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== History ==

== History ==

=== Origin ===

=== Origin ===

The scientific study of [[human evolution]] encompasses the development of the genus ''[[Homo (genus)|Homo]]'', but usually involves studying other [[hominidae|hominids]] and [[homininae|hominines]] as well, such as ''[[Australopithecus]]''. "Modern humans" are defined as the ''Homo sapiens''  [[species]], of which the only extant [[subspecies]] is ''Homo sapiens sapiens''; ''[[Homo sapiens idaltu]]'' (roughly translated as "elder wise human"), the other known subspecies, is extinct. [http://www.anth.ucsb.edu/projects/human/#] Anatomically modern humans appear in the fossil record in Africa about 130,000 years ago.[http://www.mnh.si.edu/anthro/humanorigins/ha/sap.htm]  

The scientific study of [[human]] [[evolution]] encompasses the development of the genus ''[[Homo (genus)|Homo]]'', but usually involves studying other [[hominidae|hominids]] and [[homininae|hominines]] as well, such as ''[[Australopithecus]]''. "Modern humans" are defined as the ''Homo sapiens''  [[species]], of which the only extant [[subspecies]] is ''Homo sapiens sapiens''; ''[[Homo sapiens idaltu]]'' (roughly translated as "elder wise human"), the other known subspecies, is extinct. [http://www.anth.ucsb.edu/projects/human/#] Anatomically modern humans appear in the fossil record in Africa about 130,000 years ago.[http://www.mnh.si.edu/anthro/humanorigins/ha/sap.htm]  

 

 

 

 

 

 

 

The closest living relatives of ''Homo sapiens'' are two distinct species of the genus Pan: the [[Bonobo]] (''Pan paniscus'') and the [[Common Chimpanzee]] (''Pan troglodytes''). These species share the same common ancestor. The main difference between them is the social organization: [[matriarchal]] for the Bonobo and [[patriarchal]] for the Common Chimpanzee. Full [[genome]] sequencing resulted in the conclusion that "after 6.5 [[million]] years of separate evolution, the differences between bonobo/chimpanzee and human are just 10 times greater than those between two unrelated people and 10 times less than those between rats and mice". In fact, 95 per cent of the DNA sequence is identical between the two ''Pan'' species and human.[[Frans de Waal]], ''Bonobo'' ISBN 0-520-20535-9 [http://www.2think.org/bonobo.shtml] [http://www.pnas.org/cgi/content/full/99/21/13633] [http://www.pnas.org/cgi/content/full/100/12/7181][http://mbe.oxfordjournals.org/cgi/reprint/14/3/248]| It has been estimated that the human [[lineage (evolution)|lineage]] diverged from that of chimpanzees about five million years ago, and from [[gorilla]]s about  eight million years ago. However, a hominid skull discovered in [[Chad]] in 2001, classified as ''[[Sahelanthropus tchadensis]]'', is approximately seven million years old, which may indicate an earlier divergence. [http://www.nature.com/nature/journal/v418/n6894/full/nature00879.html]  

The closest living relatives of ''Homo sapiens'' are two distinct species of the genus Pan: the [[Bonobo]] (''Pan paniscus'') and the [[Common Chimpanzee]] (''Pan troglodytes''). These species share the same common ancestor. The main difference between them is the social organization: [[matriarchal]] for the Bonobo and [[patriarchal]] for the Common Chimpanzee. Full [[genome]] sequencing resulted in the conclusion that "after 6.5 [[million]] years of separate evolution, the differences between bonobo/chimpanzee and human are just 10 times greater than those between two unrelated people and 10 times less than those between rats and mice". In fact, 95 per cent of the DNA sequence is identical between the two ''Pan'' species and human.[[Frans de Waal]], ''Bonobo'' ISBN 0-520-20535-9 [http://www.2think.org/bonobo.shtml] [http://www.pnas.org/cgi/content/full/99/21/13633] [http://www.pnas.org/cgi/content/full/100/12/7181][http://mbe.oxfordjournals.org/cgi/reprint/14/3/248]| It has been estimated that the human [[lineage (evolution)|lineage]] diverged from that of chimpanzees about five million years ago, and from [[gorilla]]s about  eight million years ago. However, a hominid skull discovered in [[Chad]] in 2001, classified as ''[[Sahelanthropus tchadensis]]'', is approximately seven million years old, which may indicate an earlier divergence. [http://www.nature.com/nature/journal/v418/n6894/full/nature00879.html]  

Geneticists Lynn Jorde and [[Henry Harpending]] of the [[University of Utah]] proposed that the variation in human DNA is minute compared to that of other species. They also propose that during the [[Late Pleistocene]], the human population was reduced to a small number of breeding pairs — no more than 10,000 and possibly as few as 1,000 — resulting in a very small residual gene pool. Various reasons for this hypothetical bottleneck have been postulated, one of those is the [[Toba catastrophe theory]].

Geneticists Lynn Jorde and [[Henry Harpending]] of the [[University of Utah]] proposed that the variation in human DNA is minute compared to that of other species. They also propose that during the [[Late Pleistocene]], the human population was reduced to a small number of breeding pairs — no more than 10,000 and possibly as few as 1,000 — resulting in a very small residual gene pool. Various reasons for this hypothetical bottleneck have been postulated, one of those is the [[Toba catastrophe theory]].

