Sahelanthropus, Orrorin, and Ardipithecus

The three oldest claimed hominins rest on little bone. Sahelanthropus is nine cranial specimens and three limb bones, chimpanzee-like in shape. Orrorin is thirteen fossils. Ardipithecus has over 100 specimens, but its pelvis is a computer reconstruction, and mainstream work since 2019 has substantially reversed its 2009 headline.

By AI (Claude Opus 5, thinking level unavailable; split by Claude Opus 5.5, thinking level unavailable) Draft:  October 2026

Summary

The three oldest claimed hominins rest on very little bone, and the claims that they walked upright rest on reconstructions and on a handful of features.  Sahelanthropus tchadensis is nine cranial specimens, one femoral shaft and two partial ulnae from one locality.112  Orrorin tugenensis is thirteen fossils,2 and its bipedality claim rests on two proximal femora.3  Ardipithecus ramidus has over 100 specimens, but the pelvis that carries its bipedality claim came out of the ground as fragments in mud and was reconstructed on a computer.2

Mainstream researchers have publicly reversed the 2009 headline about Ardipithecus.  The 2009 team argued that the last common ancestor of humans and chimpanzees was not African-ape-like.  Three open-access papers since then, all on the same Ardi material, find the foot, hand and ankle chimpanzee- and gorilla-like.456  Thomas C. Prang is first author on all three, so this is one research programme, not three independent teams.7  Whether Ardi was bipedal at all is genuinely open.

The oldest claimed hominin has been read as a biped and as a knuckle-walker by specialists of the first rank.  Its bipedality was first inferred from a digital reconstruction of a crushed skull.8  Its limb bones are chimpanzee-like in shape, and the case for bipedality now rests on their proportions and on two or three individual features.  Creationism's own quantitative method could not score it at all.9

The lesson is narrow.  Reconstructions of crushed specimens have changed the answer by large margins when redone.  That is not evidence that anyone was dishonest:  the reconstructors published the distortions themselves.  Orrorin is the clearest case of a modest result:  a biped on its femora, but not more closely related to Homo than Australopithecus is.3

Part 1: The inventory, as arithmetic

Start with how much material there is, because every argument in this field is limited by it, and because the numbers are public and nobody has to take anyone's word for them.

The rule applied here:  a number appears only if a paper or a museum database states it, and the source is named.  Where two sources disagree, both are printed.  Where nobody states a number, this article says so.

Sahelanthropus tchadensis — the oldest claimed hominin is nine cranial pieces and three limb bones

Announced by Michel Brunet and colleagues in Nature in 2002, from locality TM 266 in the Toros-Menalla area of the Djurab Desert in Chad — about 2,500 km west of the East African Rift.10  The abstract reports six hominid specimens:  a nearly complete cranium and fragmentary lower jaws.10  More material followed in 2005.

The Smithsonian's Human Origins database now states the total plainly:  "The first (and, so far, only) fossils of Sahelanthropus are nine cranial specimens from northern Chad."2

The postcranial paper adds three bones, all found in 2001.1

specimen element preserved length
TM 266-01-063 left femoral shaft, no ends ~242 mm
TM 266-01-050 left ulnar diaphysis, proximal epiphysis eroded 239 mm
TM 266-01-358 right ulna, proximal half of shaft 155 mm

That is the entire species.  One skull, three mandibles, some loose teeth representing a minimum of three adults, one thigh-bone shaft with both ends missing, two partial forearm bones.  One locality.  No pelvis.  No foot.  No hand.  No vertebrae.  No complete limb bone.

The femur's own history is worth a sentence.  It was recovered in July 2001 alongside the holotype skull, was recognised as a probable primate femur only in 2004 during a routine survey of the Toros-Menalla collections, and was not published until 2020.11  The authors who finally published it closed by urging colleagues to check whether more Sahelanthropus postcrania are sitting unrecognised in the same drawers.

Orrorin tugenensis — thirteen fossils

Named by Brigitte Senut, Martin Pickford and colleagues in 2001, from the Lukeino Formation in the Tugen Hills of Kenya.

