Bipedalism Analysis

An Analysis of Select Bipedalism Hypotheses

Bipedalism is a unique attribute of hominids and is pivotal in human evolution. There exist several Hypotheses of Bipedalism. Four hypotheses that are explored are Locomotion Efficiency (Long Distance Travel), Thermoregulation (Cooling), Freeing the Hands, and Visual Surveillance. A summary of each hypotheses’ main points and applied relevancy of each, postulating the locomotion theory as the best of the four hypothesizes.
I. Locomotors Efficiency (Long Distance Travel)
This theory posits that bipedalism occurred because of more efficient travel and multi-tasking. Analysis: It encompasses about all the below theories. Freeing of hands to tend babies, gather food and increased travel between clusters

of trees. Therefore, bipedalism offered greater efficiency for long-distance travel. The locomotion of long distance travel also activated a cooling thermoregulation of the system, standing upright to decrease sun on body. ‘‘Lucy’’ having the most complete record of locomotor morphology to place the feet directly beneath the whole body center of gravity, providing a smoother, more efficient gait. (Johanson. 2009.)

II. Thermoregulation (Cooling)
Thermoregulatory theory argues that the increased energy loss and cooling, diminished heat gain and limited requirement of water presented by a bipedal stance position in a hot, humid weather are the attributing factors to the emergence of bipedalism (Wheeler, P 1984.)
Analysis: This says that by being upright, hominids were exposed less to harmful elements to keep the body cool by minimizing the direct sun on the body. It has been recognized that bipedal posture reduces the surface area of the body exposed to the sun. There are other ways to keep cool. However, what we know is that locomotion serves as thermoregulation as it does to some degree encompassing some or all -- of the four listed theories
III.

Freeing the Hands
This theorizes that humans began walking on two feet instead of four in order to free their hands to do other tasks while moving across the world. There are several models on this origin, suggesting from food foraging and infant carrying, to stone tools and weapons. Owen Lovejoy, points out “…that if males contributed to the survival of their mates and their offspring, then their own genes would survive into the next generation. Bipedalism would have allowed males to provide their mates and offspring with high-quality food as well as to help protect them from any looming dangers. This explanation makes biological and behavioral sense. .”(Lovejoy 1981)
Analysis: Freeing of hands for carrying, food gathering, changes in climate and habitat is viable. Socialization and culture is imperative to survival of the species. The stone tools theory is unlikely as bipedalism predates the use of tools. The discovery of “Lucy” prevents it from being a driving force of evolution. (Larson. 2013) Cultural evolution is extremely important. Provisioning is central to survival. Scholar tends to agree with this theory next to locomotion.
IV. Visual

Surveillance
Another suggestion is visual theory, related to geographic changes in landscape, increased grasslands. Standing to see over the grasslands states that night vision reduced and bipedalism resulted so that our ancestors could see their prey and watch for predators.
Analysis: The fall of this theory simply is the absence of night vision in humans. Keeping in mind that we are “evolving” eventually into the humans, we are now. With that said, this is a non-credible theory, as it would contradict evolution’s survival of the fittest. The loss of night vision would have made them vulnerable to predators. “For example”, says Donald Johanson , “Lucy was only three-and-a-half feet tall as an adult and weighed roughly 60 pounds. Imagine this puny little hominid venturing out of the forest, where she and her ancestors had lived for millions of years, onto the new, challenging, and highly dangerous world of the grasslands. A major shift in habitat is not a good time to experiment with a totally new mode of locomotion; leaving the speed and agility of quadrupedalism behind for upright walking would have been a terrible choice”. (Johanson. 2009).
Bipedalism Had its Benefits and Costs; an Evolutionary Trade Off (Larson. 2013. p 238-9)
Advantages
Part of this compromise was structural, involving much more powerful arms and possibly human-proportioned hands for gripping branches rather than suspending from them.

Another part of the compromise was behavioral. The loss of a grasping foot is also a serious problem for child-rearing. In chimpanzees and other primates, the young can use their hands and feet to grasp and cling to their mother's fur. For hominid infants, such clinging would have been much more difficult, if not entirely impossible. One of the adaptations to bipedalism must, then, have been a behavioral change toward carrying dependent offspring until they were old enough to walk. (Larsen,

2013)
o Increased ability to see greater distances
o Greater ease transporting food and children,
o Ability to run greater distances,
o Freeing of hands for eventual skills as tool manufacturing
o And tool use (Larson. 2013. p 238-9)
Dis-advantages
The first is that it makes climbing considerably more difficult. Without the ability to grasp with the feet, hominids are less secure in an arboreal setting. There are many indications that climbing remained an important part of the behavior of early hominids, discussed below. The combination of features found in early hominids reflects a compromise adaptation to climbing, based on the presence of morphological adaptations to bipedalism in the pelvis and foot. (Larson. 2013. p 238-9)
o Bipedalism also places an enormous burden on circulatory system as it moves blood from legs to heart. Resulting in development of varicose veins a condition in which overwork causes the veins to bulge
o standing upright yielded better view of landscape, but brings expose to predators
o standing or walking while carrying heavy objects over long periods of time cause back injury e.g. arthritis and slipped intervertebral disks
o Lastly if one of the two feet is injured ability to walk can be severely reduced (Larsen, 2013)
Conclusion:
None of the hypothesis here actually excludes one or all of the others. Of the four theories, Locomotion is most plausible as it encompasses the best points of all. The origins of bipedalism are a complex combination of these and possibly others, states Johansen,
“ I believe that our ancestors, pre-Lucy, became upright in the protection of the forests, a familiar environment in which they faced fewer dangers. Then, armed with a new type of locomotion, bipedalism, they were pre-adapted to move onto the savannahs and expand their territory. Once we moved into open environments, we brought a whole package of advantages with us. Our hands were free to make and use tools, we could walk long distances to collect and carry food (and in doing so benefit from enhanced thermoregulation to prevent overheating), and we could look over tall grass if we needed to, and so on”. (Johansen. 2009)
Evolution, culture and humanity are complex and multifaceted. Bipedalism did not just happen overnight, therefore a solid hypothesis to answer the question of, why and how did we become, might take a few to 100,000 thousand years or so. I believe that the origins of bipedalism were a contribution of all hypothesis in one form or another.

Bibliography

Johanson. Donald. “Lucy’s Legacy: The Quest for Human Origins” Harmony Books, 2009.

Johanson. Donald, is the Virginia M. Ullman Chair in Human Origins and director of the
Institute of Human Origins at Arizona State University. He is noted for his 1974 discovery of the fossil Lucy, one of the oldest known human ancestors. He also is founder and creator of “Becoming Human” (an Interactive Educational Website) www.becominghuman.org

Larson, Clark, & Spencer. “Essentials of Physical Anthropology: Discovering Our Origins: 2nd
Edition.” Norton, W. W. & Company, Inc.. Print. 2012.

Lovejoy. Owen, C., “The Origin of Man.” Science 23 January 1981: 211 (4480), 341-350.
1981

Wheeler, P. "The evolution of Bipedality and loss of functional body hair in hominids".
Journal of Human Evolution 13: 91. 1984