Lucy may have died by falling out of a tree

August 30, 2016 • 10:15 am

Lucy” is the skeleton of an Australopithecus afarensis female, dated at 3.18 million years old and discovered by Donald Johanson’s team in 1971 in the Awash Valley of Ethiopia. Lucy has become famous because, with 40% of the skeleton recovered, all in one place, she gave a remarkably complete picture of what one of our ancestors  may have looked like soon after splitting off from our common ancestor with modern chimps. (Note: we’re not sure that modern humans are really descendants of Lucy’s species).

In short, Lucy was short (3 feet 7 inches, or 1.1 meters), an adult, and had a brain the size of a modern chimp (450 cc; modern chimps are about 400 cc and  humans are about 1150 cc). She could clearly walk bipedally, as her pelvis and legs were clearly adapted for upright walking. We also have the Laetoli footprints of two hominins walking upright—probably also A. afarensis but dated even older than Lucy (3.7 mya). Nevertheless, Lucy had fingerbones that were curved, like those of apes, suggesting that her species had either not lost all traces of their arboreal past, or that A. afarensis still clambered about in the trees.

In fact, a new paper in Nature by John Kappelman et al. (reference below, free access at link) suggests that Lucy met her death by falling from a tree. Although that conclusion is a bit controversial, the evidence shouldn’t be sniffed at. What is that evidence?

  • The main evidence is the way Lucy’s bones were broken, especially the proximal end of the right humerus, or upper arm bone (“proximal” means the end of the bone closest to the body, where the bone articulates with the shoulder). What Kappelman et al. found, by looking at casts of the bone and making 3-D prints of them, is that the end of the humerus was shattered in such a way suggesting a violent concussion with the ground. This is, in fact, what we see in modern humans who have tried to break a fall by putting out their arms. Here’s a photo of the cracked humerus from the paper, with Lucy’s full skeleton to the right:

Screen Shot 2016-08-30 at 9.14.49 AM

The fact that these fractures remained together suggests to the authors that the cracking occurred while Lucy was still alive rather than long after death, for they’ve stayed within the joint capsule, and would likely have been scattered on the ground had they been a postmortem cracking of the bones during natural burial. It also suggests that if Lucy’s death—due to both bone breakage and organ damage (the latter possibly caused by splintering bone)—was due to a fall, she stretched out her arms after she had struck the ground (see below), and thus was conscious immediately after she struck the ground.

The head of the other humerus, the left one, also shows some fracturing too, though the damage isn’t as extensive.

  • There is other fracturing of the arms as well: the shaft of the right humerus shows spiral fracturing (“d” above), and there are suggestions of fractures in the forearms, with no evidence of healing. The clavicle (shoulder bone) also shows vertical fractures.
  • There are apparent fractures in the legs and pelvis as well: breakage in the tibia, fibula left femur (severely fractured), and in the pelvis. Here are photos of those:
Screen Shot 2016-08-30 at 9.27.18 AM
Fractures of the tibia, the larger of the lower leg bones
Screen Shot 2016-08-30 at 9.29.50 AM
Fractures in the neck of the femur (upper leg bone)

The pelvis is really screwed up! Look at these putative fractures:

Screen Shot 2016-08-30 at 9.24.20 AM

  • Finally, there are other apparent fractures to the cranium, lumbar vertebrae, and mandible (jawbone).

So what happened to Lucy? Because both the arms and legs are fractured, the authors conjecture that Lucy fell considerable distance out of a tree, with the legs striking first and then the arms outstretched to break the fall. The authors give a diagram, and I’ve added the figure legend from the paper:

(From text): Figure 2 | Reconstruction of Lucy’s vertical deceleration event. We hypothesize that Lucy fell from a tall tree, landing feet-first and twisting to the right, with arrows indicating the sequence and types of fractures. a, Pilon fracture, tibial plateau fracture, and spiral shaft fracture of right tibia. b, The impact of hyperextended left knee drove the distal femoral epiphysis into the distal shaft, and fractured the femoral neck and possibly the acetabulum, sacrum, and lumbar vertebra. c, The impact of the knee drove the patella into the centre anterodistal surface of the femoral shaft. d, Impact on the right hip drove the right innominate into the sacrum, and the sacrum into the left innominate, dislocating and fracturing the sacrum and left innominate, and elevating the retroauricular surface. e, Lucy was still conscious when she stretched out her arms in an attempt to break her fall and fractured both proximal humeri, the right more severely than the left with spiral fracture near the midshaft, a Colles’ (or Smith’s) fracture of the right radius, and perhaps other fractures of the radii and ulnae. The impact depressed and retracted the right scapula, which depressed the clavicle into the first rib, fracturing both. f, Frontal impact fractured the left pubis and drove a portion of the anterior inferior pubic ramus posterolaterally, and a branch or rock possibly created the puncture mark on the pubis. g, The impact of the thorax fractured many ribs and possibly some thoracic vertebrae. h, The impact of the skull, slightly left of centre, created a tripartite guardsman fracture of the mandible and cranial fractures. See Supplementary Methods and Supplementary Video 4.

