Human

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Human
Ma
Chibanianpresent
Male (left) and female (right) adult humans, Thailand, 2007
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Genus: Homo
Species:
H. sapiens
Binomial name
Homo sapiens
Homo sapiens population density (2005)

Humans (Homo sapiens) or modern humans are the most common and widespread

mythology, religion, and other frameworks of knowledge; humans also study themselves through such domains as anthropology, social science, history, psychology, and medicine
. As of March 2024, there are estimated to be more than 8 billion humans alive.

Although some scientists equate the term "humans" with all members of the genus

extant member. Extinct members of the genus Homo are known as archaic humans, and the term "modern human" is used to distinguish Homo sapiens from archaic humans. Anatomically modern humans emerged around 300,000 years ago in Africa, evolving from Homo heidelbergensis or a similar species. Migrating out of Africa, they gradually replaced and interbred with local populations of archaic humans. Multiple hypotheses for the extinction of archaic human species such as Neanderthals
include competition, violence, interbreeding with Homo sapiens, or inability to adapt to climate change.

For most of their history, humans were

Southwest Asia around 13,000 years ago (and separately in a few other places), saw the emergence of agriculture and permanent human settlement; in turn, this led to the development of civilization and kickstarted a period of continuous (and ongoing) population growth and rapid technological change. Since then, a number of civilizations have risen and fallen, while a number of sociocultural and technological
developments have resulted in significant changes to the human lifestyle.

body fat percentage. At puberty, humans develop secondary sex characteristics. Females are capable of pregnancy, usually between puberty, at around 12 years old, and menopause
, around the age of 50.

Humans are

helpless at birth
.

Humans have a large, highly developed, and complex

reasoning and the transmission of knowledge to subsequent generations through language
.

Humans' advanced technology has enabled them to spread to all the

geological epoch: the Anthropocene (with anthropo- deriving from the Ancient Greek
word for "human", ἄνθρωπος).

Etymology and definition

Carl Linnaeus coined the name Homo sapiens and is the type specimen of the species

All modern humans are classified into the

generic name "Homo" is a learned 18th-century derivation from Latin homō, which refers to humans of either sex.[3][4] The word human can refer to all members of the Homo genus,[5] although in common usage it generally just refers to Homo sapiens, the only extant species.[6] The name "Homo sapiens" means 'wise man' or 'knowledgeable man'.[7] There is disagreement if certain extinct members of the genus, namely Neanderthals, should be included as a separate species of humans or as a subspecies of H. sapiens.[5]

Human is a loanword of Middle English from Old French humain, ultimately from Latin hūmānus, the adjectival form of homō ('man' – in the sense of humanity).[8] 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.[9]

Despite the fact that the word animal is colloquially used as an

persistent vegetative state).[12]

Evolution

Humans are apes (

superfamily Hominoidea).[13] The lineage of apes that eventually gave rise to humans first split from gibbons (family Hylobatidae) and orangutans (genus Pongo), then gorillas (genus Gorilla), and finally, chimpanzees and bonobos (genus Pan). The last split, between the human and chimpanzee–bonobo lineages, took place around 8–4 million years ago, in the late Miocene epoch.[14][15] During this split, 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.[16] Following their split with chimpanzees and bonobos, the hominins diversified into many species and at least two distinct genera. All but one of these lineages – representing the genus Homo and its sole extant species Homo sapiens – are now extinct.[17]

Reconstruction of Lucy, the first Australopithecus afarensis skeleton found

The genus Homo evolved from

archaic human species to leave Africa and disperse across Eurasia.[22] H. erectus also was the first to evolve a characteristically human body plan. Homo sapiens emerged in Africa around 300,000 years ago from a species commonly designated as either H. heidelbergensis or H. rhodesiensis, the descendants of H. erectus that remained in Africa.[23] H. sapiens migrated out of the continent, gradually replacing or interbreeding with local populations of archaic humans.[24][25][26] Humans began exhibiting behavioral modernity about 160,000–70,000 years ago,[27] and possibly earlier.[28]

