Editing Sahelanthropus (section)

==Taxonomy==
===Discovery===
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Four employees of the Centre National d'Appui à la Recherche (CNAR, National Research Support Center) of the Ministry of Higher Education of the Republic of Chad, three Chadians (Ahounta Djimdoumalbaye,<ref name="researchgate/2007191460">{{cite web |title=Ahounta Djimdoumalbaye |url=https://www.researchgate.net/scientific-contributions/Ahounta-Djimdoumalbaye-2007191460 |website=[[ResearchGate]] |access-date=23 January 2023}}</ref> Fanoné Gongdibé and Mahamat Adoum) and one French (Alain Beauvilain<ref name="researchgate/9991597">{{cite web |title=Alain Beauvilain |url=https://www.researchgate.net/scientific-contributions/Alain-Beauvilain-9991597 |website=[[ResearchGate]]}}</ref>) collected and identified the first remains in the Toros-Menalla area (TM 266 [[locality (geology)|locality]]) in the [[Djurab Desert]] of northern Chad, July 19, 2001. By the time [[Michel Brunet (paleontologist)|Michel Brunet]] and colleagues formally described the remains in 2002, a total of six specimens had been recovered: a nearly complete but heavily deformed skull, a fragment of the midline of the jaw with the [[tooth socket]]s for an [[incisor]] and [[canine tooth|canine]], a right third [[molar (tooth)|molar]], a right first incisor, a right jawbone with the last [[premolar]] to last molar, and a right canine. With the skull as the [[holotype specimen]], they were grouped into a new [[genus]] and [[species]] as ''Sahelanthropus tchadensis'', the genus name referring to the [[Sahel]], and the species name to Chad. These, along with ''[[Australopithecus bahrelghazali]]'', were the first discoveries of any fossil African [[great ape]] (outside the genus ''[[Homo]]'') made beyond eastern and southern Africa.<ref name=Brunet2002/> By 2005, a third premolar was recovered from the TM 266 locality, a lower jaw missing the region behind the second molar from the TM 292 locality, and a lower left jaw preserving the sockets for premolars and molars from the TM 247 locality.<ref name="Brunet2005">{{cite journal |last1=Brunet |first1=M. |author-link=Michel Brunet (paleontologist) |last2=Guy |first2=F. |last3=Pilbeam |first3=D. |author-link3=David Pilbeam |last4=Lieberman |first4=D. E. |last5=Likius |first5=A. |last6=Mackaye |first6=H. T. |last7=Ponce |last8=de Leon |first8=M. S. |last9=Zollikofer |first9=C. P. E. |last10=Vignaud |first10=P. |year=2005 |title=New material of the earliest hominid from the Upper Miocene of Chad |url=https://dash.harvard.edu/bitstream/handle/1/3716603/Brunet%20et%20al.pdf |journal=Nature |volume=434 |issue=7034 |pages=752–755 |bibcode=2005Natur.434..752B |doi=10.1038/nature03392 |pmid=15815627 |s2cid=3726177}}</ref>

The skull was nicknamed Toumaï by the then-president of the Republic of Chad, [[Idriss Déby]], not only because it designates in the local [[Daza language]] meaning "hope of life", given to infants born just before the dry season and who, therefore, have fairly limited chances of survival, but also to celebrate the memory of one of his comrades-in-arms, living in the north of the country where the fossil was discovered, and killed fighting to overthrow President [[Hissène Habré]] supported by France.<ref>[http://www.sangonet.com/FichHistoire/ToumaiiTchad7millA02.html The skull discovered in Chad bears the name of a comrade of the Chadian president who died in combat] Dispatch of ''Associated Press'', Denver, July 11, 2002.</ref> Toumaï also became a source of national pride, and Brunet announced the discovery before the Ministry of Foreign Affairs and a television audience in the capital of [[N'Djamena]], "''l'ancêtre de l'humanité est Tchadien...Le berceau de l'humanité se trouve au Tchad. Toumaï est votre ancêtre''" ("The ancestor of humanity is Chadian...The cradle of humanity is in Chad. Toumaï is your ancestor.").<ref>{{cite web|url= http://www.sangonet.com/FichHistoire/ToumaiiTchad7millA02.html |title=Sahelanthropus tchadensis : Découverte de Toumaï, un "Tchadien" de 7 millions d'années |access-date=2020-01-01}}</ref><ref>[https://sites.google.com/view/tchadberceaudelhumanite/valorisation-des-recherches-pal%C3%A9ontologiques N'Djamena, Conference of July 10, 2002], at 1h 0' 30"</ref>

