One of the characteristics of a human being is walking on two legs a trait scientists call bipedalism. There is compelling evidence that point towards climatic changes over long periods reduced forested areas forcing early hominins to get into habitual bipedalism allowing them to range into open landscapes. This holds both advantages and disadvantages for the bipedal species. What then are the pros and cons of bipedalism?
List of Bipedalism Pros
1. Brain Enlargement
From observation, wild chimpanzees walk bipedally most of the time allowing them to carry and transport more items. For the early hominins being bipedal enabled them to diversify the use of limbs leaving the upper limbs for moving and making tools, which led to increased intelligence and brain enlargement.
2. Use Less Energy
Bipedal walking reduces the energy requirements necessary to move from place to place. The human body stores and recovers the same energy used with each stride when walking bipedally. Being quadrupedal on the other hand requires more muscle power to support the body increasing the energy requirements of the body.
3. Safety
Being bipedal allowed hominins and the later day humans to dodge predators easily since the bipedal body is more maneuverable than quadrupedal bodies. This makes humans more conscious and able to get to safety in the face of danger.
The evolution of bipedalism also allowed for spinal evolution allowing the hominins and humans to have more flexibility during movement, allowing for easier twisting, flexing and bending. This is visible in that humans are the only mammals with the ability to lean and bend backward as well as to arch the spine.
4. Cover Long Distances
According to Professor Spencer-Wood, bipedalism is an efficient means of covering long distances given that there is less waste of energy when walking.
5. Less Heat Absorption
With the evolution of bipedalism, hominins and humans had a reduced surface area meaning that on sunny days, there is less heat absorbed into the body, compared to quadrupedal animals. This makes it more convenient to work and play in the sun without overheating.
6. Wider View
Being bipedal allows humans to have a more comprehensive view of the surroundings, unlike the quadrupedal animals who have limited view. This allows for easier spotting of danger, survival mechanisms, as well as easier food collection.
7. Less Strain on the Neck
The bipedal stance reduces the pressure on the neck since the foramen magnum is further underneath the skull compared to quadrupedal species. This means the head can balance on the spine requiring less robust neck muscles to hold it up, as is the case in the quadrupedal stance.
With the pros above, the evolution of the bipedal stance also came with its cons.
List of Bipedalism Cons
1. Ineffective in Arboreal Habitats
With evolution, bipedal species are in no position to exploit the arboreal habitats effectively since the feet are unable to grasp and climb trees during movement.
2. Reduced Flexibility
Through years of evolution, the bipedal species now have a much-reduced flexibility in their ankles. This makes climbing harder than it was before evolution took its course.
3. Increased Risk Of Injury
The knee joint works marvelously in functionality by transferring load between limbs. However, it is more prone to injury with over two million cases reported in the USA alone. The S-shaped design of the spine in bipedal species is efficient in the distribution of energy in the body as well as balance though highly prone to injury due to oblique force as well as the excessive amount of pressure put on its curved structure. This accounts for over 15 million people complaining to doctors of back pain, in the USA alone.
4. Bone Mineral Loss
The redistribution of bones in the human body is at a greater volume than in other animals. This makes humans have more surface exposure of the skeletal tissues. Over time, the bipedal nature of humans accelerates the rate of bone mineral loss, a condition known as osteopenia arising from old age. This characteristic more often than not leads to vertebral, hip and osteoporosis fractures.
5. Constricted Birth Canals
Through evolution from quadrupedalism into bipedalism, the pelvis morphed into what is now a broad and flat saddle shape allowing for the attachment of leg muscles and improved stability of the body. However, it resulted in the severe constriction of the birth canal making the birth process more difficult, and it is the leading cause of mortality rates of women while giving birth in certain parts of the world in the modern age.
6. Exposure to Predators
Though bipedalism helped to see further, they can be seen easily by predators increasing the risk of attack. Bipedalism made attacks from predators easier since it led to slow running and climbing.
Through significant anatomical changes from quadrupedalism into bipedalism, humans lost the ability to utilize other forms of locomotion on the ground except walking or running. However, bipedalism allowed humans to access deeper water, and be able to reach food in higher sources.