Modern
humans (
Homo sapiens or
Homo sapiens sapiens) are the only
extant members of the
hominin clade, a
branch of
great apes characterized by
erect posture and
bipedal locomotion;
manual dexterity and increased
tool use; and a general trend toward larger, more complex
brains and
societies.
[3][4] Early hominids, such as the
australopithecines whose brains and anatomy are in many ways more similar to non-human apes, are less often thought of or referred to as "human" than hominids of the
genus Homo.
[5] Some of the latter
used fire,
occupied much of Eurasia, and gave rise to
[6][7] anatomically modern Homo sapiens in
Africa about 200,000 years ago. They began to exhibit evidence of
behavioral modernity around 50,000 years ago, and migrated in successive waves to occupy
[8] all but the smallest, driest, and coldest lands. In the last 100 years, this has extended to permanently manned bases
in Antarctica, on
offshore platforms, and
orbiting the Earth. The spread of humans and
their large and increasing population has had a profound
impact on large areas of the environment and millions of native species worldwide. Advantages that explain this evolutionary success include a relatively
larger brain with a particularly well-developed
neocortex,
prefrontal cortex and
temporal lobes, which enable high levels of abstract
reasoning,
language,
problem solving,
sociality, and
culture through social learning. Humans use
tools to a much higher degree than any other animal, are the only extant species known to build
fires and
cook their food, as well as the only extant species to
clothe themselves and create and use numerous other
technologies and
arts.
Humans are uniquely adept at utilizing systems of symbolic communication such as language and art for self-expression, the exchange of ideas, and organization. Humans create complex
social structures composed of many cooperating and competing groups, from
families and
kinship networks to
states.
Social interactions between humans have established an extremely wide variety of values,
[9] social norms, and
rituals, which together form the basis of human society. The human desire to understand and influence their environment, and explain and manipulate phenomena, has been the foundation for the development of
science,
philosophy,
mythology, and
religion. The scientific study of humans is the discipline of
anthropology.
Humans began to practice
sedentary agriculture about 12,000 years ago, domesticating plants and animals, thus allowing for the growth of
civilization. Humans subsequently established various forms of government, religion, and culture around the world, unifying people within a region and leading to the development of states and empires.
The rapid advancement of scientific and medical understanding in the 19th and 20th centuries led to the development of fuel-driven technologies and improved health, causing the human population to rise exponentially. By 2014 the global human
population was estimated to be around 7.2 billion.
[10][11]
Etymology and definition
In common usage, the word "human" generally refers to the only extant species of the genus
Homo — anatomically and behaviorally modern
Homo sapiens. Its usage often designates differences between the species as a whole and any other nature or entity.
In scientific terms, the definition of "human" has changed with the discovery and study of the fossil ancestors of modern humans. The previously clear boundary between human and ape blurred, resulting in "Homo" referring to "human" now encompassing multiple
species. There is also a distinction between
anatomically modern humans and
Archaic Homo sapiens, the earliest fossil members of the species, which are classified as a
subspecies of
Homo sapiens, e.g.
Homo sapiens neanderthalensis.
The English adjective
human is a
Middle English loanword from
Old French humain, ultimately from
Latin hūmānus, the adjective form of
homō "man". The word's use as a noun (with a plural:
humans) dates to the 16th century.
[12] The native English term
man can refer to the species generally (a synonym for
humanity), and could formerly refer to specific individuals of either sex, though this latter use is now obsolete.
[13] Generic uses of the term "man" are declining, in favor of reserving it for referring specifically to adult males. The word is from
Proto-Germanic mannaz, from a
Proto-Indo-European (PIE) root
man-.
The species
binomial Homo sapiens was coined by
Carl Linnaeus in his 18th century work
Systema Naturae, and he himself is the
lectotype specimen.
[14] The
generic name Homo is a learned 18th century derivation from Latin
homō "man", ultimately "earthly being" (
Old Latin hemō, a
cognate to Old English
guma "man", from
PIE dʰǵʰemon-, meaning "earth" or "ground").
[15] The species-name
sapiens means "wise" or "sapient". Note that the Latin word
homo refers to humans of either gender, and that
sapiens is the singular form (while there is no word
sapien).
History
Evolution and range
The genus
Homo diverged from other
hominins in Africa, after the human clade split from the
chimpanzee lineage of the
hominids (great ape) branch of the
primates. Modern humans, defined as the species
Homo sapiens or specifically to the single extant
subspecies Homo sapiens sapiens, proceeded to colonize all the continents and larger islands, arriving in
Eurasia 125,000–60,000 years ago,
[16][17] Australia around 40,000 years ago, the
Americas around 15,000 years ago, and remote islands such as
Hawaii,
Easter Island,
Madagascar, and
New Zealand between the years 300 and 1280.
[18][19]
Evidence from molecular biology
The closest living relatives of humans are chimpanzees (genus
Pan) and gorillas (genus
Gorilla).
[20] With the
sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA
sequences range between 95% and 99%.
[20][21][22] By using the technique called a
molecular clock which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated. The gibbons (
Hylobatidae) and
orangutans (genus
Pongo) were the first groups to split from the
line leading to the humans, then
gorillas (genus
Gorilla) followed by the
chimpanzees (genus
Pan). The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late
Miocene epoch.
[23][24][25]
Evidence from the fossil record
There is little fossil evidence for the divergence of the gorilla, chimpanzee and hominin lineages.
[26][27] The earliest fossils that have been proposed as members of the hominin lineage are
Sahelanthropus tchadensis dating from
7 million years ago, and
Orrorin tugenensis dating from
5.7 million years ago and
Ardipithecus kadabba dating to
5.6 million years ago. Each of these has been argued to be a
bipedal ancestor of later hominins, but in each case the claims have been contested. It is also possible that either of these species is an ancestor of another branch of African apes, or that they represent a shared ancestor between hominins and other Hominoidea. The question of the relation between these early fossil species and the hominin lineage is still to be resolved. From these early species the
australopithecines arose around
4 million years ago, and diverged into
robust (also called
Paranthropus) and
gracile branches, one of which (possibly
A. garhi) went on to become ancestors of the genus
Homo.
The earliest members of the genus
Homo are
Homo habilis which evolved around
2.8 million years ago.
[28] Homo habilis is the first species for which there is clear evidence of the use of
stone tools. The brains of these early hominins were about the same size as that of a chimpanzee, and their main adaptation was bipedalism as an adaptation to terrestrial living. During the next million years a process of
encephalization began, and with the arrival of
Homo erectus in the fossil record, cranial capacity had doubled.
Homo erectus were the first of the hominina to leave Africa, and these species spread through Africa, Asia, and Europe between
1.3 to 1.8 million years ago. One population of
H. erectus, also sometimes classified as a separate species
Homo ergaster, stayed in Africa and evolved into
Homo sapiens. It is believed that these species were the first to use fire and complex tools. The earliest transitional fossils between
H. ergaster/erectus and
archaic humans are from Africa such as
Homo rhodesiensis, but seemingly transitional forms are also found at
Dmanisi,
Georgia. These descendants of African
H. erectus spread through Eurasia from ca. 500,000 years ago evolving into
H. antecessor,
H. heidelbergensis and
H. neanderthalensis. The earliest fossils of
anatomically modern humans are from the
Middle Paleolithic, about 200,000 years ago such as the
Omo remains of Ethiopia and the fossils of Herto sometimes classified as
Homo sapiens idaltu.
