Human being

Human Fossil range: Pleistocene - Recent
Humans as depicted on the Pioneer plaque
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae Genus: Homo Species: H. sapiens Subspecies: H. s. sapiens
Trinomial name
Homo sapiens sapiens Linnaeus, 1758

In biological terms, a human, or human being, is any member of the mammalian species Homo sapiens, a group of ground-dwelling, tail-less primates that are distributed worldwide and are characterized by bipedalism, with an erect body carriage that frees the hands for manipualting objects. Humans share with other primates the characteristics of opposing thumbs, omnivorous diet, five fingers (pentadactyl) with fingernails, and binocular, color vision. Humans are placed in the family Hominidae, which includes such apes as chimpanzees, gorillas, and orangutans, as well as such close, extinct relatives as Australopithecus, Homo habilis, and Homo erectus.

However, humans being not only define themselves biologically and anatomically, but also in social, psychological, and religious terms.

Socially, *** unique

global distributed

List: characteritics here and then determine the best definition ****

bipdedal primate mammal more highly developed brain than great apes, capable of abstract reasoning, language, and introspection abstract reasoning erect posture (erect body carriage that rrees hands for manipualting objects). capactity for speech capacity for language capactity fo introspection relious perspects emphasize soul, qi, or atman as the essence of being, and often characterizedc by belief in God, gods, spirits, or other people extended parental care

art, music, and literature used in expresing concepts and feels inherently social complex social structures altruistic behaviors, not only towards relatives but others

traditions, rituals, beauty, aesthetics, etc.

Anatomically, human beings are ***

Socially, ****

(Latin: "wise human" or "knowing human") in the family Hominidae (the great apes). Compared to other living organisms on Earth, humans have a highly developed brain capable of abstract reasoning, language, and introspection. This mental capability, combined with an erect body carriage that frees their upper limbs for manipulating objects, has allowed humans to make far greater use of tools than any other species. DNA evidence indicates that modern humans originated in Africa about 200,000 years ago, and they now inhabit every continent,  with a total population of over 6.6 billion as of 2007.

Like most primates, humans are social by nature; however, humans are particularly adept at utilizing systems of communication for self-expression, the exchange of ideas, and organization. Humans create complex social structures composed of cooperating and competing groups, ranging in scale from small families and partnerships to species-wide political, scientific and economic unions. Social interactions between humans have also established an extremely wide variety of traditions, rituals, ethics, values, social norms, and laws which form the basis of human society. Humans also have a marked appreciation for beauty and aesthetics which, combined with the human desire for self-expression, has led to cultural innovations such as art, literature and music.

Humans are also noted for their desire to understand and influence the world around them, seeking to explain and manipulate natural phenomena through science, philosophy, mythology and religion. This natural curiosity has led to the development of advanced tools and skills; humans are the only known species to build fires, cook their food, clothe themselves, and use numerous other technologies.

Humans and other primates

A primate (L. prima, first) is any mammal of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the latter category including humans. Primates are characterized by being anatomically unspecialized, with limbs capable of performing a variety of functions, refined five-digit hands and feet adapted for grasping (including opposable thumbs), comparatively flattened snouts, and prolonged pre- and postnatal development, among other features.

The Primates order is divided informally into three main groupings: Prosimians, monkeys of the New World, and monkeys and apes of the Old World. The prosimians are species whose bodies most closely resemble that of the early proto-primates. The most well known of the prosimians, the lemurs, are located on the island of Madagascar and, to a lesser extent, on the Comoros Islands, isolated from the rest of the world. The New World monkeys include the familiar capuchin, howler, and squirrel monkeys. They live exclusively in the Americas. Discounting humans, the rest of the simians (monkeys and apes), the Old World monkeys, and the apes, inhabit Africa and southern and central Asia, although fossil evidence shows many species once existed in Europe as well.

Based on purely biological aspects (DNA, proteins, morphology, etc.), it is clear the humans are primates. Indeed, humans and chimpanzees share more than 98 percent identity by various molecular comparisons (protein sequences, allele differences, DNA nucleotide sequences) (Wood 2006). However, humans are also defined in cultural, spiritual, psychological, and behavioral terms that make them qualitatively very different from other primates. Despite this, effort is sometimes made to consider humans "just primates," to the extent that efforts are actually being made to legally define other primates as "persons."