Human evolution is characterized by a number of important morphological, developmental, physiological and behavioral changes which have taken place since the split between the last common ancestor of ''Homo'' and ''Pan''. The primary change, both in terms of chronology and in terms of it being the trait that defines the human [[subtribe]] the [[Hominina]], was the evolution of a bipedal locomotor adaptation from an arboreal or semi-arboreal locomotor adaptation, with all its attendant adaptations, such as a valgus knee, low intermembral index (long legs relative to the arms) and reduced upper body strength. Following this was the evolution of a larger [[Cranial capacity|brain cavity]] and brain itself, which is typically 1,400 cm³ in modern humans; over twice that of a chimpanzee or gorilla. Other significant morphological changes included: the evolution of a power and precision grip;{{Fact|date=November 2007}} a reduced masticatory system; a reduction of the [[canine tooth]]; and the descent of the [[larynx]] and [[hyoid bone]], making speech possible. With respect to development, the pattern of human postnatal brain growth differs from that of other apes ([[heterochrony]]), allowing for an extended period of social learning and [[language acquisition]] in juvenile humans. [[Physical anthropology|Physical anthropologists]] argue that a reorganization of the structure of the brain is more important than cranial expansion itself.  One important physiological change in humans was the evolution of hidden estrus or [[concealed ovulation]] in females, which may have coincided with the evolution of important behavioral changes, such as [[pair bond]]ing. Another significant behavioral change includes the development of [[material culture]], or the (over time) increasingly wide variety of human-made objects which are used to manipulate humans' physical and social environments. How all these changes are related and what their role is in the evolution of complex social organization and culture are matters of ongoing debate.(''How Humans Evolved'', ISBN 0-393-97854-0]

Human evolution is characterized by a number of important morphological, developmental, physiological and behavioral changes which have taken place since the split between the last common ancestor of ''Homo'' and ''Pan''. The primary change, both in terms of chronology and in terms of it being the trait that defines the human [[subtribe]] the [[Hominina]], was the evolution of a bipedal locomotor adaptation from an arboreal or semi-arboreal locomotor adaptation, with all its attendant adaptations, such as a valgus knee, low intermembral index (long legs relative to the arms) and reduced upper body strength. Following this was the evolution of a larger [[Cranial capacity|brain cavity]] and brain itself, which is typically 1,400 cm³ in modern humans; over twice that of a chimpanzee or gorilla. Other significant morphological changes included: the evolution of a power and precision grip;

a reduced masticatory system; a reduction of the [[canine tooth]]; and the descent of the [[larynx]] and [[hyoid bone]], making speech possible. With respect to development, the pattern of human postnatal brain growth differs from that of other apes ([[heterochrony]]), allowing for an extended period of social learning and [[language acquisition]] in juvenile humans. [[Physical anthropology|Physical anthropologists]] argue that a reorganization of the structure of the brain is more important than cranial expansion itself.  One important physiological change in humans was the evolution of hidden estrus or [[concealed ovulation]] in females, which may have coincided with the evolution of important behavioral changes, such as [[pair bond]]ing. Another significant behavioral change includes the development of [[material culture]], or the (over time) increasingly wide variety of human-made objects which are used to manipulate humans' physical and social environments. How all these changes are related and what their role is in the evolution of complex social organization and culture are matters of ongoing debate.(''How Humans Evolved'', ISBN 0-393-97854-0]

=== Rise of civilization ===

=== Rise of civilization ===

== Biology ==

== Biology ==

=== Physiology and genetics ===

=== Physiology and genetics ===

Although humans appear relatively 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.<ref>[http://www.freerepublic.com/focus/f-news/966532/posts ''Why Humans and Their Fur Parted Way'' by Nicholas Wade, ''New York Times'',

Although humans appear relatively 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.<ref>[http://www.freerepublic.com/focus/f-news/966532/posts ''Why Humans and Their Fur Parted Way'' by Nicholas Wade, ''New York Times'',

The hue of human hair and skin is determined by the presence of [[pigment]]s called [[melanin]]s. Human skin hues can range from very dark brown to very pale pink, while human hair ranges from [[blond]] to [[brown hair|brown]] to [[red hair|red]] to, most commonly, [[black hair|black]]., depending on the amount of melanin (an effective sun blocking pigment) in the skin. Most researchers believe that skin darkening was an adaptation that evolved as a protection against [[ultraviolet]] [[solar radiation]]. More recently, however, it has been argued that particular skin colors are an adaptation to balance folate, which is destroyed by ultraviolet radiation, and vitamin D, which requires sunlight to form.<ref>Jablonski, N.G. & Chaplin, G. (2000). ''[http://www.bgsu.edu/departments/chem/faculty/leontis/chem447/PDF_files/Jablonski_skin_color_2000.pdf]The evolution of human skin coloration]'' (pdf), 'Journal of Human Evolution 39: 57-106. The skin pigmentation of contemporary humans is geographically stratified, and in general correlates with the level of ultraviolet radiation. Human skin also has a capacity to darken ([[sun tanning]]) in response to exposure to ultraviolet radiation.  

The hue of human hair and skin is determined by the presence of [[pigment]]s called [[melanin]]s. Human skin hues can range from very dark brown to very pale pink, while human hair ranges from [[blond]] to [[brown hair|brown]] to [[red hair|red]] to, most commonly, [[black hair|black]]., depending on the amount of melanin (an effective sun blocking pigment) in the skin. Most researchers believe that skin darkening was an adaptation that evolved as a protection against [[ultraviolet]] [[solar radiation]]. More recently, however, it has been argued that particular skin colors are an adaptation to balance folate, which is destroyed by ultraviolet radiation, and vitamin D, which requires sunlight to form.[http://www.bgsu.edu/departments/chem/faculty/leontis/chem447/PDF_files/Jablonski_skin_color_2000.pdf]The evolution of human skin coloration]'' (pdf), 'Journal of Human Evolution 39: 57-106. The skin pigmentation of contemporary humans is geographically stratified, and in general correlates with the level of ultraviolet radiation. Human skin also has a capacity to darken ([[sun tanning]]) in response to exposure to ultraviolet radiation.  