[29] Later fossils of archaic
Homo sapiens from
Skhul in Israel and Southern Europe begin around 90,000 years ago.
[30]
Anatomical adaptations
Reconstruction of
Homo habilis, the earliest known species of the genus
Homo and the first human ancestor to use stone tools
Human evolution is characterized by a number of
morphological,
developmental,
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 1. bipedalism, 2. increased brain size, 3. lengthened
ontogeny (gestation and infancy), 4. decreased
sexual dimorphism. The relationship between all these changes is the subject of ongoing debate.
[31] Other significant morphological changes included the evolution of a
power and precision grip, a change first occurring in
H. erectus.
[32]
Bipedalism is the basic adaption of the hominin line, and it is considered the main cause behind a suite of
skeletal changes shared by all bipedal hominins. The earliest bipedal
hominin is considered to be either
Sahelanthropus[33] or
Orrorin, with
Ardipithecus, a full bipedal, coming somewhat later. The knuckle walkers, the
gorilla and
chimpanzee, diverged around the same time, and either
Sahelanthropus or
Orrorin may be humans' last shared ancestor with those animals. The early bipedals eventually evolved into the
australopithecines and later the genus
Homo. There are several theories of the adaptational value of bipedalism. It is possible that bipedalism was favored because it freed up the hands for reaching and carrying food, because it saved energy during locomotion, because it enabled long distance running and hunting, or as a strategy for avoiding hyperthermia by reducing the surface exposed to direct sun.
The human species developed a much larger brain than that of other primates – typically 1,330
cc in modern humans, over twice the size of that of a chimpanzee or gorilla.
[34] The pattern of
encephalization started with
Homo habilis which at approximately 600 cc had a brain slightly larger than chimpanzees, and continued with
Homo erectus (800–1100 cc), and reached a maximum in Neanderthals with an average size of 1200-1900cc, larger even than
Homo sapiens (but less
encephalized).
[35] The pattern of human postnatal
brain growth differs from that of other apes (
heterochrony), and allows for extended periods of
social learning and
language acquisition in juvenile
humans. However, the differences between the structure of
human brains and those of other apes may be even more significant than differences in size.
[36][37][38][39] The increase in volume over time has affected different areas within the brain unequally – the
temporal lobes, which contain centers for language processing have increased disproportionately, as has the
prefrontal cortex which has been related to complex decision making and moderating social behavior.
[34] Encephalization has been tied to an increasing emphasis on meat in the diet,
[40][41] or with the development of cooking,
[42] and it has been proposed that intelligence increased as a response to an increased necessity for
solving social problems as human society became more complex.
The reduced degree of sexual dimorphism is primarily visible in the reduction of the male
canine tooth relative to other ape species (except
gibbons). Another important physiological change related to sexuality in humans was the evolution of
hidden estrus. Humans are the only ape in which the female is fertile year round, and in which no special signals of fertility are produced by the body (such as
genital swelling during estrus). Nonetheless humans retain a degree of sexual dimorphism in the distribution of body hair and subcutaneous fat, and in the overall size, males being around 25% larger than females. These changes taken together have been interpreted as a result of an increased emphasis on
pair bonding as a possible solution to the requirement for increased parental investment due to the prolonged infancy of offspring.
Rise of Homo sapiens
By the beginning of the
Upper Paleolithic period (50,000
BP), full
behavioral modernity, including
language,
music and other
cultural universals had developed.
[43][44] As modern humans spread out from Africa they encountered other hominids such as
Homo neanderthalensis and the so-called
Denisovans. The nature of interaction between early humans and these sister species has been a long-standing source of controversy, the question being whether humans replaced these earlier species or whether they were in fact similar enough to interbreed, in which case these earlier populations may have contributed genetic material to modern humans.
[45] Recent studies of the human and Neanderthal genomes suggest
gene flow between archaic
Homo sapiens and Neanderthals and Denisovans.
[46][47][48]
This dispersal
out of Africa is estimated to have begun about 70,000 years BP from northeast Africa. Current evidence suggests that there was only one such dispersal and that it only involved a few hundred individuals. The vast majority of humans stayed in Africa and adapted to a diverse array of environments.
[49] Modern humans subsequently spread globally, replacing earlier hominins (either through competition or
hybridization). They inhabited
Eurasia and
Oceania by 40,000 years BP, and the Americas at least 14,500 years BP.
[50][51]
Transition to civilization
Until c. 10,000 years ago, humans lived as
hunter-gatherers. They generally lived in small nomadic groups known as
band societies. The advent of agriculture prompted the
Neolithic Revolution, when access to food surplus led to the formation of permanent
human settlements, the
domestication of animals and the
use of metal tools for the first time in history. Agriculture encouraged
trade and cooperation, and led to complex society. Because of the significance of this date for human society, it is the epoch of the
Holocene calendar or Human Era.
[citation needed]
About 6,000 years ago, the first proto-states developed in
Mesopotamia,
Egypt's
Nile Valley and the
Indus Valley. Military forces were formed for protection, and government bureaucracies for administration. States cooperated and competed for resources, in some cases waging wars. Around 2,000–3,000 years ago, some states, such as
Persia,
India,
China,
Rome, and
Greece, developed through conquest into the first expansive
empires.
Ancient Greece was the seminal civilization that laid the foundations of
Western culture, being the birthplace of Western
philosophy,
democracy, major scientific and mathematical advances, the
Olympic Games,
Western literature and
historiography, as well as Western
drama, including both
tragedy and
comedy.
[52] Influential religions, such as
Judaism, originating in
West Asia, and
Hinduism, originating in South Asia, also rose to prominence at this time.
The late
Middle Ages saw the rise of revolutionary ideas and technologies. In China, an advanced and urbanized society promoted innovations and sciences, such as
printing and
seed drilling. In India, major advancements were made in mathematics, philosophy, religion and
metallurgy. The
Islamic Golden Age saw advancements in mathematics and astronomy in Muslim empires.
[53] In Europe, the rediscovery of
classical learning and inventions such as the
printing press led to the
Renaissance in the 14th and 15th centuries. Over the next 500 years,
exploration and
colonialism brought great parts of the world under European control, leading to later struggles for independence. The
Scientific Revolution in the 17th century and the
Industrial Revolution in the 18th–19th centuries promoted major innovations in transport, such as the railway and automobile;
energy development, such as coal and electricity; and government, such as
representative democracy and
Communism.
With the advent of the
Information Age at the end of the 20th century, modern humans live in a world that has become increasingly
globalized and interconnected. As of 2010, almost 2 billion humans are able to communicate with each other via the
Internet,
[54] and 3.3 billion by
mobile phone subscriptions.
[55]
Although interconnection between humans has encouraged the growth of
science,
art,
discussion, and
technology, it has also led to culture clashes and the development and use of
weapons of mass destruction. Human civilization has led to
environmental destruction and
pollution significantly contributing to the ongoing
mass extinction of other forms of life called the
Holocene extinction event,
[56] which may be further accelerated by
global warming in the future.
[57]
Habitat and population
The
Earth, as seen from
space in October 2000, showing the extent of human occupation of the planet. The bright lights signify both the most densely inhabited areas and ones financially capable of illuminating those areas.