Toumaï had been found with a femur, but this was stored with animal bones and shipped to the [[University of Poitiers]] in 2003, where it was stumbled upon by graduate student Aude Bergeret the next year. She took the bone to the head of the Department of Geosciences, Roberto Macchiarelli, who considered it to be inconsistent with [[biped]]alism contra what Brunet ''et al.'' had earlier stated in their description analysing only the distorted skull. This was conspicuous because Brunet and his team had already explicitly stated Toumaï was associated with no limb bones, which could have proven or disproven their conclusions of locomotion. Because Brunet had declined to comment on the subject, Macchiarelli and Bergeret petitioned to present their preliminary findings during an annual conference organised by the [[Society of Anthropology of Paris|Anthropological Society of Paris]], which would be held at Poitiers that year. This was rejected as they had not formally published their findings yet.<ref name=Callaway>{{cite journal|last=Callaway |first=Ewen|url= https://www.nature.com/magazine-assets/d41586-018-00972-z/d41586-018-00972-z.pdf |title=Femur findings remain a secret |journal=Nature|date= 25 January 2018 |volume=553 |issue=7689|pages=391–92|doi=10.1038/d41586-018-00972-z |bibcode=2018Natur.553..391C |pmid=29368713|doi-access=free }}</ref><ref name="Constans N. 1">{{cite web |last=Constans |first=Nicolas |date=2018-01-23 |title=L'histoire du Fémur de Toumaï |trans-title=The history of Toumai's thighbone |url=https://nicolas-constans.net/2018-01-23-lhistoire-du-femur-de-toumai/ |access-date=2020-01-01 |language=fr}}</ref> They were able to publish a full description in 2020, and concluded ''Sahelanthropus'' was not bipedal.<ref name="JHE-20201201"/>

In 2022, French primatologist Franck Guy and colleagues reported that a hominin left femur (TM 266-01-063), a right (TM 266-01-358), and a left (TM 266-01-050) [[ulna]] (forearm bone) were also discovered at the site in 2001, but were excluded originally from ''Sahelanthropus'' because they could not be reliably associated with the skull. They decided to include it because ''Sahelanthropus'' is the only hominin known from the site, and they concluded that the material is consistent with obligate bipedalism, the earliest evidence of such.<ref name="Daver Guy Mackaye Likius 2022"/> In 2023, Meyer and colleagues suggested that its phylogenetic position and its status as a hominin still remain equivocal.<ref name=M23>{{Cite journal |last1=Meyer |first1=M. R. |last2=Jung |first2=J. P. |last3=Spear |first3=J. K. |last4=Araiza |first4=I. Fx. |last5=Galway-Witham |first5=J. |last6=Williams |first6=S. A. |title=Knuckle-walking in ''Sahelanthropus''? Locomotor inferences from the ulnae of fossil hominins and other hominoids |year=2023 |journal=Journal of Human Evolution |volume=179 |at=103355 |doi=10.1016/j.jhevol.2023.103355 |pmid=37003245 |bibcode=2023JHumE.17903355M |s2cid=257874795 }}</ref>

All ''Sahelanthropus'' specimens, representing six to nine different adults, have been recovered within the {{cvt|0.73|km2}} area.<ref name="JHE-20201201">{{cite journal |author=Macchiarelli |first1=Roberto |last2=Bergeret-Medina |first2=Aude |last3=Marchi |first3=Damiano |last4=Wood |first4=Bernard |year=2020 |title=Nature and relationships of ''Sahelanthropus tchadensis'' |journal=Journal of Human Evolution |volume=149 |page=102898 |doi=10.1016/j.jhevol.2020.102898 |pmid=33142154 |s2cid=226249337 |doi-access=free |bibcode=2020JHumE.14902898M |hdl-access=free |hdl=11568/1060874}}</ref>

===Taphonomy===
Upon description, Brunet and colleagues were able to constrain the TM 266 locality to 7 or 6 million years ago (near the end of the [[Messinian|Late Miocene]]) based on the animal assemblage, which made ''Sahelanthropus'' the earliest African ape at the time.<ref name=Brunet2002/> In 2008, Anne-Elisabeth Lebatard and colleagues (which includes Brunet) attempted to [[radiometric dating|radiometrically date]] using the [[beryllium-10|<sup>10</sup>Be]]/[[beryllium-9|<sup>9</sup>Be]] ratio the sediments Toumaï was found near (dubbed the "[[Anthracotheriidae|anthracotheriid]] unit" after the commonplace ''[[Libycosaurus|Libycosaurus petrochii]]''). Averaging the ages of 28 samples, they reported an approximate date of 7.2–6.8 million years ago.<ref>{{cite journal |last1=Lebatard |first1=A.-E. |last2=Bourles |first2=D. L. |last3=Duringer |first3=P. |last4=Jolivet |first4=M. |last5=Braucher |first5=R. |last6=Carcaillet |first6=J. |last7=Schuster |first7=M. |last8=Arnaud |first8=N. |last9=Monie |first9=P. |last10=Lihoreau |first10=F. |last11=Likius |first11=A. |last12=Mackaye |first12=H. T. |last13=Vignaud |first13=P. |last14=Brunet |first14=M. |author-link14=Michel Brunet (paleontologist) |year=2008 |title=Cosmogenic nuclide dating of ''Sahelanthropus tchadensis'' and ''Australopithecus bahrelghazali'': Mio-Pliocene hominids from Chad |journal=PNAS |volume=105 |issue=9 |pages=3226–3231 |bibcode=2008PNAS..105.3226L |doi=10.1073/pnas.0708015105 |pmc=2265126 |pmid=18305174 |doi-access=free}}</ref>

