We should be looking at our potential, stretching ourselves into everything we can become. The universe and the greed of men. I am as little able to do this as the novelist is, even though my story is more important to me than any novelist's is to him - for this is my story; it is the story of a man, not of an invented, or possible, or idealized, or otherwise absent figure, but of a unique being of flesh and blood, Yet, what a real living human being is made of seems to be less understood today than at any time before, and men - each one of whom represents a unique and valuable experiment on the part of nature - are therefore shot wholesale nowadays.
If we were not something more than unique human beings, if each one of us could really be done away with once and for all by a single bullet, storytelling would lose all purpose. But every man is more than just himself; he also represents the unique, the very special and always significant and remarkable point at which the world's phenomena intersect, only once in this way and never again. That is why every man's story is important, eternal, sacred; that is why every man, as long as he lives and fulfills the will of nature, is wondrous, and worthy of every consideration.
In each individual the spirit has become flesh, in each man the creation suffers, within each one a redeemer is nailed to the cross. Die Geschichte von Emil Sinclairs Jugend. You can't subscribe to it. You need people - actual human beings - to create or curate it. No down. No sky.
No ground. Just endless dark shot through with tiny spears of sunlight older than you and your entire species stacked end to end. You want to feel small? Spend sixty seconds in a Cyclone's cockpit, chum. Look out at the nothing and feel it looking back. Then you know exactly how much you add up to. We live in a society that objectifies us as sexual objects and status symbols. The lengths of these stages, however, are not fixed, and particularly the later stages. There are striking differences in life expectancy around the world.
The developed world is quickly getting older, with the median age in around 40 years highest in Monaco at Life expectancy at birth in Hong Kong, China is While one in five Europeans is 60 years of age or older, only one in twenty Africans is 60 years of age or older CIA The number of centenarians humans of age years or older in the world was estimated by the United Nations at , in UN At least one person, Jeanne Calment, is known to have reached the age of years; higher ages have been claimed but they are not well substantiated. Worldwide, there are 81 men aged 60 or older for every women of that age group, and among the oldest, there are 53 men for every 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. 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 possibly the time of 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 B Some humans have chosen to abstain from eating some or all meat for religious, ethical, ecological, or health reasons.
Supplementation, particularly for vitamin B12, is highly recommended for people living on a pure plant diet. 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, but longer periods are known, including fasting for religious purposes. Lack of food remains a serious global problem, with about , people starving to death every year WHO Childhood malnutrition is also common and contributes to the global burden of disease Murray and Lopez 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.
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 see rise of civilization below , 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.
The scientific study of human evolution concerns the emergence of humans as a distinct species. It encompasses the development of the genus Homo , as well as studying extinct human ancestors, such as the australopithecines , and even chimpanzees genus Pan , which are usually classified together with genus Homo in the tribe Hominini. There is substantial evidence for a primate origin of humans Mayr :. 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.
Well-known members of the Homo genus include Homo habilis about 2. Between , years ago and the second interglacial period in the Middle Pleistocene , around , years ago, the trend in cranial expansion and the elaboration of stone tool technologies developed, providing evidence for a transition from H. Based on molecular evidence, the calculation of the time of divergence of all modern human populations from a common ancestor typically yields dates around , years Smithsonian a. The oldest fossil evidence for modern humans is , years old in Africa and sometime before 90, years old in the Near East Smithsonian a.
Some consider H. Notably, however, about 50, to 40, years ago, human beings appeared to have taken a Great Leap Forward, when human culture apparently changed at a much greater speed. Humans started to bury their dead carefully, made clothing out of hides, developed sophisticated hunting techniques such as pitfall traps, or driving animals to fall off cliffs , and made cave paintings.
Additionally, human culture began to become more technologically advanced, in that different populations of humans begin to create novelty in existing technologies. Artifacts such as fish hooks, buttons, and bone needles begin to show signs of variation among different population of humans, something what had not been seen in human cultures prior to 50, BP.
This "Great Leap Forward" seems connected to the arrival of modern humans beings: Homo sapiens sapiens. See modern man and the great leap forward. The Cro-Magnons form the earliest known European examples of Homo sapiens sapiens. The term falls outside the usual naming conventions for early humans and is used in a general sense to describe the oldest modern people in Europe. Cro-Magnons lived from about 40, to 10, years ago in the Upper Paleolithic period of the Pleistocene epoch.
For all intents and purposes these people were anatomically modern, only differing from their modern day descendants in Europe by their slightly more robust physiology and larger brain capacity than that of modern humans. When they arrived in Europe about 40, years ago, they brought with them sculpture, engraving, painting, body ornamentation, music, and the painstaking decoration of utilitarian objects.