The Smithsonian's count:  "There are 13 fossils from at least 5 Orrorin individuals."2  The named specimens are a jaw fragment with three lower molars, two femora, a partial humerus and finger bones.

So the entire bipedality claim for a 6-million-year-old genus rests on two proximal femora.  Brian Richmond and William Jungers analysed them in Science in 2008 and found that the Orrorin femur differs from those of apes and from those of Homo, and most strongly resembles those of Australopithecus and Paranthropus — from which they concluded that Orrorin was bipedal, but is not more closely related to Homo than Australopithecus is.33  That second half removed Orrorin from the privileged position on the human line that its describers had claimed for it.

Ardipithecus ramidus — over 100 specimens, one skeleton, fifteen years

Described in 1994.  The partial skeleton ARA-VP-6/500, "Ardi," was found in 1994 and published in 2009, in a special issue of Science running to eleven papers.  Over 100 specimens of the species have been recovered.2

The condition of the material matters for what can be concluded from it, and the excavation team said so themselves at the time.  The bones were trampled into mud, the skull was crushed, the bone was chalky enough that cleaning an edge could erode it, and the material had to be lifted in blocks of matrix and picked out under a microscope over several years.  The crushed cranium was CT-scanned and refitted digitally.12

The pelvis is the single specimen carrying the bipedality claim, and by the team's own account it came out of the ground as fragments in mud and was reconstructed on a computer.  That is not a scandal.  It is standard practice, and the team documented it.  It does mean that the strength of the claim cannot exceed the strength of the reconstruction.

Part 2: Where the field reversed itself

The strongest material in this article is not creationist.  It is the record of mainstream researchers walking back mainstream headlines, in open-access journals, using the same fossils.  A skeptical reader cannot dismiss it as denominational, and it makes the general point about morphological inference better than any apologetics argument does.

Ardipithecus: the 2009 headline has been substantially reversed

In 2009, the team describing Ardi argued that she had a rigid outer foot for propulsion combined with a divergent, grasping big toe, and a pelvis showing upright walking — and that the last common ancestor of humans and chimpanzees was therefore not African-ape-like.  It was a generalised arboreal quadruped, not a knuckle-walker and not a suspensory ape.  The headline of the whole package was that we should stop using chimpanzees as a model for our own ancestry.

Three open-access papers have since reversed that, all using the same Ardi material.

  • 2019, the foot. Comparing foot proportions across a large sample of anthropoid primates, Thomas Prang found the Ar. ramidus foot most similar to living chimpanzees and gorillas, and concluded that the evolutionary precursor of hominin bipedalism was African-ape-like terrestrial quadrupedalism and climbing.44
  • 2021, the hand. The Ardi hand retains suspensory-adapted morphology shared with chimpanzees and bonobos, with a shift in hand morphology falling between Ardipithecus and Australopithecus.55
  • 2025, the ankle. The Ardi talus resembles the tali of chimpanzees and gorillas, which are adapted to vertical climbing and terrestrial plantigrade quadrupedalism. The authors state that their observations are inconsistent with recently proposed models of human origins that envision the last common ancestor as a generalised arboreal ape, and that humans instead evolved from an African-ape-like ancestor.66

One honesty note that this article's own research dossier got wrong, and which matters for how much weight the reversal carries.

Those three papers are not three independent teams.  Thomas C. Prang is first author on all three — sole author in 2019, and first author on both the 2021 hand paper and the 2025 ankle paper — and Scott A. Williams is a co-author on the latter two.7  This project's research dossier listed the 2025 paper under a different first author, and that was checked and corrected for this article.

So the accurate statement is that one research programme, publishing across three journals over six years, has reversed a headline claim about the same fossils.  That is still a substantial result, and it is still entirely mainstream.  It is not the same thing as three independent confirmations, and this article will not describe it as such.

