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Homo

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Title: Homo  
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Subject: Stone Age, Human evolution, Human, In the news/Candidates/March 2015, Anatomically modern human
Collection: Hominina, Human Evolution, Pleistocene First Appearances, Primate Genera
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Homo

Homo
Temporal range: Gelasian-Present 2.8–0 Ma
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Reconstruction of Élisabeth Daynès, Musée de Préhistoire, Quinson, France)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Subtribe: Hominina
Genus: Homo
Linnaeus, 1758
Type species
Homo sapiens
Linnaeus, 1758
Species

Homo sapiens
Homo erectus
Homo floresiensis
Homo habilis
Homo heidelbergensis
Homo naledi
Homo neanderthalensis
other species or subspecies suggested, see below.

Synonyms

Homo is the genus that comprises the species Homo sapiens, which includes modern humans, as well as several extinct species classified as ancestral to or closely related to modern humans—as for examples Homo habilis and Homo neanderthalensis. The genus is about 2.8 million years old;[1][2][3][4][5] it first appeared as its earliest species Homo habilis, which emerged from the genus Australopithecus, which itself had previously split from the lineage of the genus Pan, the chimpanzees.[6] Homo is the only genus assigned to the subtribe Hominina which, with the subtribes Australopithecina and Panina, comprise the tribe Hominini (see evolutionary tree below). All species of the genus Homo plus those species of the australopithecines that arose after the split from Pan are called hominins.

The line to the earliest members of Homo made final separation from the lineage of Pan by late Miocene or early Pliocene times—with date estimates by several specialists ranging from 13 million years ago [7] to as recent as four million years ago—which (latter) date was soon rejected by some; [8] [9] see current estimates regarding complex speciation. Homo erectus appeared about two million years ago in East Africa (where it is dubbed Homo ergaster) and, in several early migrations, it spread throughout Africa and Eurasia. It was likely the first hominin to live in a hunter-gatherer society and to control fire. An adaptive and successful species, Homo erectus persisted for almost 2 million years before suddenly becoming extinct about 70,000 years ago (0.07 Ma)—perhaps a casualty of the Toba supereruption catastrophe.

Homo sapiens sapiens, or anatomically modern humans, emerged about 200,000 years ago (0.2 Ma) in East Africa (see Omo remains). There is division among scholars as to when H. s. sapiens became behaviorally modern; the debate is: modern behavior developed 1) simultaneously with anatomical development, or 2) separately, and was complete by 50,000 years ago (see Modern human behavior). Homo sapiens sapiens is the only surviving species of the genus Homo; all others have become extinct.

Modern humans migrated from Africa as recently as 60,000 years ago, and during Upper Paleolithic times they spread throughout Africa and Eurasia, Oceania, and the Americas; and they encountered archaic humans en route of their migrations. Some archaic humans outside Africa survived alongside modern humans until about 40,000 years ago (see H. neanderthalensis),[10] and possibly until as late as the times of the Epipaleolithic culture (about 12,000 years ago). DNA analysis provides evidence of interbreeding between archaic and modern humans.

Contents

  • Name and taxonomy 1
  • Evolution 2
  • Migration 3
  • List of species 4
  • See also 5
  • References 6
  • Further reading 7
  • External links 8

Name and taxonomy

Evolutionary tree chart emphasizing the subfamily Homininae and the tribe Hominini. After diverging from the line to Ponginae the early Homininae split into the tribes Hominini and Gorillini. The early Hominini split further, separating the line to Homo from the lineage of Pan. Currently, tribe Hominini designates the subtribes Hominina, containing genus Homo; Panina, genus Pan; and Australopithecina, with several extinct genera—the subtribes are not labelled on this chart.

See Hominidae for an overview of taxonomy.

The Latin noun homō (genitive hominis) means "human being" or "man" in the generic sense of "human being, mankind".[11] The binomial name Homo sapiens was coined by Carl Linnaeus (1758).[12] Names for other species of the genus were introduced beginning in the second half of the 19th century (H. neanderthalensis 1864, H. erectus 1892).