Current research establishes that human beings are highly genetically homogeneous, meaning that the DNA of individual Homo sapiens is more alike than usual for most species. Geneticists Lynn Jorde and Henry Harpending of the University of Utah, noting that the variation in human DNA is minute compared to that of other species, propose that during the Late Pleistocene, the human population was reduced to a small number of breeding pairs—no more than 10, and possibly as few as 1,—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.
There are two major scientific challenges in deducing the pattern of human evolution. For one, the fossil record remains fragmentary. Mayr notes that no fossils of hominids have been found for the period between 6 and 13 million years ago mya , the time when branching between the chimpanzee and human lineages is expected to have taken place. Furthermore, as Mayr notes, "most hominid fossils are extremely incomplete.
They may consist of part of a mandible, or the upper part of a skull without face and teeth, or only part of the extremities. Fossil evidence often allows a variety of interpretations, since the individual specimens may be reconstructed in a variety of ways Wells There are two dominant, and one might say polarizing, general views on the issue of human origins, the Out of Africa position and the multiregional position.
Later, approximately , years ago, there was a second migration of hominids out of Africa, and this was modern H. This view maintains a specific speciation event that led to H. The multiregional or continuity camp hold that since the origin of H. According to this view, hominids in China and Indonesia are the most direct ancestors of modern East Asians, those in Africa are the most direct ancestors of modern Africans, and the European populations either gave rise to modern Europeans or contributed significant genetic material to them, while their origins were in Africa or West Asia Kreger There is genetic flow to allow for the maintenance of one species , but not enough to prevent racial differentiation.
Overall, human evolution theory comprises two principal theories: Those related to the pattern of evolution and those related to the process of evolution. The theory of descent with modification addresses the pattern of evolution, and as applied to humans the theory is strongly supported by the fossil record, which provides evidence of skeletons that through time become more and more like the modern human skeleton.
In contrast, the theory of natural selection , which relates to the process of evolution is intrinsically more speculative as it relates to presumed causes. Substantial evidence has been marshaled for the fact that humans have descended from common ancestors by a process of branching descent with modification and for a primate origin of humans.
However, proposals for the specific ancestral-descendant relationships and for the process leading to humans tend to be speculative. And, while the theory of natural selection typically is central to scientific explanations for the process, evidence for natural selection being the directive or creative force is limited to extrapolation from the microevolutionary level changes within the level of species. Historically, a major source of controversy has been the process by which humans have developed, whether by physical forces with an exclusively random component natural selection or by the creative force of a Creator God.
Abrahamic religions believe that modern humans derive from an original couple Adam and Eve into whose material bodies God breathed spiritual life added a spirit or soul to complete the creation of a being uniquely different from animals. Up until only around 10, 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. Developed independently by geographically distant populations, evidence suggests that agriculture first appeared in Southwest Asia, in the Fertile Crescent. Around B. Though there is evidence of earlier use of wild cereals , it was not until after B. By B. About this time, agriculture was developed independently in the Far East, with rice, rather than wheat, the primary crop.
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, 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,—3, 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 fourteenth century. Over the next 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 seventeenth century and the Industrial Revolution in the eighteenth-nineteenth 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.
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 populations of prey for hunting. 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 percent live in Asia. The vast majority of the remainder live in the Americas 14 percent , Africa 13 percent , and Europe 12 percent , with 0. 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 and , two humans at a time spent brief intervals on the Moon. As of , 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, ; however, humans have made robots that have visited other celestial bodies.
From to C. In , around 2. 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. The extinction of a number of species has been attributed to anthropogenic factors, such as human predation and habitat loss, and other negative impacts include pollution, widespread loss of wetlands and other ecosystems , alteration of rivers, and introduction of invasive species.
On the other hand, humans in the past century have made considerable efforts to reduce negative impacts and provide greater protection for the environment and other living organisms, through such means as environmental law, environmental education, and economic incentives. The brain is a centralized mass of nerve tissue enclosed within the cranium skull of vertebrates. 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 is critical to "higher" order, conscious activities, such as thought, reasoning , and abstraction PBS Mayr states that the human brain "seems not to have changed one single bit since the first appearance of Homo sapiens some , years ago. A central issue in philosophy and religion is how the brain relates to the mind. The brain is defined as the physical and biological matter contained within the skull, responsible for all electrochemical neuronal processes.
The mind, however, is seen in terms of mental attributes, such as beliefs or desires. Mind is a concept developed by self-conscious humans trying to understand what is the self that is conscious and how does that self relate to its perceived world. Most broadly, mind is the organized totality of the mental processes of an organism and the structural and functional components on which they depend.
Taken more narrowly, as it often is in scientific studies, mind denotes only cognitive activities and functions, such as perceiving, attending, thinking, problem solving, language, learning, and memory VandenBos Philosophers have long sought to understand what is mind and its relationship to matter and the body. There is a concept, tracing back at least to Plato , Aristotle , and the Sankhya and Yoga schools of Hindu philosophy, that "mental" phenomena are, in some respects, "non-physical" distinct from the body.