Early human settlements were dependent on proximity to
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. But humans have a great capacity for altering their
habitats by means of technology, through
irrigation,
urban planning,
construction,
transport,
manufacturing goods,
deforestation and
desertification.
Deliberate habitat alteration is often done with the goals of increasing material
wealth, increasing
thermal comfort, improving the amount of food available, improving
aesthetics, or improving ease of access to resources or other human settlements. With the advent of large-scale trade and
transport infrastructure, proximity to these resources has become unnecessary, and in many places, these factors are no longer a driving force behind the growth and decline of a population. Nonetheless, the manner in which a habitat is altered is often a major determinant in population change.
Technology has allowed humans to colonize all of the continents and adapt to virtually all climates. Within the last century, humans have explored
Antarctica, the ocean depths, and
outer space, although large-scale colonization of these environments is not yet feasible. With a population of over seven billion, humans are among the most numerous of the large mammals. Most humans (61%) live in Asia. The remainder live in the Americas (14%), Africa (14%), Europe (11%), and Oceania (0.5%).
[citation needed]
Human habitation within
closed ecological systems in hostile environments, such as Antarctica and outer space, is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with no more than thirteen humans in space at any given time.
[58] Between 1969 and 1972, two humans at a time spent brief intervals on the
Moon. As of March 2015, no other celestial body has been visited by humans, although there has been a continuous human presence in space since the launch of the initial crew to inhabit the
International Space Station on October 31, 2000.
[59] However, other celestial bodies have been visited by human-made objects.
Since 1800, the
human population has increased from one billion
[60] to over seven billion,
[61] In 2004, some 2.5 billion out of 6.3 billion people (39.7%) lived in
urban areas. In February 2008, the U.N. estimated that half the world's population would live in
urban areas by the end of the year.
[62] Problems for humans living in
cities include various forms of pollution and
crime,
[63] especially in inner city and suburban
slums. Both overall population numbers and the proportion residing in cities are expected to increase significantly in the coming decades.
[64]
Humans have had a dramatic effect on the
environment. Humans are
apex predators, being rarely preyed upon by other species.
[65] Currently, through land development, combustion of
fossil fuels, and pollution, humans are thought to be the main contributor to global
climate change.
[66] If this continues at its current rate it is predicted that climate change will wipe out half of all plant and animal species over the next century.
[67][68]
Biology
Vitruvian Man,
Leonardo da Vinci's image is often used as an implied symbol of the essential symmetry of the human body, and by extension, of the universe as a whole.
Anatomy and physiology
Most aspects of human physiology are closely
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 (10
14)
cells. The most commonly defined
body systems in humans are the
nervous, the
cardiovascular, the
circulatory, the
digestive, the
endocrine, the
immune, the
integumentary, the
lymphatic, the
muscoskeletal, the
reproductive, the
respiratory, and the
urinary system.
[69][70]
Humans, like most of the other
apes, lack external
tails, have several
blood type systems, have
opposable thumbs, and are
sexually dimorphic. The comparatively minor anatomical differences between humans and
chimpanzees are a result of human
bipedalism. As a result, humans are slower over short distances, but are among the best long-distance runners in the animal kingdom.
[71][72] Humans' thinner body hair and more productive
sweat glands help avoid
heat exhaustion while running for long distances.
[73]
As a consequence of bipedalism, human females have narrower
birth canals. The construction of the
human pelvis differs from other
primates, as do the
toes. A trade-off for these advantages of the modern human pelvis is that
childbirth is more difficult and dangerous than in most
mammals, especially given the larger head size of human
babies compared to other primates. This means that human babies must turn around as they pass through the birth canal, which other primates do not do, and it makes humans the only species where females require help from their conspecifics
[clarification needed] to reduce the risks of birthing. As a partial
evolutionary solution, human fetuses are born less developed and more vulnerable. Chimpanzee babies are cognitively more developed than human babies until the age of six months, when the rapid development of human brains surpasses chimpanzees. Another difference between women and chimpanzee females is that women go through the
menopause and become
unfertile decades before the end of their lives. All species of non-human apes are capable of giving birth until
death. Menopause probably developed as it has provided an evolutionary advantage (more caring time) to young relatives.
[72]
Apart from bipedalism, humans differ from chimpanzees mostly in
smelling,
hearing,
digesting proteins,
brain size, and the ability of
language. Humans
brains are about three times bigger than in chimpanzees. More importantly, the brain to body ratio is much higher in humans than in chimpanzees, and humans have a significantly more developed
cerebral cortex, with a larger number of
neurons. The mental abilities of humans are remarkable compared to other apes. Humans' ability of
speech is unique among primates. Humans are able to create new and complex
ideas, and to develop
technology, which is unprecedented among other
organisms on
Earth.
[72]
It is estimated that the worldwide average height for an adult human male is about 172 cm, while the worldwide average height for adult human females is about 158 cm.
[74] Shrinkage of stature may begin in middle age in some individuals, but tends to be universal
[clarification needed] in the extremely
aged.
[75] Through history human populations have universally become taller, probably as a consequence of better
nutrition,
healthcare, and living conditions.
[76]
The average
mass of an adult human is 54–64 kg (120–140 lbs) for females and 76–83 kg (168–183 lbs) for males.
[77] Like many other conditions, body weight and body type is influenced by both genetic susceptibility and environment and varies greatly among individuals. (see
obesity)
[78][79]
Although humans appear hairless compared to other primates, with notable
hair growth occurring chiefly on the top of the head, underarms and pubic area, the average human has more
hair follicles on his or her body than the average chimpanzee. The main distinction is that human hairs are shorter, finer, and less heavily pigmented than the average chimpanzee's, thus making them harder to see.
[80] 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.
[81]
The
dental formula of humans is:
2.1.2.32.1.2.3. Humans have proportionately shorter
palates and much smaller
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, with some individuals having them congenitally absent.
[82]
Genetics
A graphical representation of the ideal human
karyotype, including both the male and female variant of the sex chromosome (number 23).
Like all mammals, humans are a
diploid 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 chromosomes. Like other mammals, humans have an
XY sex-determination system, so that
females have the sex chromosomes XX and
males have XY.
One
human genome was sequenced in full in 2003, and currently efforts are being made to achieve a sample of the genetic diversity of the species (see
International HapMap Project). By present estimates, humans have approximately 22,000 genes.
[83] The variation in human DNA is very small compared to other species, possibly suggesting 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.
[84][85] Nucleotide diversity is based on single mutations called
single nucleotide polymorphisms (SNPs). The nucleotide diversity between humans is about 0.1%, i.e. 1 difference per 1,000
base pairs.
[86][87] A difference of 1 in 1,000
nucleotides between two humans chosen at random amounts to about 3 million nucleotide differences, since the human genome has about 3 billion nucleotides. Most of these
single nucleotide polymorphisms (SNPs) are
neutral but some (about 3 to 5%) are functional and influence
phenotypic differences between humans through
alleles.
By comparing the parts of the genome that are not under natural selection and which therefore accumulate mutations at a fairly steady rate, it is possible to reconstruct a genetic tree incorporating the entire human species since the last shared ancestor. Each time a certain mutation (SNP) appears in an individual and is passed on to his or her descendants, a
haplogroup is formed including all of the descendants of the individual who will also carry that mutation. By comparing
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 200,000 years ago.
