This difference, and because the lumbar spines of Nacholapithecus (a Miocene hominoid with six lumbar vertebrae and no tail) are similar to those of early Australopithecus and early Homo, it can be assumed that the Chimpanzee-human last common ancestor (PHLCA) also had a long axial column with a long lumbar region, and that the reduction in the number of lumbar vertebrae occurred independently in each ape clade.
The problem was found to be a stress fracture in the fifth (L5) Lumbar vertebrae.
Cervical vertebrae | Thoracic vertebrae | Lumbar vertebrae | Lumbar puncture | Caudal vertebrae |