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 and early Pliocene times produced a rich mix for debating classifications. There is continuing debate on delineating Homo from Australopithecus—or, indeed, delineating Homo from Pan, as one body of scientists argue that the two species of chimpanzee should be classed with genus Homo rather than Pan. Even so, classifying the fossils of Homo coincides with evidences of: 1) competent human bipedalism in Homo habilis inherited from the earlier Australopithecus of more than four million years ago, (see Laetoli); and 2) human tool culture having begun by 2.5 million years ago.

From the late-19th to mid-20th century, 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 and singular species with a large geographic spread of early migrations. Many such names are now dubbed as "synonyms" with Homo, including Pithecanthropus,[13] Protanthropus,[14] Sinanthropus,[15] Cyphanthropus,[16] Africanthropus,[17] Telanthropus,[18] Atlanthropus,[19] and Tchadanthropus.[20]

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") in even scientific papers to avoid trinomial names or the ambiguity of classifying groups as

  • Exploring the Hominid Fossil Record (Center for the Advanced Study of Hominid Paleobiology at George Washington University)
  • Hominid species
  • Prominent Hominid Fossils
  • Mikko's Phylogeny archive
  • Homo at the Encyclopedia of Life

External links

Further reading

  1. ^ Stringer, C.B. (1994). "Evolution of early humans". In Steve Jones, Robert Martin & David Pilbeam (eds.). The Cambridge Encyclopedia of Human Evolution. Cambridge: Cambridge University Press. p. 242.   Also ISBN 0-521-46786-1 (paperback)
  2. ^ McHenry, H.M (2009). "Human Evolution". In Michael Ruse & Joseph Travis. Evolution: The First Four Billion Years. Cambridge, Massachusetts: The Belknap Press of Harvard University Press. p. 265.  
  3. ^ Wilford, John Noble (2015-03-04). "Jawbone Fossil Fills a Gap in Early Human Evolution". The New York Times.  
  4. ^ Spoor, Fred; Gunz, Philipp; Neubauer, Simon; Stelzer, Stefanie; Scott, Nadia; Kwekason, Amandus; Dean, M. Christopher (March 5, 2015). "Reconstructed Homo habilis type OH 7 suggests deep-rooted species diversity in early Homo". Nature 519 (7541): 83–86.  
  5. ^ Villmoare, Brian; Kimbel, William H.; Seyoum, Chalachew; Campisano, Christopher J.; DiMaggio, Erin N.; Rowan, John; Braun, David R.; Arrowsmith, J. Ramón; Reed, Kaye E. (2015-03-20). "Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia". Science 347 (6228): 1352–1355.  
  6. ^ Schuster, Angela M. H. (1997). "Homo"Earliest Remains of Genus . Archaeology 50 (1). Retrieved 5 March 2015. 
  7. ^ Arnason U, Gullberg A, Janke A (December 1998). "Molecular timing of primate divergences as estimated by two nonprimate calibration points". J. Mol. Evol. 47 (6): 718–27. doi:10.1007/PL00006431. PMID 9847414.
  8. ^ Patterson N, Richter DJ, Gnerre S, Lander ES, Reich D (June 2006). "Genetic evidence for complex speciation of humans and chimpanzees". Nature 441 (7097): 1103–8. doi:10.1038/nature04789. PMID 16710306
  9. ^ Wakeley J (March 2008). "Complex speciation of humans and chimpanzees". Nature 452 (7184): E3–4; discussion E4. doi:10.1038/nature06805. PMID 18337768. "Patterson et al. suggest that the apparently short divergence time between humans and chimpanzees on the X chromosome is explained by a massive interspecific hybridization event in the ancestry of these two species. However, Patterson et al. do not statistically test their own null model of simple speciation before concluding that speciation was complex, and—even if the null model could be rejected—they do not consider other explanations of a short divergence time on the X chromosome. These include natural selection on the X chromosome in the common ancestor of humans and chimpanzees, changes in the ratio of male-to-female mutation rates over time, and less extreme versions of divergence with gene flow. I therefore believe that their claim of hybridization is unwarranted."