Human accelerated regions, first described in August 2006,
[88][89] are a set of 49 segments of the
human genome that are conserved throughout
vertebrate evolution but are strikingly different in humans. They are named according to their degree of difference between humans and their nearest animal relative (
chimpanzees) (HAR1 showing the largest degree of human-chimpanzee differences). Found by scanning through genomic databases of multiple species, some of these highly
mutated areas may contribute to human-specific traits.
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.
[90]
Life cycle
As with other mammals,
human reproduction takes place as
internal fertilization by
sexual intercourse. During this process, the male inserts his
erect penis into the female's
vagina and
ejaculates semen, which contains sperm. The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for
fertilization of the ovum. Upon fertilization and
implantation, gestation then occurs within the female's
uterus.
The
zygote divides inside the female's uterus to become an
embryo, which over a period of 38 weeks (9 months) of
gestation becomes a
fetus. After this span of time, the fully grown fetus is
birthed from the woman's body and breathes independently as an infant for the first time. At this point, most modern cultures recognize the baby as a person entitled to the full protection of the law, though some jurisdictions extend various levels of
personhood earlier to human fetuses while they remain in the uterus.
Compared with other species, human childbirth is dangerous. Painful labors lasting 24 hours or more are not uncommon and sometimes lead to the death of the mother, the child or both.
[91] This is because of both the relatively large fetal head circumference and the mother's relatively narrow
pelvis.
[92][93] 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.
[94]
In developed countries, infants are typically 3–4 kg (6–9 pounds) in weight and 50–60 cm (20–24 inches) in height at birth.
[95][not in citation given] However, low
birth weight is common in developing countries, and contributes to the high levels of
infant mortality in these regions.
[96] Helpless at birth, humans continue to grow for some years, typically reaching
sexual maturity at 12 to 15 years of age. Females continue to develop physically until around the age of 18, whereas male development continues until around age 21. The
human life span can be split into a number of stages: infancy,
childhood,
adolescence,
young adulthood,
adulthood and
old age. The lengths of these stages, however, have varied across cultures and time periods. Compared to other primates, humans experience an unusually rapid growth spurt during adolescence, where the body grows 25% in size. Chimpanzees, for example, grow only 14%, with no pronounced spurt.
[97] The presence of the growth spurt is probably necessary to keep children physically small until they are psychologically mature. Humans are one of the few species in which females undergo
menopause. 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/or their children (the
grandmother hypothesis), rather than by continuing to bear children into old age.
[98][99]
For various reasons, including biological/genetic causes,
[100] women live on average about four years longer than men — as of 2013 the global average
life expectancy at birth of a girl is estimated at 70.2 years compared to 66.1 for a boy.
[101] There are significant geographical variations in human life expectancy, mostly correlated with economic development — for example life expectancy at birth in
Hong Kong is 84.8 years for girls and 78.9 for boys, while in
Swaziland, primarily because of
AIDS, it is 31.3 years for both sexes.
[102] The developed world is generally aging, with the median age around 40 years. In the
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.
[103] The number of
centenarians (humans of age 100 years or older) in the world was estimated by the
United Nations at 210,000 in 2002.
[104] At least one person,
Jeanne Calment, is known to have reached the age of 122 years;
[105] higher ages have been claimed but they are not well substantiated.
Diet
Humans are
omnivorous, capable of consuming a wide variety of plant and animal material.
[106][107] Varying with available food sources in regions of habitation, and also varying with cultural and religious norms, human groups have adopted a range of diets, from purely
vegetarian 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.
[108] 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
wild game, which must be hunted and killed in order to be consumed.
[109] It has been proposed that humans have used fire to prepare and
cook food since the time of
Homo erectus.
[110] Around ten thousand years ago,
humans developed agriculture,
[111] 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.
[112][113] Agriculture led to increased populations, the development of cities, and because of increased population density, the wider spread of
infectious diseases. The types of food consumed, and the way in which they are prepared, has varied widely by time, location, and culture.
In general, humans can survive for two to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days. About 36 million humans die every year from causes directly or indirectly related to hunger.
[114] Childhood malnutrition is also common and contributes to the
global burden of disease.
[115] However global food distribution is not even, and
obesity among some human populations has increased rapidly, leading to health complications and increased mortality in some
developed, and a few
developing countries. Worldwide over one billion people are obese,
[116] while in the United States 35% of people are obese, leading to this being described as an "
obesity epidemic".
[117] Obesity is caused by consuming more
calories than are expended, so excessive weight gain is usually caused by a combination of an energy-dense high fat diet and insufficient
exercise.
[116]
Biological variation
People in warm climates are often relatively slender, tall and dark skinned, such as these
Maasai men from
Kenya.
People in cold climates tend to be relatively short, heavily built and fair skinned such as these
Inuit women from
Canada.
Young Russian peasant women in front of traditional wooden house, in a rural area along the Sheksna River near the small town of Kirillov. Early color photograph from Russia, created by Sergei Mikhailovich Prokudin-Gorskii as part of his work to document the Russian Empire from 1909 to 1915.
No two humans – not even
monozygotic twins – are genetically identical.
Genes and
environment influence human biological variation from visible characteristics to physiology to disease susceptibly to mental abilities. The exact influence of
genes and environment on certain traits is not well understood.
[118][119]
Most current
genetic and
archaeological evidence supports a recent single
origin of modern humans in
East Africa,
[120] with first migrations placed at 60,000 years ago. Compared to the
great apes,
human gene sequences – even among
African populations – are
remarkably homogeneous.
[121] On average, genetic similarity between any two humans is 99.9%.
[122][123] There is about 2–3 times more genetic diversity within the wild chimpanzee population on a single hillside in
Gombe, than in the entire
human gene pool.
[124][125][126][127]
The human body's ability to
adapt to different environmental stresses is remarkable, allowing humans to acclimatize to a wide variety of
temperatures,
humidity, and
altitudes. As a result, humans are a cosmopolitan species found in almost all regions of the world, including
tropical rainforests,
arid desert, extremely cold
arctic regions, and heavily polluted
cities. Most other species are confined to a few geographical areas by their limited adaptability.
[128]
There is biological variation in the human species — with traits such as
blood type,
cranial features,
eye color,
hair color and type,
height and
build, and
skin color varying across the globe. Human body types vary substantially. The typical height of an adult human is between 1.4 m (4 ft 7 in) to 1.9 m (6 ft 3 in), although this varies significantly depending, among other things, on
sex and
ethnic origin.
[129][130] Body size is partly determined by genes and is also significantly influenced by environmental factors such as
diet,
exercise, and
sleep patterns, especially as an influence in
childhood. Adult height for each sex in a particular ethnic group approximately follows a
normal distribution. Those aspects of genetic variation that give clues to human evolutionary history, or are relevant to medical research, have received particular attention. For example the genes that allow adult humans to
digest lactose are present in high frequencies in populations that have long histories of cattle domestication, suggesting natural selection having favored that gene in populations that depend on
cow milk. Some hereditary diseases such as
sickle cell anemia are frequent in populations where
malaria has been endemic throughout history — it is believed that the same gene gives increased resistance to malaria among those who are unaffected carriers of the gene.