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) around 70,000 to 50,000 years ago.[29][30] H. sapiens proceeded to colonize all the continents and larger islands, arriving in Eurasia 125,000 years ago,[31][32] Australia around 65,000 years ago,[33] the Americas around 15,000 years ago, and remote islands such as Hawaii, Easter Island, Madagascar, and New Zealand in the years 300 to 1280 CE.[34][35]

Human evolution was not a simple linear or branched progression but involved interbreeding between related species.[36][37][38] Genomic research has shown that hybridization between substantially diverged lineages was common in human evolution.[39] DNA evidence suggests that several genes of Neanderthal origin are present among all non sub-Saharan-African populations, and Neanderthals and other hominins, such as Denisovans, may have contributed up to 6% of their genome to present-day non sub-Saharan-African humans.[36][40][41]

Human evolution is characterized by a number of

physiological, and behavioral changes that have taken place since the split between the last common ancestor of humans and chimpanzees. The most significant of these adaptations are hairlessness,[42] obligate bipedalism, increased brain size and decreased sexual dimorphism (neoteny). The relationship between all these changes is the subject of ongoing debate.[43]

Hominoidea (hominoids, apes
)

Hylobatidae (gibbons)

Hominidae (hominids, 
great apes
)
Ponginae
Pongo (orangutans)

Pongo abelii

Pongo tapanuliensis

Pongo pygmaeus

Homininae (hominines)
Gorillini
Gorilla (gorillas)

Gorilla gorilla

Gorilla beringei

Hominini (hominins)
Panina
Pan (chimpanzees)

Pan troglodytes

Pan paniscus

Hominina
 (homininans)

Homo sapiens (humans)

History

Prehistory

Overview map of the peopling of the world by early human migration during the Upper Paleolithic, following to the Southern Dispersal paradigm

Until about 12,000 years ago, all humans lived as

Southwest Asia and spread through large parts of the Old World over the following millennia.[46] It also occurred independently in Mesoamerica (about 6,000 years ago),[47] China,[48][49] Papua New Guinea,[50] and the Sahel and West Savanna regions of Africa.[51][52][53]

Access to food surplus led to the formation of permanent

Ancient

Great Pyramids of Giza, Egypt

An

cuneiform script, appeared around 3000 BCE.[58] Other major civilizations to develop around this time were Ancient Egypt and the Indus Valley Civilisation.[59] They eventually traded with each other and invented technology such as wheels, plows and sails.[60][61][62][63] Astronomy and mathematics were also developed and the Great Pyramid of Giza was built.[64][65][66] There is evidence of a severe drought lasting about a hundred years that may have caused the decline of these civilizations,[67] with new ones appearing in the aftermath. Babylonians came to dominate Mesopotamia while others,[68] such as the Poverty Point culture, Minoans and the Shang dynasty, rose to prominence in new areas.[69][70][71]

The Late Bronze Age collapse around 1200 BCE resulted in the disappearance of a number of civilizations and the beginning of the Greek Dark Ages.[72][73] During this period iron started replacing bronze, leading to the Iron Age.[74]

In the 5th century BCE, history started being

golden ages in their respective regions.[82][83]

Medieval

Medieval French manuscript illustration of the three classes of medieval society from the 13th-century Li Livres dou Santé

Following the

Muslims.[88]

In the Americas, complex

Incas would become the dominant powers.[90] The Mongol Empire would conquer much of Eurasia in the 13th and 14th centuries.[91] 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.[92] Oceania would see the rise of the Tuʻi Tonga Empire which expanded across many islands in the South Pacific.[93]

Modern

James Watt's steam engine

The

genocide of Native American peoples.[103] This period also marked the Scientific Revolution, with great advances in mathematics, mechanics, astronomy and physiology.[104]

The

global superpowers.[106] The Napoleonic Wars raged through Europe in the early 1800s,[107] Spain lost most of its colonies in the New World,[108] while Europeans continued expansion into Africa – where European control went from 10% to almost 90% in less than 50 years[109] – and Oceania.[110]

A tenuous

The war's destruction led to the collapse of most global empires, leading to widespread decolonization.

