Evidence Suggests Human Ancestor Walked Upright In Trees

Evidence Suggests Human Ancestor Walked Upright In Trees

Scientists have described an 11.62 million-year-old ape that moved like no other creature on Earth using its human legs and orangutan arms.

A team of scientists from Eberhard Karls University of Tübingen in Germany have presented a new paper about a species of fossilized ape found in Bavaria dating to 11.6 million years ago. Equipped with human-like legs and ape-like arms, it is said to have “clambered” across branches fleeing tree climbing feline predators. And it’s one of us!

Is Polygyny Genetic?

The scientists’ findings are published in the Nov. 7 issue of the journal Nature and perhaps the most interesting and important discovery is the creatures “weird locomotion”, if fact, the weirdest mover and shaker ever seen until now, which informed the researchers that this early human ancestor may have evolved to walk on two legs.

The 11.62-million-year-old Danuvius was discovered in a layer of clay in the municipality of Pforzen in the Swabian district of Ostallgäu and between 2015 to 2018 paleontologists made 37 individual finds of fully preserved arm and leg bones, vertebrae, finger and toe bones which showed similarities to how we move today.

The new study’s lead author, Madelaine Böhme, a paleontologist at the Eberhard Karls University of Tübingen in Germany, described Danuvius as weighing between 37 and 68 lbs. (17 and 31 kilograms) and the researchers found males were larger than females, suggesting polygyny, where the males mated with multiple female mates, according to the paper.

The 21 bones of the most complete partial skeleton of a male Danuvius. (Christoph Jäckle/ Nature)

Rethinking Our Ancient Origins

Since the 1970s many different fossils of ancient ape species have been discovered in both Europe and Africa and based on the available evidence all previous research had “assumed” humans had evolved from a four-legged creature using its palms or soles on the ground as they walked or suspended their bodies from trees, similarly to modern chimpanzees, in the middle to late Miocene epoch about 13 million to 5.3 million years ago.

From this “assumption”, it was believed ape and human lineages began diverging at this time, but this conclusion was based on fossils without intact limb bones which greatly restricted what researchers could deduce regarding our early ancestors’ locomotive habits, movement abilities and restrictions. This, according to a June 2016 Live Science article, was an “assumption” upon which a whole paradigm of research had been built.

Essentially, the new findings further paint the picture on how ancestors of modern great apes evolved to use their arms for movement which according to a report on Live Science is a “key trait” which distinguishes humans from modern great apes including chimpanzees, bonobos, gorillas and orangutans - our closest living relatives. And it is our bipedal posture; upright stance and ability to hold balance and walk on our feet that freed up our hands for tool production, a trait that could arguably be said to have “caused” or created us, as we are today.

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Scampering Made Us What We Are

Unlike us humans, chimpanzees, bonobos and gorillas walk on their knuckles and orangutans on their closed fists, and they are all able to swing effortlessly between trees using their arms in a locomotion method known formally as brachiation. But now, Böhme and her colleagues suggest the “new type of locomotion”, which they dubbed “extended limb clambering,” may be the ancestral form of movement for both modern great apes and humans.

Madelaine Böhme told Live Science that the new species has been named Danuvius guggenmosi. The “Danuvius” part of the name is taken from the Celtic-Roman river god Danuvius and the word “guggenmosi” nods to paleontologist Sigulf Guggenmos, who discovered the site where the fossil was found.

When Danuvius lived, the area was a hot flat landscape with rivers and forests from the edges of the Alps, and belonged to a species called dryopithecines which are ancestors of modern African apes.

The creature’s thick teeth enamel suggests Danuvius ate hard items and the scientists also noted its “slightly elongated” arms compared to other fossil specimens suggesting it hung from trees like is seen in modern great apes and used its arms and legs about equally, the researchers said.

Attempting to answer “why" Danuvius didn't favor either its arms or legs the scientists say perhaps, Danuvius used its long, strong and opposable big toes to “clamber quickly along tree limbs to escape larger cats”.

The full report is published in Nature DOI: 10.1038/s41586-019-1731-0


When our human ancestors first walked tall

This image shows the position of the fourth metatarsal Australopithecus afarensis (AL 333-160) recovered from Hadar, Ethiopia, in a foot skeleton. Credit: Carol Ward/University of Missouri

A fossil foot bone from an early human ancestor, 3.2 million years old, could profoundly change our understanding of human evolution. Discovered in Hadar, Ethiopia, it brings compelling evidence that this hominid, a species called Australopithecus afarensis, may have been the first human ancestor to walk upright. In a recently published paper in Science, a team of anthropologists from the United States and Ethiopia described the recently-found fossil as a fourth metatarsal, or mid-foot bone. It’s the only one ever found for Australopithecus afarensis, and it’s revealed that these ancient hominids had stiff, arched feet, similar to humans, that enabled them to walk like us.