All primates have five fingers (pentadactyl), a generalized dental pattern, and an unspecialized body plan. Another distinguishing feature of primates is fingernails. Opposing thumbs are also a characteristic primate feature, but are not limited to this order; opossums, for example, also have opposing thumbs. In primates, the combination of opposing thumbs, short fingernails (rather than claws), and long, inward-closing fingers is considered a relic of the ancestral practice of brachiating through trees.

omnivorous (generalized feeders that consume both animal protein and vegetation), their diet consisting of fruit, grass seeds, and in most cases some quantities of meat and invertebrates—either hunted or scavenged—along with anything else available and easily digested. They are native to Africa and Asia, although humans have spread to all parts of the world.

A hominid is any member of the primate family Hominidae. Recent classification schemes for the apes place extinct and extant humans, chimpanzees, gorillas, and orangutans in Hominidae, and thus technically hominid refers to members of these groups. However, historically and even in some current classification schemes, Hominidae is restricted to humans and their close, extinct relatives—those more similar to humans than to the (other) great apes, which were placed in another family. Thus, there is a tradition of using the term hominid to refer only to humans and such forebears as Australopithecus, Homo habilis, and Homo erectus. In this sense, humans are considered the only surviving hominids.

   * the family Hominidae consisting of gorillas, chimpanzees, orangutans, and humans, collectively known as the "great apes." 

However, the term "hominid" sometimes is used with the specific meaning of humans and extinct animals more closely related to humans than the other great apes (for example, australopithecines). Particularly, this is the case in anthropology, which has used the term for decades in this sense.

This more restricted use of the term hominid is common in anthropology, where it has been used for decades to refer only to humans and their extinct relatives. The more expansive meaning is becoming increasing common among zoologists and systematists.

Uniqueness of human beings

The physical similarity between humans and other members of the "great apes" is so striking—indeed, DNA analysis puts the genetic similarity between humans and chimpanzees at more than 98 percent—that efforts are underway to treat apes as "persons" with various human-like "rights" (see cultural aspects of non-human apes). However, despite the remarkable physical similarity, the gulf between humans and other great apes (and other animals in general) is qualitatively huge, in terms of cultural, psychological, spiritual, emotional, and mental aspects. Humans have a complex language, use symbols in communication, write and read books, have set up diverse systems of governance, have remarkable self-awareness, conduct scientific experiments, practice religious traditions, have developed complex technologies, and so forth.

The genus Pan is generally considered to be part of the subfamily Homininae and tribe Hominini to which humans also belong. Biologists believe that the two species of chimpanzees are the closest living evolutionary relatives to humans. It is thought that humans shared a common ancestor with chimpanzees as recently as five to seven million years ago, and that they have about 98 to 99.4 percent of their DNA in common (Wildman et al. 2003, Wood 2006).

Indeed, the anatomical and biochemical similarity between chimpanzees and humans is so striking that some scientists have proposed that the two chimpanzee species, troglodytes and paniscus, belong with sapiens in the genus Homo, rather than in Pan. One argument for this suggested reclassification is that other species have been reclassified to belong to the same genus on the basis of less genetic similarity than that between humans and chimpanzees.

For example, comparisons between chimpanzees and humans in terms of protein sequences, allele differences, and DNA heteroduplex melting points show more than 98 percent identity (King and Wilson 1975; Wood 2006). Likewise, chromosomal banding patterns reveal a high correspondence between chimp and human chromosomes (Yunis and Prakash 1982).

Ebersberger et al. (2002) found a difference of only 1.24 percent when he aligned 1.9 million nucleotides of chimpanzee DNA and compared them with the corresponding human sequences in the human genome (Wood 2006). Using a 4.97 million nucleotide portion of DNA from human chromosome 7 and comparing to chimpanzee orthologies yielded only 1.13 percent mismatches (Liu et al. 2003).

A comparison of a rough draft of the chimpanzee genome—involving 361,782 contiguous fragments with a medium length of 15,700 nucleotides, covering about 94 percent of the chimpanzee genome—with the human genome, for those sequences that could be aligned, averaged 1.23 percent nucleotide mismatches (The Chimpanzee Sequencing and Analysis Consortium 2005). This same study suggested that the fixed differences between the two genomes, based on the frequency of single nucleotide polymorphisms, may be as low 1.06 percent, with the remaining differences being variations within the chimpanzee or the human.

Comparison of chimpanzee exons and human sequences yielded only 0.6 to 0.87 percent differences (Wildman et al. 2003; Nielsen et al. 2005). Hacia's (2001) review of genetic studies indicated single nucleotide differences were between 1.24 and 1.6 percent. Only a small fraction of the chimpanzee genome consists of sequences not found at the corresponding location in humans. It further appears that human chromosome 2 corresponds to two separate chromosomes in chimpanzees (Wood 2006). Even in terms of some pseudogenes, involving nonsense codons or deletions, many share the same substitions or deletions in both humans and chimpanzees, as evidenced by the studies of Gilad et al. (2003) on olfactory receptor genes.

