Humans are mammals. They are also social animals. They usually live in groups. They help and protect each other. They care for theirchildren. Humans arebipedal, which means they walk on twolegs.
Humans have a complexbrain, which is much larger than that of the other living apes. They uselanguage, makeideas, and feelemotions. This brain, and the fact thatarms are not needed forwalking, lets humans usetools. Humans use tools far more than any other species. Their tools are very advanced.
Humans have a long period of development after birth. Their life depends less oninstinct than other animals and more onlearning. Humans are also born with theirbrains not so well developed as those of othermammals. This makes for an unusually longchildhood, sofamily life is important. If their brains were better developed at birth, their head would be larger, and this would makebirth more difficult. In birth, the baby's head has to get through the 'birth canal', the passageway through the mother'spelvis.
Many animals usesigns and sounds to communicate with each other. But humans havelanguage. It lets them express ideas by using words. Humans are capable ofabstract ideas and can communicate them to others. Human language can express things which are not present or talk about events that are not happening at that time.[8] The things might be elsewhere, and the events may also have occurred at another place or time.[9]
No known animals have a system ofcommunication that is as elaborate as human language. By using words to communicate with each other, humans makecomplexcommunities withlaws,traditions andcustoms. Humans like to understand theworld around them. They try to explain things throughmyth,science andphilosophy. Wanting to understand things has helped humans make important discoveries.
Humans are part of the animal kingdom. They aremammals, which means that they give birth to their young, and females feed their babies with breast milk. Humans belong to the order ofprimates. Apes like gorillas, orangutans, chimps, andgibbons are also primates.
The closest living relatives of humans are the two chimpanzee species: thecommon chimpanzee and thebonobo. Scientists have examined thegenes of humans and chimpanzees and compared theirDNA. The studies showed that 95% to 99% of the DNA of humans and chimpanzees is the same.[10][11][12][13][14]
Biologists explain the similarity between humans and otherhominoids by their descent from a common ancestor. In 2001, ahominid skull was discovered inChad. The skull is about 7 million years old and has been classified asSahelanthropus tchadensis. Thisskull may show that the date at which humans started toevolve (develop differently) from other primates is 2 million years earlier than scientists had previously thought.[15]
There used to be other types of hominins on Earth. They were similar to but not the same as modern humans.Homo sapiens are the only type of hominins who are alive today.[16] The earliest known fossils of genusHomo have been calledHomo habilis (handy man). The firstfossils ofHomo habilis were found inTanzania.Homo hablilis is thought to have lived about 2.2 to 1.7 million years ago.[17] Another human species thought to be an ancestor of the modern human isHomo erectus.[18] There are other extinct species ofHomo known today. Many of them were likely our 'cousins', as they developed differently to our ancestors.[19] Different species of plants and animals moved from Africa to the Middle East, and then elsewhere. Early humans may have moved from Africa to other parts of the world in the same way.
The first truly modern humans seem to have appeared between 300,000[20] and 200,000 years ago inEast Africa.[21][22][23] Inpaleontology, 200,000 years is a "short" time. So,scientists speak of a "recent single origin" of humans. Some of these early humans later moved out fromAfrica. By about 90,000 years ago, they had moved intoRussia. This was the area whereNeanderthals,Homo neanderthalensis, had been living for a long time (at least 350,000 years).
By about 42,000 to 44,000 years agoHomo sapiens had reached westernEurope, includingRussia.[24] In Europe and western Asia,Homo sapiens replaced the Neanderthals by about 35,000 years ago. The details of this event are not known.
At roughly the same time,Homo sapiens arrived inAustralia. Their arrival in theAmericas was much later, about 15,000 years ago.[25] All these earlier groups of modern man werehunter-gatherers.
Up to about 10 thousand years ago, most humans werehunter-gatherers. They did not live in one place. Instead, theymoved around as theseasons changed. The start of plantingcrops for food, calledfarming, made theNeolithic revolution. Some people chose to live insettlements. This also led to the invention ofmetal tools and the training ofanimals. About 6,000 years ago, the first proper civilizations began in places, likeEgypt,India, andSyria. The people formed governments andarmies for protection. They competed for area to live and resources, and sometimes theyfought with each other. About 4,000 years ago, some states took over or conquered other states and madeempires. Examples include ancientGreece and theRoman Empire.
Some modern-day religions also began at this time, such asJudaism andHinduism. From the Middle Ages and beyond, humanity saw an explosion of new technology and inventions. The printing press, thecar, thetrain, andelectricity are all examples of this kind of invention. As a result of the developments in technology, modern humans live in a world where everyone is connected, for example bytelephone or byinternet. People now control and change theenvironment around them in many different ways.
