calories than are expended, so excessive weight gain is usually caused by an energy-dense diet.


Biological variation

There is biological variation in the human species—with traits such as blood type, genetic diseases, Human skull, cranial features, Human face, facial features, organ systems, eye color, hair color and hair texture, texture, Human height, height and Body shape, build, and Human skin color, skin color varying across the globe. The typical height of an adult human is between , although this varies significantly depending on sex, ethnic origin, and family bloodlines. Body size is partly determined by genes and is also significantly influenced by environmental factors such as diet (nutrition), diet, exercise, and sleep patterns. There is evidence that populations have adapted genetically to various external factors. The genes that allow adult humans to Lactose tolerance, digest lactose are present in high frequencies in populations that have long histories of cattle domestication and are more dependent on cow milk. Sickle cell anemia, which may provide increased resistance to malaria, is frequent in populations where malaria is endemic. Populations that have for a very long time inhabited specific climates tend to have developed specific phenotypes that are beneficial for those environments—Allen's rule, short stature and stocky build in cold regions, tall and lanky in hot regions, and with high lung capacities or other High-altitude adaptation in humans, adaptations at high altitudes. Some populations have evolved highly unique adaptations to very specific environmental conditions, such as those advantageous to ocean-dwelling lifestyles and freediving in the Bajau. Human hair ranges in color from Red hair, red to blond to Brown hair, brown to Black hair, black, which is the most frequent. Hair color depends on the amount of melanin, with concentrations fading with increased age, leading to Grey hair, grey or even white hair. Skin color can range from Dark skin, darkest brown to Light skin, lightest peach, or even nearly white or colorless in cases of albinism. It tends to vary Clinal variation, clinally and generally correlates with the level of ultraviolet radiation in a particular geographic area, with darker skin mostly around the equator. Skin darkening may have evolved as protection against ultraviolet solar radiation. Light skin pigmentation protects against depletion of vitamin D, which requires sunlight to make. Human skin also has a capacity to darken (tan) in response to exposure to ultraviolet radiation. There is relatively little variation between human geographical populations, and most of the variation that occurs is at the individual level. Much of human variation is continuous, often with no clear points of demarcation. Genetic data shows that no matter how population groups are defined, two people from the same population group are almost as different from each other as two people from any two different population groups. Dark-skinned populations that are found in Africa, Australia, and South Asia are not closely related to each other. Genetic research has demonstrated that human populations native to the African continent are the most genetically diverse and genetic diversity decreases with migratory distance from Africa, possibly the result of Evolutionary bottleneck, bottlenecks during human migration. These non-African populations acquired new genetic inputs from local Interbreeding between archaic and modern humans, admixture with archaic populations and have much greater variation from Neanderthals and Denisovans than is found in Africa, though Neanderthal admixture into African populations may be underestimated. Furthermore, recent studies have found that populations in sub-Saharan Africa, and particularly West Africa, have ancestral genetic variation which predates modern humans and has been lost in most non-African populations. Some of this ancestry is thought to originate from admixture with an Interbreeding between archaic and modern humans#Archaic African hominins, unknown archaic hominin that diverged before the split of Neanderthals and modern humans. Humans are a Gonochorism, gonochoric species, meaning they are divided into male and female sexes. The greatest degree of genetic Sex differences in humans, variation exists between males and females. While the nucleotide diversity, nucleotide genetic variation of individuals of the same sex across global populations is no greater than 0.1%–0.5%, the genetic difference between Man, males and woman, females is between 1% and 2%. Males on average are 15% heavier and taller than females. On average, men have about 40–50% more upper body strength and 20–30% more lower body strength than women at the same weight, due to higher amounts of muscle and larger muscle fibers. Women generally have a higher
body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four primary types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the ...
percentage than men. Women have Human skin color#Sexual dimorphism, lighter skin than men of the same population; this has been explained by a higher need for vitamin D in females during pregnancy and lactation. As there are chromosomal differences between females and males, some X and Y chromosome-related conditions and Disease, disorders only affect either men or women. After allowing for body weight and volume, the male voice is usually an octave deeper than the female voice. Women have a Sex differences in longevity, longer life span in almost every population around the world.