Their methods were soon challenged by Beauvilain, who clarified that Toumaï was found on loose sediments at the surface rather than being "unearthed", and had probably been exposed to the harsh sun and wind for some time considering it was encrusted in an iron shell and [[desert varnish]]. This would mean it is unsafe to assume that the skull and nearby sediments were deposited at the same time, making such radiometric dating impossible.<ref>{{cite journal |last=Beauvilain |first=Alain |year=2008 |title=The contexts of discovery of ''Australopithecus bahrelghazali'' and of ''Sahelanthropus tchadensis'' (Toumaï) : unearthed, embedded in sandstone or surface collected? |url= http://www.scielo.org.za/scielo.php?script=sci_pdf&pid=S0038-23532008000300003&lng=en&nrm=iso&tlng=en |journal=South African Journal of Science |volume=104 |issue=3| pages=165–168 }}</ref> Further, the ''Sahelanthropus'' fossils lack white [[silicon|silaceous]] [[cementation (geology)|cement]] which is present on every other fossil in the site, which would mean they date to different time periods. Because the large mammal fossils were scattered across the area instead of concentrated like the ''Sahelanthropus'' fossils, the discoverers originally believed the ''Sahelanthropus'' fossils were dumped there by a palaeontologist or geologist, but later dismissed this because the skull was too complete to have been thrown away like that. In 2009, Alain Beauvilain and {{ill|Jean-Pierre Watté|fr}}<ref>{{Cite web|url=https://univ-rennes1.academia.edu/JeanPierreWatt%C3%A9|title=Jean-Pierre Watte &#124; Université de Rennes - Academia.edu|website=univ-rennes1.academia.edu}}</ref> argued that Toumaï was purposefully buried in a "grave", because the skull was also found with two parallel rows of large mammal fossils, seemingly forming a {{cvt|100x40|cm|ft}} box. Because the "grave" is orientated in a northeast–southwest direction towards [[Mecca]], and all sides of the skull were exposed to the wind and were eroded (meaning the skull had somehow turned), they argued that Toumaï was first buried by nomads who identified the skull as human and collected nearby limb fossils (believing them to belong with the skull) and buried them, and was reburied again sometime after the 11th century by Muslims who reorientated the grave towards Mecca when the fossils were re-exposed.<ref>{{cite journal|url= https://sites.google.com/view/chad-craddle-of-humanity/was-touma%C3%AF-sahelanthropus-tchadensis-buried-and-research-to-date-the-sk |last1=Beauvilain |first1=A. |last2=Watté |first2=J. P. |year=2009 |journal=Anthropologie |volume=47 |number=1/2 |title=Was Toumaï (''Sahelanthropus tchadensis'') Buried? |pages=1–6 |jstor=26292847}}</ref>

