Humans commonly refers to the species Homo sapiens (Latin: "wise man" or "knowing man"), the only extant member of the Homo genus of bipedal primates in Hominidae, the great ape family. However, in some cases the term is used to refer to any member of the genus Homo .
Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving. This mental capability, combined with an erect body carriage that frees the hands for manipulating objects, has allowed humans to make far greater use of tools than any other species. Mitochondrial DNA and fossil evidence indicates that modern humans originated in Africa about 200,000 years ago. Humans are a cosmopolitan species; widespread in every continent except Antarctica, with a total population of 6.8 billion as of November 2009.
Like most higher primates, humans are social by nature. However, humans are uniquely adept at utilizing systems of communication for self-expression, the exchange of ideas, and organization. Humans create complex social structures composed of many cooperating and competing groups, from families to nations. Social interactions between humans have established an extremely wide variety of values, social norms, and rituals, which together form the basis of human society.
Humans are noted for their desire to understand and influence their environment, seeking to explain and manipulate natural phenomena through science, philosophy, mythology and religion. This natural curiosity has led to the development of advanced tools and skills, which are passed down culturally; humans are the only species known to build fires, cook their food, clothe themselves, and use numerous other technologies.
Name
Further information: Man (word) and List of alternative names for the human speciesThe English adjective human is a Middle English loan from Old French humain , ultimately from Latin hūmānus , the adjective of homō "man". Use as a noun (with a plural humans ) dates to the 16th century. The native English term man is now often reserved for male adults, but can still be used for "mankind" in general in Modern English. The word is from Proto-Germanic *mannaz , from a Proto-Indo-European(PIE) root *man- , cognate to Sanskrit manu- .
The generic name Homo is a learned 18th century derivation from Latin homō "man", ultimately "earthly being" (Old Latin hemō , cognate to Old English guma "man", from PIE *dʰǵʰ e mon- , meaning 'earth' or 'ground').
History
Evolution
Main article: Human evolutionFurther information: Anthropology, Homo (genus), and Timeline of human evolutionThe scientific study of human evolution encompasses the development of the genus Homo , but usually involves studying other hominids and hominines as well, such as Australopithecus . "Modern humans" are defined as the Homo sapiens species, of which the only extant subspecies is known as Homo sapiens sapiens . Homo sapiens idaltu (roughly translated as "elder wise human"), the other known subspecies, is now extinct. Homo neanderthalensis , which became extinct 30,000 years ago, has sometimes been classified as a subspecies, " Homo sapiens neanderthalensis ", but genetic studies now suggest a divergence of the Neanderthal species from Homo sapiens about 500,000 years ago. Similarly, the few specimens of Homo rhodesiensis have also occasionally been classified as a subspecies, but this is not widely accepted. Anatomically modern humans first appear in the fossil record in Africa about 195,000 years ago, and studies of molecular biology give evidence that the approximate time of divergence from the common ancestor of all modern human populations was 200,000 years ago. The broad study of African genetic diversity headed by Dr. Sarah Tishkoff found the San people to express the greatest genetic diversity among the 113 distinct populations sampled, making them one of 14 "ancestral population clusters". The research also located the origin of modern human migration in south-western Africa, near the coastal border of Namibia and Angola.
The closest living relatives of humans are gorillas and chimpanzees, but humans did not evolve from these apes: instead these apes share a common ancestor with modern humans. Humans are probably most closely related to two chimpanzee species: Common Chimpanzee and Bonobo. Full genome sequencing has resulted in the conclusion that "after 6.5 years of separate evolution, the differences between chimpanzee and human are ten times greater than those between two unrelated people and ten times less than those between rats and mice". Suggested concurrence between human and chimpanzee DNA sequences range between 95% and 99%. It has been estimated that the human lineage diverged from that of chimpanzees about five million years ago, and from that of 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.
Human evolution is characterized by a number of important morphological, developmental, physiological and behavioural changes, which have taken place since the split between the last common ancestor of humans and chimpanzees. The first major morphological change was the evolution of a bipedal locomotor adaptation from an arboreal or semi-arboreal one, with all its attendant adaptations, such as a valgus knee, low intermembral index (long legs relative to the arms), and reduced upper-body strength.
Later, ancestral humans developed a much larger brain – typically 1,400 cm³ in modern humans, over twice the size of that of a chimpanzee or gorilla. The pattern of human postnatal brain growth differs from that of other apes (heterochrony), and allows for extended periods of social learning and language acquisition in juvenile humans. Physical anthropologists argue that the differences between the structure of human brains and those of other apes are even more significant than their differences in size.
Other significant morphological changes included: the evolution of a power and precision grip; a reduced masticatory system; a reduction of the canine tooth; and the descent of the larynx and hyoid bone, making speech possible. An important physiological change in humans was the evolution of hidden oestrus, or concealed ovulation, which may have coincided with the evolution of important behavioural changes, such as pair bonding. Another significant behavioural change was the development of material culture, with human-made objects becoming increasingly common and diversified over time. The relationship between all these changes is the subject of ongoing debate.
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 15,000 years.
Paleolithic
Further information: Recent African Origin, Archaic Homo sapiens, Upper Paleolithic, and Early human migrationsAnatomically modern humans evolved from archaic Homo sapiens in Africa in the Middle Paleolithic, about 200,000 years ago. By the beginning of the Upper Paleolithic 50,000 BP (Before Present), full behavioral modernity, including language, music and other cultural universals had developed.
The broad study of African genetic diversity headed by Dr. Sarah Tishkoff found the San people to express the greatest genetic diversity among the 113 distinct populations sampled, making them one of 14 "ancestral population clusters". The research also located the origin of modern human migration in south-western Africa, near the coastal border of Namibia and Angola.
The out of Africa migration is estimated to have occurred about 70,000 years BP. Modern humans subsequently spread to all continents, replacing earlier hominids: they inhabited Eurasia and Oceania by 40,000 BP, and the Americas at least 14,500 years BP. They displaced Homo neanderthalensis and other species descended from Homo erectus (which had inhabited Eurasia as early as 2 million years ago) through more successful reproduction and competition for resources.
Evidence from archaeogenetics accumulating since the 1990s has lent strong support to the "out-of-Africa" scenario, and has marginalized the competing multiregional hypothesis, which proposed that modern humans evolved, at least in part, from independent hominid populations.
Geneticists Lynn Jorde and Henry Harpending of the University of Utah propose that the variation in human DNA is minute compared to that of other species. They also propose that during the Late Pleistocene, the human population was reduced to a small number of breeding pairs – no more than 10,000, and possibly as few as 1,000 – resulting in a very small residual gene pool. Various reasons for this hypothetical bot
Human Life Cycle
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Human Health
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Category:Human life cycle - Wikimedia Commons
Media in category "Human life cycle" The following 6 files are in this category, out of 6 total.
YouTube - Human Life Cycle...!!!
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This section includes: Skeletons and muscles. Human life cycle
Life Cycle, Human Life Stages
The psychology of life cycle relates issues that you face in different stages of your life.
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Alternate Labels: Human life cycle; Life stages, Human; Lifecycle, Human Human life cycle Life stages, Human Lifecycle, Human
