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Ardipithecus ramidus

his species was a facultative biped and stood upright on the ground but could move on all four limbs in trees. Features of the anatomy are extremely primitive.


  • about 300-350cc, similar in size to modern female chimpanzees and bonobos

Body size and shape

  • similar in size to modern chimpanzees. The most complete specimen, a female, stood about 120cm tall
  • males were only slightly larger than females
  • the body shape was more ape-like than humans, but differed from living African apes in a number of significant features


  • mix of primitive and derived features suggest this species was able to walk upright on the ground yet efficiently climb trees
  • long powerful arms that were not used for weight-bearing or knuckle-walking as with quadrupedal apes
  • bones in the wrist (particularly the midcarpal joint) provided flexibility and the palm bones were short. These features suggest this species was not a knuckle-walker and that the palms could support the body weight when moving along branches
  • finger bones were long and curving, both features useful for grasping branches
  • upper and lower legs bones (femur and tibia) have features consistent with bipedalism
  • feet were relatively flat and lacked arches, indicating this species could probably not walk or run long distances
  • they had grasping abducted toe characteristic of gorillas and chimps
  • the foot was more rigid than chimpanzees with the bases of the four toe bones oriented to reinforce the forefoot when pushing off. Chimps have a highly flexible midfoot that improves their ability to grasp and climb but are less effective for propulsion when walking on ground