Australopithecus afarensis fossils were first discovered in Ethiopia, in 1974. One of the best known representatives of this species, also found in Hadar, was Lucy. That was the nickname given to several hundred bone pieces that made up about forty per cent of one individual believed to be female. There was great controversy about whether Lucy and her relatives were strictly bipedal or if they had also been tree-climbers, or a bit of both. But the discovery of this mid-foot bone has likely put those questions to rest.

University of Missouri and Arizona State University researchers have found a bone that indicates human ancestors had arches in their feet, a major evolutionary shift for Lucy and her species. Credit: Elizabeth Harmon

One of the team members, Professor Carol Ward, said in a recent press release by the University of Missouri-Columbia,

Now that we know Lucy and her relatives had arches in their feet, this affects much of what we know about them, from where they lived to what they ate and how they avoided predators. The development of arched feet was a fundamental shift toward the human condition, because it meant giving up the ability to use the big toe for grasping branches, signaling that our ancestors had finally abandoned life in the trees in favor of life on the ground.

Arches in the feet are a key component of human-like walking because they absorb shock and also provide a stiff platform so that we can push off from our feet and move forward. People today with ‘flat feet’ who lack arches have a host of joint problems throughout their skeletons. Understanding that the arch appeared very early in our evolution shows that the unique structure of our feet is fundamental to human locomotion. If we can understand what we were designed to do and the natural selection that shaped the human skeleton, we can gain insight into how our skeletons work today. Arches in our feet were just as important for our ancestors as they are for us.

Fossil evidence of a human ancestor that preceded Lucy’s species was Ardipithecus ramidus. This hominid, that lived about 4 million years ago, had powerful grasping legs which included a divergent mobile first toe, a feature seen in tree-dwelling primates that indicated they moved around on all four feet, occasionally walking upright. Previous fossil evidence of Lucy and her species, however, hinted that they were bi-pedal but some scientists thought they could have also been tree-dwellers. Now, with the discovery of this mid-foot bone, the only one known for Australopithecus afarensis, this new evidence strongly suggests that Lucy and her relatives stood and walked upright, perhaps the first human ancestor species to have this critical anatomical human trait.

We can only image what life must have been like for Lucy and her kind. They were small statured, perhaps covered in fur males were just under five feet and weighed under 100 lbs, while females were shorter, about three and a half feet tall and 60 lbs. Their brains were smaller than ours, and they had powerful jaws that enabled them to eat leaves, seed, roots, fruit, nuts and insects. With the discovery of this fossil foot bone, we now know that they had arched feet, much like ours. They were likely the first, in the evolutionary path towards being human, that walked upright through ancient forests and open lands of Ethiopia, foraging for food.

Scientists discovered the 3.2 million-year-old fossil at this site in Hadar, Ethiopia. Photo Credit: Kimberly Congdon


Human ancestor 'Lucy' was a tree climber, new evidence suggests

Since the discovery of the fossil dubbed Lucy 42 years ago this month, paleontologists have debated whether the 3 million-year-old human ancestor spent all of her time walking on the ground or instead combined walking with frequent tree climbing. Now, analysis of special CT scans by scientists from The Johns Hopkins University and the University of Texas at Austin suggests the female hominin spent enough time in the trees that evidence of this behavior is preserved in the internal structure of her bones. A description of the research study appears November 30 in the journal PLOS ONE.

Analysis of the partial fossilized skeleton, the investigators say, shows that Lucy's upper limbs were heavily built, similar to champion tree-climbing chimpanzees, supporting the idea that she spent time climbing and used her arms to pull herself up. In addition, they say, the fact that her foot was better adapted for bipedal locomotion (upright walking) than grasping may mean that climbing placed additional emphasis on Lucy's ability to pull up with her arms and resulted in more heavily built upper limb bones.

Exactly how much time Lucy spent in the trees is difficult to determine, the research team says, but another recent study suggests Lucy died from a fall out of a tall tree. This new study adds to evidence that she may have nested in trees at night to avoid predators, the authors say. An eight-hour slumber would mean she spent one-third of her time up in the trees, and if she also occasionally foraged there, the total percentage of time spent above ground would be even greater.

Lucy, housed in the National Museum of Ethiopia, is a 3.18 million-year-old specimen of Australopithecus afarensis—or southern ape of Afar—and is among the oldest, most complete fossil skeletons ever found of any adult, erect-walking human ancestor. She was discovered in the Afar region of Ethiopia in 1974 by Arizona State University anthropologist Donald Johanson and graduate student Tom Gray. The new study analyzed CT scan images of her bones for clues to how she used her body during her lifetime. Previous studies suggest she weighed less than 65 pounds and was under 4 feet tall.

"We were able to undertake this study thanks to the relative completeness of Lucy's skeleton," says Christopher Ruff, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. "Our analysis required well-preserved upper and lower limb bones from the same individual, something very rare in the fossil record."