For example, Saint Thomas Aquinas identified a person as being the composite substance of body and soul or mind , with soul giving form to body. Christian views after Aquinas have diverged to cover a wide spectrum, but generally they tend to focus on soul instead of mind, with soul referring to an immaterial essence and core of human identity and to the seat of reason , will, conscience , and higher emotions.
Rene Descartes established the clear mind-body dualism that has dominated the thought of the modern West. He introduced two assertions: First, that mind and soul are the same and that henceforth he would use the term mind and dispense with the term soul; Second, that mind and body were two distinct substances, one immaterial and one material, and the two existed independent of each other except for one point of interaction in the human brain.
As psychology became a science starting in the late nineteenth century and blossomed into a major scientific discipline in the twentieth century, the prevailing view in the scientific community came to be variants of physicalism with the assumption that all the functions attributed to mind are in one way or another derivative from activities of the brain. Countering this mainstream view, a small group of neuroscientists has persisted in searching for evidence suggesting the possibility of a human mind existing and operating apart from the brain.
In the late twentieth century, as diverse technologies related to studying the mind and body have been steadily improved, evidence has emerged suggesting such radical concepts as: The mind should be associated not only with the brain but with the whole body; and the heart may be a center of consciousness complementing the brain. Some envision a physical mind that mirrors the physical body, guiding its instinctual activities and development, while adding the concept for humans of a spiritual mind that mirrors a spiritual body and including aspects like philosophical and religious thought.
The human brain is generally regarded as more capable of the various 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 Sagan The human ability to think abstractly may be unparalleled in the animal kingdom.
Humans are one of only six groups of animals 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 , three elephants at the Bronx Zoo also passed this test Plotnik et al. Humans under the age of 2 typically fail this test Palmer However, this may be a matter of degree rather than a sharp divide.
Monkeys have been trained to apply abstract rules in tasks Coveney 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 center called the "mind," but that instead there is simply a collection of sensory inputs and outputs: Different kinds of "software" running in parallel Dennett 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.
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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 Block Phenomenal consciousness is the state of being conscious, such as when they say "I am conscious. 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. The genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids great apes branch of the primates.
Modern humans, defined as the species Homo sapiens or specifically to the single extant subspecies Homo sapiens sapiens , proceeded to colonize all the continents and larger islands, arriving in Eurasia ,—60, years ago,   Australia around 40, years ago, the Americas around 15, years ago, and remote islands such as Hawaii, Easter Island , Madagascar , and New Zealand between the years and The closest living relatives of humans are chimpanzees genus Pan and gorillas genus Gorilla.
The gibbons family Hylobatidae and orangutans genus Pongo were the first groups to split from the line leading to the humans, then gorillas genus Gorilla followed by the chimpanzees genus Pan. The splitting date between human and chimpanzee lineages is placed around 4—8 million years ago during the late Miocene epoch. There is little fossil evidence for the divergence of the gorilla, chimpanzee and hominin lineages.
Each of these species has been argued to be a bipedal ancestor of later hominins, but all such claims are contested. It is also possible that any one of the three is an ancestor of another branch of African apes, or is an ancestor shared between hominins and other African Hominoidea apes. The question of the relation between these early fossil species and the hominin lineage is still to be resolved.
The earliest members of the genus Homo are Homo habilis which evolved around 2. More recently, however, in , stone tools , perhaps predating Homo habilis , have been discovered in northwestern Kenya that have been dated to 3. During the next million years a process of encephalization began, and with the arrival of Homo erectus in the fossil record, cranial capacity had doubled. Homo erectus were the first of the hominina to leave Africa, and these species spread through Africa, Asia, and Europe between 1.
One population of H. It is believed that these species were the first to use fire and complex tools. The earliest transitional fossils between H. These descendants of African H. The earliest fossils of anatomically modern humans are from the Middle Paleolithic , about , years ago such as the Omo remains of Ethiopia and the fossils of Herto sometimes classified as Homo sapiens idaltu.
Human evolution is characterized by a number of morphological , developmental , physiological , and behavioral changes that have taken place since the split between the last common ancestor of humans and chimpanzees. The most significant of these adaptations are 1. The relationship between all these changes is the subject of ongoing debate. Bipedalism is the basic adaption of the hominin line, and it is considered the main cause behind a suite of skeletal changes shared by all bipedal hominins. The earliest bipedal hominin is considered to be either Sahelanthropus  or Orrorin , with Ardipithecus , a full bipedal,  coming somewhat later.
It is possible that bipedalism was favored because it freed up the hands for reaching and carrying food, because it saved energy during locomotion, because it enabled long distance running and hunting, or as a strategy for avoiding hyperthermia by reducing the surface exposed to direct sun. However, the differences between the structure of human brains and those of other apes may be even more significant than differences in size.