What was Lucy doing up there? The authors suggest that she was nesting, just like modern chimps make nests high off the ground. The height of chimp nests (8-21 meters) is sufficient to kill an animal that falls from them.

Could anything else have caused the fractures? The authors note that you could get similar fractures if the body collided with objects in a flood; if a big animal hit Lucy at high speed, or if she suffered seizures, perhaps caused by a lightning strike. But they claim these occurrences are not only uncommon, but the pattern of Lucy’s fractures is absolutely consistent with those of modern people who fall from considerable heights.  And we know that modern chimps have been killed by falling from trees.

But were there trees in that area when Lucy lived? Good question! The authors say that in the area near the village of Hadar, where Lucy’s skeleton was found, was indeed probably a “grassy woodland with sizable trees.” That evidence comes from fossil pollen, the location of the skeleton (near a water channel that probably harbored nearby trees), and isotopic evidence.

Do other experts agree? Well, not completely. Carl Zimmer interviewed several people for an article on this in the New York Times (which I just read after I wrote the above), and they disagree on whether these are even fractures, and, if so, if they resulted from a fall. And even if they resulted from a fall, maybe Lucy fell not while nesting, but for other reasons. One of the doubters is Don Johanson, who discovered Lucy. Here are some quotes from Zimmer’s piece:

But other experts said Dr. Kappelman and his colleagues had not done enough to rule out other explanations for the fractures.

Ericka N. L’Abbé, a professor of anthropology at the University of Pretoria in South Africa, said that when living bones break, some parts bend. A close inspection of Lucy’s bones might have revealed traces of that bending.

“The major drawback is that they didn’t look under a microscope,” Dr. L’Abbé said.

Dr. Johanson [who discovered Lucy] said it was far more likely that the fractures Dr. Koppelman attributes to a fall had occurred long after her death, as her skeleton was buried under sand.

“Elephant bones and hippo ribs appear to have the same kind of breakage,” Dr. Johanson said. “It’s unlikely they fell out of a tree.”

. . .Some researchers have argued that by Lucy’s time, our forerunners were no longer good tree-climbers, having evolved to find food on the ground. “Australopithecus afarensis was essentially a terrestrial animal,” Dr. Johanson said.

. . . .Dr. Kappelman and his colleagues considered the possibility that Lucy fell out of a nest in which she was sleeping. Chimpanzees build their nests an average of 40 feet above the ground. A fall from that height could have killed Lucy, the scientists calculated.

But Nathaniel Dominy, an evolutionary biologist at Dartmouth College, considers it unlikely. “For me, the much more likely scenario is that she was climbing for food,” he said.

Chimpanzees sometimes gather honey from hives that are far above their nests. They have to use one hand to hold on to a branch while jabbing a stick into a hive with the other.

“Lucy was just enduring the stings as a chimpanzee would. It would be intense,” Dr. Dominy said.

The upshot.  I’m not completely convinced that this represents a fall, especially in light of Don Johanson’s worries that the “fractures” represent postmortem events due to burial. But this is still intriguing, and shows that things remain to be learned from what is probably the most well studied hominin fossil of all time. If these do represent fractures sustained during a fall, it would be cool, for it would give us strong evidence that A. afarensis was still living part-time in the trees even after it had evolved the ability to walk upright on the ground.


Kappelman, J., R. A. Ketcham, S. Pearce, L. Todd, W. Akins, M. W. Colbert, M. Feseha, J. A. Maisano, and A. Witzel. 2016. Perimortem fractures in Lucy suggest mortality from fall out of tall tree. Nature, advance online publication,doi:10.1038/nature19332.

71 thoughts on “Lucy may have died by falling out of a tree

    1. Lucy didn’t believe in God so she got what she deserved. She should have prayed harder, especially on her way down.

      Unless of course it was part of His plan, then her death was “mysterious ways” and her suffering absolutely essential to the future of mankind. Perhaps the discovery of the fractures will lead the authors to Christianity, they will then write a “creative non-fiction” essay for Templeton, and thousands of scientists will thus be inspired to recognize the Truth of His word.

