bipedalism

Examples of bipedalism in the following topics:

• Comparison of Female and Male Pelves

  • The female pelvis has evolved to its maximum width for childbirth and the male pelvis has been optimized for bipedal locomotion.
  • In contrast, human male pelves are not constrained by the need to give birth and therefore are optimized for bipedal locomotion.

• Pelvic Structure and Childbearing

  • These changes in the pelvis enable bipedal locomotion, or upright walking.
  • Thus, the female pelvis has evolved to be as wide as possible, to make childbirth easier, without becoming so wide as to make bipedal locomotion too inefficient .
  • Male pelves are not constrained by the issue of childbirth, and thus are narrower and more optimal for bipedal locomotion.

• Early Homo

  • Though the intelligence of these early hominins was probably no more sophisticated than that of modern chimpanzees, the bipedal (two-legged) stature is the key evidence that distinguishes the group from previous primates, who were quadrupeds (four-legged).
  • Before the discovery of pelvic material of australopithecines, scientists believed that bigger brains preceded bipedalism.
  • However, this was shown to be incorrect: bipedality long antedated dramatic brain increases in hominins.

• Early Human Evolution

  • Hominins, who were bipedal in comparison to the other hominoids who were primarily quadrupedal, includes those groups that probably gave rise to our species: Australopithecus africanus, Homo habilis, and Homo erectus, along with non-ancestral groups such as Australopithecus boisei.
  • In the intervening years, several more specimens of Ardipithecus, including a new species, Ardipithecus kadabba (5.6 million years ago), demonstrated that they were bipedal.
  • Again, the status of this genus as a human ancestor is uncertain, but, given that it was bipedal, it was a hominin.

• The Evolution of Humans

  • These humans may have been bipedal, meaning they walked upright on two legs.
  • Bipedalism, or walking upright, is one of the main human evolutionary adaptations.
  • Advantages to be found in bipedalism include the freedom of the hands for labor and less physically taxing movement.
  • Bipedalism resulted in skeletal changes to the legs, knee and ankle joints, spinal vertebrae, toes, and arms.

• Early Hominins

  • A key feature that Australopithecus had in common with modern humans was bipedalism, although it is likely that Australopithecus also spent time in trees.
  • It had a slender build and was bipedal, but had robust arm bones and, as with other early hominids, may have spent significant time in trees.

• Primates

  • The first major morphological change was the evolution of a bipedal locomotor adaptation from an arboreal or semi-arboreal one (upright walking capabilities), with all its attendant adaptations (a valgus knee, long legs relative to the arms, reduced upper-body strength).
  • In body size and cranial capacity, australopithecines were similar to chimpanzees, but they were ancestral to humans because they were bipedal.

• Homo sapiens

  • Humans are distinguished from other primates by their bipedal locomotion and by their relatively larger brain with its particularly well-developed neocortex, prefrontal cortex, and temporal lobes, which enable high levels of abstract reasoning, language, problem solving, and culture through social learning.

• Sociobiology

  • A sociobiological explanation of humans running might argue that human beings are good at running because our bodies have evolved to run bipedally.

• Animal Body Planes and Cavities

  • Shown are the planes of a quadruped goat and a bipedal human.