The reduced degree of sexual dimorphism is primarily visible in the reduction of the male canine tooth relative to other ape species except gibbons. Another important physiological change related to sexuality in humans was the evolution of hidden estrus. Humans are the only ape in which the female is intermittently fertile year round, and in which no special signals of fertility are produced by the body such as genital swelling during estrus. These changes taken together have been interpreted as a result of an increased emphasis on pair bonding as a possible solution to the requirement for increased parental investment due to the prolonged infancy of offspring.
By the beginning of the Upper Paleolithic period 50, BP , full behavioral modernity , including language , music and other cultural universals had developed. Since , evidence for gene flow between archaic and modern humans during the period of roughly , to 30, years ago has been discovered. This includes modern human admixture in Neanderthals, Neanderthal admixture in modern humans,   Denisova hominin admixture in Melanesians  as well as repeated admixture from unnamed archaic humans to Sub-Saharan African populations.
The "out of Africa" migration of Homo sapiens took place in at least two waves, the first around , to , years ago, the second Southern Dispersal around 70, to 60, years ago, resulting in the colonization of Australia around 65, years ago,  This recent out of Africa migration derived from East African populations, which had become separated from populations migrating to Southern, Central and Western Africa at least , years earlier.
They inhabited Eurasia and Oceania by 40, years ago, and the Americas at least 14, years ago. Until about 12, years ago the beginning of the Holocene , all humans lived as hunter-gatherers , generally in small nomadic groups known as band societies , often in caves. The Neolithic Revolution the invention of agriculture took place beginning about 10, years ago, first in the Fertile Crescent , spreading through large parts of the Old World over the following millennia, and independently in Mesoamerica about 6, years ago. Access to food surplus led to the formation of permanent human settlements , the domestication of animals and the use of metal tools for the first time in history.
Agriculture and sedentary lifestyle led to the emergence of early civilizations the development of urban developent , complex society , social stratification and writing from about 5, years ago the Bronze Age , first beginning in Mesopotamia. Few human populations progressed to historicity , with substantial parts of the world remaining in a Neolithic, Mesolithic or Upper Paleolithic stage of development until the advent of globalisation and modernity initiated by European exploration and colonialism. The Scientific Revolution , Technological Revolution and the Industrial Revolution brought such discoveries as imaging technology , major innovations in transport, such as the airplane and automobile; energy development , such as coal and electricity.
With the advent of the Information Age at the end of the 20th century, modern humans live in a world that has become increasingly globalized and interconnected. As of [update] , almost 2 billion humans are able to communicate with each other via the Internet ,  and 3. Early human settlements were dependent on proximity to water and, depending on the lifestyle, other natural resources used for subsistence , such as populations of animal prey for hunting and arable land for growing crops and grazing livestock.
However, modern humans have a great capacity for altering their habitats by means of technology, through irrigation , urban planning , construction, transport, manufacturing goods, deforestation and desertification  , but human settlements continue to be vulnerable to natural disasters , especially those placed in hazardous locations and characterized by lack of quality of construction. 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 six of the Earth 's seven continents and adapt to virtually all climates. However the human population is not uniformly distributed on the Earth 's surface, because the population density varies from one region to another and there are large areas almost completely uninhabited, like Antarctica.
With a population of over seven billion, humans are among the most numerous of the large mammals. 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.
Scientists and human beings
As of June , no other celestial body has been visited by humans, although there has been a continuous human presence in space since the launch of the initial crew to inhabit the International Space Station on 31 October Since , the human population has increased from one billion  to over seven billion. In , some 2. In February , the U. Both overall population numbers and the proportion residing in cities are expected to increase significantly in the coming decades.
Humans have had a dramatic effect on the environment. Humans are apex predators , being rarely preyed upon by other species. Most aspects of human physiology are closely homologous to corresponding aspects of animal physiology. The human body consists of the legs , the torso , the arms, the neck , and the head.
An adult human body consists of about trillion 10 14 cells. The most commonly defined body systems in humans are the nervous , the cardiovascular , the circulatory , the digestive , the endocrine , the immune , the integumentary , the lymphatic , the musculoskeletal , the reproductive , the respiratory , and the urinary system. Humans, like most of the other apes , lack external tails , have several blood type systems, have opposable thumbs , and are sexually dimorphic.
The comparatively minor anatomical differences between humans and chimpanzees are a result of human bipedalism.
One difference is that humans have a far faster and more accurate throw than other animals. Humans are also among the best long-distance runners in the animal kingdom, but slower over short distances. As a consequence of bipedalism, human females have narrower birth canals.
The construction of the human pelvis differs from other primates , as do the toes. A trade-off for these advantages of the modern human pelvis is that childbirth is more difficult and dangerous than in most mammals , especially given the larger head size of human babies compared to other primates. This means that human babies must turn around as they pass through the birth canal, which other primates do not do, and it makes humans the only species where females usually require help from their conspecifics other members of their own species to reduce the risks of birthing.
