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'Little Foot' fossil of prehistoric ancestor helps pinpoint moment humans split from apes


Researchers from the University of Southern California (USC) have published the results of a cutting-edge study analysing a three million-year-old fossil dubbed Little Foot. The exceptionally well-preserved specimen belongs to the Australopithecus family of hominins – one of the earliest evolutionary branches in the human family tree. Although this peculiar fossil may at first glance resemble a modern-day human, many key differences are at odds with Homo sapiens (wise man).

The California researchers were particularly interested in Little Foot’s shoulders or, more specifically, its collarbones, shoulder blades and joints.

Many of the fossil’s other limbs show human-like features that allowed it to walk upright.

But the shoulders are distinctly ape-like, which sheds new light on how these human ancestors carried themselves around.

An analysis of Little Foot’s bones shows the Australopithecus was well-adapted to life in the canopy – climbing, suspending and shimmying up and down trees.

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This is in stark contrast to the sort of shoulders that made throwing speers an easier task.

According to Kristian J Carlson, the study’s lead author and associate professor of clinical integrative anatomical sciences at the Keck School of Medicine, this is some of the best evidence to date of how our ancestors used their arms more than three million years ago.

He said: “Little Foot is the Rosetta stone for early human ancestors.

“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.”

The discovery sheds new light on our split from apes, as it shows humans and apes shared skeletal similarities for much longer than previously thought.

Professor Carlson said: “We see incontrovertible evidence in Little Foot that the arm of our ancestors at 3.67 million years ago was still being used to bear substantial weight during arboreal movements in trees for climbing or hanging beneath branches.

“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 seven million to eight million years ago.”

For instance, Little Foot’s collarbone has an S-shaped curve, which is typically found in apes.

The shoulder joint also sits at a sloping angle that would make hanging from branches an easier job.

Various species of the Australopithecus are believed to have existed in Africa during the Late Pliocene and Early Pleistocene, until their extinction about 1.4 million years ago.

According to the Smithsonian National Museum of Natural History, scientists have uncovered more than 300 Australopithecus fossils, making it one of the best-known and studied human ancestor.

The most famous of Australopithecus’ discovered was Lucy, found in Ethiopia in 1974.

The USC-led study was carried out with researchers from the University of Wisconsin, the University of Liverpool and the University of the Witwatersrand in South Africa.


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