If you have a bad back, it might be because you have a chimpanzee-like spine! Writing in BMC Evolutionary Biology last week, researchers claim that it is the speedy evolutionary change from walking on all fours to standing upright which has left some people with spines poorly adapted for the vertical lifestyle.
Back pain is a common health problem, which is estimated to affect 65% of us during our lives. It can be caused by several problems, one of which is called a slipped disc. The spine is made of round bones called vertebrae with small discs in between. Each disc is made of flexible tissue which is hard on the outside and jelly-like in the middle. The vertebrae and discs face outwards from the spinal cord to protect the nerves that run from your brain to the rest of your body. When a disc ‘slips’ it doesn’t actually move, but the jelly-like core bulges out through the outer casing causing painful inflammation and sometimes pressing on spinal nerves. Nobody is certain what causes discs to slip, but researchers this week have found a link between the problem and vertebral shape.
“The vertebrae stop developing at 6 years old and after that the shape doesn’t really change. Some shapes may be less well adapted to deal with the stress of walking on two legs, than others” explains Kimberley Plomp, a postdoctoral researcher working on the project. If your spine shape is unsuitable then you are more likely to suffer from a slipped disc.
If your disc has slipped it leaves long lasting, easily identifiable depressions on the vertebrae called Schmorl’s nodes. By looking at medieval human vertebrae, and those of chimpanzees and orang-utans, the team discovered that the spines of people with Schmorl’s nodes had more in common with chimpanzee vertebrae, and were of a more ancestral shape than unafflicted spines.
Chimpanzees move on all fours, only standing if they need to carry things in their hands. Their vertebrae, and those of the humans who developed these problems, are less able to cope with the stress of moving on two legs. Unfortunately, there is no way to change your natural shape as this is something that happened millions of years down the evolutionary chain. In evolutionary terms, humans adapted to walking upright very quickly, and that’s something some of us may be suffering because of now.
To test this hypothesis the team is hoping to use medical imaging of living humans to look at the spine-shape differences between people.
“We hope that these methods will be able to help clinicians identify whether someone might be more susceptible to back problems” Kim says. “It could be a really useful tool to help prevent injury in those at high risk such as athletes.”