  10. ^ [2], BBC
  11. ^ The word "human" itself is from Latin humanus, an adjective formed on the root of homo, thought to derive from a Proto-Indo-European word for "earth" reconstructed as *dhǵhem-. dhghem The American Heritage Dictionary of the English Language: Fourth Edition. 2000.
  12. ^ Linné, Carl von (1758). Systema naturæ. Regnum animale. (10 ed.). pp. 18, 20. Retrieved 19 November 2012. . Note: In 1959, Linnaeus was designated as the lectotype for Homo sapiens (Stearn, W. T. 1959. "The background of Linnaeus's contributions to the nomenclature and methods of systematic biology", Systematic Zoology 8 (1): 4-22, p. 4) which means that following the nomenclatural rules, Homo sapiens was validly defined as the animal species to which Linnaeus belonged.
  13. ^ "ape-man", from Pithecanthropus erectus (Java Man), Eugène Dubois, Pithecanthropus erectus : eine menschenähnliche Übergangsform aus Java (1894), identified with the Pithecanthropus alalus (i.e. "non-speaking ape-man") hypothesized earlier by Ernst Haeckel
  14. ^ "early man", Protanthropus primigenius Ernst Haeckel, Systematische Phylogenie vol. 3 (1895), p. 625
  15. ^ "Sinic man", from Sinanthropus pekinensis (Peking Man), Davidson Black (1927).
  16. ^ "crooked man", from Cyphanthropus rhodesiensis (Rhodesian Man) William Plane Pycraft (1928).
  17. ^ "African man", used by T. F. Dreyer (1935) for the Florisbad Skull he found in 1932 (also Homo florisbadensis or Homo helmei). Also the genus suggested for a number of archaic human skulls found at Lake Eyasi by Weinert (1938). Leaky, Journal of the East Africa Natural History Society' (1942), p. 43.
  18. ^ "remote man"; from Telanthropus capensis (Broom and Robinson 1949), see (1961), p. 487.
  19. ^ from Atlanthropus mauritanicus, name given to the species of fossils (three lower jaw bones and a parietal bone of a skull) discovered in 1954 to 1955 by Camille Arambourg in Tighennif, Algeria. C. Arambourg, "A recent discovery in human paleontology: Atlanthropus of ternifine (Algeria)", American Journal of Physical Anthropology 13.2 (June 1955), 191–201, doi: 10.1002/ajpa.1330130203.
  20. ^ Y. Coppens, "L'Hominien du Tchad", Actes V Congr. PPEC I (1965), 329f.; "Le Tchadanthropus", Anthropologia 70 (1966), 5–16.
  21. ^ Alexandra Vivelo (2013), Characterization of Unique Features of the Denisovan Exome
  22. ^ J. E. Gray, "An outline of an attempt at the disposition of Mammalia into Tribes and Families, with a list of genera apparently appertaining to each Tribe", Annals of Philosophy', new series (1825), pp. 337–344.
  23. ^ Wood and Richmond; Richmond, BG (2000). "Human evolution: taxonomy and paleobiology". Journal of Anatomy 197 (Pt 1): 19–60.  
  24. ^ Brunet, M. et al. 2002: A new hominid from the upper Miocene of Chad, central Africa. Nature (London), 418: 145-151. Cela-Conde, C.J. and Ayala, F.J., 2003: Genera of the human lineage. PNAS, 100(13): 7684-7689. Wood, B.; Lonergan, N., 2008: The hominin fossil record: taxa, grades and clades. J. Anat., 212: 354–376. PDF
  25. ^ C. J. Cela-Conde and F. J. Ayala. 2003. "Genera of the human lineage". Proceedings of the National Academy of Sciences 100(13):7684-7689.
  26. ^ Stringer, C. (2012). "What makes a modern human". Nature 485 (7396): 33–35.  
  27. ^ Pickering, R.; Dirks, P. H.; Jinnah, Z.; De Ruiter, D. J.; Churchill, S. E.; Herries, A. I.; Berger, L. R. (2011). "Australopithecus sediba at 1.977 Ma and implications for the origins of the genus Homo". Science 333 (6048): 1421–1423.  
