3.2 million-year-old human ancestor ‘Lucy’ had massive leg muscles to stand up straight and climb trees

Published

2 years ago

June 14, 2023

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A sculptor’s rendering of the hominid Australopithecus afarensis in an exhibition that included the 3.2 million-year-old fossilized remains of “Lucy.” (Image credit: Dave Einsel via Getty Images)

Our 3.2 million-year-old ancestor “Lucy” could stand and walk upright just like modern humans do, new 3D muscle modeling reveals.

The finding bolsters a growing consensus among researchers that Australopithecus afarensis — the extinct species to which Lucy belongs — walked erect rather than with a chimpanzee-like, crouching waddle.

The hominin’s reconstructed pelvis and leg muscles also suggest that she could climb trees, meaning the species likely thrived in both forest and grassland habitats in East Africa 3 million to 4 million years ago.

“Lucy’s muscles suggest that she was as proficient at bipedalism as we are, while possibly also being at home in the trees,” Ashleigh Wiseman, a research associate at the University of Cambridge’s McDonald Institute for Archaeological Research in the U.K. who conducted the modeling study, said in a statement. “She would have been able to exploit both habitats effectively.”

Lucy’s fossils are the best-preserved Australopithecus remains ever unearthed, with 40% of her skeleton recovered from Ethiopia’s Hadar region in the mid-1970s. Her bones indicate that she stood 3.4 feet (1 meter) tall and weighed between 29 and 93 pounds (13 to 42 kilograms). Her discovery pointed to the possibility that human ancestors could walk upright long before they evolved bigger brains.

Related: Human ancestor ‘Lucy’ gets a new face in stunning reconstruction

While soft tissue is not visible in the fossil record, scientists can piece together what the extinct species’ muscles may have looked like by using modern humans (Homo sapiens) as analogs. Our bone structure and muscle attachments can inform how muscles were layered on Lucy’s skeleton.

In a study published Wednesday (June 14) in the journal Royal Society Open Science, Wiseman used a digital modeling approach to recreate 36 muscles in each of Lucy’s legs.

Wiseman used scans from modern humans as a reference to layer muscles onto a virtual model of Lucy’s skeleton. (Image credit: Dr Ashleigh Wiseman)

The reconstruction shows that Lucy could straighten her knee joints and extend her hips in a similar way to modern humans, suggesting that the species could stand and walk upright.

The model also reveals the proportions of fat and muscle in Lucy’s legs, showing they were far more muscular than a modern human’s and similar in composition to a bonobo’s (Pan paniscus). While a human thigh is about 50% muscle, Lucy’s were likely 74% and less fatty. Some of her calf and thigh muscles occupied twice as much space in her legs as they do in human legs today.

Lucy’s knees demonstrated a wider range of motion in the extension-flexion axis than a human’s. This, combined with her muscle mass, suggests that A. afarensis could utilize a wide range of habitats, from dense forests to grassy savannas. This type of locomotion is not seen in any modern animal, Wiseman said. “Lucy likely walked and moved in a way that we do not see in any living species today.”

While the finding is based on an incomplete skeleton, and it remains unknown how often A. afarensis adopted an upright posture, the results of the analysis support the current consensus of Lucy’s physical abilities.

The model revealed that Lucy’s legs were far more muscular than a modern human’s and more similar in composition to a bonobo’s. (Image credit: Dr Ashleigh Wiseman) RELATED STORIES—New fossil reveals face of oldest known ‘Lucy’ relative

—Mystery ancestor mated with ancient humans. And its ‘nested’ DNA was just found.

—Newly named human species may be the direct ancestor of modern humans

“The current paper is not a game changer in our thinking,” said Fred Spoor, a professor and researcher at the Natural History Museum in the U.K., who was not involved in the research.

However, reconstructing the muscles is a novel and exciting method to confirm bipedalism, Spoor told Live Science in an email. “This approach is certainly promising,” he said. “It goes beyond the sometimes somewhat simplistic interpretations of paleontologists when it comes to inferring what movements and locomotor pattern characterized an extinct species.”

Muscle modeling has already helped researchers gauge the walking speed of a Tyrannosaurus rex and could shed light on similar traits in archaic humans. “By applying similar techniques to ancestral humans, we want to reveal the spectrum of physical movement that propelled our evolution,” Wiseman said.

Politics

Met Police chief ‘frustrated’ at planned protest to support Palestine Action – as government moves to ban the group

Published

3 hours ago

June 23, 2025

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Met Police chief 'frustrated' at planned protest to support Palestine Action - as government moves to ban the group

Metropolitan Police Commissioner Sir Mark Rowley says he is “shocked and frustrated” at a planned protest in support of Palestine Action.

The demonstration, due to take place in Westminster later, comes as the government moves to ban the group under anti-terror laws.

Activists from Palestine Action hit the headlines last week after targeting RAF Brize Norton and damaging two military aircraft in a significant security breach.

Home Secretary Yvette Cooper will update MPs on the move to proscribe the organisation, which would make it a criminal offence to belong to or support it.

Sir Mark said that – until this happens – the force has “no power in law” to prevent the protest from taking place, but lawbreakers will be “dealt with robustly”.