Of course, the differences between chimpanzees and humans are likewise remarkable. Physiologically, chimpanzees rarely have heart attacks, are resistant to malaria caused by Plasmodium falciparum, and do not go through menopause (Wood 2006). Many cancers common to humans are not found in chimpanzees, and differences exist in terms of the genes for smell and also those that regulate the metabolism of amino acids. Chimpanzees exhibit sexual dimorphism—adult males are nearly 50 percent larger than females, while in humans the males and females are nearly the same size.

The behavioral differences are far more significant. In terms of sexual behavior, chimpanzee males compete for status among themselves, and the dominant males mate promiscuously with mature females; while female bands handle child-rearing. Humans, on the other hand, form monogamous pair bonds and raise their young in families where both parents protect and educate the youngsters. Unlike chimp young, which become independent of their mothers within the first year of life, human young require many years to reach maturity, during which the parents transmit language, culture and skills that make up the greater part of human personhood.

Chimp behavior includes infanticide by males against young of rival males, and the maiming or killing of former alpha males after they have been supplanted by a new leader. Human males, on the other hand, typically protect the children of other families of their tribe, and former male leaders are respected as honored elders. Respect for elderly males, codified in human morality as filial piety, is another means by which humans propagate and transmit culture.

As a result of social learning in family groups and filial respect for elders, humans have come to develop complex languages, use symbols in communication, have created complex technologies, practice and transmit religious belief, pursue science, and create art and literature.

Indeed, if one were to overlook the anatomical similarity, the gap between chimpanzees and humans in terms of culture, mental capacity, and various spiritual, emotional, and technological aspects is so large as to dwarf differences between chimpanzees and other animals. In this sense, philosophers have recognized humans as distinct from animals generally, including chimpanzees.

History

Evolution

For more details on this topic, see Human evolution.

The scientific study of human evolution encompasses the development of the genus Homo, but usually involves studying other hominids and 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. Anatomically modern humans appear in the fossil record in Africa about 130,000 years ago.

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. It has been estimated that the human lineage diverged from that of chimpanzees about five million years ago, and from gorillas 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.

There are two prominent scientific theories of the origins of contemporary humans. They concern the relationship between modern humans and other hominids. The single-origin, or "out-of-Africa", hypothesis proposes that modern humans evolved in Africa and later migrated outwards to replace hominids in other parts of the world. The multiregional hypothesis, on the other hand, proposes that modern humans evolved, at least in part, from independent hominid populations.

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.^{[citation needed]} Following this was the evolution of a larger 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;^{[citation needed]} 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 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 bonding. 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.

Rise of civilization

The rise of agriculture led to the foundation of stable human settlements.

For more details on this topic, see History of the world.

The most widely accepted view among current anthropologists is that Homo sapiens originated in the African savanna around 200,000 BP (Before Present), descending from Homo erectus, had inhabited Eurasia and Oceania by 40,000 BP, and finally inhabited the Americas approximately 10,000 years ago. They displaced Homo neanderthalensis and other species descended from Homo erectus (which had inhabited Eurasia as early as 2 million years ago) through more successful reproduction and competition for resources.

Up until only around 10,000 years ago, all humans lived as hunter-gatherers (with some communities persisting until this day). They generally lived in small, nomadic groups. The advent of agriculture prompted the Neolithic Revolution. Access to food surplus led to the formation of permanent human settlements, the domestication of animals, and the use of metal tools. Agriculture also encouraged trade and cooperation, leading to complex societies. Villages developed into thriving civilizations in regions such as the Middle East's Fertile Crescent.

Around 6,000 years ago, the first proto-states developed in Mesopotamia, Egypt 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, China, and Rome, developed through conquest into the first expansive empires. Influential religions, such as Judaism, originating in the Middle East, and Hinduism, a religious tradition that originated 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 economy promoted innovations such as printing and the compass, while the Islamic Golden Age saw major scientific advancements in Muslim empires. In Europe, the rediscovery of classical learning and inventions such as the printing press led to the Renaissance in the 14th century. Over the next 500 years, exploration and imperialistic conquest brought much of the Americas, Asia, and Africa 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.

As a result of such changes, modern humans live in a world that has become increasingly globalized and interconnected. Although this has encouraged the growth of science, art, and technology, it has also led to culture clashes, the development and use of weapons of mass destruction, and increased environmental destruction and pollution.