The research team first had a look at Lucy's bone structure during her U.S. museum tour in 2008, when the fossil was detoured briefly to the High-Resolution X-Ray Computed Tomography Facility in the University of Texas at Austin Jackson School of Geosciences. For 11 days, John Kappelman, Ph.D., anthropology and geological sciences professor, and geological sciences professor Richard Ketcham, Ph.D., both of the University of Texas at Austin, carefully scanned all of her bones to create a digital archive of more than 35,000 CT slices. High-resolution CT scans were necessary because Lucy is so heavily mineralized that conventional CT is not powerful enough to image the internal structure of her bones.

"We all love Lucy," Ketcham says, "but we had to face the fact that she is a rock. The time for standard medical CT scanning was 3.18 million years ago. This project required a scanner more suited to her current state."

The new study uses CT slices from those 2008 scans to quantify the internal structure of Lucy's right and left humeri (upper arm bones) and left femur (thigh bone).

"Our study is grounded in mechanical engineering theory about how objects can facilitate or resist bending," says Ruff, "but our results are intuitive because they depend on the sorts of things that we experience about objects—including body parts—in everyday life. If, for example, a tube or drinking straw has a thin wall, it bends easily, whereas a thick wall prevents bending. Bones are built similarly."

"It is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced," explains Kappelman. "Tennis players are a nice example: Studies have shown that the cortical bone in the shaft of the racquet arm is more heavily built up than that in the nonracquet arm."

A major issue in the debate over Lucy's tree climbing has been how to interpret skeletal features that might be simply "leftovers" from a more primitive ancestor that had relatively long arms, for example. The advantage of the new study, Ruff says, is that it focused on characteristics that reflect actual behavior during life.

Lucy's scans were compared with CT scans from a large sample of modern humans, who spend the majority of their time walking on two legs on the ground, and with chimpanzees, a species that spends more of its time in the trees and, when on the ground, usually walks on all four limbs.

"Our results show that the upper limbs of chimpanzees are relatively more heavily built because they use their arms for climbing, with the reverse seen in humans, who spend more time walking and have more heavily built lower limbs," says Ruff. "The results for Lucy are convincing and intuitive."

Other comparisons carried out in the study suggest that even when Lucy walked upright, she may have done so less efficiently than modern humans, limiting her ability to walk long distances on the ground, Ruff says. In addition, all of her limb bones were found to be very strong relative to her body size, indicating that she had exceptionally strong muscles, more like those of modern chimpanzees than modern humans. A reduction in muscle power later in human evolution may be linked to better technology that reduced the need for physical exertion and the increased metabolic demands of a larger brain, the researchers say.

"It may seem unique from our perspective that early hominins like Lucy combined walking on the ground on two legs with a significant amount of tree climbing," says Kappelman, "but Lucy didn't know she was "unique"—she moved on the ground and climbed in trees, nesting and foraging there, until her life was likely cut short by a fall—probably out of a tree."


Human Ancestor ‘Lucy’ Was a Tree Climber, New Evidence Suggests

AUSTIN, Texas &mdash Evidence preserved in the internal skeletal structure of the world-famous fossil, Lucy, suggests the ancient human species frequently climbed trees, according to a new analysis by scientists from The Johns Hopkins University and The University of Texas at Austin.

Since Lucy&rsquos discovery in Ethiopia 42 years ago this month by Arizona State University anthropologist Donald Johanson and graduate student Tom Gray, paleontologists have debated whether the 3.18 million-year-old specimen of Australopithecus afarensis &mdash or southern ape of Afar &mdash spent her life walking on the ground or combined walking with frequent tree climbing.

A new analysis of the partially fossilized skeleton, to be published Nov. 30 in the journal PLOS ONE, shows that Lucy&rsquos upper limbs were heavily built, similar to tree-climbing chimpanzees, supporting the idea that she often used her arms to pull herself up, most likely onto tree branches. Researchers also suggest that because her foot was better adapted for bipedal locomotion &mdash or upright walking &mdash rather than grasping, Lucy had to rely on upper-body strength when climbing, which resulted in more heavily built upper-limb bones.

&ldquoIt may seem unique from our perspective that early hominins like Lucy combined walking on the ground on two legs with a significant amount of tree climbing, but Lucy didn&rsquot know she was unique,&rdquo said UT Austin paleoanthropologist John Kappelman, whose most recent study proposed Lucy probably died after falling from a tall tree, where she may have been nesting to avoid predators. A nightly ascent would equate to one-third of her life spent in trees &mdash or more if she occasionally foraged there, Kappelman said.