Psychology

The human brain, the focal point of the central nervous system in humans, controls the peripheral nervous system. In addition to controlling "lower," involuntary, or primarily autonomic nervous system, autonomic activities such as respiration (physiology), respiration and digestion, it is also the locus of "higher" order functioning such as
thought In their most common sense, the terms thought and thinking refer to conscious cognitive Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasse ...

thought
, reasoning, and abstraction. These mental function, cognitive processes constitute the mind, and, along with their behavioral consequences, are studied in the field of psychology. Humans have a larger and more developed
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas Brodmann area 8, BA8, Brodmann area 9, BA9, Brodmann area 10, BA10, Brodmann area 11, BA ...

prefrontal cortex
than other primates, the region of the brain associated with higher cognition. This has led humans to proclaim themselves to be more intelligence, intelligent than any other known species. Objectively defining intelligence is difficult, with other animals adapting senses and excelling in areas that humans are unable to. There are some traits that, although not strictly unique, do set humans apart from other animals. Humans may be the only animals who have
episodic memory Episodic memory is the memory Memory is the faculty of the mind by which data or information is Encoding (memory), encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing futur ...
and who can engage in "mental time travel#Evolution and human uniqueness, mental time travel". Even compared with other social animals, humans have an unusually high degree of flexibility in their facial expressions. Humans are the only animals known to cry emotional tears. Humans are one of the few animals able to self-recognize in mirror tests and there is also debate over to what extent humans are the only animals with a
theory of mind In psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, including feelings and thoughts. It is an academic dis ...
.


Sleep and dreaming

Humans are generally diurnal. The average sleep requirement is between seven and nine hours per day for an adult and nine to ten hours per day for a child; elderly people usually sleep for six to seven hours. Having less sleep than this is common among humans, even though sleep deprivation can have negative health effects. A sustained restriction of adult sleep to four hours per day has been shown to correlate with changes in physiology and mental state, including reduced memory, fatigue, aggression, and bodily discomfort. During sleep humans dream, where they experience sensory images and sounds. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep. The length of a dream can vary, from a few seconds up to 30 minutes. Humans have three to five dreams per night, and some may have up to seven; however most dreams are immediately or quickly forgotten. They are more likely to remember the dream if awakened during the REM phase. The events in dreams are generally outside the control of the dreamer, with the exception of lucid dreaming, where the dreamer is self-aware. Dreams can at times make a Creativity, creative thought occur or give a sense of Artistic inspiration, inspiration.


Consciousness and thought

Human consciousness, at its simplest, is sentience or awareness of internal or external existence. Despite centuries of analyses, definitions, explanations and debates by philosophers and scientists, consciousness remains puzzling and controversial, being "at once the most familiar and most mysterious aspect of our lives". The only widely agreed notion about the topic is the intuition that it exists. Opinions differ about what exactly needs to be studied and explained as consciousness. Some philosophers divide consciousness into phenomenal consciousness, which is sensory experience itself, and access consciousness, which can be used for reasoning or directly controlling actions. It is sometimes synonymous with 'the mind', and at other times, an aspect of it. Historically it is associated with
introspection Introspection is the examination of one's own conscious thoughts and feelings. In psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious m ...
, private
thought In their most common sense, the terms thought and thinking refer to conscious cognitive Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasse ...

thought
,
imagination Imagination is the production or simulation of novel objects, sensations, and ideas in the mind without any immediate input of the senses. Stefan Szczelkun characterises it as the forming of experiences in one's mind, which can be re-creations o ...

imagination
and volition. It now often includes some kind of experience, cognition, feeling or perception. It may be 'awareness', or 'Meta-cognition, awareness of awareness', or
self-awareness In philosophy of self, self-awareness is the experience of one's own personality or individuality. It is not to be confused with consciousness in the sense of qualia. While consciousness is being aware of one's environment and body and lifesty ...
. There might be different levels or Higher-order theories of consciousness, orders of consciousness, or different kinds of consciousness, or just one kind with different features. The process of acquiring knowledge and understanding through thought, experience, and the senses is known as cognition. The human brain perception, perceives the external world through the senses, and each individual human is influenced greatly by his or her experiences, leading to subjectivity, subjective views of
existence Existence is the ability of an entity to interact with reality. In philosophy Philosophy (from , ) is the systematized study of general and fundamental questions, such as those about existence, reason, knowledge, values, mind, and la ...

existence
and the passage of time. The nature of thought is central to psychology and related fields. Cognitive psychology studies cognition, the mental function, mental processes underlying behavior. Largely focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age. This may focus on intellectual, cognitive, neural, social, or moral development. Psychologists have developed intelligence tests and the concept of intelligence quotient in order to assess the relative intelligence of human beings and study its Distribution (mathematics), distribution among population.


