1. Thanks to evolution, your back is a marvel of load-bearing support and flexibility — and kind of a mess. Our species is prone to back pain, for example, because our ancestors’ imperfect transition to upright walking essentially took a spine similar to that of our nearest living relatives, knuckle-walking chimpanzees, and forced it vertical with piecemeal adaptations.
2. A 2015 study found that some people are, well, chimpier than others. Humans prone to certain back problems have vertebrae closer in shape to those of a chimpanzee than those of pain-free humans.
3. Regardless of shape, you might have more (or fewer) of the bones than your neighbor. Not everyone has the standard 33 vertebrae: From top to tail, that’s seven cervical, 12 thoracic, five lumbar, five sacral and four coccygeal.