&ldquoWe were able to undertake this study thanks to the relative completeness of Lucy&rsquos skeleton,&rdquo said the study&rsquos lead author, Christopher Ruff, a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. &ldquoOur analysis required well-preserved upper and lower limb bones from the same individual, something very rare in the fossil record.&rdquo

The research team first examined Lucy, who is among the oldest, most complete skeletons of any adult, erect-walking human ancestor, during her U.S. museum tour in 2008, when the fossil was detoured briefly to the High-Resolution X-ray Computed Tomography Facility (UTCT) in the UT Jackson School of Geosciences. For 10 days, Kappelman and UT Austin geological sciences professor Richard Ketcham carefully scanned all of her bones to create a digital archive of more than 35,000 CT slices.

&ldquoWe all love Lucy, but we had to face the fact that she is a rock,&rdquo said Ketcham, adding that conventional CT is not powerful enough to image the internal structure of Lucy&rsquos heavily mineralized skeleton. &ldquoThe time for standard medical CT scanning was 3.18 million years ago. This project required a scanner more suited to her current state.&rdquo

Since then, researchers have relied on the scans to look for clues about how Lucy lived, died and used her body &mdash estimated to be about 3 feet 6 inches and 60 pounds &mdash during her lifetime. The most recent study focused on the internal structure of Lucy&rsquos right and left humeri (upper arm bones) and left femur (thigh bone).

A major issue in the debate about Lucy&rsquos tree climbing has been how to interpret skeletal features that might be simply &ldquoleftover&rdquo from a more primitive ancestor that had relatively long arms, for example. The advantage of the new study, Ruff said, is that it focused on characteristics that reflect actual behavior during life. Some evidence even suggests she was right-handed, researchers said.

&ldquoOur study is grounded in mechanical engineering theory about how objects can facilitate or resist bending,&rdquo Ruff said. &ldquoOur results are intuitive because they depend on the sorts of things that we experience about objects &mdash including body parts &mdash in everyday life. If, for example, a tube or drinking straw has a thin wall, it bends easily, whereas a thick wall prevents bending. Bones are built similarly.&rdquo

Lucy&rsquos scans were compared with CT scans from a large sample of modern humans, who spend the majority of their time walking on two legs on the ground, and with chimpanzees, a species that spends more of its time in the trees and, when on the ground, usually walks on all four limbs.

&ldquoIt is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced,&rdquo Kappelman said. &ldquoTennis players are a nice example: Studies have shown that the cortical bone in the shaft of the racquet arm is more heavily built up than that in the non-racquet arm.&rdquo

Other comparisons in the study suggest that even when Lucy walked upright, she may have done so less efficiently than modern humans do, limiting her ability to walk long distances on the ground, Ruff said. In addition, all of her limb bones were found to be very strong relative to her body size, indicating that she had exceptionally strong muscles, more like those of modern chimpanzees than modern humans. A reduction in muscle power later in human evolution may be linked to better technology that reduced the need for physical exertion and the increased metabolic demands of a larger brain, the researchers said.

Other scholastic materials and the 3-D files are available on eLucy.org. Permissions to scan, study and photograph Lucy were granted by the Authority for Research and Conservation of Cultural Heritage and the National Museum of Ethiopia of the Ministry of Tourism and Culture. The UTCT was supported by three grants from the U.S. National Science Foundation.

UT Austin has HD satellite and Skype studios available for media interviews.

For more information, contact: Rachel Griess, College of Liberal Arts, 512-471-2689


Ground foragers

So, rather than evolving to walk on two feet after scrabbling around on the floor on all fours, the theory suggests our ancestors already had the rudimentary means of walking on two feet before they even left the trees.

When the ancestors of chimps and gorillas left the trees, however, they needed to maintain the ability to climb tree trunks. This need for tree-climbing strength and anatomy guided their evolution at the expense of more efficient terrestrial movement, and therefore led to knuckle-walking, says Crompton.

Orang-utans are the most distant of our relatives among the great apes, followed by gorillas, and then bonobos and chimpanzees. The ancestors of the latter two species split from the human line around 6 million years ago the orang-utan ancestor split from the human ancestor around 10 million years ago.

Thorpe and colleagues suggest that at sometime in the Miocene epoch – 24 to 5 million years ago – the increased gaps in the forest canopy that came about as a result of climate fluctuations had a profound effect on our ape ancestors.

Some of them – the ancestors of chimps and gorillas – specialised on climbing high into the canopy and crossing the gaps between trees by knuckle walking. Others – the ancestors of humans – retained their ability to walk on two legs, and specialised on collecting food from smaller trees and the ground.


3.2 million-year-old human ancestor Lucy was a tree climber, new evidence suggests

Since the discovery of the fossil 42 years ago this month, paleontologists have debated whether the 3.2 million-year-old human ancestor, dubbed Lucy, spent all of her time walking on the ground or instead combined walking with frequent tree climbing.

Image caption: The fossils that make up the Lucy skeleton

Image credit : John Kappelman/University of Texas at Austin

Now, analysis of special CT scans by scientists from Johns Hopkins University and the University of Texas at Austin suggests the female hominin spent enough time in the trees that evidence of this behavior is preserved in the internal structure of her bones. A description of the research study appears today in the journal PLOS ONE.