Habitat and population

For more details on this topic, see Demography and World population.

Humans have structured their environment in extensive ways in order to adapt to problems such as high population density, as shown in this image of an Asian city, Hong Kong.

Early human settlements were dependent on proximity to water and, depending on the lifestyle, other natural resources, such as fertile land for growing crops and grazing livestock, or seasonally by hunting populations of prey. However, humans have a great capacity for altering their habitats by various methods, such as through irrigation, urban planning, construction, transport, and manufacturing goods. 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 all climates. Within the last few decades, humans have explored Antarctica, the ocean depths, and space, although long-term habitation of these environments is not yet possible. With a population of over six billion, humans are among the most numerous of the large mammals. Most humans (61%) live in Asia. The vast majority of the remainder live in the Americas (14%), Africa (13%) and Europe (12%), with 0.5% in Oceania. (See list of countries by population and list of countries by population density.)

Human habitation within closed ecological systems in hostile environments, such as Antarctica and outer space, is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with no more than thirteen humans in space at any given time. Between 1969 and 1972, two humans at a time spent brief intervals on the Moon. As of 2007, no other celestial body has been visited by human beings, although there has been a continuous human presence in outer space since the launch of the initial crew to inhabit the International Space Station on October 31, 2000; however, humans have made robots that have visited other celestial bodies.

From AD 1800 to 2000, the human population increased from one billion to six billion. In 2004, around 2.5 billion out of 6.3 billion people (39.7%) lived in urban areas, and this percentage is expected to rise throughout the 21st century. Problems for humans living in cities include various forms of pollution and crime, especially in inner city and suburban slums. Benefits of urban living include increased literacy, access to the global canon of human knowledge and decreased susceptibility to rural famines.

Humans have had a dramatic effect on the environment. It has been hypothesized that in the past, human predation has contributed to the extinction of a number of species; as humans are not generally preyed on themselves, humans have been described as the ultimate superpredators. Currently, through land development and pollution, humans are thought to be the main contributor to global climate change. This is believed to be a major contributor to the ongoing Holocene extinction event, a mass extinction which, if it continues at its current rate, is predicted to wipe out half of all species over the next century.

Biology

For more details on this topic, see Human biology.

Physiology and genetics

For more details on this topic, see Human anatomy, Human physical appearance, and Human genetics.

An old diagram of a male human skeleton.

Human body types vary substantially. Although body size is largely determined by genes, it is also significantly influenced by environmental factors such as diet and exercise. The average height of an adult human is about 5 to 6 feet (1.5 to 1.8 m) tall, although this varies significantly from place to place. Humans are capable of fully bipedal locomotion, thus leaving their arms available for manipulating objects using their hands, aided especially by opposable thumbs.

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.

An Inuit woman, circa 1907.

The hue of human hair and skin is determined by the presence of pigments called melanins. Human skin hues can range from very dark brown to very pale pink, while human hair ranges from blond to brown to red to, most commonly, black. Most researchers believe that skin darkening was an adaptation that evolved as a protection against ultraviolet solar radiation, as melanin is an effective sun-block. 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.

Humans are an eukaryotic species. Each diploid cell has two sets of 23 chromosomes, each set received from one parent. There are 22 pairs of autosomes and one pair of sex chromosomes. By present estimates, humans have approximately 20,000 – 25,000 genes. Like other mammals, humans have an XY sex-determination system, so that females have the sex chromosomes XX and males have XY. The X chromosome is larger and carries many genes not on the Y chromosome, which means that recessive diseases associated with X-linked genes, such as hemophilia, affect men more often than women.

Human embryo at 5 weeks.

Life cycle

The human life cycle is similar to that of other placental mammals. New humans develop viviparously from conception. An egg is usually fertilized inside the female by 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.

Two young human girls.

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 pounds) in weight and 50 – 60 cm (20 – 24 inches) in height at birth. However, low birth weight is common in developing countries, and contributes to the high levels of infant mortality in these regions. Helpless at birth, humans continue to grow for some years, typically reaching sexual maturity at 12 to 15 years of age. Human girls continue to grow physically until around the age of 18, and human boys 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 — 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 years (highest in Monaco at 45.1 years), while in the 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. While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older.

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. 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 philosophical questions of when human personhood begins and whether it persists after death are the subject of considerable debate. The prospect of death causes unease or fear for most humans. Burial ceremonies are characteristic of human societies, often accompanied by beliefs in an afterlife or immortality.