The average [[sleep]] requirement is between seven and eight hours a day for an adult and nine to ten hours for a child; elderly people usually sleep for six to seven hours. Experiencing less sleep than this is common in modern societies; this [[sleep deprivation]] can lead to negative 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 fatigue, aggression, and bodily discomfort.

The average [[sleep]] requirement is between seven and eight hours a day for an adult and nine to ten hours for a child; elderly people usually sleep for six to seven hours. Experiencing less sleep than this is common in modern societies; this [[sleep deprivation]] can lead to negative 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 fatigue, aggression, and bodily discomfort.

The human [[biological life cycle|life cycle]] is similar to that of other [[placenta]]l mammals. New humans develop [[vivipary|viviparously]] from [[fertilization|conception]]. An [[ovum|egg]] is usually fertilized inside the female by [[spermatozoon|sperm]] from the male through [[sexual intercourse]], though the recent technology of [[in vitro fertilization]] is occasionally used. The fertilized egg, called a [[zygote]], divides inside the female's [[uterus]] to become an [[embryo]], which over a period of thirty-eight weeks (9 months) of [[gestation]] becomes a human [[fetus]]. After this span of time, the fully-grown fetus is expelled from the female'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 personhood to human fetuses while they remain in the uterus.

The human [[biological life cycle|life cycle]] is similar to that of other [[placenta]]l mammals. New humans develop [[vivipary|viviparously]] from [[fertilization|conception]]. An [[ovum|egg]] is usually fertilized inside the female by [[spermatozoon|sperm]] from the male through [[sexual intercourse]], though the recent technology of [[in vitro fertilization]] is occasionally used. The fertilized egg, called a [[zygote]], divides inside the female's [[uterus]] to become an [[embryo]], which over a period of thirty-eight weeks (9 months) of [[gestation]] becomes a human [[fetus]]. After this span of time, the fully-grown fetus is expelled from the female'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 personhood to human fetuses while they remain in the uterus.

Compared with that of other species, human [[childbirth]] is dangerous. Painful labors lasting twenty-four hours or more are not uncommon, and may result in injury, or even death, to the child and/or mother. This is because of both the relatively large fetal head circumference (for housing the brain) and the mother's relatively narrow [[pelvis]] (a trait required for successful bipedalism, by way of natural selection).<ref>{{cite journal | author = LaVelle M | title = Natural selection and developmental sexual variation in the human pelvis | journal = Am J Phys Anthropol | volume = 98 | issue = 1 | pages = 59-72 | year = 1995 | id = PMID 8579191}}</ref><ref>{{cite journal | author = Correia H, Balseiro S, De Areia M | title = Sexual dimorphism in the human pelvis: testing a new hypothesis | journal = Homo | volume = 56 | issue = 2 | pages = 153-60 | year = 2005 | id = PMID 16130838}}</ref> 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 relatively hazardous ordeals in developing regions of the world, with maternal death rates approximately 100 times more common than in developed countries.<ref>{{cite journal | author = Rush D | title = Nutrition and maternal mortality in the developing world. | journal = Am J Clin Nutr | volume = 72 | issue = 1 Suppl | pages = 212 S-240 S | year = 2000 | id = PMID 10871588}}</ref>

Compared with that of other species, human [[childbirth]] is dangerous. Painful labors lasting twenty-four hours or more are not uncommon, and may result in injury, or even death, to the child and/or mother. This is because of both the relatively large fetal head circumference (for housing the brain) and the mother's relatively narrow [[pelvis]] (a trait required for successful bipedalism, by way of natural selection). 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 relatively hazardous ordeals in developing regions of the world, with maternal death rates approximately 100 times more common than in developed countries..  

In developed countries, infants are typically 3 – 4 kg (6 – 9&nbsp;pounds) in weight and 50 – 60 cm (20 – 24&nbsp;inches) in height at birth.<ref>{{cite web|url=http://childinfo.org/areas/birthweight/|title=Low Birthweight|accessdate=2007-05-30}}</ref> However, low [[birth weight]] is common in developing countries, and contributes to the high levels of [[infant mortality]] in these regions.<ref>{{cite journal | author = Khor G | title = Update on the prevalence of malnutrition among children in Asia. | journal = Nepal Med Coll J | volume = 5 | issue = 2 | pages = 113-22 | year = 2003 | id = PMID 15024783}}</ref> Helpless at birth, humans continue to grow for some years, typically reaching [[sexual maturity]] at 12 to 15&nbsp;years of age. Human [[girl]]s continue to grow physically until around the age of 18, and human [[boy]]s until around age 21. The human life span can be split into a number of stages: infancy, [[childhood]], [[adolescence]], [[young adulthood]], [[adult]]hood and [[old age]]. The lengths of these stages, however — particularly the later ones — are not fixed.

In developed countries, infants are typically 3 – 4 kg (6 – 9&nbsp;pounds) in weight and 50 – 60 cm (20 – 24&nbsp;inches) in height at birth.[http://childinfo.org/areas/birthweight/|title=Low Birthweight] However, low [[birth weight]] is common in developing countries, and contributes to the high levels of [[infant mortality]] in these regions. Helpless at birth, humans continue to grow for some years, typically reaching [[sexual maturity]] at 12 to 15&nbsp;years of age. Human [[girl]]s continue to grow physically until around the age of 18, and human [[boy]]s until around age 21. The human life span can be split into a number of stages: infancy, [[childhood]], [[adolescence]], [[young adulthood]], [[adult]]hood and [[old age]]. The lengths of these stages, however — particularly the later ones — are not fixed.