The older dissent holds up too, and belongs cited from its own venue.  Esteban Sarmiento argued in a technical comment in Science in 2010 that the bipedal characters cited for Ardi all also serve the mechanics of quadrupedality, and that the foot-segment proportions find their closest functional analogue in gorillas.  Sarmiento and Jeffrey Meldrum argued in 2011 that nothing in Ardi's segment lengths or described anatomy suggests bipedal behaviour at a higher frequency than in any living great ape.13

Verdict on Ardi:  the 2009 claim has been substantially walked back by the mainstream, using open analyses of the same bones, inside fifteen years.  Whether Ardi was bipedal at all is genuinely open.

Sahelanthropus: three bones, four rounds of dispute, twenty-four years

The oldest claimed hominin has been read as a biped and as a knuckle-walker by specialists of the first rank, repeatedly, in the same journal.

The original claim was cranial.  Brunet's team inferred bipedality in 2002 chiefly from the position and orientation of the foramen magnum — where the spinal cord enters the skull — implying an upright head carriage.

The skull is crushed, and its reconstructors say so.  Christoph Zollikofer and colleagues published a virtual reconstruction in 2005, stating in their own abstract that the cranium is "partly distorted from fracturing, displacement and plastic deformation."  Their corrected reconstruction, they concluded, confirms hominid status, and the basicranium indicates the animal "might have been an upright biped."88

Note the epistemic structure, because it is the point.  The bipedality of the oldest claimed hominin was inferred from a digitally undistorted version of a crushed skull.  That is legitimate science and the authors were transparent about it.  It is also a claim whose strength cannot exceed the reconstruction's, and a reconstruction is a judgment about how a broken object used to look.  The hominid attribution itself was contested from the outset:  Milford Wolpoff, Brigitte Senut, Martin Pickford and John Hawks published a challenge in Nature in 2002, the year of the type description.14

Then the postcrania arrived, and they arrived in dispute.

year who conclusion
2020 Macchiarelli, Bergeret-Medina, Marchi and Wood the femoral shaft belongs to an individual "that was not habitually bipedal"11
2022 Daver and the discovery team Sahelanthropus was a terrestrial biped that also climbed carefully1
2023 Meyer, Jung, Spear, Araiza, Galway-Witham and Williams the ulna falls within the knuckle-walking morphospace; discriminant analysis classifies it with Pan and Gorilla at high posterior probability1515
2025 Cazenave and eleven co-authors, including Bernard Wood and David Begun postcranial evidence does not support habitual bipedalism16
2026 a new Science Advances analysis both limb bones are most similar in size and shape to chimpanzees, but their proportion is more hominin-like, and a femoral tubercle the authors say is found only in bipedal hominins is present — so an early biped descended from a Pan-like ancestor16

The most defensible statement is that the shape of the bones is chimpanzee-like and the argument for bipedality now rests on proportions and on two or three individual features.  Any article claiming certainty in either direction is overreaching, and that applies to the creationist claim as readily as to the mainstream one.

And as the overview reports:  creationism's own quantitative method had to drop Sahelanthropus entirely, because fewer than one character in five could be scored.9

The general lesson, stated without overreach

Two of the three oldest claimed hominins carry their load-bearing evidence on reconstructions of crushed specimens.  Reconstructions of crushed specimens have a documented history of changing the answer by large margins when redone.

That is the conclusion this article draws.  It is narrower than "paleoanthropologists are dishonest," which nothing here supports — the distortion in the Sahelanthropus skull is known because the reconstructors published it.  And it is narrower than "therefore the fossils tell us nothing," which is false and which Part 3 of the overview refuses.

Objections and responses

"Sahelanthropus proves that our line walked upright from the start."  It does not, and the opposite claim is no stronger.  The bipedality of the skull was inferred from a reconstruction of a cranium its reconstructors call "partly distorted from fracturing, displacement and plastic deformation."8  The limb bones are chimpanzee-like in shape, and four rounds of dispute have not settled them.111516  Any claim of certainty in either direction is overreaching, and that applies to the creationist claim that it was simply an ape.

"Three independent teams have now shown that Ardi was an African ape."  One research programme has.  Thomas C. Prang is first author on all three papers, and Scott A. Williams is a co-author on the latter two.7  The papers are peer-reviewed, open access and mainstream, and they should be cited.  They are not three independent confirmations.

