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Human evolution is the phenotypic history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids
("great apes") and mammals. The study of human evolution uses many scientific disciplines, including physical anthropology, primatology, archaeology, linguistics and genetics.[1]


The term "human" in the context of human evolution refers to the genus
Homo, but studies of human evolution usually include other hominids,
such as the Australopithecines, from which the genus Homo
had diverged by about 2.3 to 2.4 million years ago in Africa.[2][3] Scientists
have estimated that humans branched off from their common ancestor with chimpanzees
about 5–7 million years ago. Several species and subspecies of Homo
evolved and are now extinct, introgressed or extant. Examples include Homo
erectus
(which inhabited Asia, Africa, and Europe) and Neanderthals (either Homo neanderthalensis or
Homo sapiens neanderthalensis) (which inhabited Europe and Asia). Archaic Homo sapiens evolved between 400,000
and 250,000 years ago.


The dominant view among scientists concerning the origin of anatomically
modern humans
is the hypothesis known as "Out of Africa", recent African origin of modern humans, ROAM, or
recent African origin hypothesis,[4][5][6] which
argues that Homo sapiens arose in Africa and migrated out of the
continent around 50,000 to 100,000 years ago, replacing populations of Homo
erectus
in Asia and Neanderthals in Europe.


Scientists supporting an alternative multiregional
hypothesis
argue that Homo sapiens evolved as geographically
separate but interbreeding populations stemming from a worldwide migration of
Homo erectus out of Africa nearly 2.5 million years ago. Evidence
suggests that Neanderthal genomes may have contributed about 4% of non-African
heredity, and the recently discovered Denisova hominin may have contributed 6% of the
genome of Melanesians.[7][8] Archaic
genetic contribution contradicts total Eurasian replacement around 100,000
years ago.

History of ideas
The word homo, the name of the biological genus to which humans
belong, is Latin for "human". It was chosen originally by Carolus Linnaeus in his classification system. The
word "human" is from the Latin humanus, the adjectival form of
homo. The Latin "homo" derives from the Indo-European root,
*dhghem, or "earth".[10]


Carolus Linnaeus and other scientists of his time also considered the great apes to be the closest relatives of humans due
to morphological and anatomical similarities. The possibility of linking
humans with earlier apes by descent only became clear after 1859 with the
publication of Charles Darwin's On
the Origin of Species
. This 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 agree that the origin of the mental capacities and the
moral sensibilities of humans could be explained by natural selection. Darwin applied the theory of
evolution and sexual selection to humans when he published The Descent of Man in 1871.[11]


A major problem at that time was the lack of fossil intermediaries. Despite
the discovery by Eugene Dubois of what is now called Homo
erectus
in 1891
at Trinil,
Java, it was only in the 1920s that such fossils were discovered in Africa, that intermediate species began to accumulate. In 1925, Raymond Dart described Australopithecus
africanus
. The type specimen was the Taung Child, an Australopithecine infant discovered
in a cave. The child's remains were a remarkably well-preserved tiny skull and
an endocranial cast of the individual's brain. 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.


The classification of humans and their relatives has
changed considerably over time. The gracile Australopithecines are now thought
to be ancestors of the genus Homo, the group to which modern humans
belong. Both Australopithecines and Homo sapiens are part of the tribe Hominini.
Recent data suggests Australopithecines were a diverse group and that A.
africanus
may not be a direct ancestor of modern humans. Reclassification of
Australopithecines that originally were split into either gracile or robust varieties has put the latter into a genus of
its own, Paranthropus. Taxonomists place humans,
Australopithecines and related species in the same family as other great apes,
in the Hominidae.




Fossil
Hominid Evolution Display at The
Museum of Osteology
, Oklahoma
City
, USA

Picture
Comparative table of Homo species view · talk
· edit


Species
Lived when (
Ma)
Lived where

Adult height

Adult mass

Cranial
capacity
(cm³)
Fossil record

Discovery / publication of name


H.
antecessor

1.2 – 0.8
Spain
1.75 m (5.7 ft)
90 kg (200 lb)
1,000
2 sites
1997

H.
cepranensis

0.9 – 0.8
Italy


1,000
1 skull cap
1994/2003

H. erectus
1.5 – 0.2
Africa, Eurasia (Java, China, India,
Caucasus)
1.8 m (5.9 ft)
60 kg (130 lb)
850 (early) – 1,100 (late)
Many
1891/1892

H.
ergaster

1.9 – 1.4
Eastern and Southern Africa
1.9 m (6.2 ft)

700–850
Many
1975

H.
floresiensis

0.10 – 0.012
Indonesia
1.0 m (3.3 ft)
25 kg (55 lb)
400
7 individuals
2003/2004

H.
gautengensis

>2 – 0.6
South Africa
1.0 m (3.3 ft)


1 individual
2010/2010

H.
georgicus

1.8
Georgia


600
4 individuals
1999/2002

H. habilis
2.3 – 1.4
Africa
1.0–1.5 m (3.3–4.9 ft)
33–55 kg (73–120 lb)
510–660
Many
1960/1964

H.
heidelbergensis

0.6 – 0.35
Europe, Africa, China
1.8 m (5.9 ft)
60 kg (130 lb)
1,100–1,400
Many
1908

H.
neanderthalensis

0.35 – 0.03
Europe, Western
Asia

1.6 m (5.2 ft)
55–70 kg (120–150 lb) (heavily built)
1,200–1,900
Many
(1829)/1864

H.
rhodesiensis

0.3 – 0.12
Zambia


1,300
Very few
1921

H.
rudolfensis

1.9
Kenya



1 skull
1972/1986

H.
sapiens idaltu

0.16 – 0.15
Ethiopia


1,450
3 craniums
1997/2003

H.
sapiens sapiens
(modern humans)

0.2 – present
Worldwide
1.4–1.9 m (4.6–6.2 ft)
50–100 kg (110–220 lb)
1,000–1,850
Still living
—/1758