There are striking differences in [[life expectancy]] around the world. The developed world is quickly getting older, with the median age around 40&nbsp;years (highest in [[Monaco]] at 45.1&nbsp;years), while in the [[third world|developing world]], the median age is 15 – 20 years (lowest in [[Uganda]] at 14.8 years). Life expectancy at birth in [[Hong Kong, China]] is 84.8 years for a female and 78.9 for a male, while in [[Swaziland]], primarily because of [[AIDS]], it is 31.3 years for both sexes.<ref>[http://hdr.undp.org/hdr2006/ "Human Development Report 2006,"] [[United Nations Development Programme]], pp. 363-366, [[November 9]] [[2006]]</ref> While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older.<ref>[[https://www.cia.gov/library/publications/the-world-factbook/ ''The World Factbook'']], U.S. Central Intelligence Agency, retrieved [[April 2]], [[2005]].</ref>

There are striking differences in [[life expectancy]] around the world. The developed world is quickly getting older, with the median age around 40&nbsp;years (highest in [[Monaco]] at 45.1&nbsp;years), while in the [[third world|developing world]], the median age is 15 – 20 years (lowest in [[Uganda]] at 14.8 years). Life expectancy at birth in [[Hong Kong, China]] is 84.8 years for a female and 78.9 for a male, while in [[Swaziland]], primarily because of [[AIDS]], it is 31.3 years for both sexes.<ref>[http://hdr.undp.org/hdr2006/ "Human Development Report 2006,"] [[United Nations Development Programme]], pp. 363-366, [[November 9]] [[2006]]</ref> While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older. [[https://www.cia.gov/library/publications/the-world-factbook/ ''The World Factbook'']]

The number of [[centenarian]]s (humans of age 100 years or older) in the world was estimated by the [[United Nations]] at 210,000 in 2002.<ref>[http://www.un.org/ageing/note5713.doc.htm U.N. Statistics on Population Ageing], United Nations press release, February 28, 2002, retrieved April 2, 2005</ref> At least one person, [[Jeanne Calment]], is known to have reached the age of 122 years; higher ages have been claimed but they are not well substantiated. Worldwide, there are 81 men aged 60 or older for every 100 women of that age group, and among the oldest, there are 53 men for every 100 women.

The number of [[centenarian]]s (humans of age 100 years or older) in the world was estimated by the [[United Nations]] at 210,000 in 2002.<ref>[http://www.un.org/ageing/note5713.doc.htm U.N. Statistics on Population Ageing], United Nations press release, February 28, 2002, retrieved April 2, 2005</ref> At least one person, [[Jeanne Calment]], is known to have reached the age of 122 years; higher ages have been claimed but they are not well substantiated. Worldwide, there are 81 men aged 60 or older for every 100 women of that age group, and among the oldest, there are 53 men for every 100 women.

Early ''Homo sapiens'' employed a hunter-gatherer method as their primary means of food collection, involving combining stationary plant and fungal food sources (such as fruits, grains, tubers, and mushrooms) with wild game which must be hunted and killed in order to be consumed. It is believed that humans have used fire to prepare and [[cooking|cook]] food prior to eating since the time of their divergence from ''[[Homo erectus]]''.  

Early ''Homo sapiens'' employed a hunter-gatherer method as their primary means of food collection, involving combining stationary plant and fungal food sources (such as fruits, grains, tubers, and mushrooms) with wild game which must be hunted and killed in order to be consumed. It is believed that humans have used fire to prepare and [[cooking|cook]] food prior to eating since the time of their divergence from ''[[Homo erectus]]''.  

Humans are [[omnivorous]], capable of consuming both plant and animal products. The view of humans as omnivores is supported by the evidence that both a pure animal and a pure vegetable diet can lead to [[deficiency diseases]] in humans. A pure animal diet can, for instance, lead to [[scurvy]], while a pure plant diet can lead to deficiency of a number of nutrients, including [[Vitamin B12]]. Supplementation, particularly for vitamin B12, is highly recommended for people living on a pure plant diet.<ref>{{cite web |url=http://www.vegansociety.com/html/food/nutrition/ |title=Healthy choices on a vegan diet |accessdate=2007-02-14 |publisher=[[Vegan Society]]}}</ref> However, according to [[American Dietetic Association]] and the [[Dietitians of Canada]], properly planned [[vegetarian]] and [[vegan]] diets are nutritionally adequate and healthy.<ref>{{cite web|url=http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/advocacy_933_ENU_HTML.htm |title=American Dietetic Association}}</ref>

Humans are [[omnivorous]], capable of consuming both plant and animal products. The view of humans as omnivores is supported by the evidence that both a pure animal and a pure vegetable diet can lead to [[deficiency diseases]] in humans. A pure animal diet can, for instance, lead to [[scurvy]], while a pure plant diet can lead to deficiency of a number of nutrients, including [[Vitamin B12]]. Supplementation, particularly for vitamin B12, is highly recommended for people living on a pure plant diet.[http://www.vegansociety.com/html/food/nutrition/] However, according to [[American Dietetic Association]] and the [[Dietitians of Canada]], properly planned [[vegetarian]] and [[vegan]] diets are nutritionally adequate and healthy.[http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/advocacy_933_ENU_HTML.htm]

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

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

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. Lack of food remains a serious problem, with about 300,000 people starving to death every year.<ref>[http://www.who.int/healthinfo/bod/en/index.html Death and DALY estimates for 2002 by cause for WHO Member States] World Health Organisation. Accessed 29 Oct 2006</ref> Childhood malnutrition is also common and contributes to the global burden of disease.<ref>{{cite journal | author = Murray C, Lopez A | title = Global mortality, disability, and the contribution of risk factors: Global Burden of Disease Study. | journal = Lancet | volume = 349 | issue = 9063 | pages = 1436-42 | year = 1997 | id = PMID 9164317}}</ref> However global food distribution is not even, and [[obesity]] among some human populations has increased to almost [[epidemic]] proportions, leading to health complications and increased mortality in some [[developed country|developed]], and a few [[developing countries]]. The United States [[Centers for Disease Control]] (CDC) state that 32% of American adults over the age of 20 are obese, while 66.5% are obese or overweight. Obesity is caused by consuming more [[calorie]]s than are expended, with many attributing excessive weight gain to a combination of overeating and insufficient [[exercise]].

