history of low back pain

I found this interesting article by Rajeev K Patel, MD,University of Rochester - Strong Memorial Health System and Curtis W Slipman, MD, University of Pennsylvania Medical Center

Here I am only putting the introduction, which I found interesting...

Descriptions of treatment for low back pain (LBP) date to Hippocrates (460-370 BCE), who reported joint manipulation and use of traction. Onset of LBP often is associated with bipedal ambulation. Theories propose that this transformation in the mechanics of locomotion is the inciting evolutionary event that made the lumbar spine susceptible to degenerative disease. Degeneration is universal to structures that comprise the functional spinal unit, composed of 2 adjacent vertebral bodies and the intervertebral disk. The disk and 2 zygapophyseal joints at the same level function as a trijoint complex.
As humans age, they endure both macrotraumas and microtraumas and undergo changes in body habitus that alter and redistribute biomechanical forces unevenly on the lumbar spine. Natural progression of degeneration of the lumbar segment with motion proceeds with characteristic anatomic, biomechanical, radiologic, and clinical findings in lumbar degenerative disk disease (LDDD).

I suppose it is comforting to know that this may be an intrisic problem of being human! I am sure that years of sitting trot did not help me. One would think that a quadruped (like my horse) would have more opportunities for back pain since gravity would tend to bring a "sag" in the middle... no?