Humans can now change their environment to solve problems. The many tall buildings inHong Kong are an example of people solving the problem oftoo many people in one place.
In early times, humans usually settled near towater and othernaturalresources. In modern times, if people need things, they cantransport them from somewhere else. Therefore, basing a settlement close to resources is no longer as important as it once was. Since 1800, the number of humans, orpopulation, hasincreased by six billion.[26] Most humans (61%) live inAsia. The rest live inthe Americas (14%),Africa (14%),Europe (11%), andOceania (0.5%).
Most people live intowns andcities. This number is expected to get higher. In 2005, theUnited Nations said that by the end of that year, over half the world would be living in cities. This is an important change in human settlement patterns: a century earlier in 1900, only 14% of people lived in cities; in 2000, 47% of the world's population lived in cities. In developed countries, like theUnited States, 80% of the population live in cities.[27]
Humans have a large effect on the world. Humans are at the top of thefood chain and are generally not eaten by any animals. Humans have been described as superpredators because of this.[28] Because ofindustry and other reasons, humans are said to be a big cause ofglobalclimate change.[29]
Theanatomy offemale andmale humans. These models had body hair and facial hair removed and head hair trimmed.
Human body measurements differ. The worldwide averageheight for an adult human male is about172cm (5ft7+1⁄2in), and the worldwide average height for adult human females is about158cm (5ft 2in). The average weight of an adult human is54–64kg (119–141lb) for females and70–83kg (154–183lb) for males.[30][31] Body weight and body type is influenced bygenetics and environment. It varies greatly among individuals.
Humanhair grows on the underarms, thegenitals, legs, arms, and on the top of thehead in adults of both genders. Hair will usually grow on theface of most adult males and on thechest and back of many adult males. In human children of both genders, long hair grows only on the top of the head. Although it might look like humans have fewer hairs than mostprimates, they actually do not. The average human has more hairfollicles, where hair grows from than most chimpanzees have.[32] Human hair can beblack,brown,red orblond.[33] When humans get older, hair can turngrey orwhite.
Humanskin colors vary greatly. They can be a very palepink all the way to darkbrown. There is a reason why people in tropical areas have dark skins. The dark pigment (melanin) in the skin protects them againstultraviolet rays insunlight. The damage caused by UV rays can and does causeskin cancer in some people. Therefore, in more sunny areas,natural selection favors darker skin color.[34][35] Sun tanning has nothing to do with this issue, because it is just a temporary process, which is not inherited. In colder climates, the advantage of light-coloured skin is two-fold. It radiates less heat and absorbs more sunlight. In weaker sunlight, a darker body produces lessvitamin D than a lighter body. The selection for lighter skin is driven by these two reasons. Therefore, in less sunny areas, natural selection favours lighter skin colour.[36][37][38]
Humans are not as strong as otherprimates of the same size. An averagefemale orangutan is at least three times as strong as an average human.[39]
The average human needs 7 to 8 hourssleep a day. People who sleep less than this are generally not ashealthy. A child needs even more sleep, 9 to 10 hours on average.
The human life cycle is similar in some ways to most othermammals. However, there are some differences. The young grow inside the femalemother for ninemonths. After this time, thebaby is pushed out of the woman'svagina, with its brain only half developed.
Unlike most other mammals, human childbirth is somewhat dangerous. Babies' heads are large, and the motherspelvisbones are not very wide. Since people walk on twolegs, their hips are fairly narrow. This means that birth can be difficult. Rarely, mother or baby maydie in childbirth.[40] The number of mothers dying in childbirth is lower in the 21st century. This is because of bettermedication and treatment. If a difficult birth is foreseen, thefoetus can be removed surgically, andincubated (developed, but not in the womb).
In many poor countries, the number of mothers dying is higher. Sometimes it is up to 10 times as many as richer countries.[41]
In the human female, her fertile period in theoestrous cycle is hidden, and mating can take place at any time. That is quite unusual. In mammals generally, the fertile period is very noticeable. Mating only takes place when the female signals her fertility. The human cycle is unusual, and it is thought that there is a reason. Humans band together in tribes which have many people. It helps the tribe if the father of a child is not known for certainty. Men live together and work together inmuch larger groups than do chimpanzees (our nearest living relatives). They have a collective interest in the tribe. It is thought that the human mating system helps this.[42][43]
The average human babyweighs 3–4kg at birth and is 50–60cm tall. Babies are often smaller in poorer countries[44] and may die early because of this.[45]
Life expectancy is how long you are expected to live. This depends on many things including where you live. The highest life expectancy is for people fromMonaco, 89.52 years. The lowest is for people fromChad where life expectancy is only 49.81 years.[46] Human lifespans can be longer than other mammals, evenelephants.