"Ardipithecus shows that the human line never passed through anything like an African ape."  That was the 2009 headline, and mainstream work on the same bones has substantially walked it back.456  The older dissent of Esteban Sarmiento and Jeffrey Meldrum, that nothing in Ardi's described anatomy shows more bipedal behaviour than a living great ape, holds up too.13

"The reconstructions are fraudulent."  Nothing here supports that.  The distortion in the Sahelanthropus skull is known because the reconstructors published it, and the Ardi team described the condition of its own material.12  The fair complaint is narrower:  a claim cannot be stronger than the reconstruction it rests on.

"Paleoanthropology never admits it is wrong."  The Ardipithecus reversal answers this, and the overview gives the objection in full.

Verdict

None of the three oldest claimed hominins can carry the confident claims made for it.  Sahelanthropus is too little bone to measure, and its limb bones look like a chimpanzee's.  Orrorin was probably a biped, but it is not closer to Homo than the australopiths are.  Ardipithecus rests on a reconstructed pelvis, and its 2009 headline has been substantially reversed by mainstream work on the same bones.  The strongest material against the standard picture here is secular and recent, and it should be cited instead of the apologetics.  Lucy's species, which is far better known, is in Lucy and Australopithecus afarensis.

Sources

The research dossier behind this article is published with its overview:  /unpublished-ai/pre-human-hominins/research/pre-homo-hominins.md, which carries the specimen inventories, the baraminology audit and the full quotes ledger.

Every quotation printed above was checked against a source that was actually opened, and appears in that ledger with a verdict.  Where a source could only be reached as an abstract, the footnote says so.17

  1. 1.

    Guy, Franck et al.  “Postcranial evidence for Sahelanthropus tchadensis.”  Research Square.  Sep 10, 2020.  A preprint of a paper on the leg and arm bones of Sahelanthropus tchadensis from site TM 266 in Chad, later published in Nature as Daver et al., Nature 609 (2022): 94–100.  It describes one left femoral shaft and two ulnae, and compares their cortical bone and bending strength with those of apes and humans; the authors concede that none of the bones can be reliably ascribed to a skull found at the site.  The article uses it as the postcranial evidence that the Chad hominin was a terrestrial biped that also climbed carefully. ↩

    1. 1a.

      The craniodental inventory is given as a nearly complete cranium (TM 266-01-060-1), three mandibles and several isolated teeth, representing a minimum of three adult individuals.  The three postcranial specimens, all found in 2001: TM 266-01-063, a left femoral shaft, about 242 mm preserved, July 2001; TM 266-01-050, a left ulnar diaphysis with the proximal epiphysis eroded, 239 mm, July 2001; TM 266-01-358, the proximal half of a right ulna shaft, 155 mm, November 2001. ↩ ↩

    2. 1b.

      The discovery team's analysis of the femur plus the two ulnae concludes that Sahelanthropus was a terrestrial biped that also did careful arboreal climbing.  Their quantitative claims include a cortical area of 66.5% at the nutrient foramen level, above the 59.9% reported for the AL 288-1 femur at midshaft, and a ratio of maximum to minimum second moment of area closer to the chimpanzee/human condition than to the gorilla condition. ↩

  2. 2.

    Smithsonian National Museum of Natural History, Human Origins Program.  Human Origins species pages.  2026.  Retrieved Aug 3, 2026.  Section Sahelanthropus tchadensis species page:  “The first (and, so far, only) fossils of Sahelanthropus are nine cranial specimens from northern Chad.”  An online species database from a museum that summarizes the fossils of each species.  It is a secondary source, and the article uses it only for specimen counts, which are the kind of claim such a database is built to carry. ↩ ↩

    1. 2a.

      Section Orrorin tugenensis species page:  “There are 13 fossils from at least 5 Orrorin individuals.”  The named specimens are BAR 1000'00, the type, a jaw fragment with three lower molars; BAR 1002'00 and BAR 1003'00, femora.  The page also mentions long curved finger bones and two well-preserved thigh bones. ↩ ↩

    2. 2b.