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. Lack of food remains a serious problem, with about 300,000 people starving to death every year.<ref>[http://www.who.int/healthinfo/bod/en/index.html Death and DALY estimates for 2002 by cause for WHO Member States] World Health Organisation. Accessed 29 Oct 2006</ref> Childhood malnutrition is also common and contributes to the global burden of disease. However global food distribution is not even, and [[obesity]] among some human populations has increased to almost [[epidemic]] proportions, leading to health complications and increased mortality in some [[developed country|developed]], and a few [[developing countries]]. The United States [[Centers for Disease Control]] (CDC) state that 32% of American adults over the age of 20 are obese, while 66.5% are obese or overweight. Obesity is caused by consuming more [[calorie]]s than are expended, with many attributing excessive weight gain to a combination of overeating and insufficient [[exercise]].

At least ten thousand years ago, [[History of agriculture|humans developed agriculture]],<ref>[http://www.archaeology.org/9707/newsbriefs/squash.html Earliest agriculture in the Americas]

At least ten thousand years ago, [[History of agriculture|humans developed agriculture]],<ref>[http://www.archaeology.org/9707/newsbriefs/squash.html Earliest agriculture in the Americas]

The human ability to think abstractly may be unparalleled in the animal kingdom. Humans are one of only six species to pass the [[mirror test]] — which tests whether an animal recognizes its reflection as an image of itself — along with [[chimpanzees]], [[orangutan]]s, [[dolphin]]s, and possibly [[dove|pigeons]]<ref>Robert W. Allan explores a few of these experiments on his webpage:

The human ability to think abstractly may be unparalleled in the animal kingdom. Humans are one of only six species to pass the [[mirror test]] — which tests whether an animal recognizes its reflection as an image of itself — along with [[chimpanzees]], [[orangutan]]s, [[dolphin]]s, and possibly [[dove|pigeons]]<ref>Robert W. Allan explores a few of these experiments on his webpage:

http://ww2.lafayette.edu/~allanr/mirror.html</ref>. In October 2006, three [[elephant]]s at the [[Bronx]] Zoo also passed this test.<ref>{{cite journal | author = | title = Self-recognition in an Asian elephant. | journal = Proc Natl Acad Sci U S A | volume = | issue = | pages = | year = | id = PMID 17075063}}</ref> Humans under the age of 2 typically fail this test.<ref>[http://www.ulm.edu/~palmer/ConsciousnessandtheSymbolicUniverse.htm Consciousness and the Symbolic Universe], by Dr. Jack Palmer, retrieved [[March 17]], [[2006]].</ref> However, this may be a matter of degree rather than a sharp divide. Monkeys have been trained to apply abstract rules in tasks.<ref>[http://web.mit.edu/newsoffice/2001/abstract-0718.html Researchers home in on how brain handles abstract thought] - retrieved [[July 29]], [[2006]]</ref>

[http://ww2.lafayette.edu/~allanr/mirror.html]. In October 2006, three [[elephant]]s at the [[Bronx]] Zoo also passed this test. Humans under the age of 2 typically fail this test.[http://www.ulm.edu/~palmer/ConsciousnessandtheSymbolicUniverse.htm Consciousness and the Symbolic Universe], by Dr. Jack Palmer. However, this may be a matter of degree rather than a sharp divide. Monkeys have been trained to apply abstract rules in tasks.[http://web.mit.edu/newsoffice/2001/abstract-0718.html] Researchers home in on how brain handles abstract thought].

The brain [[perception|perceives]] the external world through the [[sense]]s, and each individual human is influenced greatly by his or her experiences, leading to [[subjectivity|subjective]] views of [[existence]] and the passage of [[time]].

The brain [[perception|perceives]] the external world through the [[sense]]s, and each individual human is influenced greatly by his or her experiences, leading to [[subjectivity|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 [[perception|perceive]] the relationship between [[Personal identity (philosophy)|oneself]] and one's [[natural environment|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 philosopher of [[cognitive science]] [[Daniel Dennett]], for example, argues that there is no such thing as a narrative centre called the "mind", but that instead there is simply a collection of sensory inputs and outputs: different kinds of "software" running in parallel.<ref>Dennett, Daniel (1991). ''Consciousness Explained''. Little Brown & Co, 1991, ISBN 0-316-18065-3.</ref> Psychologist [[B.F. Skinner]] has argued that the mind is an explanatory fiction that diverts attention from environmental causes of behavior<ref>Skinner, B.F. About Behaviorism 1974, page 74-75</ref>. Further, that what are commonly seen as mental processes may be better conceived of as forms of covert [[Verbal Behavior]]<ref>Skinner, B.F. About Behaviorism, Chapter 7: Thinking</ref>.

