Report Suggests Walked Like A Human But Climbed Like an Ape

Life reconstruction of Australopithecus sediba. (Elisabeth Daynes/S. Entressangle)
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Life reconstruction of Australopithecus sediba. (Elisabeth Daynes/S. Entressangle)

Highlights

  • Humans became fully bipedal around 2 million years ago, but there were several milestones along the way to get through.
  • The monkey skeletal system has to be extensively reoriented from the foot to the knee joints to the spine to obtain our tall stance.

The characteristic, which researchers use to distinguish hominins from other apes, represents a defining step along the convoluted evolutionary routes to becoming human. Even though the reason why it happened is still a mystery. Humans became fully bipedal around 2 million years ago, but there were several milestones along the way to get through. Some of these milestones have yet to be discovered in our fossil records, but a new study examining the remains of a female Australopithecus dubbed Issa has discovered another story.

paleoanthropologist Lee Berger from the University of the Witwatersrand, South Africa explained that Issa had a human-like walk but could climb like an ape.

The monkey skeletal system has to be extensively reoriented from the foot to the knee joints to the spine to obtain our tall stance. Unlike monkeys and other primates, the lower section of the human spine curves inwards. This characteristic curve, known as lordosis, aids humans in bearing the weight of our soaring upper torso. Adult female Australopithecus sediba fossils dating back 2 million years were discovered in Malapa, South Africa, in 2008. Because of the missing components, it was unclear whether she had an ancestral straight spine or a recent curvature.

The very flexible foot joint, which is good for vertical climbing, and the bone structure of Issa's fingers imply she was well suited to arboreal living in the trees that shows orangutans share this characteristic. Issa's diet, like that of savannah chimps, was likely heavy in fruit and leaves, implying that he lived an arboreal existence. The angle at which her femur joins to her knee joint, on the other hand, suggests she was able to stand erect.

In 2015, two more lower spine vertebrae fossils were discovered that matched the rest of Issa's bones completely. Reconstructions based on micro-CT scans of the fossils have just revealed that her species had a curved lower spine, indicating that she was bipedal at least in part.

This, combined with evidence from other fossil vertebrae discovered along Issa's most recent fragments, implies she and her kin had a form between between current humans and giant apes. They have lordosis, but their vertebrae have lengthy costal processes, which let muscles to attach to them for more vigorous climbing.

Issa's hands have previously been examined and found to have intermediate traits between apes and humans. As a result, studying the evolution of the lower back may aid us in learning how to avoid injuries and maintain a healthy back.

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