  28. ^ Asfaw, B.; White, T.; Lovejoy, O.; Latimer, B.; Simpson, S.; Suwa, G. (1999). "Australopithecus garhi: a new species of early hominid from Ethiopia". Science 284 (5414): 629–635.  
  29. ^ In 2010, evidence was presented that seems to attribute the use of stone tools to Australopithecus afarensis, close to a million years before the first appearance of Homo. McPherron, S. P.; Alemseged, Z.; Marean, C. W.; Wynn, J. G.; Reed, D.; Geraads, D.; Bobe, R.; Bearat, H. A. (2010). "Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia". Nature 466: 857–860.   "The oldest direct evidence of stone tool manufacture comes from Gona (Ethiopia) and dates to between 2.6 and 2.5 million years (Myr) ago. [...] Here we report stone-tool-inflicted marks on bones found during recent survey work in Dikika, Ethiopia [... showing] unambiguous stone-tool cut marks for flesh removal [..., dated] to between 3.42 and 3.24 Myr ago [...] Our discovery extends by approximately 800,000 years the antiquity of stone tools and of stone-tool-assisted consumption of ungulates by hominins; furthermore, this behaviour can now be attributed to Australopithecus afarensis."
  30. ^ Erin N. DiMaggio EN, Campisano CJ, Rowan J, Dupont-Nivet G, Deino AL; et al. from Afar, Ethiopia"Homo"Late Pliocene fossiliferous sedimentary record and the environmental context of early .  
  31. ^ Cela-Conde and Ayala (2003) recognize five genera within Hominina: Ardipithecus, Australopithecus (including Paranthropus), Homo (including Kenyanthropus), Praeanthropus (including Orrorin), and Sahelanthropus. C. J. Cela-Conde and F. J. Ayala. 2003. "Genera of the human lineage". Proceedings of the National Academy of Sciences 100(13):7684-7689.
  32. ^ "A partial maxilla assigned to H. habilis reliably demonstrates that this species survived until later than previously recognized, making an anagenetic relationship with H. erectus unlikely. The discovery of a particularly small calvaria of H. erectus indicates that this taxon overlapped in size with H. habilis, and may have shown marked sexual dimorphism. The new fossils confirm the distinctiveness of H. habilis and H. erectus, independently of overall cranial size, and suggest that these two early taxa were living broadly sympatrically in the same lake basin for almost half a million years." Spoor, F; Leakey, M.G; Gathogo, P.N; Brown, F.H; Antón, S.C; McDougall, I; Kiarie, C; Manthi, F.K.; Leakey, L.N. (2007). "Implications of new early Homo fossils from Ileret, east of Lake Turkana, Kenya". Nature 448 (7154): 688–691.  
  33. ^ Green, RE; Krause, J; et al. (2010). "A draft sequence of the Neanderthal genome". Science 328 (5979): 710–22.  
  34. ^ Reich, D; Green, RE; Kircher, M; et al. (December 2010). "(December 2010). "Genetic history of an archaic hominin group from Denisova Cave in Siberia"". Nature 468 (7327): 1053–60.  
  35. ^ Reich; et al. (October 2011). "Denisova admixture and the first modern human dispersals into southeast Asia and Oceania". Am J Hum Genet 89 (4): 516–28.  
  36. ^ Biological Anthropology: 2nd Edition. 2009. Craig Stanford et al.
  37. ^ Shaun Smillie,"Homo naledi--New human ancestor buried its dead," Times Live, 10 Sept 2015.
  38. ^  
    Full list of authors: Lee R Berger, John Hawks, Darryl J de Ruiter, Steven E Churchill, Peter Schmid, Lucas K Delezene, Tracy L Kivell, Heather M Garvin, Scott A Williams, Jeremy M DeSilva, Matthew M Skinner, Charles M Musiba, Noel Cameron, Trenton W Holliday, William Harcourt-Smith, Rebecca R Ackermann, Markus Bastir, Barry Bogin, Debra Bolter, Juliet Brophy, Zachary D Cofran, Kimberly A Congdon, Andrew S Deane, Mana Dembo, Michelle Drapeau, Marina C Elliott, Elen M Feuerriegel, Daniel Garcia-Martinez, David J Green, Alia Gurtov, Joel D Irish, Ashley Kruger, Myra F Laird, Damiano Marchi, Marc R Meyer, Shahed Nalla, Enquye W Negash, Caley M Orr, Davorka Radovcic, Lauren Schroeder, Jill E Scott, Zachary Throckmorton, Matthew W Tocheri, Caroline VanSickle, Christopher S Walker, Pianpian Wei, Bernhard Zipfel.