Similarly, populations that have for a long time inhabited specific climates, such as arctic or tropical regions or high altitudes, tend to have developed specific phenotypes that are beneficial for conserving energy in those environments —
short stature and stocky build in cold regions, tall and lanky in hot regions, and with high lung capacities at high altitudes. Similarly, skin color varies
clinally with darker skin around the equator — where the added protection from the sun's ultraviolet radiation is thought to give an evolutionary advantage — and lighter skin tones closer to the poles.
[131][132][133][134]
The hue of human skin and hair is determined by the presence of
pigments called
melanins. Human skin color can range from
darkest brown to
lightest peach, or even nearly white or colorless in cases of
albinism.
[127] Human hair ranges in color from
white to
red to
blond to
brown to
black, which is most frequent.
[135] Hair color depends on the amount of melanin (an effective sun blocking pigment) in the
skin and hair, with hair melanin concentrations in hair fading with increased age, leading to
grey or even white hair. Most researchers believe that skin darkening is an adaptation that evolved as protection against ultraviolet solar radiation, which also helps balancing
folate, which is destroyed by
ultraviolet radiation. Light skin pigmentation protects against depletion of
vitamin D, which requires
sunlight to make.
[136] Skin pigmentation of contemporary humans is clinally distributed across the planet, and in general correlates with the level of ultraviolet radiation in a particular geographic area. Human skin also has a capacity to darken (tan) in response to exposure to ultraviolet radiation.
[137][138][139]
Structure of variation
The ancestors of
Native Americans, such as this
Yanomami woman, crossed into the Americas from Northeast Asia, and genetic and linguistic evidence links them to North Asian populations, particularly those of
East Siberia.
[140]
An older adult human male Caucasoid in Paris - playing chess at the Jardins du Luxembourg.
Within the human species, the greatest degree of genetic
variation exists between males and females. While the
nucleotide genetic variation of individuals of the same sex across global populations is no greater than 0.1%, the genetic difference between
males and
females is between 1% and 2%. Although different in nature
[clarification needed], this approaches the genetic differentiation between men and male chimpanzees or women and female chimpanzees.
The genetic difference between sexes contributes to anatomical, hormonal, neural, and physiological differences between men and women, although the exact degree and nature of social and environmental influences on sexes are not completely understood. Males on average are 15% heavier and 15 cm taller than females. There is a difference between body types, body organs and systems, hormonal levels, sensory systems, and muscle mass between sexes. On average, there is a difference of about 40–50% in upper body strength and 20–30% in lower body strength between men and women. Women generally have a higher
body fat percentage than men. Women have
lighter skin than men of the same population; this has been explained by a higher need for vitamin D (which is synthesized by sunlight) in females during
pregnancy and
lactation. As there are chromosomal differences between females and males, some X and Y chromosome related conditions and
disorders only affect either men or women. Other conditional differences between males and females are not related to sex chromosomes. Even after allowing for body weight and volume, the male
voice is usually an
octave deeper than females'. Women have a
longer life span in almost every population around the world.
[141][142][143][144][145][146][147][148][149]
Males typically have larger
tracheae and branching
bronchi, with about 30% greater
lung volume per unit
body mass. They have larger
hearts, 10% higher
red blood cell count, and higher
hemoglobin, hence greater oxygen-carrying capacity. They also have higher circulating
clotting factors (
vitamin K, pro
thrombin and
platelets). These differences lead to faster healing of
wounds and higher peripheral pain tolerance.
[150] Females typically have more
white blood cells (stored and circulating), more
granulocytes and B and T
lymphocytes. Additionally, they produce more
antibodies at a faster rate than males. Hence they develop fewer
infectious diseases and these continue for shorter periods.
[150] Ethologists argue that females, interacting with other females and multiple offspring in social groups, have experienced such traits as a
selective advantage.
[151][152][153][154][155] According to Daly and Wilson, "The sexes differ more in human beings than in
monogamous mammals, but much less than in extremely
polygamous mammals."
[156] But given that
sexual dimorphism in the closest relatives of humans is much greater than among humans, the human clade must be considered to be characterized by decreasing sexual dimorphism, probably due to less competitive mating patterns. One proposed explanation is that human sexuality has developed more in common with its close relative the
bonobo, which exhibits similar sexual dimorphism, is
polygynandrous and uses
recreational sex to reinforce social bonds and reduce aggression.
[157]
Humans of the same sex are 99.9% genetically identical. There is extremely little variation between human geographical populations, and most of the variation that does occur is at the personal level within local areas, and not between populations.
[127][158][159] Of the 0.1% of human genetic differentiation, 85% exists within any randomly chosen local population, be they Italians, Koreans, or Kurds. Two randomly chosen Koreans may be genetically as different as a Korean and an Italian. Any ethnic group contains 85% of the human genetic diversity of the world. Genetic data shows that no matter how population groups are defined, two people from the same population group are about as different from each other as two people from any two different population groups.
[127][160][161][162]
Most of the world's genetic diversity is represented in Africa.
Current genetic research have demonstrated that humans on the
African continent are the most genetically diverse.
[163] There is more human genetic diversity in Africa than anywhere else on Earth. The genetic structure of Africans was traced to 14 ancestral population clusters. Human genetic diversity decreases in native populations with migratory distance from Africa and this is thought to be the result of
bottlenecks during human migration.
[164][165] Humans have lived in Africa for the longest time, which has allowed accumulation of a higher diversity of genetic mutations in these populations. Only part of Africa's population migrated out of the continent, bringing just part of the original African genetic variety with them. African populations harbor genetic alleles that are not found in other places of the world. All the common alleles found in populations outside of Africa are found on the African continent.
[127]
Geographical distribution of human variation is complex and constantly shifts through time which reflects complicated human evolutionary history. Most human biological variation is
clinally distributed and blends gradually from an area to the next. Groups of people around the world have different frequencies of
polymorphic genes. Furthermore, different traits are non-concordant and each have different clinal distribution. Adaptability varies both from person to person and from population to population. The most efficient adaptive responses are found in geographical populations where the environmental stimuli are the strongest (e.g.
Tibetans are highly adapted to high altitudes). The clinal geographic genetic variation is further complicated by the migration and mixing between human populations which has been occurring since prehistoric times.
[127][166][167][168][169][170]
Human variation is highly non-concordant: most of the genes do not cluster together and are not inherited together. Skin and hair color are not correlated to height, weight, or athletic ability. Human species do not share the same patterns of variation through geography. Skin color varies with latitude and certain people are tall or have brown hair. There is a statistical correlation between particular features in a population, but different features are not expressed or inherited together. Thus, genes which code for superficial physical traits – such as skin color, hair color, or height – represent a minuscule and insignificant portion of the human genome and do not correlate with genetic affinity. Dark-skinned populations that are found in Africa, Australia, and South Asia are not closely related to each other.
[134][139][169][170][171][172] Even within the same region, physical phenotype is not related to genetic affinity: dark-skinned
Ethiopians are more closely related to light-skinned
Armenians than to dark-skinned
Bantu populations.
[173] Despite
pygmy populations of
South East Asia (
Andamanese) having similar physical features with African pygmy populations such as short stature, dark skin, and curly hair, they are not genetically closely related to these populations.
[174] Genetic variants affecting superficial anatomical features (such as skin color) – from a genetic perspective, are essentially meaningless – they involve a few hundred of the billions of nucleotides in a person's DNA.
