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Orthograde is a term derived from (Greek ὀρθός, ''orthos'' ("right", "true", "straight") + Latin ''gradi'' (to walk)] that describes a manner of walking which is upright, with the independent motion of limbs. Both New and Old World monkeys are primarily arboreal, and they have a tendency to walk with their limbs swinging in parallel to one another. This differs from the manner of walking demonstrated by the apes. Chimpanzees, gorillas, and humans, when walking, walk upright, and their limbs swing in opposition to one another for balance (unlike monkeys, apes lack a tail to use for balance). Disadvantages related to upright walking do exist for primates, since their primary mode of locomotion is quadrupedalism. This upright locomotion is called "orthograde posture". Orthograde posture in humans was made possible through millions of years of evolution. In order to walk upright with maximum efficiency, the skull, spine, pelvis, lower limbs, and feet all underwent evolutionary changes. ==Evolutionary Significance == The first definitive evidence of habitual orthograde posture in human evolutionary lineage begins with Ardipithecus ramidus kadabba, dating between 5.2 to 5.8 million years ago. The skeletal remains of this hominid exhibit a mosaic of morphological characteristics that would have been both adapted to an arboreal environment and walking upright terrestrially. The earliest evidence of a hominid exhibiting skeletal morphology capable of achieving orthograde posture dates to 9.5 million years ago, with the discovery of a Miocene ape, Dryopithecus in Can Llobateres, Spain. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Orthograde posture」の詳細全文を読む スポンサード リンク
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