uprightdoc wrote:NZer1,
What's your take on all the different pithecine Australian species that Falk describes and what does she mean by "robust" Aussies?
Well, I have had a look at the section in the book on Upright posture.
"According to the Author, physical anthropologist Dean Falk, the occipital marginal sinus system is unique to humans and huminids and is preferentially used to drain the brain during upright posture. " The occipital marginal sinus system drains into the suboccipital cavernous sinus and the VVP of the upper cervical spine and spinal canal, respectively.
Fortunately, the accessory drainage system evolved to handle the increase in venous outflow and prevent backups and interstitial edema.
My thoughts are that the article identifies the area of the skull, the lower rear portion which is the linking area for blood return flow to the spine. As Humans developed the upright posture there needed to be evolution of the skull and spine to cater for the changes required for the skull to be supported on top on the spine as opposed to horizontally in front of the spine. The flow in and out of blood to the brain had to adapt to cater for the changes in skull shape, brain size, brain cushioning/fluid support and brain cooling. The previous outlets through the skull (bone) connecting the spine were unable to cater for the required volume and flow increase, nor were the sinus's (passages) located to suit the new position and angle of the upright skull. New pathways to the vertebral venous plexuses where required in the evolution, to drain the lower rear portion of the skull.
There needed to be connection and alignment for the brain stem and cord, support for the skull which houses arteries and veins that can cater for the various postures of Upright posture.
The 'robust' Aussies I would imagine is a reference to the link to the first 'working' skeletal structure for upright posture that evolved further to huminids. I'm guessing on that part.