[175] Individuals with the same morphology do not necessarily cluster with each other by lineage, and a given lineage does not include only individuals with the same trait complex.
[127][161][176]
Due to practices of group
endogamy, allele frequencies cluster locally around kin groups and lineages, or by national, ethnic, cultural and linguistic boundaries, giving a detailed degree of correlation between genetic clusters and population groups when considering many alleles simultaneously. Despite this, there are no genetic boundaries around local populations that biologically mark off any
discrete groups of humans. Human variation is continuous, with no clear points of demarcation. There are no large clusters of relatively homogeneous people and almost every individual has genetic alleles from several ancestral groups.
[127][168][169][177][178][179][180][181][182][183][184][185]
Psychology
Drawing of the
human brain, showing several important structures
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 activities such as
respiration and
digestion, it is also the locus of "higher" order functioning such as
thought,
reasoning, and
abstraction.
[186] These
cognitive processes constitute the
mind, and, along with their
behavioral consequences, are studied in the field of
psychology.
Generally regarded as more capable of these higher order activities, the human brain is believed to be more "intelligent" in general than that of any other known species. While some non-human species are capable of creating structures and
using simple tools—mostly through instinct and mimicry—human technology is vastly more complex, and is constantly evolving and improving through time.
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.
[187] During sleep humans dream. In dreaming humans experience sensory images and sounds, in a sequence which the dreamer usually perceives more as an apparent participant than as an observer. Dreaming is stimulated by the
pons and mostly occurs during the
REM phase of sleep.
Consciousness and thought
Humans are one of the relatively few species to have sufficient self-awareness
to recognize themselves in a mirror.
[188] Already at 18 months, most human children are aware that the mirror image is not another person.
[189]
Lecture at the Faculty of Biomedical Engineering,
CTU, in Prague.
The human brain
perceives the external world through the
senses, and each individual human is influenced greatly by his or her experiences, leading to
subjective views of
existence and the passage of time. Humans are variously said to possess consciousness,
self-awareness, and a mind, which correspond roughly to the mental processes of
thought. These are said to possess qualities such as self-awareness,
sentience,
sapience, and the ability to perceive the relationship between
oneself and one's
environment. The extent to which the mind constructs or experiences the outer world is a matter of debate, as are the definitions and validity of many of the terms used above.
The physical aspects of the mind and brain, and by extension of the nervous system, are studied in the field of
neurology, the more behavioral in the field of psychology, and a sometimes loosely defined area between in the field of psychiatry, which treats mental illness and behavioral disorders. Psychology does not necessarily refer to the brain or nervous system, and can be framed purely in terms of
phenomenological or
information processing theories of the mind. Increasingly, however, an understanding of brain functions is being included in psychological theory and practice, particularly in areas such as
artificial intelligence,
neuropsychology, and
cognitive neuroscience.
The nature of thought is central to psychology and related fields.
Cognitive psychology studies
cognition, the
mental processes' underlying behavior. It uses
information processing as a framework for understanding the mind. Perception, learning, problem solving, memory, attention, language and emotion are all well researched areas as well. Cognitive psychology is associated with a school of thought known as
cognitivism, whose adherents argue for an
information processing model of mental function, informed by
positivism and
experimental psychology. Techniques and models from cognitive psychology are widely applied and form the mainstay of psychological theories in many areas of both research and applied psychology. 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.
Some philosophers divide consciousness into phenomenal consciousness, which is experience itself, and access consciousness, which is the processing of the things in experience.
[190] Phenomenal consciousness is the state of being conscious, such as when they say "I am conscious." Access consciousness is being conscious
of something in relation to abstract concepts, such as when one says "I am conscious of these words." Various forms of access consciousness include awareness, self-awareness, conscience,
stream of consciousness,
Husserl's phenomenology, and
intentionality. The concept of phenomenal consciousness, in modern history, according to some, is closely related to the concept of
qualia.
Social psychology links sociology with psychology in their shared study of the nature and causes of human social interaction, with an emphasis on how people think towards each other and how they relate to each other. The behavior and mental processes, both human and non-human, can be described through
animal cognition,
ethology,
evolutionary psychology, and
comparative psychology as well.
Human ecology is an
academic discipline that investigates how humans and human
societies interact with both their natural environment and the human
social environment.
Motivation and emotion
Motivation is the driving force of desire behind all deliberate
actions of humans. Motivation is based on emotion—specifically, on the search for
satisfaction (positive emotional experiences), and the avoidance of conflict. Positive and negative is defined by the individual brain state, which may be influenced by
social norms: a person may be driven to
self-injury or
violence because their
brain is conditioned to create a positive response to these actions. Motivation is important because it is involved in the performance of all learned responses. Within
psychology,
conflict avoidance and the
libido are seen to be primary motivators. Within
economics, motivation is often seen to be based on
incentives; these may be
financial,
moral, or
coercive.
Religions generally posit divine or
demonic influences.
Happiness, or the state of being happy, is a human emotional condition. The definition of happiness is a common
philosophical topic. Some people might define it as the best condition that a human can have—a condition of
mental and physical
health. Others define it as
freedom from want and
distress; consciousness of the
good order of things; assurance of one's place in the
universe or
society.
Emotion has a significant influence on, or can even be said to control, human behavior, though historically many
cultures and
philosophers have for various reasons discouraged allowing this influence to go unchecked. Emotional experiences perceived as
pleasant, such as
love, admiration, or joy, contrast with those perceived as
unpleasant, like
hate,
envy, or
sorrow. There is often a distinction made between refined emotions that are socially learned and
survival oriented emotions, which are thought to be innate. Human exploration of emotions as separate from other neurological phenomena is worthy of note, particularly in cultures where emotion is considered separate from physiological state. In some cultural medical theories emotion is considered so synonymous with certain forms of physical health that no difference is thought to exist. The
Stoics believed excessive emotion was harmful, while some
Sufi teachers felt certain extreme emotions could yield a conceptual perfection, what is often translated as
ecstasy.
In modern scientific thought, certain refined emotions are considered a complex neural trait innate in a variety of
domesticated and non-domesticated
mammals. These were commonly developed in reaction to superior survival mechanisms and intelligent interaction with each other and the environment; as such, refined emotion is not in all cases as discrete and separate from natural neural function as was once assumed. However, when humans function in civilized tandem, it has been noted that uninhibited acting on extreme emotion can lead to social disorder and
crime.
Sexuality and love
Human parents continue caring for their offspring long after they are born.
For humans, sexuality has important social functions: it creates physical intimacy, bonds and hierarchies among individuals, besides ensuring biological
reproduction. Sexual desire or
libido, is experienced as a bodily urge, often accompanied by strong emotions such as love,
ecstasy and
jealousy. The significance of sexuality in the human species is reflected in a number of physical features among them hidden
ovulation, the evolution of external
scrotum and
penis suggesting
sperm competition, the absence of an
os penis, permanent
secondary sexual characteristics and the forming of
pair bonds based on sexual attraction as a common social structure. Contrary to other primates that often advertise
estrus through visible signs, human females do not have a distinct or visible signs of ovulation plus they experience sexual desire outside of their fertile periods. These adaptations indicate that the meaning of sexuality in humans is similar to that found in the
bonobo, and that the complex human sexual behavior has a long
evolutionary history.
