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''Homo'' () is the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either
ancestral An ancestor, also known as a forefather, fore-elder or a forebear, is a parent or ( recursively) the parent of an antecedent (i.e., a grandparent, great-grandparent, great-great-grandparent and so forth). ''Ancestor'' is "any person from wh ...
to or closely related to modern humans (depending on the species), most notably '' Homo erectus'' and ''
Homo neanderthalensis Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
''. The genus emerged with the appearance of '' Homo habilis'' just over 2 million years ago. ''Homo'', together with the genus '' Paranthropus'', is probably sister to '' Australopithecus africanus'', which itself had previously split from the lineage of '' Pan'', the
chimpanzees The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative th ...
. '' Homo erectus'' appeared about 2 million years ago and, in several early migrations, spread throughout
Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
(where it is dubbed ''
Homo ergaster ''Homo ergaster'' is an extinct species or subspecies of archaic humans who lived in Africa in the Early Pleistocene. Whether ''H. ergaster'' constitutes a species of its own or should be subsumed into '' H. erectus'' is an ongoing and unresol ...
'') and Eurasia. It was likely that the first human species lived in a hunter-gatherer society and was able to control fire. An adaptive and successful species, ''Homo erectus'' persisted for more than a million years and gradually diverged into new species by around 500,000 years ago.
Anatomically modern humans Early modern human (EMH) or anatomically modern human (AMH) are terms used to distinguish '' Homo sapiens'' (the only extant Hominina species) that are anatomically consistent with the range of phenotypes seen in contemporary humans from exti ...
(''Homo sapiens'') emerged close to 300,000 to 200,000 years ago, in Africa, and ''
Homo neanderthalensis Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
'' emerged around the same time in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
and Western Asia. ''Homo sapiens'' dispersed from Africa in several waves, from possibly as early as 250,000 years ago, and certainly by 130,000 years ago, the so-called Southern Dispersal beginning about 70–50,000 years ago leading to the lasting colonisation of Eurasia and Oceania by 50,000 years ago. Both in Africa and Eurasia, ''Homo sapiens'' met with and interbred with archaic humans. Separate archaic (non-''sapiens'') human species are thought to have survived until around 40,000 years ago ( Neanderthal extinction).