Contemporary

Following the conclusion of the Second World War in 1945, the

USSR and the United States saw a struggle for global influence, including a nuclear arms race and a space race, ending in the collapse of the Soviet Union.[113][114] The current Information Age, spurred by the development of the Internet and Artificial Intelligence systems, sees the world becoming increasingly globalized and interconnected.[115]

Habitat and population

Population statistics

Early human settlements were dependent on proximity to

natural disasters, especially those placed in hazardous locations and with low quality of construction.[121] 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.[122]

Humans are one of the most

biogeographical realms, although their presence in the Antarctic realm is very limited to research stations and annually there is a population decline in the winter months of this realm. Humans established their nation-states in the other seven realms, such as for example South Africa, India, Russia, Australia, Fiji, United States and Brazil
(each located in a different biogeographical realm).

By using advanced tools and

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.[123][126] Most humans (61%) live in Asia; the remainder live in the Americas (14%), Africa (14%), Europe (11%), and Oceania (0.5%).[127]

Within the last century, humans have explored challenging environments such as Antarctica, the

robotic spacecraft.[129][130][131] Since the early 20th century, there has been continuous human presence in Antarctica through research stations and, since 2000, in space through habitation on the International Space Station.[132]

Humans and their domesticated animals represent 96% of all mammalian biomass on earth, whereas all wild mammals represent only 4%.[133]

Estimates of the population at the time agriculture emerged in around 10,000 BC have ranged between 1 million and 15 million.[134][135] Around 50–60 million people lived in the combined eastern and western Roman Empire in the 4th century AD.[136] 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 and North Africa alone.[137] Human population is 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.[138] It passed seven billion in 2011[139] and passed eight billion in November 2022.[140] It took over two million years of human prehistory and history for the human population to reach one billion and only 207 years more to grow to 7 billion.[141] The combined 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.[133]

In 2018, 4.2 billion humans (55%) lived in urban areas, up from 751 million in 1950.

fossil fuels have led to environmental destruction and pollution that significantly contributes to the ongoing mass extinction of other forms of life.[145][146]

Biology

Anatomy and physiology

Diagram of the human skeleton

Most aspects of human physiology are closely

third molars, with some individuals having them congenitally absent.[147]

Humans share with chimpanzees a

smelling, hearing and digesting proteins.[150] 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.[151][152] 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.[153]

It is estimated that the worldwide average

mass of an adult human is 59 kg (130 lb) for females and 77 kg (170 lb) for males.[157][158] Like many other conditions, body weight and body type are influenced by both genetic susceptibility and environment and varies greatly among individuals.[159][160]

Humans have a far faster and more accurate

throw than other animals.[161] Humans are also among the best long-distance runners in the animal kingdom, but slower over short distances.[162][150] Humans' thinner body hair and more productive sweat glands help avoid heat exhaustion while running for long distances.[163] Compared to other apes, the human heart produces greater stroke volume and cardiac output and the aorta is proportionately larger.[164][165]

Genetics

A graphical representation of the standard human karyotype, including both the female (XX) and male (XY) sex chromosomes (bottom right), as well as the mitochondrial genome (shown to scale as "MT" at bottom left).

