Medical / December 2, 2011

Trade Offs During Evolution Ensure Onset Of Backbone Fractures

Research from Case Western University now suggests that most humans are doomed to develop backbone fractures as they age and evolution from apes to humans is to blame. Though osteoporosis is often cited as the cause for backbone fractures, the researchers at the university find the structure of our spine the real culprit. (1)

If we take a look at the anatomy of our vertebrae or backbone and compare it with that of apes, we will see that our backbone is more porous than apes. It is also much larger than their’s. However, unlike apes, our backbone is encased in a significantly thinner case of shell made of bone. In apes, the encasing shell is much thicker and so it remains intact for longer even as apes age.

As long as humans are young and the bone loss phenomenon has not set in, the structural design of our vertebrae suits us fine. However, once the process of bone loss begins, the already thin shell of bone encasement becomes vulnerable to develop cracks easily and may even break.

The findings of the research which were published in online PLoS ONE pointed at the adaptation of the spine that took place when the apes stood up vertically to walk on their hind legs. However, in the spinal adaptation, there was a trade-off.

As per Meghan Cotter, an instructor in anatomy at Case Western Reserve University School of Medicine and a lead author of the study, “The structure is great for walking around, but not good when you have osteoporosis.” (2)

Bruce Latimer, Anthropology professor of the Center for Human Origins and another researcher on the study noticed that there were fractures in the vertebrae of eary humans – the ones who had just transitioned from ape to humans. They were known as hominids. These fractures were not found in any of the apes – the immediate ancestors of hominids. This was arrived at after a detailed analysis of more than 3,000 human and more than 1,200 ape specimens which were housed at the Cleveland Museum of Natural History.

Latest technology and tools were used to get good readings to enable better analysis of the observations being made on the skeletal specimens. Of particular interest was the 8th thoracic vertebra because it fractures most often in humans, if the case relates to spinal cracks. CT scans and Micro CT scans along with computer aided modelling showed the differences of size, structure, microstructure, biomechanics and strength in skeletons of humans, gorillas, chimpanzees and orangutans. (3)

During the study the scientists found that the large, broad and porous vertebral bone evolved to serve the purpose of walking better. It’s anatomy was such that it dissipates the impact walking on two legs generates. It thus protects the cartilage in the joints and inthe discs between two vertebrae. In apes the vertebral bone was broader still and shorter with a thick ring of shell around a center of porous tissue and this provided them the stability they needed to climb trees.

Apart from evolutionary reasons, there has also been rapid advancements in technology in the last hundred years and it has created a sedentary lifestyle of the race. This along with the foods we now eat together leads to making one prone to bone loss, damage and fractures.

As per Cotter, “We’re now living about twice as long as when the adaptation evolved and that results in major problems. It highlights we are not perfectly evolved specimens.”

The research has pointed that though the recording of fossil structure and evolution is far from over it does indicate that some major restructuring or re-organisation of the musculoskeletal system must have been required in the human ancestors to be able to become able upright walkers leaving treading on all fours well behind them.


1. Blame Backbone Fractures On Evolution, Not Osteoporosis: Adaptation to Upright Walking Leaves Humans Susceptible;
science Daily; October, 2011;
2. Blame backbone fractures on evolution, not osteoporosis; October, Eureka Alert; 2011;
3. Human Evolution and Osteoporosis-Related Spinal Fractures; Plos One; October, 2011;