Diet

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 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. Some humans have chosen to abstain from eating some or all meat for religious, ethical, ecological, or health reasons.

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. 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, 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 calories than are expended, with many attributing excessive weight gain to a combination of overeating and insufficient exercise.

At least ten thousand years ago, humans developed agriculture, which has substantially altered the kind of food people eat. This has 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.

Psychology

File:Davidbrain.JPG

A sketch of the human brain, imposed upon the profile of Michelangelo's David - sketch by artist Priyan Weerappuli.

For more details on this topic, see Human brain and Mind.

The human brain is the center of the central nervous system in humans, as well as the primary control center for the peripheral nervous system. The brain controls "lower", or involuntary, autonomic activities such as the respiration, and digestion. The brain also controls "higher" order, conscious activities, such as thought, reasoning, and abstraction. These cognitive processes constitute the mind, and, along with their behavioral consequences, are studied in the field of psychology.

The human brain is generally regarded as more capable of these higher order activities, and more "intelligent" in general, than that of any other species. While other animals are capable of creating structures and using simple tools — mostly as a result of instinct and learning through mimicry — human technology is vastly more complex, constantly evolving and improving with time. Even the most ancient human tools and structures are far more advanced than any structure or tool created by any other animal.

Modern Anthropology has tended to bear out Darwin's proposition that "the difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind".

Consciousness and thought

For more details on this topic, see Consciousness and Cognition.

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, orangutans, dolphins, and possibly pigeons. In October 2006, three elephants at the Bronx Zoo also passed this test. Humans under the age of 2 typically fail this test. However, this may be a matter of degree rather than a sharp divide. Monkeys have been trained to apply abstract rules in tasks.

The 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 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.

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 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 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.

Comparison to other species

Theories in psychology, like the construction of the ego as suggested in the mirror stage by Jacques Lacan reminds us about the possibility that self-consciouness and self-reflection may be at least in part a human construction. Various attempts have been made to identify a single behavioral characteristic that distinguishes humans from all other animals. Some anthropologists think that readily observable characteristics (tool-making and language) are based on less easily observable mental processes that might be unique among humans: the ability to think symbolically, in the abstract or logically, although several species have demonstrated some abilities in these areas. Nor is it clear at what point exactly in human evolution these traits became prevalent. They may not be restricted to the species Homo sapiens, as the extinct species of the Homo genus (e.g. Homo neanderthalensis, Homo erectus) are believed to also have been adept tool makers and may also have had linguistic skills.

Motivation and emotion

Goya's Tio Paquete (1820).

For more details on this topic, see Motivation and Emotion.

Motivation is the driving force of desire behind all deliberate 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 incentives, moral incentives, or coercive incentives. Religions generally posit divine or demonic influences.

Happiness, or 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 which a human can have — a condition of mental and physical health. Others may 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, inner peace, and so forth.

Human 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, like love, admiration, or joy, contrast with those perceived as unpleasant, like hate, envy, or sorrow. There is often a distinction seen between refined emotions, which 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 those cultures where emotion is considered separate from physiological state. In some cultural medical theories, to provide an example, 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 (in particular, the poet and astronomer Omar Khayyám) felt certain extreme emotions could yield a conceptual perfection, what is often translated as ecstasy.

In modern scientific thought, certain refined emotions are considered to be a complex neural trait of many domesticated and a few 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. Still, when humans function in civilized tandem, it has been noted that uninhibited acting on extreme emotion can lead to social disorder and crime.

Love and sexuality

For more details on this topic, see Love and Human sexuality.

File:Amazon-variant-sex-position.jpg

Human sexuality and copulation is expressed in diverse ways, including this position in which the partners face each other.

Human sexuality, besides ensuring biological reproduction, has important social functions: it creates physical intimacy, bonds and hierarchies among individuals; may be directed to spiritual transcendence (according to some traditions); and in a hedonistic sense to the enjoyment of activity involving sexual gratification. Sexual desire, or libido, is experienced as a bodily urge, often accompanied by strong emotions such as love, ecstasy and jealousy.

As with other human self-descriptions, humans propose that it is high intelligence and complex societies of humans that have produced the most complex sexual behaviors of any animal, including a great many behaviors that are not directly connected with reproduction.

Human sexual choices are usually made in reference to cultural norms, which vary widely. Restrictions are sometimes determined by religious beliefs or social customs.

Many 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).^{[citation needed]} In a variation of this, 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). 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.

