Fossilized ankle bone from human ancestor that lived 4.5 million years ago

Fossilized bones discovered in Africa more than a decade ago may now point to a ‘pivotal’ moment in the timeline of human evolution.

A new analysis on the 4.5 million-year-old partial skeleton of a female hominin has revealed a glimpse into the anatomical details of locomotion in the human ancestor, Ardipithecus ramidus.

And, researchers now say this group may have been more adept at upright walking than previously suspected.

The remains reveal adaptations in bones from the ankle and big toe that support bipedalism, or the ability to walk on two feet, though the experts say their gait was likely far from perfect.

A new analysis on the 4.5 million-year-old partial skeleton of a female hominin has revealed a glimpse into the anatomical details of locomotion in the human ancestor, Ardipithecus ramidus. A fossil talus (a bone in the ankle) is shown

A new analysis on the 4.5 million-year-old partial skeleton of a female hominin has revealed a glimpse into the anatomical details of locomotion in the human ancestor, Ardipithecus ramidus. A fossil talus (a bone in the ankle) is shown

A new analysis on the 4.5 million-year-old partial skeleton of a female hominin has revealed a glimpse into the anatomical details of locomotion in the human ancestor, Ardipithecus ramidus. A fossil talus (a bone in the ankle) is shown

‘Our research shows that while Ardipithecus was a lousy biped, she was somewhat better than we thought before,’ said Scott W. Simpson, PhD, from Case Western Reserve University School of Medicine.

‘The fact that Ardipithecus could both walk upright, albeit imperfectly, and scurry in trees marks it out as a pivotal transitional figure in our human lineage.’

In the new analysis published in the Journal of Human Evolution, the researcher helps to paint a clearer picture of the hip, ankle, and foot function in Ardipithecus locomotion.

While previous research suggested the human ancestor was capable of bipedalism, to what extent largely remained unclear.

Simpson’s team studied fossils found in the Gona Project Study area in Ethiopia, where continuous field research has been underway since 1999 to investigate the human lineage spanning the last 6.3 million years.

In the new analysis published in the Journal of Human Evolution, the researcher helps to paint a clearer picture of the hip, ankle, and foot function in Ardipithecus locomotion.

In the new analysis published in the Journal of Human Evolution, the researcher helps to paint a clearer picture of the hip, ankle, and foot function in Ardipithecus locomotion.

In the new analysis published in the Journal of Human Evolution, the researcher helps to paint a clearer picture of the hip, ankle, and foot function in Ardipithecus (illustrated right) locomotion

The analysis focused on the area of the joints between the arch of the foot and the big toe, revealing how much range Ardipithecus may have had.

Though any cartilage has been lost to time, textures on the surface of the bone show where it once lay.

‘This evidence for cartilage shows that the big toe was used in a more human-like manner to push off,’ Simpson said.

‘It is a foot in transition, one that shows primitive, tree-climbing physical characteristics but one that also features a more human-like use of the foot for upright walking.’

Sites of ancient hominin presence have been found across the globe, beginning in Africa around 2.8 million years ago. These have included stone tools (blue) and fossils (red). The oldest form of stone tools can be traced as far back to Ethiopia

Sites of ancient hominin presence have been found across the globe, beginning in Africa around 2.8 million years ago. These have included stone tools (blue) and fossils (red). The oldest form of stone tools can be traced as far back to Ethiopia

Sites of ancient hominin presence have been found across the globe, beginning in Africa around 2.8 million years ago. These have included stone tools (blue) and fossils (red). The oldest form of stone tools can be traced as far back to Ethiopia

And, much like in humans, the researchers found Ardipithecus’ knees were positioned directly above the ankle in the standing position.

Chimps, on the other hand, are bow-legged, meaning their knees sit ‘outside’ the ankle area.

The new findings on Ardipithecus locomotion helps to further narrow our understanding of the timing and anatomical details of upright walking as it appeared in the human lineage.

WHEN DID HUMAN ANCESTORS FIRST EMERGE?

The timeline of human evolution can be traced back millions of years. Experts estimate that the family tree goes as such:

55 million years ago – First primitive primates evolve

15 million years ago – Hominidae (great apes) evolve from the ancestors of the gibbon

7 million years ago – First gorillas evolve. Later, chimp and human lineages diverge

A recreation of a Neanderthal man is pictured 

A recreation of a Neanderthal man is pictured 

A recreation of a Neanderthal man is pictured 

5.5 million years ago – Ardipithecus, early ‘proto-human’ shares traits with chimps and gorillas

4 million years ago – Ape like early humans, the Australopithecines appeared. They had brains no larger than a chimpanzee’s but other more human like features 

3.9-2.9 million years ago – Australoipithecus afarensis lived in Africa.  

2.7 million years ago – Paranthropus, lived in woods and had massive jaws for chewing  

2.6 million years ago – Hand axes become the first major technological innovation 

2.3 million years ago – Homo habilis first thought to have appeared in Africa

1.85 million years ago – First ‘modern’ hand emerges 

1.8 million years ago – Homo ergaster begins to appear in fossil record 

800,000 years ago – Early humans control fire and create hearths. Brain size increases rapidly

400,000 years ago – Neanderthals first begin to appear and spread across Europe and Asia

300,000 to 200,000 years ago – Homo sapiens – modern humans – appear in Africa

50,000 to 40,000 years ago – Modern humans reach Europe 

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