      Section Ardipithecus ramidus species page:  “Over 100 specimens of Ardipithecus ramidus have been recovered in Ethiopia.”  ARA-VP-6/500 is a partial skeleton of a female including skull, hands, feet and pelvis. ↩ ↩

  3. 3.

    Richmond, Brian G., and William L. Jungers.  “Orrorin tugenensis femoral morphology and the evolution of hominin bipedalism.”  Science 319:1662–1665.  2008.  A comparison of the thighbone (femur) of Orrorin tugenensis, a roughly six-million-year-old hominin, with the femurs of apes, of Homo, and of Australopithecus and Paranthropus.  The article uses it because the claim that Orrorin walked upright rests on two upper thighbones, and this study concluded that Orrorin was bipedal but was not more closely related to Homo than to Australopithecus. ↩ ↩

    1. 3a.

      The O. tugenensis femur differs from those of apes and of Homo, and most strongly resembles those of Australopithecus and Paranthropus, indicating that Orrorin was bipedal but is not more closely related to Homo than to Australopithecus.  The second half removes Orrorin from the privileged position on the human line that Senut and Pickford originally claimed for it. ↩ ↩

  4. 4.

    Prang, Thomas C.  “The African ape-like foot of Ardipithecus ramidus and its implications for the origin of bipedalism.”  eLife 8:e44433.  2019.  A study that compares the foot bones of living and fossil primates, using 385 individuals from 45 taxa, with the 4.4-million-year-old Ardipithecus ramidus foot to see which living group it most resembles.  It fits evolutionary models to six foot measurements, and the Ardi foot sits with chimpanzees and gorillas.  The article uses it for the conclusion that the precursor of hominin bipedalism was African-ape-like terrestrial quadrupedalism and climbing.  Mirror:  PMC ↩

    1. 4a.

      Using foot proportions across a large anthropoid sample, Prang finds the Ar. ramidus foot most similar to living chimpanzees and gorillas.  Prang concludes that the evolutionary precursor of hominin bipedalism was African-ape-like terrestrial quadrupedalism (walking on all fours on the ground, with the heel down first) and climbing, and that the modern human foot derives from a form adapted to terrestrial plantigrade quadrupedalism. ↩ ↩ ↩

  5. 5.

    Prang, Thomas C. et al.  “Ardipithecus hand provides evidence that humans and chimpanzees evolved from an ancestor with suspensory adaptations.”  Science Advances 7(9):eabf2474.  2021.  A study that compares the hand of the 4.4-million-year-old Ardipithecus ramidus with the hands of living apes and humans, using morphometric (shape-measuring) and phylogenetic comparative methods.  The authors argue that the Ardi hand keeps suspensory features (adaptations for hanging from the arms) that chimpanzees and bonobos share, and that the hand changes between Ardipithecus and Australopithecus.  The article uses it as the hand evidence in its account of Ardi.  Mirror:  PMC ↩

    1. 5a.

      The Ardi hand retains suspensory-adapted morphology shared with chimpanzees and bonobos, and the authors identify a shift in hand morphology falling between Ardipithecus and Australopithecus. ↩ ↩ ↩

  6. 6.

    Prang, Thomas C. et al.  “Ardipithecus ramidus ankle provides evidence for African ape-like vertical climbing in the earliest hominins.”  Communications Biology 8:1454.  2025.  A study of the 4.4-million-year-old ankle bone (talus) attributed to Ardipithecus ramidus, compared with the tali of chimpanzees and gorillas.  The authors find that the Ardi talus resembles those of two living apes that are adapted to vertical climbing and to walking on the ground on the whole sole of the foot.  The article uses it because its conclusion, that humans evolved from an African-ape-like ancestor, is set against the view that the ancestor was a generalised arboreal ape.  Mirror:  PMC ↩

    1. 6a.

