Colour coded model of 'Lucy' fossil
Lucy — the famous early human fossil unearthed in Ethiopia in the 1970s — could stand just as erect as we can.
This is the conclusion of a researcher from the University of Cambridge who has created the first-ever digital model of the muscles of the ancient hominin for the first time.
Developed from recently published open-source data on the 3.2 million-year-old Australopithecus afarensis skeleton — along with data on bone and muscle structures in modern humans — the 3D reconstruction covered the legs and pelvis.
The modelling of Lucy’s knee extensor muscles indicated that the hominin would have been able to straighten its knee joint just as much as the average person can today.
The findings add to the growing consensus over the last 20 years of research that Lucy was capable of walking fully upright, like we do — rather than in a crouching waddle, like our common ancestor the chimpanzees.
A. afarensis was an early hominin species that lived in East Africa from around 3.9–2.9 million years ago, during the Pliocene epoch.
Shorter than modern humans, these australopithecines had an ape-like face and a relatively small brain — a third the size of modern humans — but were capable of walking on two legs.
Also known as “AL 288–1”, Lucy was unearthed by the American palaeoanthropologist Donald Johanson and graduate student Tom Gray in the November of 1974.
She gets her name from the 1967 Beatles classic, “Lucy in the Sky with Diamonds”, which was playing on the pair’s tape recorder the evening the specimen was discovered.
Lucy is one of the most complete skeletons known to date of any Australopithecus — with 40 percent of her bones having been preserved.
A young adult, Lucy would have stood at more than three feet tall and is estimated to have weighed in at around 62 lbs.
3D model shows lower limb muscles of fossil known as 'Lucy'
The new study was undertaken by Dr Ashleigh Wiseman of the University of Cambridge’s University’s McDonald Institute for Archaeological Research.
She said: “Lucy’s ability to walk upright can only be known by reconstructing the path and space that a muscle occupies within the body.”
In her reconstruction, Dr Wiseman recreated 36 muscles in each of Lucy’s legs — most of which, she noted, were larger in the ancient hominin than in us.
The major muscles in Lucy’s calves and thighs, for example, were more than twice the size of those seen in modern humans, as we have a much higher fat-to-muscle ratio.
In fact, the reconstruction suggests that muscles made up nearly three-quarters of the total mass of Lucy’s thigh, compared to just one-half in modern humans.
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Dr Wiseman added: “We are now the only animal that can stand upright with straight knees. Lucy’s muscles suggest she was as proficient at bipedalism as we are, while possibly also being at home in the trees.
“Lucy likely walked and moved in a way that we do not see in any living species today.”
“Australopithecus afarensis would have roamed areas of open wooded grassland as well as more dense forests in East Asia around three–four million years ago.
“These reconstructions of Lucy’s muscles suggest that she would have been able to exploit both habitats effectively.”
Such reconstructions, the team explained, can help scientists to determine how this human ancestor walked.
Dr Wiseman said: “Muscle reconstructions have already been used to gauge running speeds of a T. rex, for example.
“By applying similar techniques to ancestral humans, we want to reveal the spectrum of physical movement that propelled our evolution — including those capabilities we have lost.”
The full findings of the study were published in the journal Royal Society Open Science.
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