Development of the fetal ilium--Challenging concepts of
bipedality. Journal of Anatomy 2008; 214(1):91-99.
There's a splendid description of human
bipedality at the start of 'Wanderlust: A History of Walking' by Rebecca Solnit, which was first published nearly two decades ago:
However, in terms of synapomorphy-based reasoning, this similarity is largely based on retention of plesiomorphic features below the level of Dinosauria, in combination with pedal digitigrady and with
bipedality. Lockley and Harris (2011) suggested Evazoum was made by a sauropodomorph, but again the resemblances are all symplesiomorphies below the level of the Dinosauria.
Was it the adoption of upright posture and
bipedality that caused a shift in the poise of the head on the vertebral column?
Michaud begins by detailing the evolution of
bipedality starting with the earliest ancestors of mankind, and explores theories proposing why humans transitioned from quadrupeds to upright walkers.
Birds have a unique collection of traits, such as feathers, flight,
bipedality (walking on two legs), a wishbone, and an unusual respiratory system, most of which are rare or nonexistent in any other living animal group, making it challenging to determine their closest relatives.
Why, exactly,
bipedality developed remains a contentious issue, and the author frankly admits that the sort of "pelvic adaptations" the earliest hominids had in order to accommodate
bipedality remains a mystery.
Human birth was constrained by the need to pass a head that was enlarging over geologic time through a pelvis that was being extensively modified by the requirement for
bipedality, such that cephalopelvic disproportion is not an uncommon cause of both maternal and fetal death today where Cesarean sections are not readily available.
For the most part,
bipedality has always been related to fast locomotion and to predator avoidance.
As noted,
bipedality freed our hands to become highly dexterous because of imitation.