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 [[perception|perceive]] the relationship between [[Personal identity (philosophy)|oneself]] and one's [[natural environment|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 philosopher of [[cognitive science]] [[Daniel Dennett]], for example, argues that there is no such thing as a narrative centre called the "mind", but that instead there is simply a collection of sensory inputs and outputs: different kinds of "software" running in parallel. (''Consciousness Explained''. Little Brown & Co, 1991, ISBN 0-316-18065-3). Psychologist [[B.F. Skinner]] has argued that the mind is an explanatory fiction that diverts attention from environmental causes of behavior. Further, that what are commonly seen as mental processes may be better conceived of as forms of covert [[Verbal Behavior]]

Humans study the more physical aspects of the mind and brain, and by extension of the [[nervous system]], 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 [[phenomenology|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]].

Humans study the more physical aspects of the mind and brain, and by extension of the [[nervous system]], 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 [[phenomenology|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]].

[[Motivation]] is the driving force of desire behind all deliberate [[Action (philosophy)|actions]] of human beings. 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.

[[Motivation]] is the driving force of desire behind all deliberate [[Action (philosophy)|actions]] of human beings. 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 [[financial]] [[incentive]]s, [[moral]] incentives, or [[coercive]] incentives. Religions generally posit [[Deity|divine]] or [[demon]]ic influences.

Within psychology, conflict avoidance and the [[libido]] are seen to be primary motivators. Within economics motivation is often seen to be based on [[financial]] [[incentive]]s, [[moral]] incentives, or [[coercive]] incentives. Religions generally posit [[divine]] or [[demon]]ic influences.

[[Happiness]], or being happy, is a human emotional condition. The definition of happiness is a common [[philosophy|philosophical]] topic. Some people might define it as the best condition which a human can have — a condition of mental and physical health. Others may define it as [[Freedom (philosophy)|freedom]] from want and distress; [[consciousness]] of the [[goodness and value theory|good]] order of things; assurance of one's place in the [[universe]] or [[society]], [[inner peace]], and so forth.

[[Happiness]], or being happy, is a human emotional condition. The definition of happiness is a common [[philosophy|philosophical]] topic. Some people might define it as the best condition which a human can have — a condition of mental and physical health. Others may define it as [[Freedom (philosophy)|freedom]] from want and distress; [[consciousness]] of the [[goodness and value theory|good]] order of things; assurance of one's place in the [[universe]] or [[society]], [[inner peace]], and so forth.

Human sexual choices are usually made in reference to cultural [[norm (sociology)|norms]], which vary widely. Restrictions are sometimes determined by religious beliefs or social customs.

Human sexual choices are usually made in reference to cultural [[norm (sociology)|norms]], which vary widely. Restrictions are sometimes determined by religious beliefs or social customs.

Many [[Sexology|sexologists]] believe that the majority of ''Homo sapiens'' have the inherent capacity to be attracted to both males and females (a kind of universal potential [[bisexuality]]).{{fact|date=November 2007}} In a variation of this, pioneering researcher [[Sigmund Freud]] believed that humans are born [[Psychosexual development|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]]). Recent studies of [[neurology]] and [[genetics]] suggest people may be born with one sexual orientation or another, so there is not currently a clear consensus among sex researchers.<ref> Buss, David M. (2004) "The Evolution of Desire: Strategies of Human Mating". Revised Edition. New York: Basic Books" </ref><ref> Thornhill, R., & Palmer, C. T. (2000). A Natural History of Rape. Biological Bases of Sexual Coercion. Cambridge: MIT Press.

Many [[Sexology|sexologists]] believe that the majority of ''Homo sapiens'' have the inherent capacity to be attracted to both males and females (a kind of universal potential [[bisexuality]]). In a variation of this, pioneering researcher [[Sigmund Freud]] believed that humans are born [[Psychosexual development|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]]). Recent studies of [[neurology]] and [[genetics]] suggest people may be born with one sexual orientation or another, so there is not currently a clear consensus among sex researchers.<ref> Buss, David M. (2004) "The Evolution of Desire: Strategies of Human Mating". Revised Edition. New York: Basic Books" </ref><ref> Thornhill, R., & Palmer, C. T. (2000). A Natural History of Rape. Biological Bases of Sexual Coercion. Cambridge: MIT Press.

== Culture ==

== Culture ==

[[Culture]] is defined here as a set of distinctive material, intellectual, emotional, and spiritual features of a social group, including art, literature, lifestyles, value systems, traditions, rituals, and beliefs. The link between human biology and human behavior and culture is often very close, making it difficult to clearly divide topics into one area or the other; as such, the placement of some subjects may be based primarily on convention.

[[Culture]] is defined here as a set of distinctive material, intellectual, emotional, and spiritual features of a social group, including art, literature, lifestyles, value systems, traditions, rituals, and beliefs. The link between human biology and human behavior and culture is often very close, making it difficult to clearly divide topics into one area or the other; as such, the placement of some subjects may be based primarily on convention.

Culture consists of values, social norms, and [[artifact (archaeology)|artifacts]]. A culture's [[value (personal and cultural)|values]] define what it holds to be important or [[ethics|ethical]]. Closely linked are [[norm (sociology)|norms]], expectations of how people ought to behave, bound by [[tradition]]. Artifacts, or [[archaeological culture|material culture]], are objects derived from the culture's values, norms, and understanding of the world.

Culture consists of values, social norms, and [[artifact|artifacts]]. A culture's [[value (personal and cultural)|values]] define what it holds to be important or [[ethics|ethical]]. Closely linked are [[norm (sociology)|norms]], expectations of how people ought to behave, bound by [[tradition]]. Artifacts, or [[archaeological culture|material culture]], are objects derived from the culture's values, norms, and understanding of the world.