Analysis of the partial fossilized skeleton, the investigators say, shows that Lucy's upper limbs were heavily built, similar to champion tree-climbing chimpanzees, supporting the idea that she spent time climbing and used her arms to pull herself up. In addition, they say, the fact that her foot was better adapted for bipedal locomotion (upright walking) than grasping may mean that climbing placed additional emphasis on Lucy's ability to pull up with her arms and resulted in more heavily built upper limb bones.

Exactly how much time Lucy spent in the trees is difficult to determine, the research team says, but another recent study suggests Lucy died from a fall out of a tall tree. This new study adds to evidence that she may have nested in trees at night to avoid predators, the authors say. An eight-hour slumber would mean she spent one-third of her time up in the trees, and if she also occasionally foraged there, the total percentage of time spent above ground would be even greater.

Lucy, housed in the National Museum of Ethiopia, is a 3.2 million-year-old specimen of Australopithecus afarensis—or southern ape of Afar—and is among the oldest, most complete fossil skeletons ever found of any adult, erect-walking human ancestor. She was discovered in the Afar region of Ethiopia in 1974 by Arizona State University anthropologist Donald Johanson and graduate student Tom Gray.

The new study analyzed CT scan images of her bones for clues to how she used her body during her lifetime. Previous studies suggest she weighed less than 65 pounds and was under 4 feet tall.

"We were able to undertake this study thanks to the relative completeness of Lucy's skeleton," says Christopher Ruff, a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. "Our analysis required well-preserved upper and lower limb bones from the same individual, something very rare in the fossil record."

Also see
Study suggests 3.2 million-year-old Lucy ppent a lot of time in trees

The research team first had a look at Lucy's bone structure during her U.S. museum tour in 2008, when the fossil was detoured briefly to the High-Resolution X-Ray Computed Tomography Facility in the University of Texas at Austin Jackson School of Geosciences. For 11 days, John Kappelman and Richard Ketcham, both professors at the University of Texas at Austin, carefully scanned all of her bones to create a digital archive of more than 35,000 CT slices. High-resolution CT scans were necessary because Lucy is so heavily mineralized that conventional CT is not powerful enough to image the internal structure of her bones.

"We all love Lucy," Ketcham says, "but we had to face the fact that she is a rock. The time for standard medical CT scanning was 3.18 million years ago. This project required a scanner more suited to her current state."

The new study uses CT slices from those 2008 scans to quantify the internal structure of Lucy's right and left humeri (or upper arm bones) and left femur (or thigh bone).

"Our study is grounded in mechanical engineering theory about how objects can facilitate or resist bending," Ruff says. "But our results are intuitive because they depend on the sorts of things that we experience about objects—including body parts—in everyday life. If, for example, a tube or drinking straw has a thin wall, it bends easily, whereas a thick wall prevents bending. Bones are built similarly."

Adds Kappelman: "It is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced. Tennis players are a nice example: Studies have shown that the cortical bone in the shaft of the racquet arm is more heavily built up than that in the nonracquet arm."

A major issue in the debate over Lucy's tree climbing has been how to interpret skeletal features that might be simply "leftovers" from a more primitive ancestor that had relatively long arms, for example. The advantage of the new study, Ruff says, is that it focused on characteristics that reflect actual behavior during life.

Lucy's scans were compared with CT scans from a large sample of modern humans, who spend the majority of their time walking on two legs on the ground, and with chimpanzees, a species that spends more of its time in the trees and, when on the ground, usually walks on all four limbs.

"Our results show that the upper limbs of chimpanzees are relatively more heavily built because they use their arms for climbing, with the reverse seen in humans, who spend more time walking and have more heavily built lower limbs," Ruff says. "The results for Lucy are convincing and intuitive."

Other comparisons carried out in the study suggest that even when Lucy walked upright, she may have done so less efficiently than modern humans, limiting her ability to walk long distances on the ground, Ruff says. In addition, all of her limb bones were found to be very strong relative to her body size, indicating that she had exceptionally strong muscles, more like those of modern chimpanzees than modern humans. A reduction in muscle power later in human evolution may be linked to better technology that reduced the need for physical exertion and the increased metabolic demands of a larger brain, the researchers say.

"It may seem unique from our perspective that early hominins like Lucy combined walking on the ground on two legs with a significant amount of tree climbing," Kappelman says. "But Lucy didn't know she was 'unique'—she moved on the ground and climbed in trees, nesting and foraging there, until her life was likely cut short by a fall—probably out of a tree."


Lucy, our famous ancestor, was built for tree-dwelling

Lucy, our ever-popular human ancestor, may have preferred a tree-dwelling lifestyle, based on bone scans published Wednesday in PLOS ONE. The research adds clarity to early human behavior and suggests our ancestors may have spent millions of years “monkeying around” the branches.