  39. ^ Schrenk, Friedemann; Kullmer, Ottmar; Bromage, Timothy (2007). "The Earliest Putative Homo Fossils". In Henke, Winfried;  
  40. ^ Haviland, William A.; Walrath, Dana;  H. erectus may have appeared some 2 million years ago. Fossils dated to as much as 1.8 million years ago have been found both in Africa and in Southeast Asia, and the oldest fossils by a narrow margin (1.85 to 1.77 million years ago) were found in the Caucasus, so that it is unclear whether H. erectus emerged in Africa and migrated to Eurasia, or if, conversely, it evolved in Eurasia and migrated back to Africa.
    • Ferring, R.; Oms, O.; Agusti, J.; Berna, F.; Nioradze, M.; Shelia, T.; Tappen, M.; Vekua, A.; Zhvania, D.; Lordkipanidze, D. (2011). "Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma". Proceedings of the National Academy of Sciences 108 (26): 10432.  
    • "New discovery suggests Homo erectus originated from Asia".  
    •  
  41. ^ Now also included in H. erectus are Homo ergaster, Homo floresiensis, Homo antecessor, Homo heidelbergensis and indeed Homo sapiens is not entirely clear.
  42. ^ Curnoe, Darren (June 2010). "A review of early Homo in southern Africa focusing on cranial, mandibular and dental remains, with the description of a new species (Homo gautengensis sp. nov.)". HOMO - Journal of Comparative Human Biology (Amsterdam, the Netherlands:   A species proposed in 2010 based on the fossil remains of three individuals dated between 1.9 and 0.6 million years ago. The same fossils were also classified as H. habilis, H. ergaster or Australopithecus by other anthropologists.
  43. ^ Hazarika, Manjil (2007). and Out of Africa: Recent Developments in Paleoanthropology and Prehistoric Archaeology"Homo erectus/ergaster" (PDF). EAA Summer School eBook 1. European Anthropological Association. pp. 35–41. Retrieved 2015-05-04.  "Intensive Course in Biological Anthrpology, 1st Summer School of the European Anthropological Association, 16–30 June, 2007, Prague, Czech Republic"
  44. ^ The type fossil is Mauer 1, dated to ca. 0.6 million years ago. The transition from H. heidelbergensis to H. neanderthalensis at about 0.35 to 0.25 million years ago is largely conventional. Relevant examples are fossils found at Bilzingsleben (also classified as Homo erectus bilzingslebensis).
  45. ^ Bischoff, James L.; Shamp, Donald D.; Aramburu, Arantza; et al. (March 2003). "The Sima de los Huesos Hominids Date to Beyond U/Th Equilibrium (>350 kyr) and Perhaps to 400–500 kyr: New Radiometric Dates".   The first humans with "proto-Neanderthal traits" lived in Eurasia as early as 0.6 to 0.35 million years ago (classified as H. heidelbergensis, also called a chronospecies because it represents a chronological grouping rather than being based on clear morphological distinctions from either H. erectus or H. neanderthalensis), with the first "true Neanderthals" appearing between 0.25 and 0.2 million years ago.
    • Papagianni, Dmitra; Morse, Michael A. (2013). The Neanderthals Rediscovered: How Modern Science is Rewriting Their Story. New York:  
  46. ^ Chang, Chun-Hsiang; Kaifu, Yousuke; Takai, Masanaru; Kono, Reiko T.; Grün, Rainer; Matsu’ura, Shuji; Kinsley, Les; Lin, Liang-Kong (2015). from Taiwan"Homo"The first archaic .  
  47. ^ "Homo sapiens"Fossil Reanalysis Pushes Back Origin of .   The oldest fossil remains of anatomically modern humans are the Omo remains, which date to 195,000 (±5,000) years ago and include two partial skulls as well as arm, leg, foot and pelvis bones.
    •   H. sapiens idaltu is a confirmed subspecies, based on 3 craniums dated 0.16 – 0.15 Mya found in Ethiopia (1997/2003).