Culture

Human society statistics
World population	6,637,070,000 (August 2006)
Population density	12.7 per km² (4.9 mi²) by total area 43.6 per km² (16.8 mi²) by land area
Largest agglomerations	Tokyo, Mexico City, Sao Paulo, Shanghai, New York City, Seoul, Mumbai
Major languages by number of native speakers (2000 est.)	Mandarin Chinese 14.37 % Hindi 6.02 % English 5.61 % Spanish 5.59 % Portuguese 4.9 % Arabic 4.59 %
Largest religions (2002 est.)	Christianity 32.71 % Islam 21.67 % (No religion 14.84 %) Hinduism 13.28 % Buddhism 5.84 %
Most widespread currencies	United States dollar, Euro, Japanese yen, Pound sterling.
GDP (nominal)	$36,356,240 million USD ($5,797 USD per capita)
GDP (PPP)	$51,656,251 million IND ($8,236 per capita)

For more details on this topic, see 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 consists of values, social norms, and artifacts. A culture's values define what it holds to be important or ethical. Closely linked are norms, expectations of how people ought to behave, bound by tradition. Artifacts, or "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.

Language

For more details on this topic, see Language.

The capacity humans have to transfer concepts, ideas and notions through speech and writing is unrivaled in known species. The faculty of speech is a defining feature of humanity, possibly predating phylogenetic separation of the modern population (see origin of language). Language is central to the communication between humans, as well as being central to the sense of identity that unites nations, cultures and ethnic groups.

The invention of writing systems around 5000 years ago allowed the preservation of language on material objects, and was a major step in cultural evolution. Language is closely tied to ritual and religion (cf. mantra, sacred text).

The science of linguistics describes the structure of language and the relationship between languages. There are approximately 6,000 different languages currently in use, including sign languages, and many thousands more that are considered extinct.

Human self reflection leads to the understanding of the origins of human beings.

Prehistoric notions about the status of humanity may be guessed by the etymology of ancient words for man. Latin homo (PIE *kþonyon) means "of the earth, earthling," probably in opposition to "celestial" beings. Greek ἂνθροπος (mycenaean *anthrokwos) means "low-eyed," again probably contrasting with a divine perspective.

Ancient Orient From the 3rd millennium Old Kingdom of Egypt, belief in the eternal afterlife of the human Ka is documented. From the earliest times, man made out a claim of dominance of humanity alongside radical pessimism because of the frailty and brevity of human life (In the Hebrew Bible, for example, dominion of man is promised in Genesis 1:28, but the author of Ecclesiastes bewails the vanity of all human effort).

Classical antiquity Protagoras made the famous claim that "Man is the measure of all things; of what is, that it is; of what is not, that it is not". Socrates gave the (doubtlessly tongue-in-cheek) definition of humans as "featherless bipeds" (Plato, Politicus). More serious is Aristotle's description of man as the "communal animal" (ζώον πολιτκόν), i.e., emphasizing society-building as a central trait of human nature, and "animal with sapience" (ζώον λόγoν ἒχων, animal rationale), a term that also inspired the species' taxonomy, Homo sapiens.

Middle Ages The dominant world-view of medieval Europe, as directed by the Catholic Church, was that human existence is characterized by sin, and that its aim should be to prepare for divine judgement after death. The 13th century pope Innocent III wrote about the essential misery of earthly existence in his "On the misery of the human condition" – a view that was disputed by, for example, Gianozzo Manetti in his treatise "On human dignity."

Renaissance A famous quote of Shakespeare's Hamlet (II, ii, 115-117), expressing the contrast of human physical beauty, intellectual faculty, and ephemeral nature:

What a piece of work is a man! How noble in reason! how infinite in faculties! in form and moving, how express and admirable! in action how like an angel! in apprehension, how like a god! the beauty of the world! the paragon of animals! And yet, to me, what is this quintessence of dust?

Modern era The Enlightenment was driven by a renewed conviction, that, in the words of Immanuel Kant, "Man is distinguished above all animals by his self-consciousness, by which he is a 'rational animal'." In the 19th century, Karl Marx defined man as "labouring animal" (animal laborans) in conscious opposition to this tradition. In the early 20th century, Sigmund Freud dealt a serious blow to positivism by postulating that human behaviour is to a large part controlled by the unconscious mind.

Some feel that the modern culture of materialism leaves little room for reflection; the tendency to focus on worldly goods naturally denies the opportunity to ponder one's life and its place in the universe. The idea of philosophy being discarded as it runs counter to the pursuit of pleasure is a common theme in certain works of dystopian science fiction, such as Brave New World or Fahrenheit 451.