Like most animals, humans are a

genes and environment on certain traits is not well understood.[167][168]

While no humans – not even

monozygotic twins – are genetically identical,[169] two humans on average will have a genetic similarity of 99.5%-99.9%.[170][171] This makes them more homogeneous than other great apes, including chimpanzees.[172][173] 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.[174][175] The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the genome display directional selection in the past 15,000 years.[176]

The

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.[182][183][184][185]

Life cycle

human embryo
at 5 weeks

Most

sexual intercourse, but can also occur through assisted reproductive technology procedures.[186] The average gestation period is 38 weeks, but a normal pregnancy can vary by up to 37 days.[187] 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.[188] Humans are able to induce early labor or perform a caesarean section if the child needs to be born earlier for medical reasons.[189] In developed countries, infants are typically 3–4 kg (7–9 lb) in weight and 47–53 cm (19–21 in) in height at birth.[190][191] However, low birth weight is common in developing countries, and contributes to the high levels of infant mortality in these regions.[192]

Compared with other species, human childbirth is dangerous, with a much higher risk of complications and death.

maternal death rates approximately 100 times greater than in developed countries.[197]

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.

childhood, adolescence, adulthood and old age.[202] The lengths of these stages have varied across cultures and time periods but is typified by an unusually rapid growth spurt during adolescence.[203] Human females undergo menopause and become infertile at around the age of 50.[204] 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.[205][206]

The life span of an individual depends on two major factors, genetics and lifestyle choices.

centenarians (humans of age 100 or older) worldwide.[214]

Human life stages
Infant boy and girl Boy and girl before puberty (children)
Adolescent
male and female
Adult man and woman
Elderly
man and woman

Diet

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.[217] The human diet is prominently reflected in human culture and has led to the development of food science.[218]

Until the development of agriculture, Homo sapiens employed a hunter-gatherer method as their sole means of food collection.

wild game, which must be hunted and captured in order to be consumed.[219] It has been proposed that humans have used fire to prepare and cook food since the time of Homo erectus.[220] Human domestication of wild plants began about 11,700 years ago, leading to the development of agriculture,[221] a gradual process called the Neolithic Revolution.[222] These dietary changes may also have altered human biology; the spread of dairy farming provided a new and rich source of food, leading to the evolution of the ability to digest lactose in some adults.[223][224] The types of food consumed, and how they are prepared, have varied widely by time, location, and culture.[225][226]

In general, humans can survive for up to eight weeks without food, depending on stored body fat.

developing countries. Worldwide, over one billion people are obese,[232] while in the United States 35% of people are obese, leading to this being described as an "obesity epidemic."[233] Obesity is caused by consuming more calories than are expended, so excessive weight gain is usually caused by an energy-dense diet.[232]

Biological variation

Changes in the number and order of genes (A–D) create genetic diversity within and between population.

There is biological variation in the human species – with traits such as

sleep patterns.[236]

There is evidence that populations have adapted genetically to various external factors. The genes that allow adult humans to

Human hair ranges in color from

Syrian, and an Egyptian, drawing by an unknown artist after a mural of the tomb of Seti I

There is relatively little variation between human geographical populations, and most of the variation that occurs is at the individual level.[243][249][250] Much of human variation is continuous, often with no clear points of demarcation.[251][252][253][254] 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.[255][256][257] Dark-skinned populations that are found in Africa, Australia, and South Asia are not closely related to each other.[258][259]

Genetic research has demonstrated that human populations native to the

Denisovans than is found in Africa,[180] though Neanderthal admixture into African populations may be underestimated.[263] 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 unknown archaic hominin that diverged before the split of Neanderthals and modern humans.[264][265]

Humans are a

longer life span in almost every population around the world.[276] There are intersex conditions in the human population, however these are rare.[277]

Psychology

Drawing of the human brain, showing several important structures

The

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 than other primates, the region of the brain associated with higher cognition.[279] This has led humans to proclaim themselves to be more intelligent than any other known species.[280] Objectively defining intelligence is difficult, with other animals adapting senses and excelling in areas that humans are unable to.[281]

There are some traits that, although not strictly unique, do set humans apart from other animals.[282] Humans may be the only animals who have episodic memory and who can engage in "mental time travel".[283] Even compared with other social animals, humans have an unusually high degree of flexibility in their facial expressions.[284] Humans are the only animals known to cry emotional tears.[285] Humans are one of the few animals able to self-recognize in mirror tests[286] and there is also debate over to what extent humans are the only animals with a theory of mind.[287]