===Classification===
{{Human timeline}}
[[File:Michel Brunet - Sahelanthropus.jpg|thumb|left|[[Michel Brunet (paleontologist)|Michel Brunet]] (right) and Ahounta Djimdoumalbaye look at the reconstructed ''Sahelanthropus tchadensis'' skull in N'Djamena (Chad) in the premises of the National Research Support Center.]] 
When describing the species in 2002, Brunet ''et al.'' noted the combination of features that would be considered archaic or derived for a species on the human line (the [[subtribe]] Hominina), the latter being bipedal locomotion and reduced [[canine teeth]], which they interpreted as evidence of its position near the [[chimpanzee–human last common ancestor]] (CHLCA). This classification made ''Sahelanthropus'' the oldest Hominina, shifting the centre of origin for the [[clade]] away from East Africa. They also suggested that ''Sahelanthropus'' could be a [[sister taxon|sister group]] to the 5.5-to-4.5-million-year-old ''[[Ardipithecus]]'' and later Hominina.<ref name=Brunet2002/> The classification of ''Sahelanthropus'' in Hominina, as well as ''Ardipithecus'' and the 6-million-year-old ''[[Orrorin]]'', was at odds with molecular analyses of the time, which had placed the CHLCA between 6 and 4 million years ago based on a high [[mutation rate]] of about 70 mutations per generation. All these genera were anatomically too derived to represent a basal [[hominin]] (the group containing chimps and humans), so molecular data would only permit their classification into more ancient and now-extinct lineages. This was overturned in 2012 by geneticists [[Aylwyn Scally]] and [[Richard M. Durbin|Richard Durbin]], who studied the genomes of children and their parents and found the mutation rate was actually half that, placing the CHLCA anywhere from 14 to 7 million years ago, though most geneticists and palaeoanthropologists use 8 to 7 million years ago.<ref name="ourtruedawn">{{cite journal |first=C.|last= Brahic |title=Our True Dawn |journal=New Scientist|volume=216 |issue=2892 |pages=34–37 |year=2012 |doi=10.1016/S0262-4079(12)63018-8 |bibcode= 2012NewSc.216...34B }}</ref> A recent phylogenetic analysis classified ''Orrorin'' as a hominin, but placed ''Sahelanthropus'' as a stem-hominid outside hominins,<ref>{{Cite journal |last1=Sevim-Erol |first1=Ayla |last2=Begun |first2=D. R. |last3=Sözer |first3=Ç Sönmez |last4=Mayda |first4=S. |last5=van den Hoek Ostende |first5=L. W. |last6=Martin |first6=R. M. G. |last7=Alçiçek |first7=M. Cihat |date=2023-08-23 |title=A new ape from Türkiye and the radiation of late Miocene hominines |journal=Communications Biology |language=en |volume=6 |issue=1 |page=842 |doi=10.1038/s42003-023-05210-5 |issn=2399-3642 |pmc=10447513 |pmid=37612372}}</ref> though dental metric analysis supports its position as a hominin.<ref>{{Cite journal |last1=Neves |first1=W. |last2=Valota |first2=L. |last3=Monteiro |first3=C. |title=Dental metrics of ''Sahelanthropus tchadensis'': A comparative analysis with apes and Plio-Pleistocene hominins |year=2024 |journal=South African Journal of Science |volume=120 |issue=7/8 |at=16362 |doi=10.17159/sajs.2024/16362 |doi-access=free }}</ref>

A further possibility is that Toumaï is not ancestral to either humans or chimpanzees at all, but rather an early representative of the [[Gorillini]] lineage. [[Brigitte Senut]] and [[Martin Pickford]], the discoverers of ''[[Orrorin]] tugenensis'', suggested that the features of ''S. tchadensis'' are consistent with a female proto-[[gorilla]]. Even if this claim is upheld the find would lose none of its significance, because at present very few chimpanzee or gorilla ancestors have been found anywhere in Africa. Thus, if ''S. tchadensis'' is an ancestral relative of the chimpanzees or gorillas, then it represents the earliest known member of ''their'' lineage. ''S. tchadensis'' does indicate that the last common ancestor of humans and chimpanzees is unlikely to closely resemble extant chimpanzees, as had been previously supposed by some paleontologists.<ref>{{cite journal|last1=Guy |first1=F. |last2=Lieberman |first2=D.E. |last3=Pilbeam |first3=D. |last4=Ponce de Leon |first4=M.S. |last5=Likius |first5=A. |last6=Mackaye |first6=H.T. |last7=Vignaud |first7=P. |last8=Zollikofer |first8=C.P. E. |last9=Brunet |first9=M. |year=2005 |title=Morphological affinities of the ''Sahelanthropus tchadensis'' (Late Miocene hominid from Chad) cranium |journal=[[PNAS]] |volume=102 |issue=52 |pages=18836–18841 |display-authors=3 |doi=10.1073/pnas.0509564102|pmid=16380424 |pmc=1323204 |bibcode=2005PNAS..10218836G |doi-access=free }}</ref><ref name=":0">{{cite journal |last1=Wolpoff |first1=Milford H. |author-link=Milford H. Wolpoff |last2=Hawks |first2=John |last3=Senut |first3=Brigitte |author-link3=Brigitte Senut |last4=Pickford |first4=Martin |author-link4=Martin Pickford |last5=Ahern |first5=James |year=2006 |title=An Ape or ''the'' Ape : Is the Toumaï Cranium TM 266 a Hominid? |url=http://www.paleoanthro.org/journal/content/PA20060036.pdf |journal=PaleoAnthropology |volume=2006 |pages=36–50}}</ref> Additionally, with the significant [[sexual dimorphism]] known to have existed in early hominins, the difference between ''[[Ardipithecus]]'' and ''Sahelanthropus'' may not be large enough to warrant a separate genus for the latter.<ref name="MioceneTeeth">{{cite journal |last1=Haile-Selassie |first1=Yohannes |author-link=Yohannes Haile-Selassie |last2=Suwa |first2=Gen |last3=White |first3=Tim D. |year=2004 |title=Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution |journal=[[Science (journal)|Science]] |volume=303 |issue=5663 |pages=1503–1505 |bibcode=2004Sci...303.1503H |doi=10.1126/science.1092978 |pmid=15001775 |s2cid=30387762}}</ref>