He added: “This is an organised extremist criminal group, whose proscription as terrorists is being actively considered.

“Members are alleged to have caused millions of pounds of criminal damage, assaulted a police officer with a sledgehammer and last week claimed responsibility for breaking into an airbase and damaging aircraft.

“Multiple members of the group are awaiting trial accused of serious offences.”

He added that – while the right to protest is essential – “actions in support of such a group go beyond what most would see as a legitimate protest”.

Over the weekend, Business Secretary Jonathan Reynolds said he could not rule out the possibility of a foreign power being behind Palestine Action.

Any move to proscribe the group must be debated and approved by MPs and peers.

Speaking to Sunday Morning With Trevor Phillips on Sky News, former justice secretary Lord Charlie Falconer suggested that vandalising aircraft would not solely provide legal justification for such a move.

Lord Falconer said: “I am not aware of what Palestine Action has done beyond the painting of things on the planes in Brize Norton, they may have done other things I didn’t know.

“But generally, that sort of demonstration wouldn’t justify proscription so there must be something else that I don’t know about.”

Palestine Action has staged a series of protests in recent months – spraying the offices of Allianz Insurance in London, and vandalising Donald Trump’s golf course in Ayrshire.

US

Regime change: Is Trump about to ‘Make Iran Great Again’?

Published

3 hours ago

June 23, 2025

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Regime change: Is Trump about to 'Make Iran Great Again'?

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The US bombs Iran. Three nuclear sites heavily hit. Cue condemnation from Iran – and promises of retribution.

As the Iranian foreign minister heads to Moscow to meet Vladimir Putin and discuss what to do next, we ask: what has happened, why did the Trump administration decide to take action, what’s the response domestically and internationally – and what on earth could happen next.

If you’ve got a question you’d like the Trump100 team to answer, you can email it to trump100@sky.uk.

Don’t forget, you can also watch all episodes on our YouTube channel.

US

The Americans want the attack on Iran’s nuclear sites to be a ‘one-and-done’

Published

3 hours ago

June 23, 2025

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The Americans want the attack on Iran's nuclear sites to be a 'one-and-done'

The Pentagon briefing was big on what happened but short on detail of what happens next.

Neither defence secretary Pete Hegseth nor General Dan “Raisin” Caine, chair of the joint chiefs of staff, can answer that.

Mr Hegseth called the bombing an “incredible and overwhelming success” with “focused and clear” instructions from President Trump.

The focus now is on what follows and that’s not so clear.

The briefing laid out the details of the military deception plan behind Operation Midnight Hammer.

B-2 stealth aircraft were flown west towards the Pacific on Saturday as a decoy, while the B-2s with bunker-busting bombs on board flew east towards Iran.

Israel-Iran live: World continues to react to US attack on nuclear facilities

Mr Hegseth called it a plan that took months and weeks of positioning and came down, in the end, to “precision, misdirection and operational security”.

Gen Caine, Mr Trump’s top military man, offered a measured assessment. While Mr Trump had spoken of Iran’s nuclear sites being “obliterated”, Gen Caine revised that downwards when he spoke of “extremely severe damage”.

Full battle damage assessment will reveal the complete picture – only then can the mission’s success be measured in full, mindful that Iran had shifted at least some of its enriched uranium in the days before the strike.

On the politics of it, Mr Hegseth said this wasn’t about regime change in Iran. It might offer precious little reassurance to Tehran, particularly as he also said part of the operation was to defend Israel and the ongoing defence of Israel.

If the US is tethered to Israel’s interests to the extent of an unprecedented attack on Iran, where does its influence end?

Israeli Prime Minister Benjamin Netanyahu appeared almost giddy in response to the US attack. He is a PM strengthened by Mr Trump’s spectacular response to his rhetoric around Iran.

Suspicions weren’t softened around Netanyahu’s influence over Mr Trump when Mr Hegseth was asked about the basis for the attack. He has long lobbied the US president on Iran being close to building a nuclear bomb, contrary to American intelligence which indicates otherwise.

Mr Hegseth was asked what was the new intelligence, was it American or from other countries? He avoided a direct answer, saying only that Mr Trump had looked at all the intelligence information and concluded Iran was a threat.

There were a number of questions about what comes next, with an assortment of non-answers in response from Mr Hegseth.

A consistent line was that the US wanted Iran to negotiate peace, coupled with the threat of further aggression if it doesn’t.

The US defence secretary said Washington was in touch with Tehran privately and publicly, giving it every opportunity to come to the table, every opportunity for peace.

He made the point that America hadn’t targeted Iranian troops or civilians – clearly, a measure by the US to limit response and leave open a door.

The Americans want this attack to have been a “one-and-done”.

The scenario it’s left with, however, is an Iran talking of a diplomatic door closed and sending its foreign minister travelling to Moscow to meet Vladimir Putin.

Iran is wounded, no doubt. Combined attacks have left it degraded and, without a network of support in the Middle East, its ability to strike back is limited. For now, if not necessarily forever.

Donald Trump clearly enjoyed the sugar rush of military success but he will be wary of the come-down and all of its uncertainties.

In circumstances with world implications, he won’t be alone.