Editing Sahelanthropus (section)

===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>