The evolution of bipedalism approximately four million years ago[1] has led to significant changes in the anatomy of Homo sapiens. Bipedalism is a form of Terrestrial locomotion where an organism moves by means of its two rear limbs Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The morphological alterations to the human skeleton that have occurred since the first bipedal hominid include changes in foot bone arrangement and size, hip size and shape, knee size, leg length, and vertebral column shape and orientation. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism The human skeleton consists of both fused and individual Bones supported and supplemented by Ligaments Tendons Muscles and Cartilage The foot is an Anatomical structure found in many Animals It is the terminal portion of a limb which bears weight and allows Locomotion. The knee is the lower extremity Joint connecting the Femur, Patella, and the Tibia. In common usage the human leg is the lower limb of the Body, extending from the Hip to the Ankle, and including the Thigh, the In Human anatomy, the vertebral column ( backbone or spine) is a column of 34 Vertebrae the Sacrum, Intervertebral
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Foot
The human foot has been redesigned to act as a platform to support the entire weight of the body, rather than acting as a grasping structure, as it did in early hominids. The foot is an Anatomical structure found in many Animals It is the terminal portion of a limb which bears weight and allows Locomotion. The foot is an Anatomical structure found in many Animals It is the terminal portion of a limb which bears weight and allows Locomotion. In the Physical sciences weight is a Measurement of the gravitational Force acting on an object A hominid is any member of the biological family Hominidae (the "great apes" including the extinct and extant Humans Chimpanzees Humans therefore have smaller toes than their bipedal ancestors. This includes a non-opposable hallux, which is relocated in line with the other toes. The hallux, commonly referred to as the big toe (also as great toe or thumb toe) even though it's not actually the biggest toe on the foot of some [2] Moreover, humans have a foot arch rather than flat feet. The arches of the foot are formed by the Tarsal and Metatarsal bones and strengthened by Ligaments and Tendons, allow the foot to support the [2] When non-human hominids walk upright, weight is transmitted from the heel, along the outside of the foot, and then through the middle toes. The heel is the prominence at the posterior end of the Foot. It is based on the projection of one Bone, the Calcaneus, behind the articulation of the Conversely, a human foot transmits weight from the heel, along the outside of the foot, across the ball of the foot, and finally through the big toe; this transference of weight contributes to energy conservation during locomotion. The ball of the foot is where the Toes join with the rest of the foot In Physics, the law of conservation of energy states that the total amount of Energy in an isolated system remains constant and cannot be created although it may Terrestrial locomotion has Evolved as Animals adapted from aquatic to terrestrial environments [1]
Hip
Modern human hip joints are larger than quadrupedal ancestral species to better support the greater amount of body weight passing through them,[2] as well as a shorter, broader shape. A joint is the location at which two or more Bones make contact Quadrupedalism (from Latin meaning "four legs" is a form of land animal locomotion using four legs. A group of organisms is said to have common descent if they have a common Ancestor. This alteration in shape brought the vertebral column closer to the hip joint, providing a stable base for support of the trunk while walking upright. In Human anatomy, the vertebral column ( backbone or spine) is a column of 34 Vertebrae the Sacrum, Intervertebral [3] Also, because bipedal walking requires humans to balance on a relatively unstable ball and socket joint the placement of the vertebral column closer to the hip joint allows humans to invest less muscular effort to balance. A ball and socket joint ( enarthrosis, spheroidal joint) is a Joint in which the distal bone is capable of motion around an indefinite number of axes In Biomechanics, balance is an ability to maintain the Center of gravity of a body within the Base of support with minimal Postural sway. [2] The shape change of the hip may have led to the decrease in the degree of hip extension, an energy efficient adaptation. Extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint [1]
Knee
Human knee joints are enlarged for the same reason as the hip – to better support an increased amount of body weight. The knee is the lower extremity Joint connecting the Femur, Patella, and the Tibia. The knee is the lower extremity Joint connecting the Femur, Patella, and the Tibia. [2] The degree of knee extension (the angle between the thigh and shank in a walking cycle) has decreased. The changing pattern of the knee joint angle of humans shows a small extension peak, called the “double knee action,” in the midstance phase. Double knee action decreases energy lost by vertical movement of the center of gravity. [1] Humans walk with their knees kept straight and the thighs bent inward so that the knees are almost directly under the body, rather than out to the side, as is the case in ancestral hominids. In humans the thigh is the area between the Pelvis and the Knee. This type of gait also increases balance. [2]
Leg
An increase in leg length since the evolution of bipedalism changed how leg muscles functioned in upright gait. In common usage the human leg is the lower limb of the Body, extending from the Hip to the Ankle, and including the Thigh, the In humans, the push in walking comes from the leg muscles acting at the ankle. A longer leg allows the use of the natural swing of the limb so that when walking, humans do not need to use muscle to swing the other leg forward for the next step. [2]
Vertebral column
The vertebral column of humans takes a forward bend in the lumbar (lower) region and a backward bend in the thoracic (upper) region. In Human anatomy, the vertebral column ( backbone or spine) is a column of 34 Vertebrae the Sacrum, Intervertebral Without the lumbar curve, the vertebral column would always lean forward, a position that requires much more muscular effort for bipedal animals. With a forward bend, humans use less muscular effort to stand and walk upright. [3] Together, the lumbar and thoracic curves bring the body's center of gravity directly over the feet. [2] Also, the degree of body erection (the angle of body incline to a vertical line in a walking cycle) is significantly smaller[1] to conserve energy.
Significance
Even with much anatomical modification, some features of the human skeleton remain poorly adapted to bipedalism, leading to negative implications prevalent in humans today. The lower back and knee joints are plagued by osteological malfunction, with lower back pain among the leading causes of lost working days. [4] These problems resulted because human joints are forced to support weight for which they were not originally designed to, now that the body’s full weight is borne on two legs rather than four. In fact, arthritis has been a problem since hominids became bipedal. Scientists have discovered instances of vertebral arthritis in prehistoric hunter-gatherers; arthritis is not merely pathology of modern lifestyles. [4] Physical design constraints have made it difficult to modify the joints in a way that could maintain full stability while being not being so large as to impede locomotion. [2]
References
- ^ a b c d e Kondō, Shirō (1985). Primate morphophysiology, locomotor analyses, and human bipedalism. Tokyo: University of Tokyo Press. ISBN 4-13-066093-4.
- ^ a b c d e f g h i Aiello,Leslie and Christopher Dean (1990). An Introduction to Human Evolutionary Anatomy. Oxford: Elsevier Academic Press.
- ^ a b Wang, W. ; Crompton, R. H. ; Carey, T. S. ; Günther, M. M. ; Li, Y. ; Savage, R. ; Sellers, W. I. (2004). "Comparison of inverse-dynamics musculo-skeletal models of AL 288-1 Australopithecus afarensis and KNM-WT 15000 Homo ergaster to modern humans, with implications for the evolution of bipedalism". Journal of Human Evolution 47 (6): 453-478.
- ^ a b Jacob C. Koella; Stearns, Stephen K. (2008). Evolution in Health and Disease. Oxford University Press, USA. ISBN 0-19-920746-1.
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