As a partial evolutionary solution, human fetuses are born less developed and more vulnerable. Chimpanzee babies are cognitively more developed than human babies until the age of six months, when the rapid development of human brains surpasses chimpanzees. Another difference between women and chimpanzee females is that women go through the menopause and become unfertile decades before the end of their lives. All species of non-human apes are capable of giving birth until death. Menopause probably developed as it has provided an evolutionary advantage more caring time to young relatives.
Apart from bipedalism, humans differ from chimpanzees mostly in smelling , hearing , digesting proteins , brain size , and the ability of language. Humans' brains are about three times bigger than in chimpanzees. More importantly, the brain to body ratio is much higher in humans than in chimpanzees, and humans have a significantly more developed cerebral cortex , with a larger number of neurons.
The mental abilities of humans are remarkable compared to other apes. Humans' ability of speech is unique among primates. Humans are able to create new and complex ideas , and to develop technology, which is unprecedented among other organisms on Earth. Although humans appear hairless compared to other primates, with notable hair growth occurring chiefly on the top of the head, underarms and pubic area , the average human has more hair follicles on his or her body than the average chimpanzee.
The main distinction is that human hairs are shorter, finer, and less heavily pigmented than the average chimpanzee's, thus making them harder to see. The dental formula of humans is: 2. Humans have proportionately shorter palates and much smaller teeth than other primates. They are the only primates to have short, relatively flush canine teeth.
Humans have characteristically crowded teeth, with gaps from lost teeth usually closing up quickly in young individuals. Humans are gradually losing their wisdom teeth , with some individuals having them congenitally absent. Like all mammals, humans are a diploid eukaryotic species. Each somatic cell has two sets of 23 chromosomes , each set received from one parent; gametes have only one set of chromosomes, which is a mixture of the two parental sets.
Among the 23 pairs of chromosomes there are 22 pairs of autosomes and one pair of sex chromosomes. Like other mammals, humans have an XY sex-determination system , so that females have the sex chromosomes XX and males have XY. One human genome was sequenced in full in , and currently efforts are being made to achieve a sample of the genetic diversity of the species see International HapMap Project. By present estimates, humans have approximately 22, genes. The nucleotide diversity between humans is about 0.
By comparing the parts of the genome that are not under natural selection and which therefore accumulate mutations at a fairly steady rate, it is possible to reconstruct a genetic tree incorporating the entire human species since the last shared ancestor. Each time a certain mutation SNP appears in an individual and is passed on to his or her descendants, a haplogroup is formed including all of the descendants of the individual who will also carry that mutation.
By comparing mitochondrial DNA , which is inherited only from the mother, geneticists have concluded that the last female common ancestor whose genetic marker is found in all modern humans, the so-called mitochondrial Eve , must have lived around 90, to , years ago. Human accelerated regions , first described in August ,   are a set of 49 segments of the human genome that are conserved throughout vertebrate evolution but are strikingly different in humans.
They are named according to their degree of difference between humans and their nearest animal relative chimpanzees HAR1 showing the largest degree of human-chimpanzee differences. Found by scanning through genomic databases of multiple species, some of these highly mutated areas may contribute to human-specific traits. The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the genome display directional selection in the past 15, years.
As with other mammals, human reproduction takes place by internal fertilization via sexual intercourse. During this process, the male inserts his erect penis into the female's vagina and ejaculates semen, which contains sperm. The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for fertilization of the ovum. Upon fertilization and implantation , gestation then occurs within the female's uterus. The zygote divides inside the female's uterus to become an embryo , which over a period of 38 weeks 9 months of gestation becomes a fetus.
After this span of time, the fully grown fetus is birthed from the woman's body and breathes independently as an infant for the first time. At this point, most modern cultures recognize the baby as a person entitled to the full protection of the law, though some jurisdictions extend various levels of personhood earlier to human fetuses while they remain in the uterus.
Compared with other species, human childbirth is dangerous. Painful labors lasting 24 hours or more are not uncommon and sometimes lead to the death of the mother, the child or both. In contrast, pregnancy and natural childbirth remain hazardous ordeals in developing regions of the world, with maternal death rates approximately times greater than in developed countries.
Females continue to develop physically until around the age of 18, whereas male development continues until around age The human life span can be split into a number of stages: infancy, childhood , adolescence, young adulthood , adulthood and old age. The lengths of these stages, however, have varied across cultures and time periods. Humans are one of the few species in which females undergo menopause.
It has been proposed that menopause increases a woman's overall reproductive success by allowing her to invest more time and resources in her existing offspring, and in turn their children the grandmother hypothesis , rather than by continuing to bear children into old age. Evidence-based studies indicate that the life span of an individual depends on two major factors, genetics and lifestyle choices. Humans are omnivorous , capable of consuming a wide variety of plant and animal material.
