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10 Oct 14
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09 Apr 14
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A major problem at that time was the lack of fossil intermediaries.
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n 1925, Raymond Dart described Australopithecus africanus. The type specimen was the Taung Child, an Australopithecine infant which was discovered in a cave. The child's remains were a remarkably well-preserved tiny skull and an endocranial cast of the brain.
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Although the brain was small (410 cm3), its shape was rounded, unlike that of chimpanzees and gorillas, and more like a modern human brain. Also, the specimen showed short canine teeth, and the position of the foramen magnum was evidence of bipedal locomotion. All of these traits convinced Dart that the Taung baby was a bipedal human ancestor, a transitional form between apes and humans.
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The East African fossils
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During the 1960s and 1970s, hundreds of fossils were found, particularly in East Africa in the regions of the Olduvai gorge and Lake Turkana. The driving force in the East African researches was the Leakey family, with Louis Leakey and his wife Mary Leakey, and later their son Richard and daughter in-law Meave being among the most successful fossil hunters and palaeoanthropologists. From the fossil beds of Olduvai and Lake Turkana they amassed fossils of australopithecines, early Homo and even Homo erectus.
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Human dispersal
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Anthropologists in the 1980s were divided regarding some details of reproductive barriers and migratory dispersals of the Homo genus. Subsequently, genetics has been used to investigate and resolve these issues. According to the Sahara pump theory evidence suggests that genus Homo have migrated out of Africa at least three times (e.g. Homo erectus, Homo hiedelbergensis and Homo sapiens)
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Anatomical changes
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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 bipedalism, increased brain size, lengthened ontogeny (gestation and infancy), and decreased sexual dimorphism.
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Other significant morphological changes included the evolution of a power and precision grip, a change first occurring in H. erectus.
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Bipedalism[edit]
Bipedalism is the basic adaption of the Hominin line and 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[45] or Orrorin, with Ardipithecus, a full bipedal, coming somewhat later. The knuckle walkers, the gorilla and chimpanzee, diverged around the same time, and either Sahelanthropus or Orrorin may be our last shared ancestor.
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The early bipedals eventually evolved into the australopithecines and later the genus Homo. There are several theories of the adaptation value of bipedalism. It is possible that bipedalism was favored because it freed up the hands for reaching and carrying food, saved energy during locomotion,[46] enabled long distance running and hunting, enhanced field of vision and helped avoid hyperthermia by reducing the surface area exposed to direct sun; all this mainly for thriving in the new grassland type environment rather than the previous forest type.
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Anatomically the evolution of bipedalism has been accompanied by a large number of skeletal changes, not just to the legs and pelvis, but also to the vertebral column, feet and ankles, and skull.[48] The femur evolved into a slightly more angular position to move the center of gravity toward the geometric center of the body. The knee and ankle joints became increasingly robust to better support increased weight. To support the increased weight on each vertebra in the upright position, the human vertebral column became S-shaped and the lumbar vertebrae became shorter and wider. In the feet the big toe moved into alignment with the other toes to help in forward locomotion. The arms and forearms shortened relative to the legs making it easier to run.
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The most significant changes are in the pelvic region, where the long downward facing iliac blade was shortened and became wide as a requirement for keeping the center of gravity stable while walking
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ipedal hominids have a shorter but broad, bowl-like pelvis due to this
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The shortening of the pelvis and smaller birth canal evolved as a requirement for bipedalism and had significant effects on the process of human birth which is much more difficult in modern humans than in other primates.
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The human species developed a much larger brain than that of other primates – typically 1,330 cm3 in modern humans, over twice the size of that of a chimpanzee or gorilla.[53] The pattern of encephalization started with Homo habilis, which at approximately 600 cm3 had a brain slightly larger than that of chimpanzees, and continued with Homo erectus (800–1,100 cm3), reaching a maximum in Neanderthals with an average size of (1,200–1,900 cm3), larger even than Homo sapiens. 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. However, the differences between the structure of human brains and those of other apes may be even more significant than differences in size.
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31 Oct 13
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Homo erectus and Homo ergaster were the first of the hominina to leave Africa, and these species spread through Africa, Asia, and Europe between 1.3 to 1.8 million years ago. It is believed that these species were the first to use fire and complex tools. According to the Recent African Ancestry theory, modern humans evolved in Africa possibly from Homo heidelbergensis, Homo rhodesiensis or Homo antecessor and migrated out of the continent some 50,000 to 100,000 years ago, replacing local populations of Homo erectus, Homo denisova, Homo floresiensis and Homo neanderthalensis.[5][6][7][8][9]
Archaic Homo sapiens, the forerunner of anatomically modern humans, evolved between 400,000 and 250,000 years ago.[10][11] Recent DNA evidence suggests that several haplotypes of Neanderthal origin are present among all non-African populations, and Neanderthals and other hominids, such as Denisova hominin may have contributed up to 6% of their genome to present-day humans, suggestive of a limited inter-breeding between these species.[12][13][14] Anatomically modern humans evolved from archaic Homo sapiens in the Middle Paleolithic, about 200,000 years ago.[15] The transition to behavioral modernity with the development of symbolic culture, language, and specialized lithic technology happened around 50,000 years ago according to many anthropologists[16] although some suggest a gradual change in behavior over a longer time span.[17]
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The possibility of linking humans with earlier apes by descent became clear only after 1859 with the publication of Charles Darwin's On the Origin of Species, in which he argued for the idea of the evolution of new species from earlier ones. Darwin's book did not address the question of human evolution, saying only that "Light will be thrown on the origin of man and his history".