[191]
Human choices in acting on sexuality are commonly influenced by cultural norms which vary widely. Restrictions are often determined by religious beliefs or social customs. The pioneering researcher
Sigmund Freud believed that humans are born
polymorphously perverse, which means that any number of objects could be a source of pleasure. According to Freud humans then pass through five stages of
psychosexual development and can fixate on any stage because of various traumas during the process. For
Alfred Kinsey, another influential sex researcher, people can fall anywhere along a continuous scale of
sexual orientation, with only small minorities fully
heterosexual or
homosexual.
[192][193] Recent studies of
neurology and
genetics suggest people may be born predisposed to various sexual tendencies.
[194][195]
Culture
| Human society statistics |
| World population |
7.2 billion |
Population density
[citation needed] |
12.7 per km² (4.9 mi²) by total area
43.6 per km² (16.8 mi²) by land area |
Largest agglomerations
[citation needed] |
Beijing, Bogotá, Buenos Aires, Cairo, Delhi, Dhaka, Guangzhou, Istanbul, Jakarta, Karachi, Kinshasa, Kolkata, Lagos, Lima, London, Los Angeles, Manila, Mexico City, Moscow, Mumbai, New York City, Osaka, Paris, Rio de Janeiro, São Paulo, Seoul, Shanghai, Shenzhen, Tehran, Tianjin, Tokyo, Wuhan |
| Most widely spoken native languages[196] |
Chinese, Spanish, English, Hindi, Arabic, Portuguese, Bengali, Russian, Japanese, Javanese, German, Lahnda, Telugu, Marathi, Tamil, French, Vietnamese, Korean, Urdu, Italian, Malay, Persian, Turkish, Polish, Oriya |
| Most popular religions[197] |
Christianity, Islam, Hinduism, Buddhism, Sikhism, Judaism, Baha'i |
GDP (nominal)
[citation needed] |
$36,356,240 million USD
($5,797 USD per capita) |
GDP (PPP)
[citation needed] |
$51,656,251 million IND
($8,236 per capita) |
Humans often live in family-based social structures.
Humans are highly social beings and tend to live in large complex social groups. More than any other creature, humans are capable of utilizing systems of
communication for self-expression, the exchange of ideas, and
organization, and as such have created complex
social structures composed of many cooperating and competing groups. Human groups range from the size of families to
nations. Social interactions between humans have established an extremely wide variety
[clarification needed] of values, social norms, and rituals, which together form the basis of human
society.
Culture is defined here as patterns of complex symbolic behavior, i.e. all behavior that is not innate but which has to be learned through social interaction with others; such as the use of distinctive
material and
symbolic systems, including language, ritual, social organization, traditions, beliefs and technology.
Language
While many species
communicate,
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, using words to represent things and happenings that are not presently or locally occurring, but reside in the shared imagination of interlocutors.
[82] Language differs from other forms of communication in that it is
modality independent; the same meanings can be conveyed through different media, auditively in speech, visually by sign language or writing, and even 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. The invention of writing systems at least five thousand years ago allowed the preservation of language on material objects, and was a major technological advancement. The science of
linguistics describes the structure and function of language and the relationship between languages. There are approximately six thousand different languages currently in use, including
sign languages, and many thousands more that are
extinct.
[198]
Gender roles
The sexual division of humans into male and female has been marked culturally by a corresponding division of roles, norms,
practices, dress, behavior,
rights,
duties,
privileges,
status, and
power.
Cultural differences by gender have often been believed to have arisen naturally out of a division of reproductive labor; the biological fact that women give birth led to their further cultural responsibility for nurturing and caring for children. Gender roles have varied historically, and challenges to predominant gender norms have recurred in many societies.
Kinship
All human societies organize, recognize and classify types of social relationships based on relations between parents and children (
consanguinity), and relations through marriage (
affinity). These kinds of relations are generally called kinship relations. In most societies kinship places mutual responsibilities and expectations of solidarity on the individuals that are so related, and those who recognize each other as kinsmen come to form networks through which other social institutions can be regulated. Among the many functions of kinship is the ability to form
descent groups, groups of people sharing a common line of descent, which can function as political units such as
clans.
Another function is the way in which kinship unites families through marriage, forming
kinship alliances between groups of wife-takers and wife-givers. Such alliances also often have important political and economical ramifications, and may result in the formation of political organization above the community level. Kinship relations often includes regulations for whom an individual should or shouldn't marry. All societies have rules of
incest taboo, according to which marriage between certain kinds of kin relations are prohibited – such rules vary widely between cultures. Some societies also have rules of preferential marriage with certain kin relations, frequently with either
cross or parallel cousins. Rules and norms for marriage and social behavior among kinsfolk is often reflected in the systems of
kinship terminology in the various languages of the world. In many societies kinship relations can also be formed through forms of co-habitation, adoption, fostering, or companionship, which also tends to create relations of enduring solidarity (
nurture kinship).
Ethnicity
Humans often form ethnic groups, such groups tend to be larger than kinship networks and be organized around a common identity defined variously in terms of shared ancestry and history, shared cultural norms and language, or shared biological phenotype. Such ideologies of shared characteristics are often perpetuated in the form of powerful, compelling narratives that give legitimacy and continuity to the set of shared values. Ethnic groupings often correspond to some level of political organization such as the
band,
tribe,
city state or
nation. Although ethnic groups appear and disappear through history, members of ethnic groups often conceptualize their groups as having histories going back into the deep past. Such ideologies give ethnicity a powerful role in defining
social identity and in constructing solidarity between members of an ethno-political unit. This unifying property of ethnicity has been closely tied to the rise of the
nation state as the predominant form of political organization in the 19th and 20th century.
[199][200][201][202][203][204]
Society, government, and politics
Russian honor guard at Tomb of the Unknown Soldier, Alexander Garden welcomes Michael G. Mullen.
Society is the system of organizations and institutions arising from interaction between humans. A state is an organized political community occupying a definite territory, having an organized government, and possessing internal and external
sovereignty. Recognition of the state's claim to independence by other states, enabling it to enter into international agreements, is often important to the establishment of its statehood. The "state" can also be defined in terms of domestic conditions, specifically, as conceptualized by
Max Weber, "a state is a human community that (successfully) claims the monopoly of the 'legitimate' use of physical force within a given territory."
[205]
Government can be defined as the political means of creating and enforcing
laws; typically via a
bureaucratic hierarchy. Politics is the process by which decisions are made within groups; this process often involves conflict as well as compromise. Although the term is generally applied to behavior within governments, politics is also observed in all human group interactions, including corporate, academic, and religious institutions. Many different political systems exist, as do many different ways of understanding them, and many definitions overlap. Examples of governments include
monarchy,
Communist state,
military dictatorship,
theocracy, and
liberal democracy, the last of which is considered dominant today. All of these issues have a direct relationship with economics.
Trade and economics
Trade is the voluntary exchange of goods and services, and is a form of economics. A mechanism that allows trade is called a
market. Modern traders instead generally negotiate through a medium of exchange, such as money. As a result, buying can be separated from selling, or
earning. Because of specialization and
division of labor, most people concentrate on a small aspect of manufacturing or service, trading their labor for products. Trade exists between regions because different regions have an
absolute or
comparative advantage in the production of some tradable commodity, or because different regions' size allows for the benefits of
mass production.
