Assignment 3: Bipedal Locomotion

Take Home Writing Assignment 3: Bipedal Locomotion
1. Briefly describe the morphological features that distinguish the skeleton of bipedal hominids from that of chimpanzees and other apes. Make sure to explain how the features are different in bipedal hominids compared to the apes.
a. Cranium
Ape and human craniums are very different from one another. Ape craniums are designed for chewing giving them more muscles in the cranium to bite don on hard foods. These muscles apes obtain in their cranium also helps avoid injury but these muscles also don’t allow for a bigger brain size meaning that apes do not have big brains. Humans on the contrary have big craniums for bigger brains but humans hardly have any chewing muscles.
b. Wrist
Most apes who are knuckle walkers need a stable hand wrist in order to avoid injuries hen knuckle walking. On the other side humans don’t mainly because we don’t knuckle walk and doing so can be dangerous because humans have a rotatable hand wrists. We have more flexible wrists to help us grab things.
c. Foot
Apes are great at climbing trees but what allows them to be such great climbers are their flat feet with divergent, opposable big toes.
On the other hand human feet are very different from apes. The human foot has arches that help decrease the incidence of fatigue. Our big toe is enlarged and lines up with other toes for increasing balance.
d. Femur and knee
The difference in the Femur between hominids and apes is what in many cases defines whether early ancestors were bipedal or quadruped. Apes rotate their pelvis toward the side every time they take a step meaning that their femur is straight. Human’s femur angles inward and is also very long allowing us to be more efficient walkers. For apes in order to climb they must have a mobile knee to help the knee rotate. Human’s knee, on the contrary, needs to be more stable to support the upper bodies weight and to increase balance.
e. Pelvis
In order for the pelvis to support the internal organs while humans are upright the iliac blades need to be rotated inward. The curved pelvis of humans allows them to balance the weight of the trunk effectively over the hips. For apes the iliac blades are not inward and the pelvis is narrow and flat. These aspects make it impossible for an ape to easily balance on one foot while walking
bipedal.
f. Spine
The human spine has an “S” shape and is composed of two curves called lumbar curves. These curves allow humans to bend forward at the hips and bend sideways and backwards. One of the lumbar curves helps human position the body inward, over the pelvis helping humans position their weight of the trunk forward over the hips. Apes have no lumbar curves this helps them pull the upper body back over their pelvis.
2. Briefly explain why bipedal locomotion is energy efficient.
Being bipedal helps us with energy efficiency. If we were quadruped like apes are it would disenable us to walk greater distances in search of food and to having our hands free to be used for other things. Being bipedal is the reason why humans grew hairless. Being hairless allowed us to sweat which gave us the advantage of keeping fresh while running or walking for long distances. All this contributed to making bipedal locomotion energy efficient.