Friday, February 11, 2011

Fossil Foot Shows Bipedalism

I recently did a post on the taxonomy of the African Wolf, (formally the Golden Jackal) where I talked about how as scientists gather more information and make new discoveries, they revise their theories. There is an interesting article in the BBC today about a new fossil find that has helped scientists fine-tune their theories about how the human-like species Australopithecus afarensis moved. This fossil is a great example of scientists learning from new discoveries.

A. afarensis is the species made famous by the "Lucy" skeleton discovered by Donald Johanson in 1974 in the Hadar region of Ethiopia. Previously, researchers had fossilized remains of the spine, hips, and knees of A. afarensis and developed a theory about how the species moved based on those fossilized remains. Researchers believed that A. afarensis was bipedial (walked upright on two feet, like humans).

Until recently the theory that A. afarensis was bipedal lacked certainty because while researchers were confident that the spine, hips, and knees supported the bipedal theory, A. afarensis foot bones had never been found. Without the foot bones, the researchers could not confirm just how the species walked, or how much it relied on walking.

Source: Anthropology.net
Now a research team from Arizona State University (including Donald Johanson) has found a fossilized fourth metatarsal bone from A. afarensis, in the same Hadar region of Ethiopia where the Lucy skeleton was found. The metatarsal is a foot bone that provides evidence of how the foot was arched. Understanding how the foot was arched goes a long way to explaining how the creatures would have walked, confirming the researchers long-standing bipedal theory.

In addition to supporting the bipedal theory, the foot bone and the fact that it is arched shows that A. afarensis would have been able to move quickly and easily on two feet. The arches in feet serve to help the foot move the body forward, and act as a "shock absorber" each time the feet pound the ground. The fact that A. afarensis had arched feet makes it even more similar to the anatomy of modern humans showing an important link in the evolution of upright walking.

I think this is such a great example of how science changes and revises itself because it showcases how very specific details and pieces of information can shape entire theories. In this case, finding the fossilized metatarsal bone confirmed a theory and also shed more light on how the species would have walked, providing additional information. It is a good example of science changing - and getting better.

4 comments:

  1. How fascinating that finding one small bone - a fourth metatarsal - has changed science's understanding of how an entire species moved. I don't remember - was A. afarensis a direct ancestor of H. sapiens sapiens? I also wonder what implications this discovery will have for theories of A. afarensis' social interactions or use of tools (in any?). Fascinating!

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