Bipedalism, skeletal and soft part changes

Bipedalism, Skeletal and soft part changes

The physical ancestors of man were effective bipedals. This ability to walk upright led to diverse changes in the skeleton. Some of the most important changes would include the curving of the spinal column which is a complete adaptation to bipedalism. This S-shaped spinal column allowed for the weight of the body to be distributed in such a way that it can be borne by the feet. The spinal column of the great apes is not as curved as the human one because these are not bipedal, they still use their hands to support themselves and as such do not need to have this type of spinal column.

The attachment of the spinal column to the skull has also changed in position in relation to that of the great apes in that it has become more narrow, whereas in the gorilla, for example, because of its heavy head needs a wider extension to support the latter. Because of the bipedalism of man the pelvis has changed; it has become shorter and wider and the muscles attached to it have been rearranged. The arms have become shorter than the legs which is an adaptation to complete bipedalism because these are no more used to support the weight of the body. The hands have become precision instruments for manipulation and grasping. We now have an elongated thumb which can rotate freely and which is fully opposable to the other fingers. This indeed allows for precise manipulation of objects.

A knee that locks and an elongated heel bone are adaptations which allows for proper balance in the upright position. The gorilla, for example, has bent knees because basically it still move on all fours. Another adaptation to the upright position is the fact that the foot is no longer grasping thereby keeping all the toes in line for weight sharing. The development of foot arches also help in this weight sharing. Considerable amount of time spent standing has led to the development of thicker shaft of bone. The main soft tissue changes are related to the skin. This, with time has become relatively hairless, the hairs being confined to certain parts of the body. There is considerable variation in the body size and this is more difficult to assess because of racial differences.

The fossil evidence we have has not really given something definitive about the weights, but other evidences suggest that earlier man would have been heavier built more in line with the heavier nature of his activities which is more related to hunting and so on. As man began to use more of the brain, he gradually decreased in size because he began to use what was available in his environment for his purposes, for example, the employment of beasts of burden. Because man no longer engaged himself in the heavier duties having learnt to use animals for this purpose, he did not need to develop all the muscles anymore for these tasks.

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