Motivation and emotion

Human motivation is not yet wholly understood. From a psychological perspective, Maslow's hierarchy of needs is a well-established theory that can be defined as the process of satisfying certain needs in ascending order of complexity. From a more general, philosophical perspective, human motivation can be defined as a commitment to, or withdrawal from, various goals requiring the application of human ability. Furthermore, incentive and preference are both factors, as are any perceived links between incentives and preferences. Volition (psychology), Volition may also be involved, in which case willpower is also a factor. Ideally, both motivation and volition ensure the selection, striving for, and Realisation (metrology), realization of goals in an optimal manner, a Function (biology), function beginning in childhood and continuing throughout a lifetime in a process known as socialization. Emotions are biological states associated with the nervous system brought on by Neurophysiology, neurophysiological changes variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or Suffering, displeasure. They are often Reciprocal influence, intertwined with Mood (psychology), mood, temperament, Personality psychology, personality, disposition, creativity, and motivation. Emotion has a significant influence on human behavior and their ability to learn. Acting on extreme or uncontrolled emotions can lead to social disorder and crime, with studies showing criminals may have a lower emotional intelligence than normal. Emotional experiences perceived as pleasure, pleasant, such as joy, Interest (emotion), interest or contentment, contrast with those perceived as suffering, unpleasant, like anxiety, sadness, anger, and Depression (mood), despair. Happiness, or the state of being happy, is a human emotional condition. The definition of happiness is a common philosophical topic. Some define it as experiencing the feeling of positive Affect (psychology), emotional affects, while avoiding the negative ones. Others see it as an appraisal of life satisfaction or quality of life. Recent research suggests that being happy might involve experiencing some negative emotions when humans feel they are warranted.


Sexuality and love

For humans, sexuality involves biological, erotic, Physical intimacy, physical, Emotional intimacy, emotional, social, or Spirituality, spiritual feelings and behaviors. Because it is a broad term, which has varied with historical contexts over time, it lacks a precise definition. The biological and physical aspects of sexuality largely concern the Human reproduction, human reproductive functions, including the human sexual response cycle. Sexuality also affects and is affected by cultural, political, legal, philosophical, Morality, moral, ethical, and religious aspects of life. Sexual desire, or ''libido'', is a basic mental state present at the beginning of sexual behavior. Studies show that men desire sex more than women and Masturbation, masturbate more often. Humans can fall anywhere along a continuous scale of sexual orientation, although most humans are heterosexual. While homosexuality, homosexual behavior Homosexual behavior in animals, occurs in some other animals, only humans and Sheep, domestic sheep have so far been found to exhibit exclusive preference for same-sex relationships. Most evidence supports nonsocial, biology and sexual orientation, biological causes of sexual orientation, as cultures that are very tolerant of homosexuality do not have significantly higher rates of it. Research in neuroscience and genetics suggests that other aspects of human sexuality are biologically influenced as well. Love most commonly refers to a feeling of strong attraction or emotional Attachment (psychology), attachment. It can be impersonal (the love of an object, ideal, or strong political or spiritual connection) or interpersonal (love between humans). When in love dopamine, norepinephrine, serotonin and other chemicals stimulate the brain's pleasure center, leading to side effects such as increased heart rate, loss of Anorexia (symptom), appetite and Insomnia, sleep, and an Euphoria, intense feeling of excitement.


Culture

Humanity's unprecedented set of intellectual skills were a key factor in the species' eventual technological advancement and concomitant domination of the biosphere. Disregarding extinct hominids, humans are the only animals known to teach generalizable information, innately deploy recursive embedding to generate and communicate complex concepts, engage in the "folk physics" required for competent tool design, or cook food in the wild. Teaching and learning preserves the cultural and ethnographic identity of human societies. Other traits and behaviors that are mostly unique to humans include starting fires, phoneme structuring and vocal learning.


Language

While many species animal communication, communicate,
language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...

language
is unique to humans, a defining feature of humanity, and a cultural universal. Unlike the limited systems of other animals, human language is open—an infinite number of meanings can be produced by combining a limited number of symbols. Human language also has the capacity of Displacement (linguistics), displacement, using words to represent things and happenings that are not presently or locally occurring but reside in the shared imagination of interlocutors. Language differs from other forms of communication in that it is Origin of speech#Modality-independence, modality independent; the same meanings can be conveyed through different media, audibly in speech, visually by sign language or writing, and through tactile media such as braille. Language is central to the communication between humans, and to the sense of identity that unites nations, cultures and ethnic groups. There are approximately six thousand different languages currently in use, including sign languages, and many thousands more that are extinct language, extinct.