The mainstream [[anthropological]] view of [[culture]] implies that most people experience a strong resistance when reminded that there is an animal as well as a spiritual aspect to human nature.<ref name="AnthropologyTodayApr07" />

The mainstream [[anthropological]] view of [[culture]] implies that most people experience a strong resistance when reminded that there is an animal as well as a spiritual aspect to human nature.<ref name="AnthropologyTodayApr07" />

[[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 [[genre]]s as [[epic poetry|epic]], [[legend]], [[mythology|myth]], [[ballad]], and [[folklore]].

[[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 [[genre]]s as [[epic poetry|epic]], [[legend]], [[mythology|myth]], [[ballad]], and [[folklore]].

=== Spirituality and religion ===

=== Spirituality and religion ===

[[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]].  

[[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]].  

A more organized, but related, concept is [[religion]] — sometimes used interchangeably with "[[faith]]" — which is commonly defined as a [[belief]] system concerning the [[supernatural]], [[sacred]], or [[divinity|divine]], and the [[moral code]]s, practices, values, institutions and rituals associated with such belief. In the course of its [[development of religion|development]], religion has taken on many forms that vary by culture and individual perspective.

A more organized, but related, concept is [[religion]] — sometimes used interchangeably with "[[faith]]" — which is commonly defined as a [[belief]] system concerning the [[supernatural]], [[sacred]], or [[divinity|divine]], and the [[moral code]]s, practices, values, institutions and rituals associated with such belief. In the course of its [[development of religion|development]], religion has taken on many forms that vary by culture and individual perspective.

Science is the discovery of knowledge about the world by verifiable means. Technology is the objects humans make to serve their purposes.

Science is the discovery of knowledge about the world by verifiable means. Technology is the objects humans make to serve their purposes.

Human cultures are both characterized and differentiated by the objects that they make and use. [[Archaeology]] attempts to tell the story of past or lost cultures in part by close examination of the [[Artifact (archaeology)|artifacts]] they produced. Early humans left [[stone tools]], [[pottery]] and [[jewelry]] that are particular to various regions and times.

Human cultures are both characterized and differentiated by the objects that they make and use. [[Archaeology]] attempts to tell the story of past or lost cultures in part by close examination of the [[Artifact|artifacts]] they produced. Early humans left [[stone tools]], [[pottery]] and [[jewelry]] that are particular to various regions and times.

Improvements in technology are passed from one culture to another. For instance, the cultivation of crops arose in several different locations, but quickly spread to be an almost ubiquitous feature of human life. Similarly, advances in [[weapons]], [[architecture]] and [[metallurgy]] are quickly disseminated.

Improvements in technology are passed from one culture to another. For instance, the cultivation of crops arose in several different locations, but quickly spread to be an almost ubiquitous feature of human life. Similarly, advances in [[weapons]], [[architecture]] and [[metallurgy]] are quickly disseminated.

Such techniques can be passed on by [[oral tradition]]. The development of [[writing]], itself a kind of technology, made it possible to pass information from generation to generation and from region to region with greater accuracy.

Such techniques can be passed on by [[oral tradition]]. The development of [[writing]], itself a kind of technology, made it possible to pass information from generation to generation and from region to region with greater accuracy.

=== Race and ethnicity ===

=== Race and ethnicity ===

Humans often categorize themselves in terms of [[race]] or [[ethnic group|ethnicity]], although the validity of human races as true biological categories is questionable.<ref>{{cite journal | author = Royal C, Dunston G | title = Changing the paradigm from 'race' to human genome variation. | url=http://www.nature.com/ng/journal/v36/n11s/full/ng1454.html | journal = Nat Genet | volume = 36 | issue = 11 Suppl | pages = S5-7 | year = 2004 | id = PMID 15508004}}</ref> Human racial categories are based on both [[ancestry]] and visible [[trait (biological)|traits]], especially [[human skin color|skin color]] and facial features. These categories may also carry some information on non-visible biological traits, such as the risk of developing particular diseases such as [[sickle-cell disease]].<ref>{{cite journal | author = Risch, N., Burchard, E., Ziv, E. and Tang, H. | year = 2002 | month = | title = Categorization of humans in biomedical research: genes, race and disease | journal = Genome Biology | volume = 3 | issue = 7 | pages = comment2007.2001 - comment2007.2012 | pmid=12184798 | url = http://genomebiology.com/2002/3/7/comment/2007 }}</ref>

Humans often categorize themselves in terms of [[race]] or [[ethnic group|ethnicity]], although the validity of human races as true biological categories is questionable.[http://www.nature.com/ng/journal/v36/n11s/full/ng1454.html] Human racial categories are based on both [[ancestry]] and visible [[trait (biological)|traits]], especially [[human skin color|skin color]] and facial features. These categories may also carry some information on non-visible biological traits, such as the risk of developing particular diseases such as [[sickle-cell disease]].[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=10712212] However, compared to many other animals, human gene sequences are remarkably homogeneous. It has been claimed that the majority of genetic variation occurs within "racial groups", with only 5 to 15% of total variation occurring between racial groups.[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=16175499] However, this remains an area of active debate.

