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Makaloni U. Prescott
Professor: Dr. Teri Potter
ANTH 1020-008
July 19, 2016
Insights into the evolution of human bipedalism from experimental
studies of humans and other primates
One of the features that separate humans from all other primates is the habitual use of a
bipedal gait. This single feature is seen as such a defining characteristic that skeletal
adaptations to bipedalism are used to identify our extinct hominid ancestors (Schmitt).
Scientist over many years have research and experiment analysis into the locomotion of
humans and primates; to improve the understanding of the mechanics in human locomotion
and the evolution of human bipedalism.
Bipedalism has a number of advantages over quadrupedalism. Bipedalism allows for one to
carry items for longer distances such as babies or food. It allows one to move more energy
efficient than quadrupedalism, and allows for foraging and the use of tools as well as protecting
oneself (Early Hominids). Bipedalism has a number of characteristics, which have evolved over
millions of years. The differences exist between Australopithecus, Paranthropus, and Homo.
Both Paranthropus and Australopithecus evolution have noticeable steps because they are
among the earliest hominids recorded to adapt to bipedalism. Most significant changes include
the cranium brain size, lumbar vertebra, sacrum and pelvis, the femur, knee, tibia & talus, arms
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and legs, hands and fingers, feet and toes. Australopithecus were similar to humans below the
neck their heads were significantly different from people today. Their adult brain size was
about 1/3 that of ours today (Early Hominids). In the cranium, the foramen magnum is
perpendicular to the orbital plane and is located inferiorly. Where as in quadruped the foramen
magnum is dorsally placed. The lumbar vertebra has an (S) curve with lumbar lordosis. This
shape helps with maintaining balance, as well as puts the center of gravity closer to the pelvis.
In quadrupedal center of gravity is closer to the torso and the spine has a (C) curve. The sacrum
articulates with the last lumbar vertebra. Included in the sacrum are the shape of the iliac
blades, which are short, wide, curved and mediolaterally located to help support the vertical
trunk (Prost J.H). You see how primates have a diversity of locomotive behaviors. Apes,
Orangutans and Gorillas show a wide range of locomotor habits, including acrobatic armswinging, climbing, knuckle- or fist-walking, which shows bipedal locomotion actions.
In class we learned that most arboreal primates have longer arms than legs, a short
stocky back, long grasping fingers etc. In bipeds their legs are longer than their arms. Primates
that tend to spend most of their time in branches have curved toes and fingers, which limited
the capacity for precision. Primates that are non-arboreal have flat toes and fingers, which
make for more precise hand movements. Laboratory-based studies of primates also suggest
that human bipedalism arose not from a terrestrial ancestor but rather from a climbing,
arboreal forerunner. Experimental data, in conjunction with anatomical data on early human
ancestors, show clearly that a relatively stiff modern human gait and associated physiological
and anatomical adaptations are not primitive retentions from a primate ancestor, but are
instead recently acquired characters of our genus (Schmitt).
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Conclusion - Experimental data collected on humans and nonhuman primates suggest
that early hominid bipedalism evolved in an arboreal, climbing primate. The earliest mode of
bipedalism included many aspects of locomotion seen in modern humans, but probably did not
involve inverted pendulum-like mechanics. This difference in locomotor styles between early
hominids and modern humans appears to be associated with small, gracile and poorly stabilized
hind limbs in our earliest ancestors (Stern and Susman, 1983). Through the articles I read, I
discovered there are various debates and hypotheses as to how and why bipedalism evolved in
humans and possible reasons for the evolution of human bipedalism include freeing the hands
for tool use and carrying and gathering of food. I learned that bipedal specializations are found
in Australopithecus fossils from 4.2-3.9 million years ago.
I learned there are multiple factors and behaviors to understand the evaluation human
bipedal and that other mammals engage in limited, non-locomotor, bipedalism. A number of
animals like rats, raccoons, and beavers will squat on their hind legs to manipulate some
objects but will revert to four limbs when moving. The beaver (bipedally) will move when
transporting wood for their dams, as will the raccoon when holding food. Bears will also fight
(in) a bipedal stance, using their forelegs as weapons. I found various hypothesis and narratives
interesting to read and I conclude The Evolution of Human Bipedalism was a developing and
gradual study.
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Work cited
1) Schmitt, D. "Insights into the evolution of human bipedalism from experimental
studies of humans and other primates." The Journal of experimental biology 206.Pt 9
(2003): 1437.
2) Prost, J. H. (1980), Origin of bipedalism. Am. J. Phys. Anthropol., 52: 175–189. Web.
17 July. 2016. doi: 10.1002/ajpa.1330520204
3) "Early Hominin Evolution: Analysis of Early Hominids." Early Hominin Evolution:
Analysis of Early Hominids. Web. 17 July. 2016.
<http://anthro.palomar.edu/hominid/australo_2.htm>.
4) Stern, J. and Susman, R. (1983). The locomotor anatomy of Australopithecus
afarensis. Am. J. Phys. Anthropol. 60,279 -317
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