Walking is a physiological trait that defines mankind from other species. It is also believed that walking may have even been a key step in the evolution of the Neo-cortex which gave us the capacity for creative thinking.
There is still some debate within the scientific community as to how mankind evolved from four to two legs.
Since Charles Darwin theory of evolution in the late 1800s, scientists have supposed humans evolved from an ancestor that shared similar traits as apes – a creature that supposedly used arms and legs to manoeuvre.
Discoveries over the last century, however, indicate that this common ancestor probably had a primitive form of locomotion. Evidence suggests there was a species that spent time in the trees and on the ground.
Although we don’t know quite what this common ancestor was, it is apparent that mankind’s ancestors have been walking for over 7 million years.
The Evolution of the Species
Walking upright enabled early man to carry objects and manipulate wood and rocks to make tools. It enabled man to walk further and run faster.
In 1871, Charles Darwin wrote:
“…the hands and arms could hardly have become perfect enough to have manufactured weapons, or to have hurled stones and spears with a true aim, as long as they were habitually used for locomotion.”
In the 1920s Raymond Dart discovered the skull of a small child in South Africa. To Dart’s surprise, the foramen magnum, where the spinal cord connects the brain with the body, indicated that “Tuang Child” could walk upright.
The skull was carbon-dated to more than 3 million years old.
Dart’s theory was more or less confirmed in 1974 when the skeletal remains of a 3.2 million-year-old Australopithecus afarensis fossil were found. The now-famous Lucy, suggested that early species of hominids were able to walk upright.
The timeline was pushed even further back with the discovery Ardipithecus ramidus, a hominid fossil that was carbon-dated to 4.4 million years ago.
In 2001, another discovery had scientists scrambling to adjust their version of history. This time, the discovery of a skull in Chad revealed that hominids were walking 7 million years ago.
The Sahelanthropus tchadensis skull reveals the neck had a vertical structure, much like humans have today. Chimpanzees, on the other hand, hold their neck horizontally.
Theories about how we came to stand upright and walk continue to confuse academics, but scientists have been able to fathom the transition from four legs to two.
Anatomical Phases of Walking
Experimental studies of locomotion in humans and members of the ape families suggest the evolution of walking occurred in a series of transitions.
The most striking features between humans and apes is a high ridge on the top of the shinbone and our “bowl-shaped” pelvis. The pelvis in humans is shorter and gives muscles better leverage so that we can move our hips.
The nozzle that developed just below the knee is a cruciate ligament that stabilises the knee joint. This enabled man to change direction quickly so we were more mobile and fleeting – presumably enabling us to become better hunters. This stabilising ligament also allowed the hip to extend so the foot could be placed flat on the floor.
The angle of the thigh bone came to point inwards so we could bring our feet into the centre of gravity and maintain balance. Our spines also adopted an S-shape curve which helps to shift the weight of the upper body over the hips whilst walking.
Our feet changed too. Researchers know that hominids that lived 3 million years ago had arched feet – unlike Apes that have long, opposable big toes they use for grabbing branches.
The development of arched feet was a significant shift toward the skeletal structure of modern man. It meant the big toe became shorter so we could have a platform to push from and absorbs the shock of the ground when walking and running.
We may not fully understand how or why our ancestors evolved to walk upright, but it is clear that walking is a significant part of our evolution and our survival.
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