Yoga and the Spine 25
A straight spine, such as that of the fish if it were supported on four limbs, would be
subjected to gravity’s maximum destabilizing force at its very weakest point: the center
of the span between the two supported ends (figure 2.6). Once raised up on its limbs,
the most successful newly terrestrial creatures would be those that arched their spines in
response to gravitational stress in order to direct that stress toward the supported ends,
rather than the unsupported middle.^1 This is the development of the primary curve of the
terrestrial spine—what we know as our thoracic curve. It is primary in the sense that it is
the first anterioposterior (front–back) curve to emerge, and also in the sense that it is the
first curve that a human spine exhibits prenatally.
The curve of the neck was the next to evolve. Our fish ancestors had no real necks; their
heads and bodies moved as a single unit with the gills placed directly behind the brain.
The gradual downward shift of the breathing structures allowed for the development of a
highly mobile neck that was capable of producing quick, precise movements of the head
and sensory organs, offering an ever further look into its environment and tremendous
survival advantages. This orientation of the cervical region signaled the first development
of a secondary, or lordotic curve in the spine, which can be seen in the cat (figure 2.7).
E5267/Kaminoff/fig2.7/417582/alw/pulled-r2(^1) Think of the difference between Greek and Roman architecture. Far more of the Romans’ buildings are still standing
because they built with arches and the Greeks didn’t.
Figure 2.6 A supported arch is more stable than a straight line.
E5267/Kaminoff/fig2.8/417583/alw/pulled-r2
Figure 2.7 The first secondary curve: the cervical.