In some cases, dietary restrictions in humans can lead to deficiency diseases ; however, stable human groups have adapted to many dietary patterns through both genetic specialization and cultural conventions to use nutritionally balanced food sources. Until the development of agriculture approximately 10, years ago, Homo sapiens employed a hunter-gatherer method as their sole means of food collection.
This involved combining stationary food sources such as fruits, grains, tubers, and mushrooms, insect larvae and aquatic mollusks with wild game , which must be hunted and killed in order to be consumed. This change in diet may also have altered human biology; with the spread of dairy farming providing a new and rich source of food, leading to the evolution of the ability to digest lactose in some adults.
The types of food consumed, and the way in which they are prepared, have varied widely by time, location, and culture. In general, humans can survive for two to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days. About 36 million humans die every year from causes directly or indirectly related to starvation. No two humans—not even monozygotic twins —are genetically identical.
Genes and environment influence human biological variation in visible characteristics, physiology, disease susceptibility and mental abilities. The exact influence of genes and environment on certain traits is not well understood. Most current genetic and archaeological evidence supports a recent single origin of modern humans in East Africa,  with first migrations placed at 60, years ago. Compared to the great apes , human gene sequences —even among African populations—are remarkably homogeneous. The human body's ability to adapt to different environmental stresses is remarkable, allowing humans to acclimatize to a wide variety of temperatures, humidity , and altitudes.
As a result, humans are a cosmopolitan species found in almost all regions of the world, including tropical rainforests , arid desert , extremely cold arctic regions , and heavily polluted cities. Most other species are confined to a few geographical areas by their limited adaptability. There is biological variation in the human species—with traits such as blood type , cranial features , eye color , hair color and type, height and build , and skin color varying across the globe. Human body types vary substantially.
The typical height of an adult human is between 1. Body size is partly determined by genes and is also significantly influenced by environmental factors such as diet , exercise, and sleep patterns , especially as an influence in childhood. Adult height for each sex in a particular ethnic group approximately follows a normal distribution. Those aspects of genetic variation that give clues to human evolutionary history, or are relevant to medical research, have received particular attention.
For example, the genes that allow adult humans to digest lactose are present in high frequencies in populations that have long histories of cattle domestication, suggesting natural selection having favored that gene in populations that depend on cow milk. Some hereditary diseases such as sickle cell anemia are frequent in populations where malaria has been endemic throughout history—it is believed that the same gene gives increased resistance to malaria among those who are unaffected carriers of the gene.
Similarly, populations that have for a long time inhabited specific climates, such as arctic or tropical regions or high altitudes, tend to have developed specific phenotypes that are beneficial for conserving energy in those environments— short stature and stocky build in cold regions , tall and lanky in hot regions, and with high lung capacities at high altitudes. Similarly, skin color varies clinally with darker skin around the equator—where the added protection from the sun's ultraviolet radiation is thought to give an evolutionary advantage—and lighter skin tones closer to the poles.
The hue of human skin and hair is determined by the presence of pigments called melanins. Human skin color can range from darkest brown to lightest peach , or even nearly white or colorless in cases of albinism. Most researchers believe that skin darkening is an adaptation that evolved as protection against ultraviolet solar radiation, which also helps balancing folate , which is destroyed by ultraviolet radiation. Light skin pigmentation protects against depletion of vitamin D , which requires sunlight to make.
Human skin also has a capacity to darken tan in response to exposure to ultraviolet radiation. Within the human species, the greatest degree of genetic variation exists between males and females. While the nucleotide genetic variation of individuals of the same sex across global populations is no greater than 0. The genetic difference between sexes contributes to anatomical, hormonal, neural, and physiological differences between men and women, although the exact degree and nature of social and environmental influences on sexes are not completely understood.
There is a difference between body types, body organs and systems, hormonal levels, sensory systems, and muscle mass between sexes. Women generally have a higher body fat percentage than men. Women have lighter skin than men of the same population; this has been explained by a higher need for vitamin D which is synthesized by sunlight in females during pregnancy and lactation.
As there are chromosomal differences between females and males, some X and Y chromosome related conditions and disorders only affect either men or women. Other conditional differences between males and females are not related to sex chromosomes. Even after allowing for body weight and volume, the male voice is usually an octave deeper than the female voice. Women have a longer life span in almost every population around the world. They also have higher circulating clotting factors vitamin K , pro thrombin and platelets. These differences lead to faster healing of wounds and higher peripheral pain tolerance.
Additionally, they produce more antibodies at a faster rate than males. Hence they develop fewer infectious diseases and these continue for shorter periods. One proposed explanation is that human sexuality has developed more in common with its close relative the bonobo , which exhibits similar sexual dimorphism, is polygynandrous and uses recreational sex to reinforce social bonds and reduce aggression. Humans of the same sex are There is extremely little variation between human geographical populations, and most of the variation that does occur is at the personal level within local areas, and not between populations.