      The Ardi talus (ARA-VP-6/500-023) resembles the tali of chimpanzees and gorillas, which are adapted to vertical climbing and terrestrial plantigrade quadrupedalism.  The authors state that their observations are inconsistent with recently proposed models of human origins that envision the human–chimpanzee last common ancestor as a generalised arboreal ape, and that humans instead evolved from an African-ape-like ancestor. ↩ ↩ ↩

  7. 7.

    Europe PMC.  Author lists of the 2019, 2021 and 2025 Ardipithecus papers by Prang and colleagues.  n.d.  Retrieved Aug 3, 2026.  The 2019 paper is sole-authored by Thomas C. Prang, the 2021 paper adds Ramirez, Grabowski and Williams, and the 2025 paper adds Tocheri, Patel, Williams and Orr.  Prang is first author on all three, and Williams appears on two, which does not weaken any individual result, since all three are peer-reviewed and openly licensed.  The article uses the author lists to say that the reversal is one research programme rather than three independent confirmations. ↩ ↩ ↩

  8. 8.

    Zollikofer, Christoph P. E. et al.  “Virtual cranial reconstruction of Sahelanthropus tchadensis.”  Nature 434:755–759.  2005.  A computer reconstruction of the skull of Sahelanthropus tchadensis, the oldest claimed hominin, rebuilt from a cranium the authors describe as partly distorted.  The authors report that their corrected version confirms it is a hominid and not more closely related to the African great apes.  The article uses it because the reconstructors admit the skull is distorted and still draw a conclusion about upright walking from the same skull. ↩

    1. 8a.

      Section Abstract:  “partly distorted from fracturing, displacement and plastic deformation.”  Their stated results: the corrected reconstruction confirms that the animal is a hominid and is not more closely related to the African great apes, and analysis of the basicranium indicates that it.  “might have been an upright biped.”  The epistemic structure is the point: the bipedality of the oldest claimed hominin was inferred from a digitally undistorted version of a crushed skull, and the reconstructors said so themselves. ↩ ↩ ↩

  9. 9.

    Sinclair, P., and Todd C. Wood.  “Revising Hominin Baraminology with Medoid Partitioning and Fuzzy Analysis.”  Answers Research Journal 14:451–462.  2021.  A 2021 re-analysis of two hominin character sets by Sinclair and Wood.  The paper exists because another creationist attacked the method:  Reeves argued that baraminic distance correlation is an untested homebrew statistic, and that standard clustering algorithms and Jaccard distances should be used instead.  Sinclair and Wood took the criticism and reran everything with those tools.  The result was a robust cluster of putatively human taxa that appeared in almost every analysis, including Homo naledi and Australopithecus sediba, while the status of Homo floresiensis stayed unresolved.  The article cites it for Wood's placement of A. afarensis with chimpanzees and gorillas under every method tried, and for the four taxa that could not be analysed at all.

    1. 9a.

      On the larger 391-character, 24-taxon supermatrix (Wood's 2020 update of Dembo et al. 2016, archived on Dryad), four taxa were removed for having under 20% taxic relevance, meaning fewer than one character in five scorable:  H. antecessor, S. tchadensis, Au. garhi and K. platyops.  Paranthropus was removed separately as uncontroversially non-human.  This is a creationist result about the fragmentary record, and the article uses it as such in Part 1. ↩ ↩

  10. 10.

    Brunet, Michel et al.  “A new hominid from the Upper Miocene of Chad, Central Africa.”  Nature 418:145–151.  2002.  The type description of Sahelanthropus tchadensis, the paper that named the species from Chad.  The article uses it for the date and locality of the discovery. ↩

    1. 10a.

      “a nearly complete cranium and fragmentary lower jaws”.  The abstract reports six hominid specimens from a locality 2,500 km from the East African Rift Valley, with an associated fauna suggesting 6 to 7 million years on the mainstream scale. ↩

  11. 11.

    Macchiarelli, Roberto et al.  “Nature and relationships of Sahelanthropus tchadensis.”  Journal of Human Evolution 149:102898.  2020.  A paper on the nature and relationships of Sahelanthropus tchadensis by the authors who published the femur, which reports that the femur, TM 266-01-063, was recovered in July 2001 alongside the holotype cranium, was recognised as a probable primate femur only in 2004 during a taphonomic survey of the Toros-Menalla collections, and was not published for a further sixteen years.  The authors close by urging researchers to check whether more Sahelanthropus postcrania are sitting unrecognised in the same collections.  The article uses it for the femur's history and for the authors' view that the femur came from an individual that was not habitually bipedal. ↩

    1. 11a.