References

See also

Comparative table of Homo species
Species Temporal range Mya Habitat Adult height Adult mass Cranial capacity (cm³) Fossil record Discovery / publication of name
H. habilis 2.1 – 1.5[39] Africa 150 cm (4 ft 11 in) 33–55 kg (73–121 lb) 510–660 Many 1960/1964
H. erectus 1.9 – 0.07

[40]

Africa, Eurasia (Java, China, India, Caucasus) 180 cm (5 ft 11 in) 60 kg (130 lb) 850 (early) – 1,100 (late) Many[41] 1891/1892
H. rudolfensis
membership in Homo uncertain
1.9 Kenya 700 2 sites 1972/1986
H. gautengensis
also classified as H. habilis
1.9 – 0.6 South Africa 100 cm (3 ft 3 in) 3 individuals[42] 2010/2010
H. ergaster
also classified as H. erectus
1.8 – 1.3[43] Eastern and Southern Africa 700–850 Many 1975
H. antecessor
also classified as H. heidelbergensis
1.2 – 0.8 Spain 175 cm (5 ft 9 in) 90 kg (200 lb) 1,000 2 sites 1997
H. cepranensis
a single fossil, possibly H. erectus
0.9 – 0.35 Italy 1,000 1 skull cap 1994/2003
H. heidelbergensis 0.6 – 0.35[44] Europe, Africa, China 180 cm (5 ft 11 in) 90 kg (200 lb) 1,100–1,400 Many 1908
H. neanderthalensis
possibly a subspecies of H. sapiens
0.35 – 0.04[45] Europe, Western Asia 170 cm (5 ft 7 in) 55–70 kg (121–154 lb) (heavily built) 1,200–1,900 Many (1829)/1864
H. naledi
2.5 South Africa 150 centimetres (4 ft 11 in) tall 45 kilograms (99 lb) 450 15 individuals 2013/2015
H. tsaichangensis
possibly H. erectus
0.19 – 0.01[46] Taiwan 1 individual pre-2008/2015
H. rhodesiensis
also classified as H. heidelbergensis
0.3 – 0.12 Zambia 1,300 Very few 1921
H. sapiens
(modern humans)
0.2[47]

 – present

Worldwide 150 - 190 cm (4 ft 7 in - 6 ft 3 in) 50–100 kg (110–220 lb) 950–1,800 (extant) —/1758
H. floresiensis
classification uncertain
0.10 – 0.012 Indonesia 100 cm (3 ft 3 in) 25 kg (55 lb) 400 7 individuals 2003/2004
Denisova hominin
possible H. sapiens subspecies or hybrid
0.04 Russia 1 site 2010
Red Deer Cave people
possible H. sapiens subspecies or hybrid
0.0145–0.0115 China Very few 2012

Homo naledi was discovered near Johannesburg, South Africa in 2013 and announced on 10 Sept. 2015 by the University of the Witwatersrand (Wits University), the National Geographic Society, the Department of Science and Technology and the National Research Foundation of South Africa. Fossils indicate the hominid was 1.45-1.5 meters tall and had a small brain.[37] The fossils have yet to be dated but are estimated to be roughly 2.5 million years old.[38]

The species status of H. antecessor, H. cepranensis, H. rhodesiensis, Homo neanderthalensis, Denisova hominin, Red Deer Cave people and Homo floresiensis remains under debate. H. heidelbergensis and H. neanderthalensis are closely related to each other and have been considered to be subspecies of H. sapiens. Recently, nuclear DNA from a Neanderthal specimen from Vindija Cave has been sequenced using two different methods that yield similar results regarding Neanderthal and H. sapiens lineages, with both analyses suggesting a date for the split between 460,000 and 700,000 years ago, though a population split of around 370,000 years is inferred. The nuclear DNA results indicate about 30% of derived alleles in H. sapiens are also in the Neanderthal lineage. This high frequency may suggest some gene flow between ancestral human and Neanderthal populations due to mating between the two.[36]

