human ancestors never passed through a knuckle-walking phase

http://tinyurl.com/2lv228
Human Ancestors Learnt to Walk Upright in the Trees, Say Experts

Liverpool, UK: 31 May 2007 Scientists at the University of Liverpool have
found that humans' ability to walk upright developed from ancestors foraging
for food in forest tree tops and not from walking on all fours on open land.

It was traditionally thought that humans became upright walkers in a slow
process which had its origins in ?knuckle-walking¹ ­ movement on all fours ­
just as chimpanzees and gorillas walk today. It was believed that this
developed once human ancestors moved out of the forests into the savannahs
of East Africa.

Study at the University of Liverpool, in collaboration with the University
of Birmingham, into the behaviour of the orang-utan, has now suggests that
knuckle-walking evolved quite recently in chimpanzees and gorillas, as a way
of moving on the forest floor, whilst walking on two legs ­ assisted by the
support of tree branches ­ is an older trait and evolved from tree walking.
The study suggests that walking on two legs was always a feature of
great-ape behaviour and human ancestors never passed through a
knuckle-walking phase.

Skeletons of early human ancestors show a combination of short legs and long
arms, which are adaptations for moving amongst tree tops, with hindlimbs
adapted for walking on two legs. To understand why bipedalism ­ walking on
two legs ­ would be necessary for the tree-living ancestors of humans,
scientists studied the movement of the only completely arboreal great ape,
the Sumatran orang-utan. It appears that they use bipedalism to forage for
food from small branches of tree tops, and to cross directly from tree top
to tree top.


Professor Robin Crompton explains: ³We found that orang-utans walking
bipedally on springy branches act much like athletes running on springy
tracks; they use extended postures of knee and hip to give them straighter
legs. Other recent work by the team shows that orang-utans use the natural
springiness of branches to save energy in movement, especially when crossing
from one tree to another, and this may also be the case when they move
bipedally in small branches.

³Walking upright on two legs, gripping branches with the feet and balancing
themselves by holding or touching higher branches with their hands is
actually a very effective way of moving on smaller branches. It helps to
explain how early human ancestors learnt to walk upright whilst living in
the trees and how they would have used this way of movement when they left
the trees for a life on the ground.

³The traditional theory of human origins states that we evolved to walk
upright from ancestors who walked on all fours when on the forest floor.
This new study suggests the opposite. Upright walking evolved in the
ancestors of all apes, including humans, as a means of foraging for food in
the small branches of the tropical forests and these techniques were later
used by human ancestors to allow them to adapt to walking on two feet on the
ground.

³Around 15 million years ago the tropical forests which once covered East
Africa began to break up, and although the forest sometimes grew back
temporarily, eventually trees became separated and further apart, preventing
our ape ancestors from swinging from one tree to the next. This forced them
to go down to the ground in order to move between trees.

³Our ancestors made use of the way they moved through the trees to adapt to
their life on the ground. Ancestors of chimps and gorillas, however, tried
to maintain access to the canopy as well as the ground by developing very
strong arms to climb vertically up and down tree-trunks and as a consequence
became ?top-heavy¹. When they are on the ground, therefore, they move
predominantly by knuckle-walking, propping themselves on their long, heavy
forelimbs.²

The research is published in Science.

.

Relevant Pages

  • Re: OT - ancestry.co.uk
    ... the tree somewhere where other family members who have relevant information can see it and add to it - and yes, I can export the tree as GEDCOM. ... I would never put my whole tree online. ... GeDCom files. ... GenCircles and various other to my direct ancestors and their siblings and siblings' spouses. ...
    (uk.media.radio.archers)
  • collapsing a tree into a list
    ... I have a tree where a node can have multiple parents and multiple ... a child cannot be ahead of any of its ancestors, ... So far I am evaluating in order of top node of longest ancestry chain, ... have been inserting by walking from the top of the new ranking past its ...
    (comp.theory)
  • Hybridization is the key
    ... Our ancestors spread.... ... the ship owner discovered that the African ... Jefferson had a number of children ... until so recently that the tree and non ...
    (sci.anthropology.paleo)
  • Re: New Study Suggests Australopithecus Afarensis Used Tools
    ... >>> the new study appear to have been cut and crushed by stone tools wielded ... >>> a scientific rethink of how the brain sizes of our early ancestors were ... the early human ancestors were scavengers who used stones ... >Homo Erectus made and used stone tools while he lived in Africa. ...
    (talk.origins)
  • Re: Longevity and ancestry
    ... one tree, I trace back to Odin, b. ... whether person A was really the descendant of person B, ... Many of the siblings of our ancestors did ... The popular explanation is that medical care is now so wonderful ...
    (talk.origins)