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.[288]

During sleep humans dream, where they experience sensory images and sounds. Dreaming is stimulated by the

self-aware.[292] Dreams can at times make a creative thought occur or give a sense of inspiration.[293]

Consciousness and thought

Human consciousness, at its simplest, is

awareness of awareness', or self-awareness.[300] There might be different levels or orders of consciousness,[301] or different kinds of consciousness, or just one kind with different features.[302]

The process of acquiring knowledge and understanding through thought, experience, and the senses is known as cognition.

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 among population.[308]

Motivation and emotion

Illustration of grief from Charles Darwin's 1872 book The Expression of the Emotions in Man and Animals

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.[309] 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 may also be involved, in which case willpower is also a factor. Ideally, both motivation and volition ensure the selection, striving for, and realization of goals in an optimal manner, a function beginning in childhood and continuing throughout a lifetime in a process known as socialization.[310]

Emotions are

intertwined with mood, temperament, personality, disposition, creativity,[315] and motivation. Emotion has a significant influence on human behavior and their ability to learn.[316] Acting on extreme or uncontrolled emotions can lead to social disorder and crime,[317] with studies showing criminals may have a lower emotional intelligence than normal.[318]

Emotional experiences perceived as pleasant, such as joy, interest or contentment, contrast with those perceived as unpleasant, like anxiety, sadness, anger, and despair.[319] 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 emotional affects, while avoiding the negative ones.[320][321] Others see it as an appraisal of life satisfaction or quality of life.[322] Recent research suggests that being happy might involve experiencing some negative emotions when humans feel they are warranted.[323]

Sexuality and love

familial love
for their children.

For humans, sexuality involves

ethical, and religious aspects of life.[324][325] 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 masturbate more often.[326]

Humans can fall anywhere along a continuous scale of

heterosexual.[328][329] While homosexual behavior occurs in some other animals, only humans and domestic sheep have so far been found to exhibit exclusive preference for same-sex relationships.[328] Most evidence supports nonsocial, biological causes of sexual orientation,[328] as cultures that are very tolerant of homosexuality do not have significantly higher rates of it.[329][330] Research in neuroscience and genetics suggests that other aspects of human sexuality are biologically influenced as well.[331]

Love most commonly refers to a feeling of strong attraction or emotional

pleasure center, leading to side effects such as increased heart rate, loss of appetite and sleep, and an intense feeling of excitement.[333]

Culture

Human society statistics
Most widely spoken languages
Standard Arabic, Bengali, French, Russian, Portuguese, Urdu
Most practiced religions[335][336]Christianity, Islam, Hinduism, Buddhism, folk religions, Sikhism, Judaism, unaffiliated

Humanity's unprecedented set of intellectual skills were a key factor in the species' eventual technological advancement and concomitant domination of the biosphere.

folk physics" required for competent tool design,[340][341] or cook food in the wild.[342] Teaching and learning preserves the cultural and ethnographic identity of human societies.[343] Other traits and behaviors that are mostly unique to humans include starting fires,[344] phoneme structuring[345] and vocal learning.[346]

Language

Principal language families of the world (and in some cases geographic groups of families). For greater detail, see Distribution of languages in the world.

While many species communicate, language is unique to humans, a defining feature of humanity, and a cultural universal.[347] 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.[348][349] Human language also has the capacity of displacement, using words to represent things and happenings that are not presently or locally occurring but reside in the shared imagination of interlocutors.[147]

Language differs from other forms of communication in that it is 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.[350] Language is central to the communication between humans, and to the sense of identity that unites nations, cultures and ethnic groups.[351] There are approximately six thousand different languages currently in use, including sign languages, and many thousands more that are extinct.[352]

The arts