title: Origin of human bipedalism as an adaptation for locomotion on flexible branches.
abstract: 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 increasing knee and hip extension, whereas all other primatesdothe reverse. Human bipedalism is thus less an innovation than an exploitation of a locomotor behavior retained from the common great ape ancestor.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: S K S
authors.initials: SK
authors.lastname: Thorpe
authors.forename: R L
authors.initials: RL
authors.lastname: Holder
authors.forename: R H
authors.initials: RH
authors.lastname: Crompton
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D005075:Biological Evolution; D001696:Biomechanical Phenomena; D017753:Ecosystem; D006225:Hand / Q000033:anatomy & histology / Q000502:physiology; D006614:Hindlimb / Q000033:anatomy & histology / Q000502:physiology; D015186:Hominidae / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D008124:Locomotion; D011148:Pongo pygmaeus / Q000033:anatomy & histology / Q000502:physiology*; D011187:Posture; D014197:Trees; D016138:Walking