The arts

Human arts can take many forms including Visual arts, visual, Literary arts, literary and Performing arts, performing. Visual art can range from paintings and sculptures to film, interaction design and architecture. Literary arts can include prose, poetry and dramas; while the performing arts generally involve theatre, music and dance. Humans often combine the different forms (for example, music videos). Other entities that have been described as having artistic qualities include Culinary arts, food preparation, Video games as an art form, video games and medicine. As well as providing entertainment and transferring knowledge, the arts are also used for The arts and politics, political purposes. Art is a defining characteristic of humans and there is evidence for a relationship between creativity and language. The earliest evidence of art was shell engravings made by ''Homo erectus'' 300,000 years before modern humans evolved. Art attributed to ''H. sapiens'' existed at least 75,000 years ago, with jewellery and drawings found in caves in South Africa. There are various hypotheses as to why humans have Adaptation, adapted to the arts. These include allowing them to better problem solve issues, providing a means to control or influence other humans, encouraging cooperation and contribution within a society or increasing the chance of attracting a potential mate. The use of imagination developed through art, combined with logic may have given early humans an evolutionary advantage. Evidence of humans engaging in musical activities predates cave art and so far music has been Cultural universal, practiced by virtually all known human cultures. There exists a wide variety of music genres and ethnic musics; with humans' musical abilities being related to other abilities, including complex social human behaviours. It has been shown that human brains respond to music by becoming synchronized with the rhythm and beat, a process called Entrainment (biomusicology), entrainment. Dance is also a form of human expression found in all cultures and may have evolved as a way to help early humans communicate. Listening to music and observing dance stimulates the orbitofrontal cortex and other pleasure sensing areas of the brain. Unlike speaking, reading and writing does not come naturally to humans and must be taught. Still, literature has been present before the invention of words and language, with 30,000-year-old paintings on walls inside some caves portraying a series of dramatic scenes. One of the oldest surviving works of literature is the ''Epic of Gilgamesh'', first engraved on ancient Babylonian tablets about 4,000 years ago. Beyond simply passing down knowledge, the use and sharing of imaginative fiction through stories might have helped develop humans' capabilities for communication and increased the likelihood of securing a mate. Storytelling may also be used as a way to provide the audience with moral lessons and encourage cooperation.


Tools and technologies

Stone tools were used by proto-humans at least 2.5 million years ago. The use and manufacture of tools has been put forward as the ability that defines humans more than anything else and has historically been seen as an important evolutionary step. The technology became much more sophisticated about 1.8 million years ago, with the Control of fire by early humans, controlled use of fire beginning around 1 million years ago. The wheel and wheeled vehicles appeared simultaneously in several regions some time in the fourth millennium BC. The development of more complex tools and technologies allowed land to be Arable land, cultivated and animals to be Domestication, domesticated, thus proving essential in the development of
agriculture Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

agriculture
—what is known as the
Neolithic Revolution The Neolithic Revolution, or the (First) Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunter-gatherer, hunting and gathering to one of agriculture and sedentism, ...
. China developed paper, the printing press, gunpowder, the compass and List of Chinese inventions, other important inventions. The continued improvements in smelting allowed forging of copper, bronze, iron and eventually steel, which is used in railways, skyscrapers and many other products. This coincided with the Industrial Revolution, where the invention of automated machines brought major changes to humans' lifestyles. Modern technology is observed as Accelerating change, progressing exponentially, with major innovations in the 20th century including: Electricity generation, electricity, penicillin, semiconductors, internal combustion engines, the Internet, Fertilizer, nitrogen fixing fertilisers, airplanes, computers, Car, automobiles, Combined oral contraceptive pill, contraceptive pills, nuclear fission, the Green Revolution, green revolution, radio, scientific plant breeding, rockets, air conditioning, television and the assembly line.