Psychology is the study of how the humanmind works. The humanbrain is the main controller of what a person does. Everything frommoving andbreathing tothinking is done by the brain. The humanneocortex is huge compared with othermammals. It gives us our thinking ability and the ability to speak and understandlanguage.
Neurology is the study of how the brain works whilepsychology is the study of how and why people think andfeel. Many aspects of life are also influenced by thehormone system, includinggrowth and sexual development. The hormonal system (especially thepituitary gland) is partly controlled by the brain.
Human behaviour is hard to understand, so sometimes, psychologists studyanimals because they may be simpler and easier to know. Psychology overlaps with many other sciences, includingmedicine,biology,computer science andlinguistics.
Language at its most basic is talking,reading andwriting. The study of language is calledlinguistics. Humans have the most complicated languages on Earth. Although almost all animals communicate, human language is unique. Its use ofsyntax and its huge learntvocabulary are its main features.[9][47] There are over 7,300 languages spoken around the world. The world's most spokenfirst language isMandarin Chinese, and the most spoken language is English.[48] This includes speakers of English as asecond language.
This is to explain the difference between features which are long established, and ones which are relatively recent in evolution. The human ability to walk and run upright on two legs is recent. The ability to speak is even more recent. Contrast those two with something ancient, like the way most land vertebrates walk on four legs.
In every case, the older way is very reliable in its development, and the new tactic is more variable, and involves some learning.
Art has existed almost as long as humans. People have been doing some types of art for thousands of years as the picture on the right shows. Art represents how someone feels in the form of apainting, asculpture or aphotograph.
Music has also been around for thousands of years. Music can be made with only yourvoice, but most of the time, people useinstruments. Music can be made using simple instruments only such as simpledrums all the way up toelectric guitars,keyboards andviolins. Music can be loud, fast, quiet, slow or many other different styles. Music represents how the people who are playing the music feel.
Humans often categorize themselves by race or ethnicity. Modernbiologists know that humangene sequences are very similar compared to many other animals.[49][50][51] This is because of the "recent single origin" of modern humans.[23] That is one reason why there is only one human race.[52][53]:360
Ethnic groups are often linked by linguistic, cultural, ancestral, and national or regional ties. Race and ethnicity can lead to different social treatment calledracism.
Religion is abelief offaith in a higher being, spirit, or any system of ideas that a group of people believe in. To havefaith in a belief is to have the belief without proof that it is true. Faith can bring people together because they all believe in the same thing. Some of the things that religions talk about are what happens afterdeath, why humans exist, how humans came to exist (creation), and what is good to do and not to do (morality). Some people are veryreligious. Many people believe in one all-powerfulgod; some people believe in more than one god; some people areatheists who do not believe in a god; and some people areagnostics who are not sure if there is a god.
In the 20th century, technology moved forward enough to allow a person to land onthe Moon.
Technology are the things and methods which humans use to make tasks easier. Science is understanding how theuniverse and the things in it work. Technology used to be quite simple. It was passed on by people telling others untilwriting was invented. This allowed technology todevelop much quicker. Now people understand more and more about the world and the universe. The use of thetelescope byGalileo,Einstein's theory ofrelativity,lasers, andcomputing are all scientific discoveries. Technology is important to science, to medicine, and to everyday life.
Awar is alethal fight between large groups of people, usuallycountries orstates. A war involves the use of lethal weapons as both sides try to kill the other. It is estimated that during the 20th century, between 167 and 188 million humansdied because of war.[54] The people who fight for a state in wars are calledsoldiers. The people who fight in wars, but not for a state, are usually called "fighters".
Modern wars are very different from wars a thousand or even a hundred years ago. Modern war involves sabotage,terrorism,propaganda, andguerrilla warfare. In modern-day wars, civilians (people who are not soldiers) are often targets. An example of this is thenuclear bomb dropped onHiroshima andNagasaki at the end ofWorld War II. The bombs killed as many as 140,000 people in Hiroshima and 80,000 in Nagasaki by the end of 1945,[55] about half on the days of the bombings. Since then, thousands more have died from wounds or illness because ofexposure to radiation released by the bombs.[56] In both cities, the overwhelming majority of the dead were civilians. In Germany, Austria, and Great Britain, conventional bombs were used. About 60,595 British[57] and 550,000 German[58] civilians were killed by planes bombing cities.
