Acquired spinal conditions in humans: the roles of spinal curvature, the shape of the lumbar vertebrae, and evolutionary history

Back pain has serious impacts on individual people and society, but its causes remain poorly understood. One long-standing hypothesis contends that many common back problems may be due at least partly to the stresses caused by our evolutionarily novel form of bipedalism. This chapter discusses this hypothesis and shows how recent palaeopathological, comparative and clinical evidence has been interpretated within an evolutionary framework to develop a new version of the hypothesis. We begin by outlining how the spine in humans differs from those in the great apes. We then review clinical evidence that suggests that there is a link between spinal column and individual vertebral shape on the one hand, and spinal diseases on the other. Next, we outline palaeopathological and comparative anatomical evidence that also supports the link between spinal/vertebral shape and disease. Thereafter, we discuss recent studies that not only indicate that two important acquired spinal diseases—intervertebral disc herniation and spondylolysis—are associated with vertebral shape, but also suggest that the pathology-linked morphologies can be understood in terms of our evolutionary history. Subsequently, we discuss potential biomechanical explanations for the putative link between vertebral shape and intervertebral disc herniation and spondylolysis.