Religion and spirituality

Religion is generally defined as a belief system concerning the supernatural, sacred or divinity, divine, and practices, values, institutions and
ritual A ritual is a sequence of activities involving gestures, words, actions, or objects, performed according to a set sequence. Rituals may be prescribed by the traditions of a community, including a religious community. Rituals are characterized, b ...

ritual
s associated with such belief. Some religions also have a moral code. The Evolutionary psychology of religion, evolution and the history of the Evolutionary origin of religions, first religions have recently become areas of active scientific investigation. While the exact time when humans first became religious remains unknown, research shows credible evidence of religious behaviour from around the Middle Paleolithic era (45-200 Tya (unit), thousand years ago). It may have evolved to play a role in helping enforce and encourage cooperation between humans. There is no accepted academic definition of what constitutes religion. Religion has taken on many forms that vary by culture and individual perspective in alignment with the geographic, social, and linguistic diversity of the planet. Religion can include a belief in life after death (commonly involving belief in an afterlife), the origin of life, the nature of the universe (religious cosmology) and its ultimate fate (eschatology), and what is morality, moral or immoral. A common source for answers to these questions are beliefs in transcendence (religion), transcendent divine beings such as deities or a singular God, although not all religions are theistic. Although the exact level of religiosity can be hard to measure, a majority of humans profess some variety of religious or spiritual belief. In 2015 the plurality were Christians, Christian followed by Muslims, Hindus and Buddhism, Buddhists. As of 2015, about 16%, or slightly under 1.2 billion humans, were irreligious, including those with no religious beliefs or no identity with any religion.


Science and philosophy

An aspect unique to humans is their ability to Knowledge transfer, transmit knowledge from one generation to the next and to continually build on this information to develop tools, scientific laws and other advances to pass on further. This accumulated knowledge can be tested to answer questions or make predictions about how the universe functions and has been very successful in advancing human ascendancy. Aristotle has been described as the first scientist, and preceded the rise of scientific thought through the Hellenistic period. Other early advances in science came from the Science and technology of the Han dynasty, Han Dynasty in China and during the Islamic Golden Age. The Scientific Revolution, scientific revolution, near the end of the Renaissance, led to the emergence of modern science. A chain of events and influences led to the development of the scientific method, a process of observation and experimentation that is used to differentiate science from pseudoscience. An understanding of mathematics is unique to humans, although other species of animals have some numerical cognition. All of science can be divided into three major branches, the formal sciences (e.g., logic and mathematics), which are concerned with formal systems, the applied sciences (e.g., engineering, medicine), which are focused on practical applications, and the empirical sciences, which are based on empirical observation and are in turn divided into natural sciences (e.g., physics, chemistry, biology) and social sciences (e.g., psychology, economics, sociology). Philosophy is a field of study where humans seek to understand fundamental truths about themselves and the world in which they live. Philosophical inquiry has been a major feature in the development of humans' intellectual history. It has been described as the "no man's land" between definitive scientific knowledge and dogmatic religious teachings. Philosophy relies on reason and evidence, unlike religion, but does not require the empirical observations and experiments provided by science. Major fields of philosophy include metaphysics, epistemology, Logic (philosophy), logic, and axiology (which includes ethics and aesthetics).


Society

Society is the system of organizations and institutions arising from interaction between humans. Humans are highly social and tend to live in large complex social groups. They can be divided into different groups according to their income, wealth, power (social and political), power, reputation and other factors. The structure of social stratification and the degree of social mobility differs, especially between modern and traditional societies. Human groups range from the size of Family, families to nations. The first form of human social organization is thought to have resembled hunter-gatherer Band society, band societies.


Gender

Human societies typically exhibit Gender identity, gender identities and gender roles that distinguish between Masculinity, masculine and Femininity, feminine characteristics and prescribe the range of acceptable behaviours and attitudes for their members based on their sex. The most common categorisation is a gender binary of men and women. Many societies recognise a third gender, or less commonly a fourth or fifth. In some other societies, Non-binary gender, non-binary is used as an umbrella term for a range of gender identities that are not solely male or female. Gender roles are often associated with a division of social norm, norms, practice (social theory), practices, clothing, dress, social behavior, behavior, rights, duty, duties, Privilege (social inequality), privileges, social status, status, and power (social and political), power, with men enjoying more rights and privileges than women in most societies, both today and in the past. As a Social constructionism, social construct, gender roles are not fixed and vary historically within a society. Challenges to predominant gender norms have recurred in many societies. Little is known about gender roles in the earliest human societies. Early modern humans probably had a range of gender roles similar to that of modern cultures from at least the Upper Paleolithic, while the
Neanderthal Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an Extinction, extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ag ...
s were less sexually dimorphic and there is evidence that the behavioural difference between males and females was minimal.


