The cause of modern human's back problems may lie in the development of vertebrae
Most people will suffer some form of back pain in their lifetime. It is thought that the causes of back pain stem from the upright posture of people. This is supported by the fact that back problems seem to be less common in other primates. A new finding is that the shape of the vertebrae may play a role in the development of back problems.
In her PhD thesis in archaeology, which will be examined on 19 December, Niina Korpinen, M.Sc., studied how vertebrae have evolved and what role upright posture and walking on two legs have played in them.
The shape of the vertebral node has not changed much during evolution. However, changes over the last two hundred years or so suggest that the vertebral node has become rounded. This may have implications for the durability of the vertebra and the health of the intervertebral discs. Human and gorilla vertebrae are relatively similar in shape, which seems to suggest that the weight applied to the vertebrae has a greater influence on the shape of the vertebrae than the way they move.
This is also suggested by the finding that the shape of the vertebrae of chimpanzees differed markedly from those of humans and gorillas but were relatively round compared to fossil human apes.
Bone loss due to ageing would appear to have been less in the historical population than in modern humans. Bone loss, especially in females, was less severe about 100 years ago. The reason for both short-term changes is thought to be reduced physical activity.
The variation in bone density throughout the spine appears to be similar between humans and chimpanzees. However, differences in bone density variation were found between chimpanzees, suggesting a smaller effect of physical activity.
Evolutionary changes were examined by studying how the shape of vertebral nodes differs between modern humans, African apes and fossil great apes. In addition, vertebral bone density measurements in African apes were examined and how they differ from humans. Shorter-term changes were examined by studying differences in vertebral node size and shape between Finnish archaeological specimens (from the 1600-1800s) and modern humans (data from birth cohorts in northern Finland). Age-related changes in bone density were also studied in a 20th century American population. The work focused mainly on the lower back, as this is the most common problem area for back pain.
The study will help us understand how the back has adapted to new postures and movement patterns over time, and the impact of our current lifestyle on the vertebrae. Our lifestyle currently involves the least amount of physical activity in our history, creating new health challenges.