Chimpanzees have a difficult time walking upright for long periods at a time in part because the shape of the chimp spine is better adapted to walking quadrupedally. Humans, on the other hand, have evolved a number of skeletal adaptations — spine shape included — that makes bipedal locomotion possible. But according to new research by scientists from Scotland, Canada and Iceland, not all humans are as evolved as others in this respect, reports the BBC.

It turns out that many people who experience chronic lower back pain have vertebrae that look almost exactly like chimpanzee vertebrae. 

"Our findings show that the vertebrae of humans with disc problems are closer in shape to those of our closest ape relatives, the chimpanzee, than are the vertebrae of humans without disc problems," explained Professor Mark Collard, one of the study's researchers.

That is worth repeating so that it sinks in. Remarkably, the study found that the vertebrae of pathological humans were actually closer in appearance and functionality to chimpanzee vertebrae than they were to those of healthy humans. 

For the study, the team compared the vertebrae of chimpanzees, orangutans and humans with and without back pain. Chimpanzee and orangutan and healthy human vertebrae were easy to tell apart. It was just the vertebrae of chimpanzees and pathological humans that were nearly indistinguishable.

So does this mean that some people with lower back pain are less evolved than everyone else? Well, not exactly. Evolution is a messy process, and there is a lot of variation across the population. Not everyone has adapted in exactly the same way. Those with chimpanzee-like vertebrae still have a whole range of other traits that make them better suited for bipedalism than chimpanzees are.

In other words, those with lower back pain don't need to start walking around on their knuckles. Though perhaps this can give us all a greater appreciation for the kinship we share with our closest living relatives, the chimpanzees.

Researchers hope that the study will help doctors better understand, diagnose, treat and even predict lower back pain. It should also shed light on human evolution in general, and more specifically, the evolution of bipedalism.

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