 

Currently available [[Genetic anthropology|genetic]] and archaeological evidence is generally interpreted as supportive of a [[recent single origin hypothesis|recent single origin]] of modern humans in [[East Africa]].<ref>{{cite journal | author = Hua Liu, et al | title = A Geographically Explicit Genetic Model of Worldwide Human-Settlement History | url = http://www.journals.uchicago.edu/AJHG/journal/issues/v79n2/43550/43550.html | journal = The American Journal of Human Genetics | volume = 79 | pages = 230–237 | year = 2006}}</ref>  Genetic studies have demonstrated that humans on the [[Africa]]n continent are most genetically diverse ([[Y-chromosome]] and [[MtDNA]] lineages).<ref>{{cite journal | author = Jorde L, Watkins W, Bamshad M, Dixon M, Ricker C, Seielstad M, Batzer M | title = The distribution of human genetic diversity: a comparison of mitochondrial, autosomal, and Y-chromosome data. | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=10712212 | journal = Am J Hum Genet | volume = 66 | issue = 3 | pages = 979-88 | year = 2000 | id = PMID 10712212}}</ref> However, compared to many other animals, human gene sequences are remarkably homogeneous. It has been claimed that the majority of genetic variation occurs within "racial groups", with only 5 to 15% of total variation occurring between racial groups.<ref>{{cite journal | author = | title = The use of racial, ethnic, and ancestral categories in human genetics research. | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=16175499 | journal = Am J Hum Genet | volume = 77 | issue = 4 | pages = 519-32 | year = 2005 | id = PMID 16175499}}</ref> However, this remains an area of active debate.<ref>{{cite journal |author=Edwards A |title=Human genetic diversity: Lewontin's fallacy |journal=Bioessays |volume=25 |issue=8 |pages=798-801 |year=2003 |pmid=12879450}}</ref><ref>Keita, S. O. Y., Kittles, R. A., Royal, C. D. M., Bonney, G. E., Furbert-Harris, P., Dunston, D. M., and Rotimi, C. M. (2004). ''Conceptualizing human variation'': '''Nature Genetics''' 36, S17 - S20 (2004) {{doi|10.1038/ng1455}}</ref>

Ethnic groups, on the other hand, are more often linked by linguistic, cultural, ancestral, and national or regional ties. Self-identification with an ethnic group is based on [[kinship and descent]]. Race and ethnicity can lead to variant treatment and impact [[social identity]], giving rise to [[racism]] and the theory of [[identity politics]].

Ethnic groups, on the other hand, are more often linked by linguistic, cultural, ancestral, and national or regional ties. Self-identification with an ethnic group is based on [[kinship and descent]]. Race and ethnicity can lead to variant treatment and impact [[social identity]], giving rise to [[racism]] and the theory of [[identity politics]].

== Society ==

== Society ==

[[Society]] is the system of organizations and institutions arising from interaction between humans.

[[Society]] is the system of organizations and institutions arising from interaction between humans.

=== Government and politics ===

=== Government and politics ===

A [[state]] is an organized [[politics|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."<ref>[http://www.mdx.ac.uk/www/study/xweb.htm Max Weber's definition of the modern state 1918], by [[Max Weber]], 1918, retrieved [[March 17]], [[2006]].</ref>

A [[state]] is an organized [[politics|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."<ref>[http://www.mdx.ac.uk/www/study/xweb.htm Max Weber's definition of the modern state 1918], by [[Max Weber]], 1918, retrieved [[March 17]], [[2006]].</ref>

All of these issues have a direct relationship with [[economics]].

All of these issues have a direct relationship with [[economics]].

=== War ===

=== War ===

War is a state of widespread [[conflict]] between [[state]]s, [[organization]]s, or relatively large groups of people, which is characterized by the use of lethal [[violence]] between [[combatant]]s or upon [[civilian]]s. It is estimated that during the 20th century between 167 and 188 million humans died as a result of war.<ref>Ferguson, Niall. "The Next War of the World." Foreign Affairs, Sep/Oct 2006</ref>

War is a state of widespread [[conflict]] between [[state]]s, [[organization]]s, or relatively large groups of people, which is characterized by the use of lethal [[violence]] between [[combatant]]s or upon [[civilian]]s. It is estimated that during the 20th century between 167 and 188 million humans died as a result of war.<ref>Ferguson, Niall. "The Next War of the World." Foreign Affairs, Sep/Oct 2006</ref>

=== Trade and economics ===

=== Trade and economics ===

[[Trade]] is the voluntary exchange of [[good (accounting)|goods]], [[Service (economics)|service]]s, or both, and a form of [[economics]]. A mechanism that allows trade is called a [[market]]. The original form of trade was [[barter (economics)|barter]], the direct exchange of goods and services. Modern traders instead generally negotiate through a medium of exchange, such as [[money]]. As a result, buying can be separated from selling, or [[earning]]. The invention of money (and later [[Credit (finance)|credit]], paper money and non-physical money) greatly simplified and promoted trade.

[[Trade]] is the voluntary exchange of [[good (accounting)|goods]], [[Service (economics)|service]]s, or both, and a form of [[economics]]. A mechanism that allows trade is called a [[market]]. The original form of trade was [[barter (economics)|barter]], the direct exchange of goods and services. Modern traders instead generally negotiate through a medium of exchange, such as [[money]]. As a result, buying can be separated from selling, or [[earning]]. The invention of money (and later [[Credit (finance)|credit]], paper money and non-physical money) greatly simplified and promoted trade.

== External links ==

== External links ==

* [http://www.mnsu.edu/emuseum/biology/humanevolution/sapiens.html MNSU]

* [http://www.mnsu.edu/emuseum/biology/humanevolution/sapiens.html MNSU]

* [http://www.archaeologyinfo.com/homosapiens.htm Archaeology Info]

* [http://www.archaeologyinfo.com/homosapiens.htm Archaeology Info]

* [http://www.breitbart.com/article.php?id=070824121653.65mgd37f Chororapithecus abyssinicus] Possible human-orangutan split 20 million years ago. (Aug 26 2007)

* [http://www.breitbart.com/article.php?id=070824121653.65mgd37f Chororapithecus abyssinicus] Possible human-orangutan split 20 million years ago. (Aug 26 2007)