Economics is a
social science which studies the production, distribution, trade, and consumption of goods and services. Economics focuses on measurable variables, and is broadly divided into two main branches:
microeconomics, which deals with individual agents, such as households and businesses, and macroeconomics, which considers the economy as a whole, in which case it considers
aggregate supply and
demand for money,
capital and
commodities. Aspects receiving particular attention in economics are
resource allocation, production, distribution, trade, and
competition. Economic logic is increasingly applied to any problem that involves choice under scarcity or determining economic
value.
War
Soldiers in front of the wood of Hougoumont during the reenactment of the battle of Waterloo (1815), June 2011, Waterloo, Belgium.
War is a state of organized armed conflict between
states or
non-state actors. War is characterized by the use of lethal
violence between
combatants and/or upon
non-combatants to achieve military goals through force. Lesser, often spontaneous conflicts, such as brawls,
riots,
revolts, and
melees, are not considered to be warfare.
Revolutions can be
nonviolent or an organized and armed revolution which denotes a state of war. During the 20th century, it is estimated that between 167 and 188 million people died as a result of war.
[206] A common definition defines war as a series of
military campaigns between at least two opposing sides involving a dispute over
sovereignty, territory,
resources,
religion, or other issues. A war between internal elements of a state is a
civil war. Among animals, all-out war against fellow members of the same species occurs only among large societies of humans and
ants.
There have been a wide variety of
rapidly advancing tactics throughout the history of war, ranging from
conventional war to
asymmetric warfare to
total war and
unconventional warfare. Techniques include
hand to hand combat, the use of
ranged weapons,
naval warfare, and, more recently,
air support. Military intelligence has often played a key role in determining victory and defeat. Propaganda, which often includes information, slanted opinion and disinformation, plays a key role in maintaining unity within a warring group, and/or sowing discord among opponents. In
modern warfare,
soldiers and
combat vehicles are used to control the land,
warships the sea, and
aircraft the sky. These fields have also overlapped in the forms of
marines,
paratroopers,
aircraft carriers, and
surface-to-air missiles, among others.
Satellites in
low Earth orbit have made outer space a factor in warfare as well as it is used for detailed intelligence gathering, however no known aggressive actions have been
taken from space.
Material culture and technology
An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools.
Stone tools were used by proto-humans at least 2.5 million years ago.
[207] The
controlled use of fire began around 1.5 million years ago. Since then, humans have made major advances, developing complex technology to create tools to aid their lives and allowing for other advancements in culture. Major leaps in technology include the discovery of
agriculture – what is known as the
Neolithic Revolution, and the invention of automated machines in the
Industrial Revolution.
Archaeology attempts to tell the story of past or lost cultures in part by close examination of the
artifacts they produced. Early humans left
stone tools,
pottery, and
jewelry that are particular to various regions and times.
Body culture
Throughout history, humans have altered their appearance by wearing clothing
[208][209] and
adornments, by trimming or
shaving hair or by means of body modifications.
Body modification is the deliberate altering of the
human body for any non-medical reason, such as aesthetics, sexual enhancement, a rite of passage, religious reasons, to display group membership or affiliation, to create
body art, shock value, or self-expression.
[210] In its most broad definition it includes
plastic surgery, socially acceptable decoration (e.g. common
ear piercing in many societies), and religious rites of passage (e.g.
circumcision in a number of cultures).
[210]
Religion and spirituality
His Grace Dr Rowan Williams, Archibishop of Canterbury, visiting Abbaye du Bec in le Bec-Hellouin on the 26th & 27th of May 2005.
Religion is generally defined as a
belief system concerning the
supernatural,
sacred or
divine, and practices,
values, institutions and
rituals associated with such belief. Some religions also have a
moral code. The
evolution and the history of the
first religions have recently become areas of active scientific investigation.
[212][213][214] However, in the course of its
development, religion has taken on many forms that vary by culture and individual perspective. Some of the chief questions and issues religions are concerned with include life after death (commonly involving belief in an
afterlife), the
origin of life, the nature of the
universe (
religious cosmology) and its
ultimate fate (
eschatology), and what is
moral or immoral. A common source for answers to these questions are beliefs in
transcendent divine beings such as
deities or a singular
God, although not all religions are
theistic. Spirituality, belief or involvement in matters of the
soul or
spirit, is one of the many different approaches humans take in trying to answer fundamental questions about humankind's place in the universe, the
meaning of life, and the ideal way to live one's life. Though these topics have also been addressed by philosophy, and to some extent by science, spirituality is unique in that it focuses on
mystical or supernatural concepts such as
karma and God.
Although the exact level of religiosity can be hard to measure,
[215] a majority of humans professes some variety of religious or spiritual belief, although many (in some countries a majority) are
irreligious. This includes humans who have no religious beliefs or do not identify with any religion.
Humanism is a philosophy which seeks to include all of humanity and all issues common to humans; it is usually non-religious. Most religions and spiritual beliefs are clearly distinct from science on both a philosophical and methodological level; the two are not generally considered mutually exclusive and a majority of humans hold a mix of both scientific and religious views. The distinction between philosophy and religion, on the other hand, is at times less clear, and the two are linked in such fields as the
philosophy of religion and
theology.
Philosophy and self-reflection
Philosophy is a discipline or field of study involving the investigation, analysis, and development of ideas at a general, abstract, or fundamental level. It is the discipline searching for a general understanding of reality, reasoning and values. Major fields of philosophy include
logic,
metaphysics,
epistemology,
philosophy of mind, and
axiology (which includes
ethics and
aesthetics). Philosophy covers a very wide range of approaches, and is used to refer to a
worldview, to a perspective on an issue, or to the positions argued for by a particular philosopher or school of philosophy.
Science and mathematics
Another unique aspect of human culture and thought is the development of complex methods for acquiring knowledge through observation and quantification. The
scientific method has been developed to acquire knowledge of the physical world and the rules, processes and principles of which it consists, and combined with mathematics it enables the prediction of complex patterns of causality and consequence. Some other animals are able to recognize differences in small quantities,
[citation needed] but humans are able to understand and recognize much larger, even abstract, quantities, and to recognize and understand algorithmic patterns which enables infinite
counting routines and algebra, something that is not found in any other species.
Art, music, and literature
Art is a
cultural universal, and humans have been producing artistic works at least since the days of
Cro Magnon. As a form of
cultural expression, art may be defined by the pursuit of
diversity and the usage of
narratives of liberation and exploration (i.e.
art history,
art criticism, and
art theory) to mediate its boundaries. This distinction may be applied to objects or performances, current or historical, and its prestige extends to those who made, found, exhibit, or own them. In the modern use of the word, art is commonly understood to be the process or result of making material works that, from concept to creation, adhere to the "creative impulse" of human beings. Art is distinguished from other works by being in large part unprompted by necessity, by biological drive, or by any undisciplined pursuit of recreation.
Music is a natural
intuitive phenomenon based on the three distinct and interrelated organization structures of rhythm, harmony, and melody. Listening to music is perhaps the most common and universal form of
entertainment, while learning and understanding it are popular
disciplines.
[citation needed] There are a wide variety of
music genres and
ethnic musics.
Literature, the body of written—and possibly oral—works, especially creative ones, includes prose, poetry and drama, both fiction and
non-fiction. Literature includes such genres as
epic, legend, myth, ballad, and folklore.
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