Names and taxonomy

The
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
noun ''homō'' (genitive ''hominis'') means "human being" or "
man A man is an adult male human. Prior to adulthood, a male human is referred to as a boy (a male child or adolescent). Like most other male mammals, a man's genome usually inherits an X chromosome from the mother and a Y chromo ...
" in the generic sense of "human being, mankind". The binomial name ''Homo sapiens'' was coined by
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
(1758). Names for other species of the genus were introduced beginning in the second half of the 19th century (''H. neanderthalensis'' 1864, ''H. erectus'' 1892). Even today, the genus ''Homo'' has not been strictly defined. Since the early human fossil record began to slowly emerge from the earth, the boundaries and definitions of the genus ''Homo'' have been poorly defined and constantly in flux. Because there was no reason to think it would ever have any additional members,
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
did not even bother to define ''Homo'' when he first created it for humans in the 18th century. The discovery of Neanderthal brought the first addition. The genus ''Homo'' was given its taxonomic name to suggest that its member species can be classified as human. And, over the decades of the 20th century, fossil finds of pre-human and early human species from late
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
and early
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Australopithecus''—or, indeed, delineating ''Homo'' from '' Pan.'' Even so, classifying the fossils of ''Homo'' coincides with evidence of: (1) competent human bipedalism in '' Homo habilis'' inherited from the earlier '' Australopithecus'' of more than four million years ago, as demonstrated by the Laetoli footprints; and (2)  human tool culture having begun by 2.5 million years ago. From the late-19th to mid-20th centuries, a number of new taxonomic names including new generic names were proposed for early human fossils; most have since been merged with ''Homo'' in recognition that '' Homo erectus'' was a single species with a large geographic spread of early migrations. Many such names are now dubbed as " synonyms" with ''Homo'', including ''Pithecanthropus'', ''Protanthropus'', ''Sinanthropus'', ''Cyphanthropus'', ''Africanthropus'', ''Telanthropus'', ''Atlanthropus'', and ''Tchadanthropus''. Classifying the genus ''Homo'' into species and subspecies is subject to incomplete information and remains poorly done. This has led to using common names ("Neanderthal" and "Denisovan"), even in scientific papers, to avoid trinomial names or the ambiguity of classifying groups as ''
incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...
'' (uncertain placement)—for example, ''H. neanderthalensis'' vs. ''H. sapiens neanderthalensis'', or ''H. georgicus'' vs. ''H. erectus georgicus''. Some recently extinct species in the genus ''Homo'' have only recently been discovered and do not as yet have consensus binomial names (see Denisova hominin). Since the beginning of the Holocene, it is likely that ''Homo sapiens'' (anatomically modern humans) has been the only extant species of ''Homo''. John Edward Gray (1825) was an early advocate of classifying taxa by designating tribes and families. Wood and Richmond (2000) proposed that Hominini ("hominins") be designated as a tribe that comprised all species of early humans and pre-humans ancestral to humans back to ''after'' the chimpanzee-human last common ancestor; and that Hominina be designated a subtribe of Hominini to include ''only'' the genus ''Homo'' — that is, ''not'' including the earlier upright walking hominins of the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Australopithecus'', ''
Orrorin tugenensis ''Orrorin tugenensis'' is a postulated early species of Homininae, estimated at and discovered in 2000. It is not confirmed how ''Orrorin'' is related to modern humans. Its discovery was used to argue against the hypothesis that australopitheci ...
'', ''
Ardipithecus ''Ardipithecus'' is a genus of an extinct hominine that lived during the Late Miocene and Early Pliocene epochs in the Afar Depression, Ethiopia. Originally described as one of the earliest ancestors of humans after they diverged from the chimp ...
'', or ''
Sahelanthropus ''Sahelanthropus tchadensis'' is an extinct species of the Homininae (African apes) dated to about , during the Miocene epoch. The species, and its genus ''Sahelanthropus'', was announced in 2002, based mainly on a partial cranium, nicknamed '' ...
''. Designations alternative to Hominina existed, or were offered: ''Australopithecinae'' (Gregory & Hellman 1939) and ''Preanthropinae'' (Cela-Conde & Altaba 2002); and later, Cela-Conde and Ayala (2003) proposed that the four genera ''Australopithecus'', ''Ardipithecus'', ''Praeanthropus'', and ''Sahelanthropus'' be grouped with ''Homo'' within Hominini (sans ''Pan'').


Evolution


''Australopithecus'' and the appearance of ''Homo''

Several species, including ''
Australopithecus garhi ''Australopithecus garhi'' is a species of australopithecine from the Bouri Formation in the Afar Region of Ethiopia 2.6–2.5 million years ago (mya) during the Early Pleistocene. The first remains were described in 1999 based on several skele ...
'', '' Australopithecus sediba'', '' Australopithecus africanus'', and '' Australopithecus afarensis'', have been proposed as the ancestor or sister of the ''Homo'' lineage. These species have morphological features that align them with ''Homo'', but there is no consensus as to which gave rise to ''Homo''. Especially since the 2010s, the delineation of ''Homo'' in ''Australopithecus'' has become more contentious. Traditionally, the advent of ''Homo'' has been taken to coincide with the first use of stone tools (the
Oldowan The Oldowan (or Mode I) was a widespread stone tool archaeological industry (style) in prehistory. These early tools were simple, usually made with one or a few flakes chipped off with another stone. Oldowan tools were used during the Lower ...
industry), and thus by definition with the beginning of the Lower Palaeolithic. But in 2010, evidence was presented that seems to attribute the use of
stone tools A stone tool is, in the most general sense, any tool made either partially or entirely out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric (particularly Stone Ag ...
to ''Australopithecus afarensis'' around 3.3 million years ago, close to a million years before the first appearance of ''Homo''.
LD 350-1 LD 350-1 is the earliest known specimen of the genus ''Homo'', dating to 2.8–2.75 million years ago (mya), found in the Ledi-Geraru site in the Afar Region of Ethiopia. The specimen was discovered in silts above the Gurumaha Tuff section of th ...
, a fossil mandible fragment dated to 2.8 Mya, discovered in 2013 in Afar, Ethiopia, was described as combining "primitive traits seen in early ''Australopithecus'' with derived morphology observed in later ''Homo''. Some authors would push the development of ''Homo'' close to or even past 3 Mya. Others have voiced doubt as to whether ''Homo habilis'' should be included in ''Homo'', proposing an origin of ''Homo'' with ''Homo erectus'' at roughly 1.9 Mya instead. The most salient physiological development between the earlier australopithecine species and ''Homo'' is the increase in endocranial volume (ECV), from about in ''A. garhi'' to in ''H. habilis'' and further to in ''H. erectus'', in ''H. heidelbergensis'' and up to in ''H. neanderthalensis''. However, a steady rise in cranial capacity is observed already in ''Autralopithecina'' and does not terminate after the emergence of ''Homo'', so that it does not serve as an objective criterion to define the emergence of the genus.