Kinship

All human societies organize, recognize and classify types of social relationships based on relations between parents, children and other descendants (consanguinity), and relations through marriage (Affinity (law), affinity). There is also a third type applied to godparents or Adoption, adoptive children (Fictive kinship, fictive). These culturally defined relationships are referred to as kinship. In many societies, it is one of the most important social organizing principles and plays a role in transmitting status and inheritance. All societies have rules of incest taboo, according to which marriage between certain kinds of kin relations are prohibited, and some also have rules of preferential marriage with certain kin relations.


Ethnicity

Human ethnic groups are a social category that Identity (social science), identifies together as a group based on shared attributes that distinguish them from other groups. These can be a common set of traditions, ancestry,
language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...

language
, history,
society A society is a group of individuals involved in persistent social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same political Politics (from , ) is the set of activitie ...

society
,
culture Culture () is an umbrella term which encompasses the social behavior, institutions, and Social norm, norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the ...

culture
, nation,
religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or religious organization, organizations, that generally relates hu ...

religion
, or social treatment within their residing area. Ethnicity is separate from the concept of Race (human categorization), race, which is based on physical characteristics, although both are socially constructed. Assigning ethnicity to a certain population is complicated, as even within common ethnic designations there can be a diverse range of subgroups, and the makeup of these ethnic groups can change over time at both the collective and individual level. Also, there is no generally accepted definition of what constitutes an ethnic group. Ethnic groupings can play a powerful role in the social identity and solidarity of ethnopolitical units. This has been closely tied to the rise of the nation state as the predominant form of political organization in the 19th and 20th centuries.


Government and politics

As farming populations gathered in larger and denser communities, interactions between these different groups increased. This led to the development of governance within and between the communities. Humans have evolved the ability to change affiliation with various social groups relatively easily, including previously strong political alliances, if doing so is seen as providing personal advantages. This cognitive flexibility allows individual humans to change their political ideologies, with those with higher flexibility less likely to support authoritarian and nationalistic stances. Governments create laws and policies that affect the citizens that they govern. There have been List of forms of government, many forms of government throughout human history, each having various means of obtaining power and the ability to exert diverse controls on the population. As of 2017, more than half of all national governments are democracy, democracies, with 13% being autocracy, autocracies and 28% containing elements of both. Many countries have formed Intergovernmental organization, international political organizations and alliances, the largest being the United Nations with 193 member states.


Trade and economics

Trade, the voluntary exchange of goods and services, is seen as a characteristic that differentiates humans from other animals and has been cited as a practice that gave ''Homo sapiens'' a major advantage over other hominids. Evidence suggests early ''H. sapiens'' made use of long-distance trade routes to exchange goods and ideas, leading to cultural explosions and providing additional food sources when hunting was sparse, while such trade networks did not exist for the now extinct Neanderthals. Early trade likely involved materials for creating tools like obsidian. The first truly international trade routes were around the spice trade through the Roman and medieval periods. Early human Economy, economies were more likely to be based around Gift economy, gift giving instead of a bartering system. Early money consisted of Commodity money, commodities; the oldest being in the form of cattle and the most widely used being cowrie shells. Money has since evolved into governmental issued coins, Paper money, paper and electronic money. Human study of economics is a social science that looks at how societies distribute scarce resources among different people. There are massive Economic inequality, inequalities in the division of wealth among humans; the eight richest humans are worth the same monetary value as the poorest half of all the human population.


Conflict

Humans commit violence on other humans at a rate comparable to other primates, but have an increased preference for killing adults, Infanticide (zoology), infanticide being more common among other primates. It is predicted that 2% of early ''H. sapiens'' would be murdered, rising to 12% during the medieval period, before dropping to below 2% in modern times. There is great variation in violence between human populations with rates of homicide in societies that have legal systems and strong cultural attitudes against violence at about 0.01%. The willingness of humans to kill other members of their species en masse through organized conflict (i.e., war) has long been the subject of debate. One school of thought holds that war evolved as a means to eliminate competitors, and has always been an innate human characteristic. Another suggests that war is a relatively recent phenomenon and has appeared due to changing social conditions. While not settled, current evidence indicates warlike predispositions only became common about 10,000 years ago, and in many places much more recently than that. War has had a high cost on human life; it is estimated that during the 20th century, between 167 million and 188 million people died as a result of war.


See also

* * * List of human evolution fossils


Notes


References


External links

{{Authority control, state=expanded Humans, Apex predators Articles containing video clips Mammals described in 1758 Taxa named by Carl Linnaeus Tool-using mammals