Since American paleoanthropologist Donald Johanson discovered Lucy’s remains in 1974, they have traveled the world to be carefully examined. Scientists have determined that she certainly walked upright like a human and had proportions somewhere between a human and a chimp. However, controversy and questions still surround how she behaved.

Lucy had long arms like a chimp, but did she move and live like one? Or did she merely inherit those leftover features from a tree-dwelling ancestor?

By analyzing high-resolution X-ray scans of Lucy’s upper arm bone, evolutionary anatomist Christopher Ruff demonstrated that early hominins developed arm strength through consistent use — likely by tree-climbing.

“She was still climbing trees on a regular basis,” Ruff said of his team’s new study. “You don’t develop this kind of strong upper-limb bones if you climb a tree once a week.”

Ruff’s team also examined Lucy’s femur and concluded that her walking gait would have been less efficient than humans.

Lucy’s inherited her long arms, so these features don’t expose much about her day-to-day behavior. However, the strength of your limb bones is a more “plastic” trait that changes based on how you use them as you grow. That’s why Lucy’s strong arms indicate that she was, in fact, supporting her weight in trees.

Scientists have speculated for a long time that Lucy and her family must have spent at least some time in trees, especially as recent analysis has demonstrated that she died falling out of one. That study found injuries at or around the time of Lucy’s death are consistent with wounds suffered by people who have fallen from a great height and then have put their arms in front of them to break the impact. Ruff noted that those results are further evidence of tree-dwelling.

But other experts disagree and believe Lucy lived a more terrestrial life. Evolutionary anatomy professor Carol Ward, who focuses on apes and early hominins, said that Lucy had many more adaptations for living on the ground.

For example, humans and Lucy have flat feet, which are suited for walking on the ground. Plus, tree-dwelling apes have grasping big toes, with feet that look like hands.

“We gave that up, Lucy gave that up, in favor of feet that were better at being on the ground.” Ward said. “So not only do we know that the most important thing was for these animals to be able to move effectively on the ground, we also know that being in the trees wasn’t very important to them.”

However, scientists agree that Lucy and her Australopithecus afarensis family moved in both land and tree environments.

“The question in some ways isn’t whether Lucy was able to climb trees,” Ward said. “My kids climb trees, people climb trees now.”

Likewise, tree-dwelling apes can walk on the ground when needed, but not as well or as upright as a human or Australopithecus.

Left: A composite image of Lucy the Australopithecus (center) and two Malapa hominins (sides.) Photo by Peter Schmid


Human ancestor "Lucy" was a tree climber, evidence suggests

She was discovered 42 years ago, but the 3-million-year-old human ancestor dubbed &ldquoLucy&rdquo is still providing new insights on the human origin story. Now, new research suggests this predecessor to modern humans was an adept tree climber.

The fossils that make up Lucy&rsquos skeleton. John Kappelman/University of Texas at Austin

The evidence of Lucy&rsquos tree-climbing habits was found in high-resolution CT scans of her fossilized bones, according to scientists from the Johns Hopkins University and the University of Texas at Austin. Those CT scans were intricately 3D printed, allowing for direct comparisons to the bones of early hominids, modern humans, and modern chimpanzees. The researchers&rsquo work was published this week in the journal PLOS ONE.

Lucy&rsquos arms were heavily toned, supporting the idea that she routinely used them to pull herself up on branches, the researchers said. Her muscle mass would have been similar to that of tree-climbing chimpanzees. Meanwhile, her feet were better suited to walking upright than gripping branches.

&ldquoThe upper limbs of chimpanzees are relatively more heavily built because they use their arms for climbing, with the reverse seen in humans, who spend more time walking and have more heavily built lower limbs,&rdquo Christopher Ruff, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine, said in a press statement.

&ldquoThe results for Lucy are convincing and intuitive.&rdquo

A three-dimensional model of the early human ancestor, Australopithecus afarensis, known as Lucy, on display at the Houston Museum of Natural Science. Pat Sullivan, AP

Clues found in Lucy&rsquos skeleton are key to understanding the lifestyle she led, according to study co-author John Kappelman.

&ldquoIt is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced,&rdquo Kappelman said.

Trending News

Tree climbing may have helped Lucy forage for food and escape from nearby predators.

Scholars have debated whether Lucy spent all her time walking on the ground or combined walking with tree climbing.

Previous research has suggested that perhaps Lucy died from falling from a tree.

Lucy&rsquos skeleton is one of the oldest, most complete fossils ever found of an adult human ancestor who walked upright. Previous studies suggest she stood less than 4 feet tall and weighed less than 65 pounds.

Lucy&rsquos bones were found in Ethiopia in 1974. About 40 percent of the complete skeleton was recovered and pieced together.


Human Ancestor ‘Lucy’ Was a Tree Climber, New Evidence Suggests

A new analysis using CT scans of the world-famous, ancient human fossil, Lucy, suggests she was a tree climber.