''Homo habilis''

'' Homo habilis'' emerged about 2.1 Mya. Already before 2010, there were suggestions that ''H. habilis'' should not be placed in genus ''Homo'' but rather in ''Australopithecus''. The main reason to include ''H. habilis'' in ''Homo'', its undisputed tool use, has become obsolete with the discovery of ''Australopithecus'' tool use at least a million years before ''H. habilis''. Furthermore, ''H. habilis'' was long thought to be the ancestor of the more gracile ''
Homo ergaster ''Homo ergaster'' is an extinct species or subspecies of archaic humans who lived in Africa in the Early Pleistocene. Whether ''H. ergaster'' constitutes a species of its own or should be subsumed into '' H. erectus'' is an ongoing and unresol ...
'' ('' Homo erectus''). In 2007, it was discovered that ''H. habilis'' and ''H. erectus'' coexisted for a considerable time, suggesting that ''H. erectus'' is not immediately derived from ''H. habilis'' but instead from a common ancestor. With the publication of Dmanisi skull 5 in 2013, it has become less certain that Asian ''H. erectus'' is a descendant of African ''H. ergaster'' which was in turn derived from ''H. habilis''. Instead, ''H. ergaster'' and ''H. erectus'' appear to be variants of the same species, which may have originated in either Africa or Asia and widely dispersed throughout Eurasia (including
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
, Indonesia, China) by 0.5 Mya.


''Homo erectus''

''Homo erectus'' has often been assumed to have developed anagenetically from ''Homo habilis'' from about 2 million years ago. This scenario was strengthened with the discovery of '' Homo erectus georgicus'', early specimens of ''H. erectus'' found in the
Caucasus The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly comprising Armenia, Azerbaijan, Georgia (country), Georgia, and parts of Southern Russia. The Caucasus Mountains, including the Greater Caucasus range ...
, which seemed to exhibit transitional traits with ''H. habilis''. As the earliest evidence for ''H. erectus'' was found outside of Africa, it was considered plausible that ''H. erectus'' developed in Eurasia and then migrated back to Africa. Based on fossils from the
Koobi Fora Koobi Fora refers primarily to a region around Koobi Fora Ridge, located on the eastern shore of Lake Turkana in the territory of the nomadic Gabbra people. According to the National Museums of Kenya, the name comes from the Gabbra language: ...
Formation, east of Lake Turkana in Kenya, Spoor et al. (2007) argued that ''H. habilis'' may have survived beyond the emergence of ''H. erectus'', so that the evolution of ''H. erectus'' would not have been anagenetically, and ''H. erectus'' would have existed alongside ''H. habilis'' for about half a million years (), during the early Calabrian. A separate South African species '' Homo gautengensis'' has been postulated as contemporary with ''Homo erectus'' in 2010.