However, it could be argued that a culture of self obsession leads to more self-reflection, since, in the quest for the ideal life, individuals will constantly analyse their characters, faults and ambitions. This can be shown in the trend to seek psychotherapy as the panacea to one's emotional woes. The current popularity of the Humanities amongst the academic disciplines also shows an increased public interest in mankind and its place in the cosmos.

Spiritual movements that encourage the reflective arts of prayer and meditation as a practice are on the rise, both as branches of existing religions and as part of more eclectic movements like the New Age.

Art, music and literature

Allegory of Music (ca. 1594), a painting of a woman writing sheet music by Lorenzo Lippi.

For more details on this topic, see Art, Music, and Literature.

Artistic works have existed for almost as long as humankind, from early pre-historic art to contemporary art. Art is one of the most unusual aspects of human behavior and a key distinguishing feature of humans from other species.

As a form of cultural expression by humans, 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 which, 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 for humans, while learning and understanding it are popular disciplines. 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.

File:7BrahmanMH.jpg

Sculpture of a man meditating.

Spirituality and religion

For more details on this topic, see 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.

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 divine, and the moral codes, practices, values, institutions and rituals associated with such belief. 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 source of a variety of origin beliefs), the nature of the universe (religious cosmology) and its ultimate fate (eschatology), and what is moral or immoral. A common source in religions for answers to these questions are transcendent divine beings such as deities or a singular God, although not all religions are theistic — many are nontheistic or ambiguous on the topic, particularly among the Eastern religions.

Although a majority of humans profess some variety of spiritual or religious belief, some are irreligious, lacking or rejecting belief in the supernatural or spiritual. Additionally, although most religions and spiritual beliefs are clearly distinct from science on both a philosophical and methodological level, the two are not generally considered to be mutually exclusive; 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.

File:Thinker.jpg

The Thinker, Artist's rendering of the sculpture by Auguste Rodin.

Philosophy and self-reflection

For more details on this topic, see Philosophy, Human self-reflection, and Human nature.

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 values and reality by chiefly speculative means.

The core philosophical disciplines are logic, ontology or metaphysics, epistemology, and axiology, which includes the branches of ethics and aesthetics. Philosophy covers a very wide range of approaches, and is also 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.

Plato and Aristotle in a detail from The School of Athens by Raphael.

Metaphysics is a branch of philosophy concerned with the study of first principles, being and existence (ontology). In between the doctrines of religion and science, stands the philosophical perspective of metaphysical cosmology. This ancient field of study seeks to draw logical conclusions about the nature of the universe, humanity, god, and/or their connections based on the extension of some set of presumed facts borrowed from religion and/or observation.

Humans often consider themselves to be the dominant species on Earth, and the most advanced in intelligence and ability to manage their environment. This belief is especially strong in modern Western culture. Alongside such claims of dominance is often found radical pessimism because of the frailty and brevity of human life.

Humanism is a philosophy which defines a socio-political doctrine the bounds of which are not constrained by those of locally developed cultures, but which seeks to include all of humanity and all issues common to human beings. Because spiritual beliefs of a community often manifests as religious doctrine, the history of which is as factious as it is unitive, secular humanism grew as an answer to the need for a common philosophy that transcended the cultural boundaries of local moral codes and religions. Many humanists are religious, however, and see humanism as simply a mature expression of a common truth present in most religions. Humanists affirm the possibility of an objective truth and accept that human perception of that truth is imperfect. The most basic tenets of humanism are that humans matter and can solve human problems, and that science, freedom of speech, rational thought, democracy, and freedom in the arts are worthy pursuits or goals for all peoples. Humanism depends chiefly on reason and logic without consideration for the supernatural.

Science and technology

In the mid- to late 20th century, humans achieved a level of technological mastery sufficient to leave the atmosphere of Earth for the first time, explore space and walk on the moon.

For more details on this topic, see Science and Technology.

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 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.

Space science provides a new perspective on human significance

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.

Together, these developments made possible the commencement of civilization and urbanization, with their inherently complex social arrangements. Eventually this led to the institutionalization of the development of new technology, and the associated understanding of the way the world functions. This science now forms a central part of human culture.

In recent times, physics and astrophysics have come to play a central role in shaping what is now known as physical cosmology, that is, the understanding of the universe through scientific observation and experiment. This discipline, which focuses on the universe as it exists on the largest scales and at the earliest times, begins by arguing for the big bang, a sort of cosmic expansion from which the universe itself is said to have erupted ~13.7 ± 0.2 billion (10⁹) years ago. After its violent beginnings and until its very end, scientists then propose that the entire history of the universe has been an orderly progression governed by physical laws.

