Origin of Human Bipedalism As an Adaptation for Locomotion on Flexible Branches

@article{Thorpe2007OriginOH,
  title={Origin of Human Bipedalism As an Adaptation for Locomotion on Flexible Branches},
  author={Susannah K S Thorpe and R. L. Holder and Robin H. Crompton},
  journal={Science},
  year={2007},
  volume={316},
  pages={1328 - 1331}
}
Human bipedalism is commonly thought to have evolved from a quadrupedal terrestrial precursor, yet some recent paleontological evidence suggests that adaptations for bipedalism arose in an arboreal context. However, the adaptive benefit of arboreal bipedalism has been unknown. Here we show that it allows the most arboreal great ape, the orangutan, to access supports too flexible to be negotiated otherwise. Orangutans react to branch flexibility like humans running on springy tracks, by… 

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Comment on "Origin of Human Bipedalism As an Adaptation for Locomotion on Flexible Branches"

TLDR
It is found that humans share knuckle-walking characters with African apes that are absent in orangutans, and these are most parsimoniously explained by positing a knuckles-walking precursor to human bipedalism.

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The final part of this chapter reviews why bipedalism was selected for and suggests an environmental shift would have involved strong selection for new behavioral strategies most likely linked to the efficient procurement of food.

The arboreal origins of human bipedalism

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The evidence is set out for the existence of a much earlier origin for bipedalism in a Miocene primate ancestor that was still predominantly tree-dwelling, and the notion that the common ancestor of great apes and humans was a knuckle-walking terrestrial species, as are gorillas and chimpanzees today is rejected.

Bipedal locomotion in zoo apes: Revisiting the hylobatian model for bipedal origins

TLDR
The data support hypotheses of an orthograde, long-backed and arboreal LCA, which is consistent with hominoid fossils from the middle-to-late Miocene, and if true, knuckle-walking evolved in parallel in Pan and Gorilla, and the human body form, particularly the long lower back and Orthograde posture, is conserved.

Response to Comment on "Origin of Human Bipedalism As an Adaptation for Locomotion on Flexible Branches"

TLDR
The knuckle-walking hypothesis, which lacks support from the fossil record and is highly unparsimonious, is reiterated.

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Since the evidence for stone tool production and use was pushed back to ∼3.4 Ma and the oldest secure evidence for habitual bipedalism somewhere between 3.66 Ma and 4.2 Ma, the temporal gap is closing and Darwin's hypothesis about the origins of upright walking may deserve a second look.

Origin of Bipedal Locomotion

Bipedalism is a highly specialized and unusual form of primate locomotion that is found today only in modern humans. The majority of extinct taxa within the Hominini were bipedal, but the degree to
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