↑Poe, Marshall T. 2011.A history of communications: media and society from the evolution of speech to the internet. Cambridge University Press.ISBN9780521179447
↑By usinggenome sequencing, scientists have compared:
The difference between two humans that are related
The difference between two humans that are not related
The difference between a human and a chimpanzee
The difference between two other animals that look like each other- rats and mice
The studies showed that, after 6.5 million years of evolution as separate species, between 95% and 99% of the DNA of humans and chimpanzees is the same. The difference between a human and a chimpanzee was about ten times greater than the difference between two unrelated humans. When this difference is compared with the difference between the DNA of mice and rats, the difference between a mouse and a rat is ten times greater than the difference between a human and a chimpanzee.
↑Except that, in the opinion of some, chimpanzees are also hominins.
↑New York TimesArchived 2017-08-10 at theWayback Machine articleFossils in Kenya challenge linear evolution published August 9, 2007 says "Scientists who dated and analyzed the specimens — a 1.44 million-year-oldHomo habilis and a 1.55 million-year-oldHomo erectus — said their findings challenged the conventional view that these species evolved one after the other. Instead, they apparently lived side by side in eastern Africa for almost half a million years".
↑"Mass of an adult". The Physics Factbook: an encyclopedia of scientific essays.Archived from the original on 1 January 2018. Retrieved31 December 2017.
↑Why humans and their fur parted way by Nicholas Wade,New York Times, August 19 2003.
↑Harding, Rosalind M.et al. 2000. Evidence for variable selective pressures at MC1R.American Journal of Human Genetics66: 1351–1361.
↑Jablonski N.G. & Chaplin G. 2000. The evolution of human skin coloration (pdf),Journal of Human Evolution39: 57–106.Archived 2012-01-14 at theWayback Machine
↑Robin, Ashley 1991.Biological perspectives on human pigmentation. Cambridge: Cambridge University Press.
↑Muehlenbein, Michael 2010.Human evolutionary biology. Cambridge University Press, 192–213.
↑Schwartz, Jeffrey (1987).The red ape: orangutans and human origins. Basic Books. p.286.ISBN0813340640.
↑According to the July 2, 2007Newsweek magazine, a woman dies in childbirth every minute, most often due to uncontrolled bleeding andinfection, with the world's poorest women most vulnerable. The lifetime risk is 1 in 16 inAfrica, compared to 1 in 2,800 in developed countries.
↑Rush D (2000). "Nutrition and maternal mortality in the developing world".The American Journal of Clinical Nutrition.72 (1 Suppl): 212 S–240 S.doi:10.1093/ajcn/72.1.212S.PMID10871588.
↑Buss D.M. 2004.Evolutionary psychology: the new science of the mind, especially Part III: Challenges of sex and mating. Boston, Pearson, 2nd ed.ISBN 0-205-37071-3
↑Jones S; Martin R. & Pilbeam D. (eds) 1992.The Cambridge Encyclopedia of Human Evolution. 4.2, p150: Matimg and parental care.
↑Tishkoff SA, Kidd KK (November 2004). "Implications of biogeography of human populations for 'race' and medicine".Nat. Genet.36 (11 Suppl): S21–7.doi:10.1038/ng1438.PMID15507999.S2CID1500915.
↑American Association of Physical Anthropologists (27 March 2019)."AAPA Statement on Race and Racism".American Association of Physical Anthropologists.Archived from the original on 22 March 2020. Retrieved19 June 2020.
↑Rezelman, David; F.G. Gosling and Terrence R. Fehner (2000)."The atomic bombing of Hiroshima". U.S. Department of Energy. Archived fromthe original on 2006-09-29. Retrieved2007-09-18. page on Hiroshima casualties.
60,000, (bombing): John KeeganThe Second World War (1989);
60,000: Boris Urlanis,Wars and Population (1971)
60,595: Harper Collins Atlas of the Second World War
60,600: John Ellis, World War II: a statistical survey (Facts on File, 1993) "killed and missing"
92,673, (incl. 30,248 merchant mariners and 60,595 killed by bombing): Encyclopaedia Britannica, 15th edition, 1992 printing. "Killed, died of wounds, or in prison .... excluding those who died of natural causes or were suicides."
92,673: Norman Davies,Europe A History (1998) same as Britannica's war dead in most cases
92,673: Michael ClodfelterWarfare and Armed Conflict: A Statistical Reference to Casualty and Other Figures, 1618–1991;
100,000: William Eckhardt, a 3-page table of his war statistics printed in World Military and Social Expenditures 1987–88 (12th ed., 1987) by Ruth Leger Sivard. "Deaths", including "massacres, political violence, and famines associated with the conflicts."
The British kept accurate records during WWII: 60,595 was the official death toll with 30,248 for the British merchant mariners (most of whom are listed on the Tower Hill Memorial)
