Knuckle-walking in Sahelanthropus?
Locomotor inferences from the ulnae of fossil hominins and other hominoids >Marc R Meyer cs 2023 JHE 179,103355
doi org/10.1016/j.jhevol.2023.103355
The ulna supports & transmits forces during movement:
its morphology can signal aspects of functional adaptation.
Did some hominins (like extant apes) habitually recruit the forelimb in locomotion?
We separate the ulna shaft & ulna proximal complex for independent shape analyses (elliptical Fourier methods), to identify functional signals.
We examine the rel. influence of locomotion, taxonomy & body-mass on ulna contours:
22 Hs, 33 extant (5 spp) & 2 Miocene apes (Hispanopith. & Danuvius), 17 fossil hominin spms: Sahelanthr., Ardipith., Australopith., Paranthropus, early Homo.
Ulna proximal complex contours correlate with body-mass, but not locomotor patterns,
ulna shafts significantly correlate with locomotion.
Afr.apes' ulna shafts are
- more robust & curved than Asian apes',
- unlike other terrestrial mammals (incl. other primates), curving ventrally rather than dorsally,
this distinctive curvature is absent in orangs & hylobatids:
it is likely a function of powerful flexors, engaged in wrist+hand stabilization during KWing, not an adaptation to climbing or suspension.
OH-36 (Par.boisei?) & TM-266 (Sahelanthr.tchadensis?) differ from other hominins:
they fall within the KWing morpho-space = forelimb morphology cons.x terrestrial locomotion.
Discriminant function analysis classifies OH-36 & TM-266 with Pan & Gorilla, with high posterior probability.
Along with its associated femur, the TM-266 ulna shaft contours & its deep, keeled trochlear notch comprise a suite of traits signaling Afr.ape-like QPalism.
Implications for the phylogenetic position & hominin status of Sah.tchadensis remain equivocal,("hominin"??--mv)
but this study supports the growing body of evidence:
Sah.tchadensis was not an obligate BP, but a late-Miocene hominid with KWing adaptations.
Knuckle-walking in Sahelanthropus?
Locomotor inferences from the ulnae of fossil hominins and other hominoids >Marc R Meyer cs 2023 JHE 179,103355 doi org/10.1016/j.jhevol.2023.103355 >The ulna supports & transmits forces during movement:
its morphology can signal aspects of functional adaptation.
Did some hominins (like extant apes) habitually recruit the forelimb in locomotion?
We separate the ulna shaft & ulna proximal complex for independent shape analyses (elliptical Fourier methods), to identify functional signals.
We examine the rel. influence of locomotion, taxonomy & body-mass on ulna contours:
22 Hs, 33 extant (5 spp) & 2 Miocene apes (Hispanopith. & Danuvius), 17 fossil hominin spms: Sahelanthr., Ardipith., Australopith., Paranthropus, early Homo.
Ulna proximal complex contours correlate with body-mass, but not locomotor patterns,
ulna shafts significantly correlate with locomotion.
Afr.apes' ulna shafts are
- more robust & curved than Asian apes',
- unlike other terrestrial mammals (incl. other primates), curving ventrally rather than dorsally,
this distinctive curvature is absent in orangs & hylobatids:
it is likely a function of powerful flexors, engaged in wrist+hand stabilization during KWing, not an adaptation to climbing or suspension.
OH-36 (Par.boisei?) & TM-266 (Sahelanthr.tchadensis?) differ from other hominins:
OH 36 is category C-3 sensu Grine et al. (2022): Low confidence
taxonomic attribution, isolated postcranial bones that lack a
taxon-specific temporal and/or geographic context. https://www.sciencedirect.com/science/article/abs/pii/S0047248422001154
The same goes for L40-19 from Omo Shungura, which Meyer cs. also
assign to P. boisei and classify as "Suspensory" (Table 2).
All A. afarensis specimens (A.L.438-1, A.L.288-1, KSD-VP-1/1) are
classified as "Bipedal".
they fall within the KWing morpho-space = forelimb morphology cons.x terrestrial locomotion.
Discriminant function analysis classifies OH-36 & TM-266 with Pan & Gorilla, with high posterior probability.
Along with its associated femur, the TM-266 ulna shaft contours & its deep, keeled trochlear notch comprise a suite of traits signaling Afr.ape-like QPalism.
Implications for the phylogenetic position & hominin status of Sah.tchadensis remain equivocal,("hominin"??--mv)
but this study supports the growing body of evidence:
Sah.tchadensis was not an obligate BP, but a late-Miocene hominid with KWing adaptations.