Two randomly chosen Koreans may be genetically as different as a Korean and an Italian. Genetic data shows that no matter how population groups are defined, two people from the same population group are about as different from each other as two people from any two different population groups. Current genetic research has demonstrated that humans on the African continent are the most genetically diverse.
The genetic structure of Africans was traced to 14 ancestral population clusters. Human genetic diversity decreases in native populations with migratory distance from Africa and this is thought to be the result of bottlenecks during human migration. Only part of Africa's population migrated out of the continent, bringing just part of the original African genetic variety with them. African populations harbor genetic alleles that are not found in other places of the world. All the common alleles found in populations outside of Africa are found on the African continent.
Geographical distribution of human variation is complex and constantly shifts through time which reflects complicated human evolutionary history. Most human biological variation is clinally distributed and blends gradually from one area to the next. Groups of people around the world have different frequencies of polymorphic genes. Furthermore, different traits are non-concordant and each have different clinal distribution.
Adaptability varies both from person to person and from population to population. The most efficient adaptive responses are found in geographical populations where the environmental stimuli are the strongest e. Tibetans are highly adapted to high altitudes. The clinal geographic genetic variation is further complicated by the migration and mixing between human populations which has been occurring since prehistoric times.
Human variation is highly non-concordant: most of the genes do not cluster together and are not inherited together. Skin and hair color are not correlated to height, weight, or athletic ability. Human species do not share the same patterns of variation through geography. Skin color varies with latitude and certain people are tall or have brown hair. There is a statistical correlation between particular features in a population, but different features are not expressed or inherited together. Thus, genes which code for superficial physical traits—such as skin color, hair color, or height—represent a minuscule and insignificant portion of the human genome and do not correlate with genetic affinity.
Dark-skinned populations that are found in Africa, Australia, and South Asia are not closely related to each other. Despite pygmy populations of South East Asia Andamanese having similar physical features with African pygmy populations such as short stature, dark skin, and curly hair, they are not genetically closely related to these populations. Due to practices of group endogamy , allele frequencies cluster locally around kin groups and lineages, or by national, ethnic, cultural and linguistic boundaries, giving a detailed degree of correlation between genetic clusters and population groups when considering many alleles simultaneously.
Despite this, there are no genetic boundaries around local populations that biologically mark off any discrete groups of humans. Human variation is continuous, with no clear points of demarcation. There are no large clusters of relatively homogeneous people and almost every individual has genetic alleles from several ancestral groups. The human brain, the focal point of the central nervous system in humans, controls the peripheral nervous system. In addition to controlling "lower," involuntary, or primarily autonomic activities such as respiration and digestion , it is also the locus of "higher" order functioning such as thought , reasoning , and abstraction.
Generally regarded as more capable of these higher order activities, the human brain is believed to be more "intelligent" in general than that of any other known species. While some non-human species are capable of creating structures and using simple tools —mostly through instinct and mimicry—human technology is vastly more complex, and is constantly evolving and improving through time.
Humans are generally diurnal. The average sleep requirement is between seven and nine hours per day for an adult and nine to ten hours per day for a child; elderly people usually sleep for six to seven hours. Having less sleep than this is common among humans, even though sleep deprivation can have negative health effects. A sustained restriction of adult sleep to four hours per day has been shown to correlate with changes in physiology and mental state, including reduced memory, fatigue, aggression, and bodily discomfort. In dreaming humans experience sensory images and sounds, in a sequence which the dreamer usually perceives more as an apparent participant than as an observer.
Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep. Humans are one of the relatively few species to have sufficient self-awareness to recognize themselves in a mirror. The human brain perceives the external world through the senses , and each individual human is influenced greatly by his or her experiences, leading to subjective views of existence and the passage of time. Humans are variously said to possess consciousness, self-awareness , and a mind, which correspond roughly to the mental processes of thought. These are said to possess qualities such as self-awareness, sentience , sapience , and the ability to perceive the relationship between oneself and one's environment.
The extent to which the mind constructs or experiences the outer world is a matter of debate, as are the definitions and validity of many of the terms used above. The physical aspects of the mind and brain, and by extension of the nervous system, are studied in the field of neurology , the more behavioral in the field of psychology, and a sometimes loosely defined area between in the field of psychiatry, which treats mental illness and behavioral disorders.
Water for human beings
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. Psychologists have developed intelligence tests and the concept of intelligence quotient in order to assess the relative intelligence of human beings and study its distribution among population.
Some philosophers divide consciousness into phenomenal consciousness, which is experience itself, and access consciousness, which is the processing of the things in experience. The concept of phenomenal consciousness, in modern history, according to some, is closely related to the concept of qualia. Social psychology links sociology with psychology in their shared study of the nature and causes of human social interaction, with an emphasis on how people think towards each other and how they relate to each other.