AUSTIN, Texas — Evidence preserved in the internal skeletal structure of the world-famous fossil, Lucy, suggests the ancient human species frequently climbed trees, according to a new analysis by scientists from The Johns Hopkins University and The University of Texas at Austin.

Since Lucy’s discovery in Ethiopia 42 years ago this month by Arizona State University anthropologist Donald Johanson and graduate student Tom Gray, paleontologists have debated whether the 3.18 million-year-old specimen of Australopithecus afarensis — or southern ape of Afar — spent her life walking on the ground or combined walking with frequent tree climbing.

A new analysis of the partially fossilized skeleton, to be published Nov. 30 in the journal PLOS ONE, shows that Lucy’s upper limbs were heavily built, similar to tree-climbing chimpanzees, supporting the idea that she often used her arms to pull herself up, most likely onto tree branches. Researchers also suggest that because her foot was better adapted for bipedal locomotion — or upright walking — rather than grasping, Lucy had to rely on upper-body strength when climbing, which resulted in more heavily built upper-limb bones.

“It may seem unique from our perspective that early hominins like Lucy combined walking on the ground on two legs with a significant amount of tree climbing, but Lucy didn’t know she was unique,” said UT Austin paleoanthropologist John Kappelman, whose most recent study proposed Lucy probably died after falling from a tall tree, where she may have been nesting to avoid predators. A nightly ascent would equate to one-third of her life spent in trees — or more if she occasionally foraged there, Kappelman said.

“We were able to undertake this study thanks to the relative completeness of Lucy’s skeleton,” said the study’s lead author, Christopher Ruff, a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. “Our analysis required well-preserved upper and lower limb bones from the same individual, something very rare in the fossil record.”

The research team first examined Lucy, who is among the oldest, most complete skeletons of any adult, erect-walking human ancestor, during her U.S. museum tour in 2008, when the fossil was detoured briefly to the High-Resolution X-ray Computed Tomography Facility (UTCT) in the UT Jackson School of Geosciences. For 10 days, Kappelman and UT Austin geological sciences professor Richard Ketcham carefully scanned all of her bones to create a digital archive of more than 35,000 CT slices.

“We all love Lucy, but we had to face the fact that she is a rock,” said Ketcham, adding that conventional CT is not powerful enough to image the internal structure of Lucy’s heavily mineralized skeleton. “The time for standard medical CT scanning was 3.18 million years ago. This project required a scanner more suited to her current state.”

Since then, researchers have relied on the scans to look for clues about how Lucy lived, died and used her body — estimated to be about 3 feet 6 inches and 60 pounds — during her lifetime. The most recent study focused on the internal structure of Lucy’s right and left humeri (upper arm bones) and left femur (thigh bone).

A major issue in the debate about Lucy’s tree climbing has been how to interpret skeletal features that might be simply “leftover” from a more primitive ancestor that had relatively long arms, for example. The advantage of the new study, Ruff said, is that it focused on characteristics that reflect actual behavior during life. Some evidence even suggests she was right-handed, researchers said.

“Our study is grounded in mechanical engineering theory about how objects can facilitate or resist bending,” Ruff said. “Our results are intuitive because they depend on the sorts of things that we experience about objects — including body parts — in everyday life. If, for example, a tube or drinking straw has a thin wall, it bends easily, whereas a thick wall prevents bending. Bones are built similarly.”

Lucy’s scans were compared with CT scans from a large sample of modern humans, who spend the majority of their time walking on two legs on the ground, and with chimpanzees, a species that spends more of its time in the trees and, when on the ground, usually walks on all four limbs.

“It is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced,” Kappelman said. “Tennis players are a nice example: Studies have shown that the cortical bone in the shaft of the racquet arm is more heavily built up than that in the non-racquet arm.”

Other comparisons in the study suggest that even when Lucy walked upright, she may have done so less efficiently than modern humans do, limiting her ability to walk long distances on the ground, Ruff said. In addition, all of her limb bones were found to be very strong relative to her body size, indicating that she had exceptionally strong muscles, more like those of modern chimpanzees than modern humans. A reduction in muscle power later in human evolution may be linked to better technology that reduced the need for physical exertion and the increased metabolic demands of a larger brain, the researchers said.

Other scholastic materials and the 3-D files are available on eLucy.org. Permissions to scan, study and photograph Lucy were granted by the Authority for Research and Conservation of Cultural Heritage and the National Museum of Ethiopia of the Ministry of Tourism and Culture. The UTCT was supported by three grants from the U.S. National Science Foundation.