Phylogeny

A taxonomy of ''Homo'' within the
great apes The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); ''Gorilla'' (the ...
is assessed as follows, with ''Paranthropus'' and ''Homo'' emerging within ''Australopithecus'' (shown here
cladistically Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...
granting ''Paranthropus'', ''Kenyanthropus'', and ''Homo''). The exact phylogeny within ''Australopithecus'' is still highly controversial. Approximate radiation dates of daughter clades are shown in millions of years ago (Mya). ''
Graecopithecus ''Graecopithecus'' is an extinct species of hominid that lived in southeast Europe during the late Miocene around 7.2 million years ago. Originally identified by a single lower jaw bone bearing a molar tooth found in Pyrgos Vasilissis, Athens, ...
,'' ''
Sahelanthropus ''Sahelanthropus tchadensis'' is an extinct species of the Homininae (African apes) dated to about , during the Miocene epoch. The species, and its genus ''Sahelanthropus'', was announced in 2002, based mainly on a partial cranium, nicknamed '' ...
'', ''
Orrorin ''Orrorin tugenensis'' is a postulated early species of Homininae, estimated at and discovered in 2000. It is not confirmed how ''Orrorin'' is related to modern humans. Its discovery was used to argue against the hypothesis that australopithecin ...
'', possibly sisters to ''Australopithecus'', are not shown here. Note that the naming of groupings is sometimes muddled as often certain groupings are presumed before any cladistic analysis is performed. Several of the ''Homo'' lineages appear to have surviving progeny through introgression into other lines. Genetic evidence indicates an archaic lineage separating from the other human lineages 1.5 million years ago, perhaps ''H. erectus'', may have interbred into the Denisovans about 55,000 years ago. Fossil evidence shows ''Homo erectus'' s.s. survived at least until 117,000 yrs ago, and the even more basal ''Homo floresiensis'' survived until 50,000 years ago. A 1.5 million years Homo erectus-like lineage appears to have made its way into modern humans through the Denisovans and specifically into the Papuans and aboriginal Australians. The genomes of non-sub-Saharan African humans show what appear to be numerous independent introgression events involving Neanderthal and in some cases also Denisovans around 45,000 years ago. The genetic structure of some sub-Saharan African groups seems to be indicative of introgression from a west Eurasian population some 3,000 years ago. Some evidence suggests that '' Australopithecus sediba'' could be moved to the genus ''Homo'', or placed in its own genus, due to its position with respect to e.g. '' Homo habilis'' and ''
Homo floresiensis ''Homo floresiensis'' also known as "Flores Man"; nicknamed "Hobbit") is an extinct species of small archaic human that inhabited the island of Flores, Indonesia, until the arrival of modern humans about 50,000 years ago. The remains of an in ...
''.


Dispersal

By about 1.8 million years ago, ''Homo erectus'' is present in both East Africa (''
Homo ergaster ''Homo ergaster'' is an extinct species or subspecies of archaic humans who lived in Africa in the Early Pleistocene. Whether ''H. ergaster'' constitutes a species of its own or should be subsumed into '' H. erectus'' is an ongoing and unresol ...
'') and in Western Asia (''
Homo georgicus The Dmanisi hominins, Dmanisi people, or Dmanisi man were a population of Early Pleistocene hominins whose fossils have been recovered at Dmanisi, Georgia. The fossils and stone tools recovered at Dmanisi range in age from 1.85–1.77 million y ...
''). The ancestors of Indonesian ''
Homo floresiensis ''Homo floresiensis'' also known as "Flores Man"; nicknamed "Hobbit") is an extinct species of small archaic human that inhabited the island of Flores, Indonesia, until the arrival of modern humans about 50,000 years ago. The remains of an in ...
'' may have left Africa even earlier. ''Homo erectus'' and related or derived
archaic human A number of varieties of '' Homo'' are grouped into the broad category of archaic humans in the period that precedes and is contemporary to the emergence of the earliest early modern humans (''Homo sapiens'') around 300 ka. Omo-Kibish I (Omo I) f ...
species over the next 1.5 million years spread throughout Africa and Eurasia (see: Recent African origin of modern humans). Europe is reached by about 0.5 Mya by ''
Homo heidelbergensis ''Homo heidelbergensis'' (also ''H. sapiens heidelbergensis''), sometimes called Heidelbergs, is an extinct species or subspecies of archaic human which existed during the Middle Pleistocene. It was subsumed as a subspecies of '' H. erectus'' i ...
''. ''
Homo neanderthalensis Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the ...
'' and '' Homo sapiens'' develop after about 300 kya. ''
Homo naledi '' Homo naledi'' is an extinct species of archaic human discovered in 2013 in the Rising Star Cave, Cradle of Humankind, South Africa dating to the Middle Pleistocene 335,000–236,000 years ago. The initial discovery comprises 1,550 specimens ...
'' is present in Southern Africa by 300 kya. ''H. sapiens'' soon after its first emergence spread throughout Africa, and to Western Asia in several waves, possibly as early as 250 kya, and certainly by 130 kya. In July 2019, anthropologists reported the discovery of 210,000 year old remains of a ''H. sapiens'' and 170,000 year old remains of a ''H. neanderthalensis'' in
Apidima Cave The Apidima Cave (, ''Spilaio Apidima'') is a complex of five caves four small caves located on the western shore of Mani Peninsula in Southern Greece. A systematic investigation of the cave has yielded Neanderthal and ''Homo sapiens'' fossils f ...
, Peloponnese,
Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...
, more than 150,000 years older than previous ''H. sapiens'' finds in Europe. Most notable is the Southern Dispersal of ''H. sapiens'' around 60 kya, which led to the lasting peopling of Oceania and Eurasia by
anatomically modern humans Early modern human (EMH) or anatomically modern human (AMH) are terms used to distinguish '' Homo sapiens'' (the only extant Hominina species) that are anatomically consistent with the range of phenotypes seen in contemporary humans from exti ...
. ''H. sapiens'' interbred with archaic humans both in Africa and in Eurasia, in Eurasia notably with Neanderthals and Denisovans. Among extant populations of '' Homo sapiens'', the deepest temporal division is found in the San people of Southern Africa, estimated at close to 130,000 years, or possibly more than 300,000 years ago. Temporal division among non-Africans is of the order of 60,000 years in the case of Australo-Melanesians. Division of Europeans and East Asians is of the order of 50,000 years, with repeated and significant admixture events throughout Eurasia during the Holocene. Archaic human species may have survived until the beginning of the Holocene, although they were mostly extinct or absorbed by the expanding ''H. sapiens'' populations by 40 kya ( Neanderthal extinction).