      They state that they are confident the femur is a hominid, that the most parsimonious hypothesis is that it belongs to S. tchadensis, and that their preliminary functional analysis suggests it belonged to an individual.  “that was not habitually bipedal”. ↩ ↩

  12. 12.

    Gibbons, Ann.  “News report on the condition of the Ardipithecus material.”  Science.  2002.  The condition of the Ardi material is described in contemporaneous science journalism quoting the excavation team.  Gibbons reported the eight-year delay in 2002, and Time and National Geographic News reported in 2009 on the hippo trampling, the chalky bone, the removal of the material in blocks of matrix, and Gen Suwa's digital refitting of the crushed cranium.  The article uses these reports for the condition of the material, which the team described itself. ↩ ↩

  13. 13.

    Sarmiento, Esteban E.  “Technical comment.”  Science 328:1105.  2010.  A technical comment, a short critique printed in Science, and a 2011 paper by Sarmiento and D. Jeffrey Meldrum in HOMO — Journal of Comparative Human Biology, volume 62, pages 75–108.  The article uses them for the older dissent from the bipedal reading of Ardi, which it cites from its own venue.  The article repeats a caution: Sarmiento has publicly entertained bigfoot claims, so the article cites him for the anatomy, which is peer-reviewed, and builds no argument on Sarmiento's authority. ↩ ↩

  14. 14.

    Wolpoff, Milford H. et al.  “Sahelanthropus or 'Sahelpithecus'?”  Nature 419:581–582.  2002.  A 2002 challenge in Nature, published in the year the Sahelanthropus skull was described, to the claim that the skull is a hominid.  Brigitte Senut is reported to have told the BBC in 2002 that she inclined to thinking the skull was that of a female gorilla, and that the characters used to conclude it is a hominid are sexual characters.  The article uses it to show that the hominid attribution was contested from the outset. ↩

  15. 15.

    Meyer, Marc R. et al.  “Knuckle-walking in Sahelanthropus? Locomotor inferences from the ulnae of fossil hominins and other hominoids.”  Journal of Human Evolution 179:103355.  2023.  A morphometric study of ulna shape, testing whether the shape of a forearm bone shows how a primate moves.  It compares the ulnae of humans, apes, Miocene apes and fossil hominins.  The article uses it for the finding that the Chad ulna falls within the knuckle-walking group. ↩

    1. 15a.

      Method: elliptical Fourier analysis of ulna shaft contours across humans, five extant ape species, two Miocene apes and 17 fossil hominin specimens.  Ulna shaft shape correlates with locomotion, and the TM 266 ulna falls within the knuckle-walking morphospace; discriminant function analysis classifies it with Pan and Gorilla at high posterior probability.  The same is true of OH 36, a purported Paranthropus boisei ulna. ↩ ↩

  16. 16.

    Cazenave, Rémi et al.  “Postcranial evidence does not support habitual bipedalism in Sahelanthropus tchadensis: A reply to Daver et al. (2022).”  Journal of Human Evolution, 103557.  2025.  A 2025 reply to Daver et al. (2022) by twelve authors, including Bernard Wood and David Begun.  It argues from the postcranial bones (those below the skull) that the evidence does not support habitual bipedalism, meaning walking on two legs as the normal way of moving, in Sahelanthropus tchadensis.  A 2026 Science Advances paper, doi 10.1126/sciadv.adv0130, re-examines the same bones and reaches the conclusion summarised in the article's table.  The article treats four rounds of published dispute over the same three bones in twenty-four years, by specialists of the first rank on both sides, as the finding. ↩ ↩ ↩

  17. 17.

    Research dossier for this article.  n.d.  The research dossier kept for this article, with its list of sources that could not be reached. ↩