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Human ancestor 'Lucy' was a tree climber, new evidence suggests

Since the discovery of the fossil dubbed Lucy 42 years ago this month, paleontologists have debated whether the 3 million-year-old human ancestor spent all of her time walking on the ground or instead combined walking with frequent tree climbing. Now, analysis of special CT scans by scientists from The Johns Hopkins University and the University of Texas at Austin suggests the female hominin spent enough time in the trees that evidence of this behavior is preserved in the internal structure of her bones. A description of the research study appears November 30 in the journal PLOS ONE.

Analysis of the partial fossilized skeleton, the investigators say, shows that Lucy's upper limbs were heavily built, similar to champion tree-climbing chimpanzees, supporting the idea that she spent time climbing and used her arms to pull herself up. In addition, they say, the fact that her foot was better adapted for bipedal locomotion (upright walking) than grasping may mean that climbing placed additional emphasis on Lucy's ability to pull up with her arms and resulted in more heavily built upper limb bones.

Exactly how much time Lucy spent in the trees is difficult to determine, the research team says, but another recent study suggests Lucy died from a fall out of a tall tree. This new study adds to evidence that she may have nested in trees at night to avoid predators, the authors say. An eight-hour slumber would mean she spent one-third of her time up in the trees, and if she also occasionally foraged there, the total percentage of time spent above ground would be even greater.

Lucy, housed in the National Museum of Ethiopia, is a 3.18 million-year-old specimen of Australopithecus afarensis -- or southern ape of Afar -- and is among the oldest, most complete fossil skeletons ever found of any adult, erect-walking human ancestor. She was discovered in the Afar region of Ethiopia in 1974 by Arizona State University anthropologist Donald Johanson and graduate student Tom Gray. The new study analyzed CT scan images of her bones for clues to how she used her body during her lifetime. Previous studies suggest she weighed less than 65 pounds and was under 4 feet tall.

"We were able to undertake this study thanks to the relative completeness of Lucy's skeleton," says Christopher Ruff, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine. "Our analysis required well-preserved upper and lower limb bones from the same individual, something very rare in the fossil record."

The research team first had a look at Lucy's bone structure during her U.S. museum tour in 2008, when the fossil was detoured briefly to the High-Resolution X-Ray Computed Tomography Facility in the University of Texas at Austin Jackson School of Geosciences. For 11 days, John Kappelman, Ph.D., anthropology and geological sciences professor, and geological sciences professor Richard Ketcham, Ph.D., both of the University of Texas at Austin, carefully scanned all of her bones to create a digital archive of more than 35,000 CT slices. High-resolution CT scans were necessary because Lucy is so heavily mineralized that conventional CT is not powerful enough to image the internal structure of her bones.

"We all love Lucy," Ketcham says, "but we had to face the fact that she is a rock. The time for standard medical CT scanning was 3.18 million years ago. This project required a scanner more suited to her current state."

The new study uses CT slices from those 2008 scans to quantify the internal structure of Lucy's right and left humeri (upper arm bones) and left femur (thigh bone).

"Our study is grounded in mechanical engineering theory about how objects can facilitate or resist bending," says Ruff, "but our results are intuitive because they depend on the sorts of things that we experience about objects -- including body parts -- in everyday life. If, for example, a tube or drinking straw has a thin wall, it bends easily, whereas a thick wall prevents bending. Bones are built similarly."

"It is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced," explains Kappelman. "Tennis players are a nice example: Studies have shown that the cortical bone in the shaft of the racquet arm is more heavily built up than that in the nonracquet arm."

A major issue in the debate over Lucy's tree climbing has been how to interpret skeletal features that might be simply "leftovers" from a more primitive ancestor that had relatively long arms, for example. The advantage of the new study, Ruff says, is that it focused on characteristics that reflect actual behavior during life.

Lucy's scans were compared with CT scans from a large sample of modern humans, who spend the majority of their time walking on two legs on the ground, and with chimpanzees, a species that spends more of its time in the trees and, when on the ground, usually walks on all four limbs.

"Our results show that the upper limbs of chimpanzees are relatively more heavily built because they use their arms for climbing, with the reverse seen in humans, who spend more time walking and have more heavily built lower limbs," says Ruff. "The results for Lucy are convincing and intuitive."

Other comparisons carried out in the study suggest that even when Lucy walked upright, she may have done so less efficiently than modern humans, limiting her ability to walk long distances on the ground, Ruff says. In addition, all of her limb bones were found to be very strong relative to her body size, indicating that she had exceptionally strong muscles, more like those of modern chimpanzees than modern humans. A reduction in muscle power later in human evolution may be linked to better technology that reduced the need for physical exertion and the increased metabolic demands of a larger brain, the researchers say.

"It may seem unique from our perspective that early hominins like Lucy combined walking on the ground on two legs with a significant amount of tree climbing," says Kappelman, "but Lucy didn't know she was "unique" -- she moved on the ground and climbed in trees, nesting and foraging there, until her life was likely cut short by a fall -- probably out of a tree."

Graduate student M. Loring Burgess of the Johns Hopkins University School of Medicine was also an author on the paper.