Human Evolution and Its Link to Bipedalism Essay

Excerpt from Essay :

Bipedalism – Human Evolution


Human evolution takes into account the biotic as well as cultural development of humans. Human philosophies of the manner in which evolution of man came to be is ascertained by beliefs that have been espoused by scientists and societies dating as back as 400 decades ago. Human species, scientifically referred to as homo sapiens has extremely evolved in the last number of billion years. There have been numerous scientific developments and dissimilar events that gave rise to the ultimate evolution of mankind. One of the key changes that have taken place through evolution is bipedalism, which encompasses alterations in body features, for instance, increase in brain capacity. In particular, bipedalism is a kind of locomotion conducted on two feet and is the one aspect that that distinguishes humans from other kinds of hominoids (Ishida et al., 2006). The purpose of this paper is to examine and lay emphasis on the origination of bipedalism in terms of the different theories predominant regarding it and the manner in which it has given rise to numerous developments in the origin story of human being. In addition, the paper will undertake an analysis of the bodily adaptations that took place so as to endure bipedalism and the consequences this new means of locomotion came along with it.

Savannah and Mosaic Theories

The very first endeavor of trying to elucidate the aspect of evolution was by Darwin through the Savannah theory. Basically, this theory made the argument that an ape living on a tree starting subsisting in the open savannah for lengthier periods as the forest home started to decline owing to change in climate. As a result, the ape progressively developed and adapted a bipedal posture so as to permit its forelimbs to be utilized for exercising primitive weapons like stones as well as sticks. Nonetheless, taking into account that in the end it was acknowledged that all of the attributes aforementioned, as well as bipedalism, could have been chosen against the savannah ecology, a great of the proponents of this theory lacked merit. Moreover, there continues to be primates that presently live in that environment and they lack such attributes. Another theory that lacked merit in this regard at the time was the Mosaic theory. The argument in this model was the ape aforementioned started subsisting in a mixed environment consisting of forest, swamp and savannah. The downside to it is that failed to offer any convincing reason for the evolution of the ape into a bipedal form of locomotion (Kraak, 1991).

Postural Feeding Theory

Chimpanzee biology together with australopithecine functional morphology give the suggestion of a mutual land-dwelling and arboreal postural feeding origin for bipedalism amongst hominids. In accordance to Hunt (1996), bipedalism amongst chimpanzees usually appears whilst feeding fruits of trees in the forest. This is more often than not done through reaching up to pluck the fruits while erect or through attaining poise and balance in tree branches clutching on in a semi-arm dangling position. Some anatomical features of Australopithecus mutual with apes are modified for decreasing muscle action and physical exhaustion in the course of hanging by the arm. Additional features of apes amongst hominids, comprising for instance, assemblages and metacarpals that are curved, are adaptations to both upper limb hanging and erect climbing. The anatomy of the australopithecines especially with respect to the hind limb and hip regions, is suggestive of characteristic bipedal locomotion while on the ground. However, when likened to modern human beings, it is imperative to note that their movement was less efficacious and created increased strains in the hip. Taking this into consideration, it is posited that hominid bipedalism might have emanated as feeding position, with arboreal hanging of the arm, bipedalism, and erect climbing as significant means of gathering for food, that was only well ahead developed into an efficacious locomotor adaptation (Hunt, 1996).

This theory is further advanced by Skoyles (2006) who delineates that a novel model of the distinctiveness, nature, and evolution of human bipedalism is shown in the perspective of the etiology of the equilibrium dysequilibrium syndrome disorder. From a biological perspective, human bipedalism is newfangled in numerous noteworthy respects. To begin with, humans are obligate, characteristic and varied in their bipedalism, and they also embrace their body posture spinally vertical in a multi-segmental standing against gravity. Third, they utilize their forelimbs for other purposes aside from locomotion. In addition, human body weight is fully supported by vertical poise and such bipedalism is included with upper body movements that rapidly shift the physique's center of mass. “Due to the situation that humans are obligate erect terrestrial animals, two frameworks - the body- and gravity- defined frameworks - are in constant alignment in the vertical z-axis.” This allows human sense of balance to become accustomed to egocentric body perceptions to become aware of body deviances from the gravitational erect. The argument made is that cortical parts handling the three-dimensional and other intuitions required to permit vertical balance was a significant reason for brain size development of Homo erectus (Skoyles, 2006).

