Human
Physiology and genetics
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 a North American adult female is 162
centimetres (5 feet 4 inches), and the average weight is 62
kilograms (137
pounds). Human males are typically larger than females: the average height and weight of a North American adult male is 175 centimeters (5 feet 9 inches) and 78 kilograms (172 pounds).
Humans are capable of fully
bipedal
locomotion, thus leaving their arms available for manipulating objects using their
hands, aided especially by opposable
thumbs. Because human physiology has not fully adapted to bipedalism, the pelvic region and
vertebral column tend to become worn, creating locomotion difficulties in old age.
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 on his or her body than the average
chimpanzee. The main distinction is that human hairs are shorter, finer, and less colored than the average chimpanzee's, thus making them harder to see.
[Why Humans and Their Fur Parted Way by Nicholas Wade, New York Times, August 19 2003, retrieved March 17, 2006.] |
An Inuit woman, circa 1907. |
The color of human hair and skin is determined by the presence of
pigments called
melanins. Human skin color can range from very dark brown to very pale pink, while human hair ranges from
blond to
brown to
red, but most commonly,
black.
Most researchers believe that skin darkening was an adaptation that evolved as a defense against
ultraviolet solar radiation: melanin is an effective sun-block.
[Jablonski, N.G. & Chaplin, G. (2000). The evolution of human skin coloration (pdf), 'Journal of Human Evolution 39: 57-106.] The skin color 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.
[Harding, Rosalind M., Eugene Healy, Amanda J. Ray, Nichola S. Ellis, Niamh Flanagan, Carol Todd, Craig Dixon, Antti Sajantila, Ian J. Jackson, Mark A. Birch-Machin, and Jonathan L. Rees (2000). Evidence for variable selective pressures at MC1R. American Journal of Human Genetics 66: 1351â€"1361.][Robin, Ashley (1991). Biological Perspectives on Human Pigmentation. Cambridge: Cambridge University Press.]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. Negative effects result from restriction of sleep. For instance, 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. It is common in modern societies for people to get less sleep than they need, leading to a state of
sleep deprivation.
Humans are a
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 20,000â€"25,000 genes and share 98.4% of their
DNA with their closest living evolutionary relatives, the two species of
chimpanzees.
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.
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 also 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 becomes a human
fetus. At birth, 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 fairly complicated. Painful labors lasting twenty-four hours or more are not uncommon, and may result in injury, or even death, to the child or mother. This is due to 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 labour increased significantly during the 20th century in wealthier countries with the advent of new medical technologies.
Natural childbirth remains a common, and relatively dangerous ordeal in unindustrialized regions of the world and for poor people in industrialized regions.
Human children are born after a nine-month
gestation period, and are typically 3â€"4 kilograms (6â€"9 pounds) in weight and 50â€"60 centimeters (20â€"24 inches) in height in developed countries.
[Low Birthweight] Helpless at birth, they continue to grow for some years, typically reaching
sexual maturity at twelve to fifteen years of age. Human girls continue to grow physically until around the age of eighteen, while human boys continue growing until around the age of twenty-one.
The human life span can be split into a number of stages:
infancy,
childhood,
adolescence,
young adulthood,
maturity 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 15â€"20 years (lowest in
Uganda at 14.8 years). Life expectancy at birth is 77.2 years in the U.S. as of 2001.
[Life expectancy in the U.S., 2001, National Center for Health Statistics, Centers for Disease Control and Prevention, December 8, 2004, retrieved April 2, 2005.] The expected life span at birth in
Singapore is 84.29 years for a female and 78.96 years for a male, while in
Botswana, due largely to
AIDS, it is 30.99 years for a male and 30.53 years for a female. One in five Europeans, but one in twenty Africans, is 60 years or older.
[[https://www.cia.gov/cia/publications/factbook/ The World Factbook], U.S. Central Intelligence Agency, retrieved April 2, 2005.]The number of
centenarians (humans 100 years or older) in the world was estimated by the
United Nations at 210,000 in 2002.
[U.N. Statistics on Population Ageing, United Nations press release, February 28, 2002, retrieved April 2, 2005] The current
maximum life span of humans is about 120 years (
Jeanne Calment lived for 122 years and 164 days). Worldwide, there are 81 men aged 60 or older for every 100 women of the same age, 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 inspired by beliefs in an
afterlife or
immortality.
Race and ethnicity
Humans often categorize themselves in terms of
race or
ethnicity, although the scientific validity of human races as categories is disputed. Human racial categories are based on both
ancestry and visible
traits, especially
skin color and facial features. Ethnic groups, on the other hand, are more often linked by linguistic, cultural, 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 the theory of
identity politics.
Although most humans recognize that variances occur within a species, it is often a point of dispute as to what these differences entail, their importance, and whether discrimination based on race (
racism) is acceptable. Some societies have placed a great deal of emphasis on race, while others have not.
Evolution
|
Reconstructed skull of Peking Man, a representative of the extinct species believed to be the nearest ancestor of Homo sapiens, Homo erectus. |
The study of
human evolution encompasses the development of the genus
Homo, but usually involves studying other
hominids and
hominines as well, such as the
australopithecines. "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 man"), the other known subspecies, is extinct.