List of lineages

The species status of '' H. rudolfensis'', '' H. ergaster'', '' H. georgicus'', '' H. antecessor'', '' H. cepranensis'', '' H. rhodesiensis'', '' H. neanderthalensis'', Denisova hominin, and '' H. floresiensis'' remain under debate. '' H. heidelbergensis'' and ''H. neanderthalensis'' are closely related to each other and have been considered to be subspecies of ''H. sapiens''. There has historically been a trend to postulate new human species based on as little as an individual fossil. A "minimalist" approach to human taxonomy recognizes at most three species, '' Homo habilis'' (2.1–1.5 Mya, membership in ''Homo'' questionable), '' Homo erectus'' (1.8–0.1 Mya, including the majority of the age of the genus, and the majority of archaic varieties as subspecies, including ''H. heidelbergensis'' as a late or transitional variety) and '' Homo sapiens'' (300 kya to present, including ''H. neanderthalensis'' and other varieties as subspecies). "Species" does in this context not necessarily mean that hybridization and introgression were impossible at the time. However, it is often used as a convenient term, but it should be taken to mean to be a generic lineage at best, and clusters at worst. In general definitions and methodology of "species" delineation criteria are not generally agreed upon in anthropology or paleontology. Indeed, mammals can typically interbreed for 2 to 3 million years or longer, so all contemporary "species" in the genus ''Homo'' would potentially have been able to interbreed at the time, and introgression from beyond the genus ''Homo'' can not ''a priori'' be ruled out. It has been suggested that ''H. naledi'' may have been a hybrid with a late surviving ''Australipith'' (taken to mean beyond ''Homo'', ed.), despite the fact that these lineages generally are regarded as long extinct. As discussed above, many introgressions have occurred between lineages, with evidence of introgression after separation of 1.5 million years.


See also

*
List of human evolution fossils The following tables give an overview of notable finds of hominin fossils and remains relating to human evolution, beginning with the formation of the tribe Hominini (the divergence of the human and chimpanzee lineages) in the late Miocene, roug ...
''(with images)'' * Multiregional origin of modern humans


Footnotes


References


Bibliography

*


External links


Exploring the Hominid Fossil Record
( Center for the Advanced Study of Hominid Paleobiology at George Washington University)
Hominid species




*
Human Timeline (Interactive)
Smithsonian, National Museum of Natural History (August 2016). {{Authority control * * Hominina Primate genera Human evolution Taxa named by Carl Linnaeus Mammal genera with one living species