Behavioral Theory

The behavioral theory of the origin of bipedalism was developed by Owen C. Lovejoy. The main position advocated for by this theory is that the social behavior of human beings are precisely what impelled them to become bipedal. To be more specific, Lovejoy lay emphasis on the social behaviors that had an impact on human survival and birth. He further posited that the sexual behaviors of the early man together with his anatomy gave the implication that a monogamous arrangement of reproducing and that this was perceived as a common necessity for the male species. The mannerism of carefully choosing the suitable mates on the basis of their locomotion or the manner in which they walked was further advanced by having the notion that if a male utilized the body’s upper limbs to fetch and bring sustenance to a mate, then the companion perceived this as a significant selection element for the formation of offspring owing to the bipedalism. This is for the reason that it was an indication of a longer lifespan for the offspring and the ability to survive longer. It also indicated that the offspring would likely be more resilient and have a superior rate of procreation as compared to its parents. Therefore, it was necessary for all male species to use two limbs for locomotion in order to secure mates (Kinzey, 1987).

However, the shortcoming of this theory is its argument that hominids had a monogamous arrangement of mating as it is an aspect that is not in line with the sexual dimorphism in the size of hominids. Specifically, with respect to primates that are not human beings, sexual dimorphism with respect to the size of the body is ideally elucidated by sexual selection owing to sexual dissimilarities in procreative potential. It is hard to consent that bigger male size in hominids did not come along with superior difference in male than female procreative achievement and some magnitude of polygyny. Taking this into consideration, it can be argued that Lovejoy’s conceptions regarding dissimilarities in size to decrease competition in food are not completely resounding and definite. It is solely the orangutans and chimpanzees, as the primates that have noticeable magnitude of sexual separation in food utilization. This is largely for the reason that in both of these two non-human primates, sexual dimorphism in terms of the size of the body is in alignment with male procreation competition and mating arrangements that are polygamous (Kinzey, 1987).

Thermoregulatory Structures Theory

This is a theory of the origin of bipedalism developed by P. E. Wheeler. On the basis of this model, bipedalism causes an increase in gaining of heat and facilitating the dispelling of heat. Wheeler’s main argument is that human bipedalism causes a rise in the mean body surface to some extent above the surface of the ground, a posture in which the rapidity of how the wind moves is conductive and the existing temperatures are satisfactory. As a result, the augmented current and tide of wind is turned in increased convective temperature dissipation. According to this theory, bipedalism gives rise to a diminished rate of cooling in evaporation and as a result conserves water in the body. The upright alignment of hominids is also significant in making the most of being directly exposed to sunlight in the course of the day, a period when the energy arising from sunshine is most powerful and forceful (Wheeler, 1991).

A great deal of Wheeler’s deductions emanated from the measurement of body outlines and shapes in the vertical and frontal sides and approximating the same body shapes in Australopithecines. Moreover, he lays emphasis that mammals that have adapted to living in the savannah have a tendency of having a more developed number of features to preclude the overheating of the brain. Bearing in mind that human beings do not possess these features,…

Sources Used in Document:


Hunt, K. D. (1996). The postural feeding hypothesis: an ecological model for the evolution of bipedalism. South African Journal of Science, 92(2), 77-90.

Ishida, H., Tuttle, R., Pickford, M., Ogihara, N., & Nakatsukasa, M. (Eds.). (2006). Human origins and environmental backgrounds. New Jersey: Springer Science & Business Media.

Kinzey, W. G. (Ed.). (1987). Evolution of human behavior: primate models. SUNY Press.

Kraak, S. B. (1991). The answer: the aquatic ape theory and the savannah theory combined. Roede, M., Wind, J., Patrick, J. et al., The Aquatic Ape: Fact or Fiction, 293-296.

Ruxton, G. D., & Wilkinson, D. M. (2011). Avoidance of overheating and selection for both hair loss and bipedality in hominins. Proceedings of the National Academy of Sciences, 108(52), 20965-20969.

Skoyles, J. R. (2006). Human balance, the evolution of bipedalism and dysequilibrium syndrome. Medical hypotheses, 66(6), 1060-1068.

Stanford, C. B. (2006). Arboreal bipedalism in wild chimpanzees: Implications for the evolution of hominid posture and locomotion. American Journal of Physical Anthropology, 129(2), 225-231.

Westergaard, G. C., Kuhn, H. E., & Suomi, S. J. (1998). Bipedal posture and hand preference in humans and other primates. Journal of Comparative Psychology, 112(1), 55.

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