As long as we can trace the history of human beings, we can see that there were two main activities which were necessary to perform in order to survive. One of these activities was moving from one place to another like walking, running or jumping. Another activity was to carry goods, mainly in the hands and on the shoulders.
Till recently, human’s rarely travelled, even for small distances, without carrying some goods in the hands or on the shoulders.
These two activities (travelling and at the same time carrying goods on the shoulders and/or in the hands) have big influences in forming the body posture. Because of these activities, the way the body postures, from the bottom of the feet to the top of the shoulder, has evolved to be able to carry goods in the hands and on the shoulders, and at the same time be able to maintain postural stability.
By doing this activity, the surrounding environment demanded from the human to see where he was going and where he was stepping.
The two main things that humans had to take care of when moving (walking, running and occasionally jumping) from one place to another was, where he is stepping and how he is transferring its body weight from one leg to another, with the intention not to hurt the surface of the bottom of the feet and not to lose balance (if he losses balance, he will fall on the ground). Because of that, independently from the speed of the movement, he was transferring his body weight form one leg to another carefully.
The holding of the head and the neck has developed in such a way that he can with a minimum movement of the head, to see where he is stepping and where he is going. Because of that, his neck and head, in relaxed position, was slightly leaning forward. For example, when walking through a forest, we need to be able to see where we are going and where we are stepping. The time span between looking in the direction where we are going and looking on the ground where we are stepping must be short. Because if we watch for too long where we are stepping, we will in a short time hit the tree and if we watch too long where we are going, we will in a short time trip on the birch or some other objects which is lying on the ground.
As we change our focus in a short time, from where we are going and where we are stepping, the head and the neck from itself starts to lean slightly forward to enable us to see where we are going and where we are stepping, by mainly just moving our eyes or just with a minimum movement of the head.
If we walk through a forest without carrying some weight in the hands and on the shoulders, we can still do that with the many different types of body postures.
But if we carry some weight on the shoulders, or in the hands, on the long term we can do this activity only if our body from the bottom of the feet to the top of the shoulder is in an upright position and the neck with the head is in a slightly forward leaning position.
The humans have carried goods on the backs of other animals for millennia, and these other animals do not have an upright stance.
From a biomechanical point of view, carrying goods on the shoulder and carrying goods on the back are two completely different situations.
Carry goods on the shoulder was only possible using upright stance because the hands are used to hold the object when is carried in the hands or to support weight and to hold in the place when the weight carried on the shoulders.
If some another animal was enough clever and used humans to carry goods on human’s back, humans would never have adopted the upright stance and bipedal locomotion..
If humans invented backpack before adopting upright body posture than in this case humans will be still walking on four limbs.
Carrying the goods in the hands and on the shoulder and occasionally in the arms was the important activities that guided the evolution of the human body posture and an important factor in the evolution of the human race.
Without evolution of humans’ body posture there will be no significant progressive evolution of humans’ race.
By no other species the process of evolution is visible as it is by the humans’ race.
Humans still didn’t completely adopt the bipedal stance and upright body posture.
- Young humans who have been adopted by animals have adopted four leg stances.
- Young four legged animals adopted by humans never adopted bipedal stance.
This is to conclude that for humans, to some extent; it is still natural to walk on four legs.
Humans are not genetically programmed to walk upright. Humans have to learn walk upright.
Humans are still not born to use bipedal locomotion and upright body posture. . Humans have to learn to walk on two legs as well as it has to learn to maintain the upright body posture.
Only Penguin is born to use bipedal stance and upright body posture.
Birds and some other animals are bipedal but maintaining their torso parallel with the ground (excepting legs and neck) and humans are also bipedal but maintaining upright body posture.
Apes are not fully bipedal and they don’t’ have fully the upright body posture.
In the early infancy, doing any activity on two legs is much strenuous than on four legs. It is much easier to maintain balance-postural stability using legs and arms like all another four legs animals than by using just two legs.
By children, a driving force to adopt bipedal stance and upright body posture is the wish to imitate the surrounding social environment and to be part of the social environment – to be accepted by the community.
Acquiring ability to walk with upright body posture is correlated with acquiring the ability to talk.
Attempt to walk on two legs it requires more mental and nervous input than what is necessary to walk on four limbs. Process of learning to walk provides a physical and mental challenge. On the other hand, the process of learning to walk is the process of acquiring postural strength, postural stability and motor skill ability and on the other side is the process of acquiring cognitive ability.
Bipedal Locomotion, Upright Body posture and Prenatal Development
Before adopting bipedal locomotion and upright body posture, a development of embryo in the womb was happening in always the same position to the pull of gravity.
After adopting bipedal stance and upright body posture, development of embryo is happening in one position (concerning the direction of the pull of gravity) when human walking and in another position when humans sleeping.
How it Came that Humans are even Capable of Walking Upright
Human become capable to walk upright by trying to walk upright. Driving force to attempt to walk upright was a motive to carry goods in the hands, arms or on the shoulder.
How it Came that Humans Have Adopted Bipedal Locomotion and Upright Body Posture
Before carrying gods and tools comfortable stance was four leg stances. It is much easier to maintain balance using four legs like all another four legs animals than by using just two legs.
Carry goods in the hands and/or on the shoulder cause gain more postural strength and postural stability than what is minimum necessary to carry just weight of own body.
By carrying some weight on the shoulder or/and in the hands we need to put more mental and physical effort to support own weight and weight of carrying object than what is necessary to support and to carry just its own body weight.
It is because by doing this activity hands are used to keep the loads on the shoulder or to hold the loads and legs alone have to hold the weight of the body and to perform locomotion.
Carrying goods in the hands and on the shoulders has consequences of gaining postural strength and postural stability to a greater extent than what is the minimum necessary to carry our own body weight.
Improvement in postural strength, postural stability and motor skill, enable humans to carry our own body weight with more easiness.
After improving postural strength, postural stability and motor skill the human find more comfortable to walk, run and jump on two legs in upright body posture than in for limb stance.
The process of gaining more postural strength and postural stability and motor skill ability than what is necessary to support and to carry our own body weight happened in upright body posture, and because of that fact the human start to be more strong and balanced in bipedal stance in upright position than in bipedal stance in semi upright position or in for limbs stance in body position parallel with the ground.
Without carrying some weight in the hands and on the shoulder humans would never have adopted the upright body posture, because it would never have gained enough postural strength and postural stability to be able to carry own body weight with more easiness by bipedal stance in upright body posture than by bipedal stance in semi upright body posture or in four legs stance.
The human adopted upright body posture because it was more comfortably to support and to carry own body weight by doing every day activity.
Indirect cause of adopting upright body posture was motive to carry significant loads for a significant amount of time.
Direct cause for adopting bipedal; stance and upright body posture is feeling more comfortable in bipedal stance and upright position than in four legged stance or bipedal stance with parallel or semi parallel position to the ground.
Are Humans Fully Bipedal
Most part of the life humans are not fully bipedal, because humans using work of the arms to maintain balance by performing every day’s locomotion. On one side the humans support the weight of own body by using bipedal stance on the other side to carry own body weight (performing locomotion) humans using the legs and to a lesser extent the arms.
Humans are fully bipedal only when carrying something in the hands (except the case when carrying small weight in the hands that still enable arms to swing) and/or in the shoulders by supporting weight whit hands.
Humans by standing are bipedal. But by walking, running and jumping humans are semi bipedal.
Comparing to the Apes:
- Humans are to a greater extent bipedal than Apes.
- Humans have a full upright body posture and Apes have semi upright posture.