The behavior and mental processes, both human and non-human, can be described through animal cognition , ethology , evolutionary psychology , and comparative psychology as well. Human ecology is an academic discipline that investigates how humans and human societies interact with both their natural environment and the human social environment.
Motivation is the driving force of desire behind all deliberate actions of humans. Motivation is based on emotion—specifically, on the search for satisfaction positive emotional experiences , and the avoidance of conflict. Positive and negative is defined by the individual brain state, which may be influenced by social norms : a person may be driven to self-injury or violence because their brain is conditioned to create a positive response to these actions.
Motivation is important because it is involved in the performance of all learned responses. Within psychology , conflict avoidance and the libido are seen to be primary motivators. Within economics, motivation is often seen to be based on incentives ; these may be financial, moral, or coercive. Religions generally posit divine or demonic influences. Happiness, or the state of being happy, is a human emotional condition. The definition of happiness is a common philosophical topic. Some people might define it as the best condition that a human can have—a condition of mental and physical health.
Others define it as freedom from want and distress ; consciousness of the good order of things; assurance of one's place in the universe or society. Emotion has a significant influence on, or can even be said to control, human behavior, though historically many cultures and philosophers have for various reasons discouraged allowing this influence to go unchecked. Emotional experiences perceived as pleasant , such as love, admiration , or joy , contrast with those perceived as unpleasant , like hate , envy , or sorrow.
There is often a distinction made between refined emotions that are socially learned and survival oriented emotions, which are thought to be innate. Human exploration of emotions as separate from other neurological phenomena is worthy of note, particularly in cultures where emotion is considered separate from physiological state.
In some cultural medical theories emotion is considered so synonymous with certain forms of physical health that no difference is thought to exist. The Stoics believed excessive emotion was harmful, while some Sufi teachers felt certain extreme emotions could yield a conceptual perfection, what is often translated as ecstasy. In modern scientific thought, certain refined emotions are considered a complex neural trait innate in a variety of domesticated and non-domesticated mammals.
These were commonly developed in reaction to superior survival mechanisms and intelligent interaction with each other and the environment; as such, refined emotion is not in all cases as discrete and separate from natural neural function as was once assumed. However, when humans function in civilized tandem, it has been noted that uninhibited acting on extreme emotion can lead to social disorder and crime. For humans, sexuality has important social functions: it creates physical intimacy, bonds and hierarchies among individuals, besides ensuring biological reproduction.
Sexual desire or libido , is experienced as a bodily urge, often accompanied by strong emotions such as love, ecstasy and jealousy. The significance of sexuality in the human species is reflected in a number of physical features among them hidden ovulation , the evolution of external scrotum and among great apes a relatively large penis suggesting sperm competition in humans , the absence of an os penis , permanent secondary sexual characteristics and the forming of pair bonds based on sexual attraction as a common social structure.
Contrary to other primates that often advertise estrus through visible signs, human females do not have a distinct or visible signs of ovulation, plus they experience sexual desire outside of their fertile periods. These adaptations indicate that the meaning of sexuality in humans is similar to that found in the bonobo , and that the complex human sexual behavior has a long evolutionary history. Human choices in acting on sexuality are commonly influenced by cultural norms which vary widely.
Restrictions are often determined by religious beliefs or social customs. For Alfred Kinsey , an influential sex researcher, people can fall anywhere along a continuous scale of sexual orientation. Humans are highly social beings and tend to live in large complex social groups. More than any other creature, humans are capable of using systems of communication for self-expression, the exchange of ideas, and organization , and as such have created complex social structures composed of many cooperating and competing groups.
Human groups range from the size of families to nations. Social interactions between humans have established an extremely wide variety [ clarification needed ] of values, social norms, and rituals, which together form the basis of human society. Culture is defined here as patterns of complex symbolic behavior, i. While many species communicate , language is unique to humans, a defining feature of humanity, and a cultural universal. Unlike the limited systems of other animals, human language is open—an infinite number of meanings can be produced by combining a limited number of symbols.
Human language also has the capacity of displacement , using words to represent things and happenings that are not presently or locally occurring, but reside in the shared imagination of interlocutors. Language is central to the communication between humans, and to the sense of identity that unites nations, cultures and ethnic groups. The invention of writing systems at least five thousand years ago allowed the preservation of language on material objects, and was a major technological advancement.
The science of linguistics describes the structure and function of language and the relationship between languages. There are approximately six thousand different languages currently in use, including sign languages , and many thousands more that are extinct. The sexual division of humans into male, female, and in some societies other genders  has been marked culturally by a corresponding division of roles, norms, practices , dress, behavior, rights, duties , privileges , status , and power.
Cultural differences by gender have often been believed to have arisen naturally out of a division of reproductive labor; the biological fact that women give birth led to their further cultural responsibility for nurturing and caring for children. Gender roles have varied historically, and challenges to predominant gender norms have recurred in many societies.
Related Human Beings
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