We have known for years that humans have evolved, but also, that humans have many design flaws. For instance, humans are the only mammals that develop scoliosis – a condition in which the spine has an abnormal curvature. In fact, one of the first known cases of scoliosis dates back 1.5 million years.
At first, human spines were stiffer, which agrees with the lifestyle and survival needs at the time. The spine was meant to support the somewhat erect posture, allowing humans to reach for fruit in trees, and move for longer distances.
Humans come from a line of ancestors, whose skeletons were designed to carry their weight on all four limbs. About 20 million years ago, our ape ancestors evolved to carry themselves horizontally. Over the next million years, they grew larger and taller and began using their hands to reach for fruit. Then about six or seven million years ago, human’s ancestors stood up and began to walk on their legs. By 3.3 million years ago, around the time the renowned Lucy (Australopithecus afarensis) appeared, our ancestors had already adopted walking as their primary form of getting around.
Many evolutionary biologists believe behavioral shifts can often drive change in anatomy. Standing upright started numerous anatomical alterations. The biomechanics of walking upright is drastically different from quadrupedal locomotion, which is why the bones from the neck down had to evolve.
The skull and spine were realigned, which brought the torso and head into a vertical line over the hips and feet. This was mainly to support the body’s weight and absorb forces of upright locomotion. The spine was not the only bone that evolved due to this drastic shift. Joints, the foot, and the pelvis also changed, to improve stability.
Finally, over 4 million years ago, the human spine began to form its current shape which resembles an “S.” This curvature mainly formed as a mechanism to support the head and lower back pressure caused by erect standing. Once humans were able to extend their knees fully, the weight on their legs was far more that what their bodies were used to. As evolution took its turn, the spine began to gradually evolve to carry the head’s weight and support the lower back.
Evolution & Back Pain
Humans progressed from horizontal backs, parallel to the ground. Once the spine evolved to be erect, the body looked for stability over hips and feet, which is why the spine evolved to have curves in it. This radical shift the spine had to take to adjust to the body’s evolution may be the cause of many modern back pain problems.
Originally, human’s vertebral column was designed to act as an arch, and when we became upright, it shifted to turn into a weight-bearing column. Moving on from this first change, in order to support our head and balance our weight right over our hip joints and lower extremities, the spine had to evolve once again, obtaining a series of S-curves – a deep forward curve in the lower back, and backward curve in the upper back.
Over the course of time, with the pressures and loads of daily activities, humans became susceptible to problems such as herniated discs. Even walking results in constant torquing and twisting of the spine. No other animal has to handle with a mechanical system like this.
On top of this, humans are the only mammals that carry things in front of them. Another high point that backs the evolution of the spine to resemble an “S” shape. The current design of the spine is not an optimal one. It evolved as needed to support human’s lifestyle changes, and through its evolution, a few flaws became problematic for back health.
Our current anatomy does not resemble what it was originally designed for. It is because of the way humans have evolved, unique from other mammals, that we also experience a lot of aches and discomforts that our close relatives do not experience.
In fact, back pain is one of the most common health complaints, accounting for over 1.5 million doctor visits a year. Most of us will experience weakening back pain at some point in our lives, and it all may be due to the spine’s evolution.
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