The first debates about the nature of human evolution arose between Thomas Huxley and Richard Owen. Huxley argued for human evolution from apes by illustrating many of the similarities and differences between humans and apes, and did so particularly in his 1863 book Evidence as to Man's Place in Nature. However, many of Darwin's early supporters (such as Alfred Russel Wallace and Charles Lyell) did not initially agree that the origin of the mental capacities and the moral sensibilities of humans could be explained by natural selection, though this later changed. Darwin applied the theory of evolution and sexual selection to humans when he published The Descent of Man in 1871.[19]
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The most significant of these adaptations are bipedalism, increased brain size, lengthened ontogeny (gestation and infancy), and decreased sexual dimorphism. The relationship between these changes is the subject of ongoing debate.[43] Other significant morphological changes included the evolution of a power and precision grip, a change first occurring in H. erectus
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The evidence
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18 Oct 13
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07 Apr 13
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Evolutionary history of the primates can be traced back 65 million years.
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David Begun[66] concluded that early primates flourished in Eurasia and that a lineage leading to the African apes and humans, including Dryopithecus, migrated south from Europe or Western Asia into Africa.
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The surviving tropical population of primates
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gave rise to all living species—lemurs of Madagascar, lorises of Southeast Asia, galagos or "bush babies" of Africa, and the anthropoids: platyrrhine or New World monkeys, catarrhines or Old World monkeys, and the great apes, including humans.
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Fossils at 20 million years ago include fragments attributed to Victoriapithecus, the earliest Old World Monkey.
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29 Jan 13
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According to genetic studies, primates diverged from other mammals about 85 million years ago in the Late Cretaceous period, and the earliest fossils appear in the Paleocene, around 55 million years ago.
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The family Hominidae diverged from the Hylobatidae (Gibbon) family 15-20 million years ago, and around 14 million years ago, the Ponginae (orangutans), diverged from the Hominidae family.
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Bipedalism is the basic adaption of the Hominin line
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The gorilla and chimpanzee diverged around the same time, about 4-6 million years ago
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The early bipedals eventually evolved into the australopithecines and later the genus Homo.
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The earliest documented members of the genus Homo are Homo habilis which evolved around 2.3 million years ago;
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earliest species for which there is positive evidence of use of stone tools.
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Anatomically modern humans evolved from archaic Homo sapiens in the Middle Paleolithic, about 200,000 years ago
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The Out-of-Africa model proposed that modern H. sapiens speciated in Africa recently (approx. 200,000 years ago) and their subsequent migration through Eurasia resulted in complete replacement of other Homo species
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Out of Africa is also supported by the fact that mitochondrial genetic diversity is highest among African populations.[
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Studies of haplogroups in Y-chromosomal DNA and mitochondrial DNA have largely supported a recent African origin.
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Evidence
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fossil record,
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offer considerable insight into the evolution of all life, including how humans evolved
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The closest living relatives of humans are gorillas
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and chimpanzees
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DNA sequences range between 95% and 99%.
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human and chimpanzee genome
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the last female common ancestor whose genetic marker is found in all modern humans, the so-called mitochondrial Eve, must have lived around 200,000 years ago.
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28 Nov 12
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31 Oct 12
Robert ParkerFirst Steps
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Archaic Homo sapiens, the forerunner of anatomically modern humans, evolved between 400,000 and 250,000 years ago.[10][
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m archaic Homo sapiens in the Middle Paleolit
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1 site 2010 H. antecessor 1.2 – 0.8 Spain 1.75 m (5.7 ft) 90 kg (200 lb) 1,000 2 sites
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29 Jan 12
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Species Lived when (MYA) Lived where Adult length (m) Adult mass (kg) Brain volume (cm³) Fossil record Discovery / publication of name H. habilis 2.5–1.5 Africa 1.0–1.5 30–55 660[27] many 1960/1964 H. rudolfensis 1.9 Kenya 1 skull 1972/1986 H. georgicus 1.8–1.6 Georgia 600 few 1999/2002 H. ergaster 1.9–1.4 E. and S. Africa 1.9 700–850 many 1975 H. erectus 2 – 0.03 [27] Africa, Eurasia (Java, China, Caucasus) 1.8 60 850(early) – 1100(late)[27] many 1891/1892 H. cepranensis 0.8? Italy 1000 1 skull cap 1994/2003 H. antecessor 0.8–0.35 Spain, England 1.75 90 1000 3 sites 1997 H. heidelbergensis 0.6–0.25 Europe, Africa, China 1.8 60 1100–1400 many 1908 H. neanderthalensis 0.35–0.03 Europe, W. Asia 1.6 55–70 (heavily built) 1200–1700 many (1829)/1864 H. rhodesiensis 0.3–0.12 Zambia 1300 very few 1921 H. sapiens 0.25–present worldwide 1.4–1.9 55–80 1000–1850 still living —/1758 H. sapiens idaltu 0.16–0.15 Ethiopia 1450 3 craniums 1997/2003 H. floresiensis 0.10–0.012 Indonesia 1.0 25 400 7 individuals 2003/2004
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09 Nov 06
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31 Aug 06
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After 50,000 BP, what Jared Diamond, author of Guns, Germs, and Steel, and other anthropologists characterize as a Great Leap Forward, human culture apparently started to change at much greater speed: "modern" 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. This speed-up of cultural change seems connected with the arrival of modern humans, homo sapiens sapiens. Additionally, human culture began to become more 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 that has not been seen in human cultures prior to 50,000 BP.
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19 Mar 06
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