[Human evolution: the fossil evidence in 3D, by Philip L. Walker and Edward H. Hagen, Dept of Anthropology, University of California, Santa Barbara, retrieved April 5, 2005.]The closest living relatives of
Homo sapiens are the
Common Chimpanzee and the
Bonobo. Full
genome sequencing resulted in the conclusion that "After 6.5 [million] years of separate evolution, the differences between 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, chimpanzee and human DNA is 96% identical.
[Human and chimp DNA is 96% identical, by Clive Cookson, Financial Times, August 13, 2005, retrieved March 17, 2006.] 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.
[Eswaran, Vinayak, Harpending, Henry & Rogers, Alan R. Genomics refutes an exclusively African origin of humans, Journal of Human Evolution, In Press, Corrected Proof, retrieved May 6, 2005.]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, and that during the
Late Pleistocene, the human population was reduced to a small number of breeding pairs—no more than 10,000â€"resulting in a very small residual gene pool. Various reasons for this hypothetical bottleneck have been postulated, the most popular being the
Toba catastrophe theory.
Human evolution is characterized by a number of important physiological trends, including the
expansion of the
brain cavity and brain itself, which is typically 1,400 cm³ in volume, over twice that of a chimpanzee or gorilla. The pattern of human postnatal brain growth differs from that of other apes (
heterochrony), allowing for an extended period of
social learning in juvenile humans.
Physical anthropologists argue that a reorganization of the structure of the brain is more important than cranial expansion itself. Other significant evolutionary changes included a reduction of the
canine tooth, development of
bipedal locomotion, and the descent of the
larynx and
hyoid bone, making speech possible. How these trends are related and what their role is in the evolution of complex social organization and culture are matters of ongoing debate in the field of
physical anthropology.
[Boyd, Robert & Silk, Joan B. (2003). How Humans Evolved. New York: Norton & Company. ISBN 0393978540.][Dobzhansky, Theodosius (1963). Anthropology and the natural sciences-The problem of human evolution, Current Anthropology 4 (2): 138-148.]Habitat and population
The most widely accepted view among current
anthropologists is that
Homo sapiens originated in the
African
savanna between 200,000 and 250,000 years ago, descending from
Homo erectus, and colonized
Eurasia and
Oceania by 40,000 years ago, and finally colonized the
Americas by 10,000 years ago.
[Templeton, Alan (2002). "Out of Africa again and again" Nature 416: 45 - 51.] They displaced
Homo neanderthalensis,
Homo floresiensis and other species descended from
Homo erectus (which had colonized Eurasia as early as 2 million years ago) through more successful reproduction and competition for resources.
The earliest humans were
hunter-gatherers, a lifestyle well-suited to the savanna. Some later groups of humans were
nomads, often to facilitate animal
herding, and still later humans established permanent settlements, which was made possible by the development of
agriculture. Permanent 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, and 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 2006, no other celestial body has been visited by human beings, although there has been a continuous human presence in space since the launch of the initial crew to inhabit the
International Space Station on
October 31,
2000.
From AD 1800 to 2000, the human population increased from one 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,
crime, and
poverty, especially in inner city and suburban slums.
Diet
The human diet, similar to most mammals, centers around regular intake of
food and
drink. It is prominently reflected in human culture, and has led to the development of
food science. Failure to obtain food leads to
hunger and eventually
starvation, while failure to obtain water leads to
thirst and
dehydration. Both starvation and dehydration cause death if not alleviated. 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. In modern times,
obesity among some human populations has increased to almost
epidemic proportions, leading to health complications and increased mortality in some
developed, and, increasingly, in
developing countries. The United States Center for Disease Control states that 32% of adults over the age of 20 are obese, while 66.5% are obese or overweight. Obesity is believed to be caused by a number of factors, with many attributing excessive weight gain to overeating.
Humans are animals who can consume both plant and animal products. Most biologists agree humans are
omnivorous.
[Vegetarianism in a Nutshell - Humans are Omnivores - retrieved July 20 2006] A minority believes they are an anatomically
herbivorous species, many members of which have begun consuming food of animal origin.
[Comparison of human anatomy with herbivore anatomy by biologist John Cole - retrieved July 20 2006] Another minority believes that anatomically, they are primarily
carnivorous, and have started using agriculture only recently.
[The design of our digestive organs and digestive enzymes today by Barry Groves, using data collected by Walter Voegtlin - retreived August 3 2006]Early
Homo sapiens employed a "hunter-gatherer" methodology 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. Some humans choose to be
vegans or
vegetarians, abstaining from eating meat for religious, ethical, ecological, or health reasons. 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—possibly even earlier.
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, due to 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.
The last century or so has produced enormous improvements in food production, preservation, storage and shipping. Today almost every locale in the world has access to not only its traditional cuisine, but many other world cuisines.