List of species

Some of H. ergaster migrated to Asia, where they are named Homo erectus, and to Europe with Homo georgicus. H. ergaster in Africa and H. erectus in Eurasia evolved separately for almost two million years and presumably separated into two different species. Homo rhodesiensis, who were descended from H. ergaster, migrated from Africa to Europe and became Homo heidelbergensis and later (about 250,000 years ago) Homo neanderthalensis and the Denisova hominin in Asia. The first Homo sapiens, descendants of H. rhodesiensis, appeared in Africa about 250,000 years ago. About 100,000 years ago, some H. sapiens sapiens migrated from Africa to the Levant and met with resident Neanderthals, with some admixture.[33] Later, about 70,000 years ago, perhaps after the Toba catastrophe, a small group left the Levant to populate Eurasia, Australia and later the Americas. A subgroup among them met the Denisovans[34] and, after further admixture, migrated to populate Melanesia. In this scenario, non-African people living today are mostly of African origin ("Out of Africa model"). However, there was also some admixture with Neanderthals and Denisovans, who had evolved locally (the "multiregional hypothesis"). Recent genomic results from the group of Svante Pääbo also show that 30,000 years ago at least three major subspecies coexisted: Denisovans, Neanderthals and anatomically modern humans.[35] Today, only H. sapiens remains, with no other extant species.

Migration

Homo erectus has often been assumed to have developed Caucasus, 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 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 with H. habilis for about half a million years (), during the early Calabrian.[32]

The most salient physiological development between the earlier australopithecine species and Homo is the increase in cranial capacity, from about 450 cm3 (27 cu in) in A. garhi to 600 cm3 (37 cu in) in H. habilis. Within the Homo genus, cranial capacity again doubled from H. habilis through Homo ergaster or H. erectus to Homo heidelbergensis by 0.6 million years ago. The cranial capacity of H. heidelbergensis overlaps with the range found in modern humans.

A fossil jawbone dated to 2.8 million years ago which may represent an intermediate stage between Australopithecus and Homo was discovered in 2015 in Afar, Ethiopia.[30] Some authors would push the development of Homo past 3 Mya, by including Kenyanthropus (a fossil dated 3.2 to 3.5 Mya, usually classified as an australopithecine species) into the Homo genus.[31]

Several species, including Australopithecus garhi, Australopithecus sediba, Australopithecus africanus, and Australopithecus afarensis, have been proposed as the direct ancestor of the Homo lineage.[27][28] These species have morphological features that align them with Homo, but there is no consensus as to which gave rise to Homo. The advent of Homo was traditionally taken to coincide with the first use of stone tools (the Oldowan industry), and thus by definition with the beginning of the Lower Palaeolithic.[29] The emergence of Homo also coincides roughly with the onset of Quaternary glaciation, the beginning of the current ice age.

A model of the evolution of the genus Homo over the last 2 million years (vertical axis). The rapid "Out of Africa" expansion of H. sapiens is indicated at the top of the diagram, with admixture indicated with Neanderthals, Denisovans, and unspecified archaic African hominins.[26]

Evolution

John Edward Gray (1825) was an early advocate of classifying taxa by designating tribes and families.[22] 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 such as Australopithecus, Orrorin tugenensis, Ardipithecus, or Sahelanthropus.[23] Designations alternative to Hominina existed, or were offered: Australopithecinae (Gregory & Hellman 1939) and Preanthropinae (Cela-Conde & Altaba 2002);[24] and later, Cela-Conde and Ayala (2003) proposed that the four genera Australopithecus, Ardipithecus, Praeanthropus, and Sahelanthropus be grouped with Homo within Hominina.[25]

). Red Deer Cave people and Denisova hominin are only recently discovered and do not as yet have consensus binomial names (see Homo Some recently extinct species in the genus [21]

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