Race and ethnicity

For more details on this topic, see Race and Ethnic group.

Humans often categorize themselves in terms of race or ethnicity, although the validity of human races as true biological categories is questionable. Human racial categories are based on both ancestry and visible traits, especially 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.

Currently available genetic and archaeological evidence is generally interpreted as supportive of a recent single origin of modern humans in East Africa. Genetic studies have demonstrated that humans on the African continent are most genetically diverse (Y-chromosome and MtDNA lineages). 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. However, this remains an area of active debate.

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

For more details on this topic, see Society.

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

Government and politics

The United Nations complex in New York City, which houses one of the largest human political organizations in the world.

For more details on this topic, see Government, Politics, and State.

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."

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. 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. The most common form of government worldwide is a republic, however other examples include monarchy, social democracy, military dictatorship and theocracy.

All of these issues have a direct relationship with economics.

The atomic bombings of Hiroshima and Nagasaki immediately killed over 120,000 humans.

War

For more details on this topic, see War.

War is a state of widespread conflict between states, organizations, or relatively large groups of people, which is characterized by the use of lethal violence between combatants or upon civilians. It is estimated that during the 20th century between 167 and 188 million humans died as a result of war.

A common perception of war is a series of military campaigns between at least two opposing sides involving a dispute over sovereignty, territory, resources, religion or other issues. A war said to liberate an occupied country is sometimes characterized as a "war of liberation", while a war between internal elements of a state is a civil war. Full scale pitched-battle wars between adversaries of comparable strength appear to have nearly disappeared from human activity, with the last major one in the Congo region winding down in the late 1990's. Nearly all war now is asymmetric warfare, in which campaigns of sabotage, guerrilla warfare and sometimes acts of terrorism disrupt control and supply of better-equipped occupying forces, resulting in long low-intensity wars of attrition.

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, and ethnic cleansing. Military intelligence has often played a key role in determining victory and defeat. Propaganda, which often includes factual 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 armoured fighting vehicles are used to control the land, warships the sea, and air power the sky. Outer space has recently become a factor in warfare as well, although no actual warfare is currently carried out in space.

War is a strong catalyst in technology. Throughout history there has been a constant struggle between defense and offense, armour, and the weapons designed to breach it. Modern examples include the bunker buster bomb, and the bunkers which they are designed to destroy. Important inventions such as medicine, navigation, metallurgy, mass production, nuclear power, rocketry and computers have been completely or partially driven by war.

Trade and economics

Buyers and sellers bargain in Chichicastenango Market, Guatemala.

For more details on this topic, see Trade and Economics.

Trade is the voluntary exchange of goods, services, or both, and a form of economics. A mechanism that allows trade is called a market. The original form of trade was 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, paper money and non-physical money) greatly simplified and promoted trade.

Trade exists for many reasons. Because of specialization and division of labor, most people concentrate on a small aspect of manufacturing or service, trading their labour for products. Trade exists between regions because different regions have an absolute or comparative advantage in the production of some tradeable commodity, or because different regions' size allows for the benefits of mass production.

Economics is a social science that studies the production, distribution, trade and consumption of goods and services.

Economics, which focuses on measurable variables, 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. Mainstream economics focuses on how prices reflect supply and demand, and uses equations to predict consequences of decisions.

References

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Wikispecies has information related to:

Homo sapiens sapiens

External links

Wikimedia Commons has media related to:

Homo sapiens

• MNSU
• Archaeology Info
• Human article at Wikinfo
• Chororapithecus abyssinicus Possible human-orangutan split 20 million years ago. (Aug 26 2007)

Part of the series on Human evolution

Hominini

Sahelanthropus tchadensis • Orrorin tugenensis • Ardipithecus

Australopithecines

Australopithecus: A. anamensis • A. afarensis • A. bahrelghazali • A. africanus • A. garhi

Paranthropus: P. aethiopicus • P. boisei • P. robustus

Humans and Proto-humans

Kenyanthropus platyops

Homo: H. habilis • H. rudolfensis • H. georgicus • H. ergaster • H. erectus (H. e. lantianensis • H. e. palaeojavanicus • H. e. pekinensis • H. e. soloensis) • H. cepranensis • H. antecessor • H. heidelbergensis • H. neanderthalensis • H. rhodesiensis • H. floresiensis • Homo sapiens (H. s. idaltu • H. s. sapiens)

Topics: Timeline of human evolution • List of human fossils • Human evolutionary genetics

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