Bipedalism in Humans is by no means a well evolved task. We
still have issues of lower back pain, knee joint stresses, ankle injuries and
hip fractures. Many of these aliments are conditions of aging but it shows
during our life time where we are taking the stresses and risks of standing
upright.
When we discovered the skeletal remains of Australopithecus afarensis commonly known as
‘Lucy’, we had proof that bipedal hominids were around 3.5million years ago.
When we look at her pelvis we can see more in common with our species than that
of our distant relations like chimpanzees who are better adapted to climbing
and quadruped walking. Lucy’s anatomy showed us that moving from quadruped to
biped relied on a reconfiguration of the bony plains of the pelvis and the
function of some locomotor muscles to provide lateral support while walking.
The ilia of most quadrupeds are thin and flat to the back of
the torso, a gradual bending of these has formed the bony rounded ridge of the
iliac crests, giving an anchor point for muscles bearing lateral support, very
important for stabilising the hip of a biped.
This video is taken from the BBC’s ‘Prehistoric Autopsy’
Series. You can clearly see how similar Lucy walks compared to modern humans.
In contrast the Chimpanzee on the right does not have the required skeletal and
muscular configuration of its hip to allow it to walk effectively on two legs.
Pelvic configuration in humans has slowly adapted to provide
quite a host of requirements: the most advantageous configuration of
musculature for locomotion, transfer of weight during locomotion and to hold
the torso upright during locomotion, along with providing the space to
adequately hold the internal viscera, and
importantly, the birthing passage for offspring. Because of the above, I feel
that the pelvis is one of those areas that is quite pivotal in considering an
anthro characters design. Without having to delve too deep into bio-mechanics
it’s good to take a look at some of the requirements needed to make a pelvis
fit our characters given needs to see what ‘rules’ we may need to follow when
making them more anthropomorphic.
For some reason my back started aching just reading this! :P I'm interested in seeing how you go about working out the knee and digigrade and unguligrade stance :-)
ReplyDeleteCool stuff. Be interesting to see someone design an anthro that had that specific hip roll like the chimp did as part of its character. Sort of cowboy-like. :"D
ReplyDeleteI firmly believe that the pelvis, as you've nicely illustrated here, is the central structure for change in making a quad into a biped. What happens distal to the knee is a whole different argument. It has to start in the pelvis, both to accommodate what is above it, and what is immediately below it.
ReplyDeleteThis clip with the two-legged dog is another great example of what happens when you don't change the pelvis.
http://www.youtube.com/watch?v=5QKG3CKZTYU
Standing up a quad hyperextends the hip, so there's literally no way for the a given leg to trail while the opposite takes the forward stride. She has to throw each leg forward while using the tipping of the upper body to 'fall' forward. The legs stop her from a nosedive with each 'step.'
Thanks for giving a clear explanation of the differences in muscle origin, insertion, and action! It cleared up a lot of nebulous ideas.