Brain, mind, and consciousness
 |
The human brain. |
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
heart rate,
respiration, and
digestion. The brain also controls "higher" order, conscious activities, such as
thought,
reasoning, and
abstraction.
[3-D Brain Anatomy, The Secret Life of the Brain, Public Broadcasting Service, retrieved April 3 2005.] The human brain is generally regarded as more capable of these higher order activities, and more "
intelligent" in general, than 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.
[Sagan, Carl (1978). The Dragons of Eden. A Balantine Book. ISBN 0345346297.]The human ability to think abstractly may be unparalleled in the animal kingdom. Human beings 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,
bonobos,
orangutans,
dolphins and
pigeons. Human beings under the age of 2 typically fail this test.
[Consciousness and the Symbolic Universe, by Dr. Jack Palmer, retrieved March 17, 2006.] However, this may be a matter of degree rather than a sharp divide. Monkeys have been trained to apply abstract rules in tasks.
[Researchers home in on how brain handles abstract thought - retrieved July 29, 2006]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.
Cognitive scientist 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.
[Dennett, Daniel (1991). Consciousness Explained. Little Brown & Co, 1991, ISBN 0316180653.]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.
Social psychology links
sociology with psychology in their shared study of the nature and causes of human social behavior, with an emphasis on how people think towards each other and how they relate to each other. The behavior and mental processes of animals, 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.
Complete scientific classification
The complete scientific classification of the modern human consists of many sub- and super- sections to the basic chart:
Eukaryota (Domain)
Animalia (Kingdom)
Eumetazoa (Subregnum)
Bilateria [having bilateral symmetery]
Deuterostomia (Superphylum)
Chordate (Phylum)
Craniata [animals with skulls]
Vertebrata (Subphylum) [...and backbones]
Gnathostomata (Infraphylum) [...and jaws]
Teleostomi [advanced fish and descendants]
Tetrapoda (Superclass) [...and four legs]
Amniota (Series) [...and amniotic eggs]
Synapsida [mammal-like reptiles]
MammaliaformesMammalia (Class) [all mammals]
Eutheria (Subclass)
Euarchontoglires (Superorder)
Euarchonta (Superorder)
Primates (Order)
Haplorrhini (Suborder)
Simiiformes (Infraorder)
Catarrhini (Parvorder)
Hominoidea (Superfamily)
Hominidae (Family)
Homininae (Subfamily)
Hominini (Tribe)
Hominina (Subtribe)
Homo (Genus)
Homo sapiens (Species)
Homo sapiens sapiens (Subspecies)
Society is here defined as the organizations and institutions arising from interaction between humans, while
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 on convention more than reality.
Culture and society consist 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.
Language
The capacity for humans to share ideas 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 (c.f.
mantra,
sacred text).
The science of
linguistics describes the structure of language and the relationship between languages. There are estimated to be approximately 6,000 different languages, including sign languages, currently in use, and many thousands more that are considered
extinct.
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"—that is, 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.
Motivation and emotion
Motivation is the driving force of
desire behind all
actions of any
organism. Motivation is based on
emotion—specifically, on the search for
satisfaction (positive emotional experiences), and the avoidance of
conflict; positive and negative are defined by the individual brain state, not 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
Godly or
demonic influences.
|
Goya's Tio Paquete Thyssen-Bornemisza museum, Madrid (1820) |
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. 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, developed commonly 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
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; 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). 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, we then pass through five stages of
psychosexual development (and can fixate on any stage due to 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 may suggest people may be born with one sexual orientation or another, so there is not currently a clear consensus among sex researchers.
[ Buss, David M. (2004) "The Evolution of Desire: Strategies of Human Mating". Revised Edition. New York: Basic Books" ] [ Thornhill, R., & Palmer, C. T. (2000). A Natural History of Rape. Biological Bases of Sexual Coercion. Cambridge: MIT Press. ]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 mankind'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.
Philosophy and self-reflection
Philosophy is a discipline or field of study involving the investigation, analysis, and development of ideas at a general, abstract, or fundamental level. It is the discipline searching for a general understanding of values and reality by chiefly speculative, rather than observational, 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.
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
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.
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 explosion from which the universe itself is said to have erupted ~13.7 ± 0.2
billion (10
9) 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.
Government and politics
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."
[Max Weber's definition of the modern state 1918, by Max Weber, 1918, retrieved March 17, 2006.]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.
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.
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.
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 have nearly always included
hand to hand combat, the usage of
ranged weapons,
propaganda,
Shock and Awe, and
ethnic cleansing.
Military intelligence has always played a key role in determining victory and defeat. In
modern warfare, soldiers and
armored fighting vehicles are used to control the land,
warships the seas, and
air power the skies.
Outer space has recently become an important factor in warfare as well, although no actual warfare is currently carried out within space.
Throughout history there has been a constant struggle between
defense and
offense,
armor, and the
weapons designed to breach it. Modern examples include the
bunker buster bomb, and the
bunkers which they are designed to destroy.
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. Due to 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 tradable commodity, or because different regions' size allows for the benefits of
mass production. As such, trade between locations benefits both locations.
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.
