Editing Sahelanthropus (section)

==Anatomy==
===Cranium===
[[File:Sahelanthropus tchadensis - TM 266-01-060-1 Global fond.jpg|thumb|upright=1.5|left|Toumaï skull from different angles]]
Existing fossils include a relatively small [[Skull|cranium]], five pieces of [[jaw]], and some [[Tooth|teeth]], making up a head that has a mixture of derived and primitive features. A virtual reconstruction of the interior of the braincase indicated a cranial capacity of 378&nbsp;cm<sup>3</sup>, similar to that of extant chimpanzees and approximately a third the size of modern human brains.<ref>{{Cite web |last=Wong |first=Kate |title=Brain Shape Confirms Controversial Fossil as Oldest Human Ancestor |url=https://blogs.scientificamerican.com/observations/brain-shape-confirms-controversial-fossil-as-oldest-human-ancestor/ |access-date=2022-07-19 |website=Scientific American Blog Network |language=en}}</ref>

The teeth, brow ridges, and facial structure differ markedly from those found in modern humans. Cranial features show a flatter face, U-shaped tooth rows, small [[Canine tooth|canines]], an anterior [[foramen magnum]], and heavy brow ridges. The only known skull suffered a large amount of distortion during the time of fossilisation and discovery, as the cranium is dorsoventrally flattened, and the right side is depressed.<ref name=Brunet2002/>

===Locomotion===
In the original description in 2002, Brunet ''et al.'' said it "would not be unreasonable" to speculate that ''Sahelanthropus'' was capable of maintaining an upright posture while walking [[biped]]ally. Because they had not reported any limb bones or other post-cranial material (anything other than the skull), this was based on the reconstructed original orientation of the [[foramen magnum]] (where the skull connects the spine), and their classification of ''Sahelanthropus'' into Hominina based on facial comparisons (one of the diagnostic characteristics of Hominina is bipedalism).<ref name=Brunet2002/> This was soon disputed because the orientation of the foramen magnum is not an entirely conclusive piece of evidence in regard to the question of habitual posture, and the features used to classify ''Sahelanthropus'' into Hominina are not entirely unique to Hominina.<ref>{{cite journal |last1=Wolpoff |first1=Milford H. |author-link=Milford H. Wolpoff |last2=Senut |first2=Brigitte |author-link2=Brigitte Senut |last3=Pickford |first3=Martin |author-link3=Martin Pickford |last4=Hawks |first4=John |year=2002 |title=Palaeoanthropology (communication arising): Sahelanthropus or 'Sahelpithecus'? |url=https://deepblue.lib.umich.edu/bitstream/2027.42/62951/1/419581a.pdf |journal=[[Nature (journal)|Nature]] |volume=419 |issue=6907 |pages=581–582 |bibcode=2002Natur.419..581W |doi=10.1038/419581a |pmid=12374970 |s2cid=205029762 |hdl-access=free |hdl=2027.42/62951}}</ref>

In 2020, the femur had been formally described, and the study concluded it was not consistent with habitual bipedalism.<ref name="JHE-20201201"/> But, in 2022, Daver and colleagues suggested that the ulnar and femoral morphologies do show characteristics consistent with habitual bipedalism.<ref name="Daver Guy Mackaye Likius 2022">{{cite journal |last1=Daver |first1=G. |last2=Guy |first2=F. |last3=Mackaye |first3=H. T. |last4=Likius |first4=A. |last5=Boisserie |first5=J. -R. |last6=Moussa |first6=A. |last7=Pallas |first7=L. |last8=Vignaud |first8=P. |last9=Clarisse |first9=N. D. |title=Postcranial evidence of late Miocene hominin bipedalism in Chad |journal=Nature |publisher=Springer Science and Business Media LLC |date=2022-08-24 |volume=609 |issue=7925 |pages=94–100 |issn=0028-0836 |doi=10.1038/s41586-022-04901-z |pmid=36002567 |bibcode=2022Natur.609...94D |s2cid=234630242 |url=https://hal.archives-ouvertes.fr/hal-03037386/file/383956_0_merged_1598881798.pdf }}</ref> In 2023, however, Meyer and colleagues examined its ulna shaft and argued that ''Sahelanthropus'' is not an obligate biped based on the mathematical analysis of its locomotor behavior which indicated that its forelimbs had different functions compared to modern humans and hominins, and that it probably [[knuckle-walking|walked on its knuckles]] like modern gorillas and chimpanzees, so more examination is required to truly identify its locomotor behavior (i.e. whether it exhibited [[facultative bipedalism]]) and its phylogenetic position as a hominin in the evolution of humans.<ref name=M23/> A 2024 study re-examined the 2022 study's postcranial evidence, and concluded that it is not sufficient to determine whether ''Sahelanthropus'' was a habitual biped, since none of the features are consistent with or unique to bipedal hominins, but with non-hominin apes or even non-primates.<ref name=C24>{{Cite journal|last1=Cazenave |first1=M. |last2=Pina |first2=M. |last3=Hammond |first3=A. S. |last4=Böhme |first4=M. |last5=Begun |first5=D. R. |last6=Spassov |first6=N. |last7=Vecino Gazabón |first7=A. |last8=Zanolli |first8=C. |last9=Bergeret-Medina |first9=A. |last10=Marchi |first10=D. |last11=Macchiarelli |first11=R. |last12=Wood |first12=B. |year=2024 |title=Postcranial evidence does not support habitual bipedalism in ''Sahelanthropus tchadensis'': A reply to Daver et al. (2022) |journal=Journal of Human Evolution |at=103557 |doi=10.1016/j.jhevol.2024.103557 |pmid=38918139 }}</ref>