High-tech analysis of the shoulder assembly of ‘Little Foot’, an Australopithecus that lived more than 3 million years ago, opens a window to the crucial period when our human ancestors diverged from apes.

A clue to interpreting the human evolutionary tree

Scientists at the Keck School of Medicine of USC examined the upper body of the famed fossil “Little Foot”, and may have found confirmation of how our human ancestors used their arms, Science Daily reported.

The Little Foot fossil is a rare specimen because it is a near-complete skeleton of an Australopithecus individual much older than most other human ancestors. The creature was called “Little Foot” because the first bones discovered by scientists consisted of a few small foot bones. The remains were found in a cave in South Africa in the 1990s, and researchers spent years excavating it from its rock encasement.

The Little Foot fossil proved to be the best evidence of how human ancestors used their arms more than 3 million years ago as the shoulder components were clearly apelike. “When we compare the shoulder assembly with living humans and apes, it shows that Little Foot’s shoulder was probably a good model of the shoulder of the common ancestor of humans and other African apes like chimpanzees and gorillas,” said Kristian J. Carlson, lead author of the study and associate professor of clinical integrative anatomical sciences at the Keck School of Medicine.

The apelike characteristics will likely attract considerable intrigue among scientists

Journal of Human Evolution devoted a special issue to Little Foot research conducted by a global research group. The scientists had to look at other parts of the creature’s skeleton and examine each part in coordination with others.

The USC-led research team focused on examining The Little Foot’s shoulder assemblies. The researchers compared the creature’s shoulder parts to apes, hominins and humans. “In fact, based on comparisons with living humans and apes, we propose that the shoulder morphology and function of Little Foot is a good model for that of the common ancestor of humans and chimpanzees 7 million to 8 million years ago,” said Carlson.

The scientists were able to achieve remarkably clear images of the fossils. The researchers concluded that Little Foot was a creature adapted to living in trees. The study proved that the arm of our ancestors at 3.67 million years ago was still being used to bear substantial weight during movements in trees for climbing or hanging beneath branches.

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