They also classify StW 573, "Little Foot", a nearly complete
Australopithecus skeleton from Sterkfontein as "Knuckle-walking",
while the total skeletal morphology of this specimen clearly indicates habitual bipedalism with some degree of arborealism.
Moreover, "the hand morphology and the limb ratios of StW 573 bear no anatomical evidence that it was a knuckle-walker." https://www.karger.com/Article/FullText/519723
Locomotor inferences should not be based on morphometrics of single
skeletal elements.
Kudu runner:Knuckle-walking in Sahelanthropus?
Locomotor inferences from the ulnae of fossil hominins and other hominoids
Marc R Meyer cs 2023 JHE 179,103355 doi org/10.1016/j.jhevol.2023.103355 >The ulna supports & transmits forces during movement:
its morphology can signal aspects of functional adaptation.
Did some hominins (like extant apes) habitually recruit the forelimb in locomotion?
We separate the ulna shaft & ulna proximal complex for independent shape analyses (elliptical Fourier methods), to identify functional signals.
We examine the rel. influence of locomotion, taxonomy & body-mass on ulna contours:
22 Hs, 33 extant (5 spp) & 2 Miocene apes (Hispanopith. & Danuvius), 17 fossil hominin spms: Sahelanthr., Ardipith., Australopith., Paranthropus, early Homo.
Ulna proximal complex contours correlate with body-mass, but not locomotor patterns,
ulna shafts significantly correlate with locomotion.
Afr.apes' ulna shafts are
- more robust & curved than Asian apes',
- unlike other terrestrial mammals (incl. other primates), curving ventrally rather than dorsally,
this distinctive curvature is absent in orangs & hylobatids:
it is likely a function of powerful flexors, engaged in wrist+hand stabilization during KWing, not an adaptation to climbing or suspension.
OH-36 (Par.boisei?) & TM-266 (Sahelanthr.tchadensis?) differ from other hominins:
OH 36 is category C-3 sensu Grine et al. (2022): Low confidenceAre you really incapable to understand?? or do you only pretend?
taxonomic attribution, isolated postcranial bones that lack a taxon-specific temporal and/or geographic context. https://www.sciencedirect.com/science/article/abs/pii/S0047248422001154 The same goes for L40-19 from Omo Shungura, which Meyer cs. also
assign to P. boisei and classify as "Suspensory" (Table 2).
All A. afarensis specimens (A.L.438-1, A.L.288-1, KSD-VP-1/1) are classified as "Bipedal".
Today only humans & hylobatids are still BP, but *all* Hominoidea had BP ancestors:
they waded upright in swamp forests & climbed arms overhead in the branches above the water,
this is still seen occasionally (in spite of Pleist.coolings?) in bonobos, lowland gorillas & orangutans:
google "bonobo wading" or "aquarboreal" etc.
they fall within the KWing morpho-space = forelimb morphology cons.x terrestrial locomotion.
Discriminant function analysis classifies OH-36 & TM-266 with Pan & Gorilla, with high posterior probability.
Along with its associated femur, the TM-266 ulna shaft contours & its deep, keeled trochlear notch comprise a suite of traits signaling Afr.ape-like QPalism.
Implications for the phylogenetic position & hominin status of Sah.tchadensis remain equivocal,("hominin"??--mv)
but this study supports the growing body of evidence:
Sah.tchadensis was not an obligate BP, but a late-Miocene hominid with KWing adaptations.
They also classify StW 573, "Little Foot", a nearly complete Australopithecus skeleton from Sterkfontein as "Knuckle-walking",*Everything* points into the same direction: as I argued already a few times,
while the total skeletal morphology of this specimen clearly indicates habitual bipedalism with some degree of arborealism.
Moreover, "the hand morphology and the limb ratios of StW 573 bear no anatomical evidence that it was a knuckle-walker." https://www.karger.com/Article/FullText/519723
Locomotor inferences should not be based on morphometrics of single skeletal elements.
more frequent KWing began apparently a few mill.yrs earlier in Gorilla (E.Afr.apiths cs) than in Pan (S.Afr.apiths).
Implications for the phylogenetic position & hominin status of Sah.tchadensis remain equivocal,("hominin"??--mv)
but this study supports the growing body of evidence:
Sah.tchadensis was not an obligate BP, but a late-Miocene hominid with KWing adaptations.
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