      1. I have another explanation. G*d selected Lucy to die suddenly and be fossilized so that, after a few millions of years, she would be discovered in the 20th century and shed light on human evolution. This is because G*d likes evolution by natural selection ever since He switched to it because creation was too much hard work, and He wants humans to understand and believe in evolution. The same way, in the 19th century He inspired the theology graduate Charles Darwin to develop interest in natural history and arranged for him to be on the Beagle. Maybe Lucy was sacrificed, but maybe G*d mercifully selected an australopithecus already burdened by a painful terminal disease. Do you think I can develop these ideas in an essay on “Science & Religion” and make a nice try for the Templeton money? (I suspect, however, that only Americans can participate, and only those with decent English have a chance.)

        1. Excellent theory!

          And your English is better than most, as I’m sure others will agree. As a NZer, I’m forever getting wavy red lines because Americans don’t know how to spell English but dominate the Internet! 😀

      2. This is probably what gave God his idea for The Fall. Once he had refined his perfect plan enough to make proper humans he would make Eve fall too so he would have something to be angry about and could tell us what we had to do to make him forgive us… or something like that. 🙂

        1. That metaphor is too good. And Lucy does sound an awful like another mischievous character; cf. Mr. Diety. Coincidence…I think not. 😊

  1. “The authors note that you could get similar fractures if the body collided with objects in a flood;”

    Uh-oh —–

      1. My hypothesis is that she was killed while helping Noah and his sons build the Ark. Working high on the upper superstructure, she accidentally hit her thumb with a hammer, lost her grip and fell to her death. Only her bereaved mate was left on board to survive the Flood. That’s why Australopithecus afarensis isn’t around today.

        Do you think I should expand this and send it to Templeton?

  2. Well, it’s an idea based on evidence, and it is good to get it out. It is also good to question that evidence right now. What I would like to see is more work.

      1. Well, chimps build their nests with walls, so they can’t fall out. I expect A. Afarensis would have done the same, if they slept in tree nests like chimps.

        1. Hmmm,
          My first force 12+ night on a rig (about my 10th ever night on a rig ; the notorious “Fish not-A-Hurricane” hurricane) had one person on board break his wrist by rolling over in bed as the rig was rolling the other way (bad idea in the top bunk!). That was a good solid 3-4in plank on the not-wall side of the bunk. Probably somewhat stiffer than a chimp’s (putative) nest wall.
          On the other hand, I also had a friend who was camping one night at very-ground level, who woke up one morning with both legs broken. Rolling caravan, force 11+ wind, SNAFU.

  3. There is considerable push back on those conclusions by Tim White and John Hawks (both paleoanthropologists). Hawks points out the lack of comparative examples from x-rays of modern people with similar fractures. White shows several fossils of horse and rhino humeri with similar fractures. These animals most certainly didn’t fall from trees. The fractures are due to compression during fossilization (taphonomic processes).

    1. I seem to remember reading that many fossil bones become broken when heavy, hoofed animals tread on them. Elephants or zebra, for example. Although in those cases the bones would not often remain in close formation, but would be spread out.

      1. You are correct. AK Beherensmeyer published on that. Such trampling will often leave scratches that are sometimes confused with stone tool cut marks. I also studied bones on modern landscapes to help understand taphonomic processes (my work was in forest environments), which is where I came across many skeletal remains of primates, including chimps.

        1. It occurs to me that a lot of research on such things as environments and the condition of bones, etc. are a continuing process of developing a more complete picture of our world and it’s history. It is only when someone is able to assemble new facts into an important new perspective that all that work by many scientists over a long time becomes widely known and appreciated.

    2. As I read him, Hawks says plainly that the authors did properly compare Lucy’s fractures to similar fractures in modern humans — and that part works, for him. And he doesn’t discount the probability that A. afarensis climbed trees, with the inevitable Darwinian consequences. What seems to get his sceptic glasses on is that the authors over-interpret — EVERY fracture seems to be part of the ‘plane crash’. So, like White, he thinks the Nature reviewers were asleep in not requiring evidence that similar [seemingly] ‘green’ compressive fractures don’t occur in elephants and oxen that don’t fall out of trees.. Unlike White, I think Hawks’ criticism is constructive: I’d like to see the authors’ response.

      White seems, more and more, to go to the “Get off my lawn, and I know australopiths and I know they were terrestrial” mode.

    3. I found this link in my inbox this morning, where John Hawks puts down his objections.
      Short version : The number of fractures assigned to the near-death event, “If Lucy really had fractures on more than 75% of her preserved bones, she didn’t fall out of a tree, she fell out of an airplane.”
      Disregard of common taphonomic processes “But there is another process that breaks first ribs very commonly in the fossil record: Becoming a fossil. I am not aware of any first rib from a Plio-Pleistocene hominin that is intact. ” So, did every Pliocene-Pleistocene hominin in the fossil record die by falling out of a tree?
      The nature of many of the fractures : “the authors describe some of these breaks as “hinge fractures”? Dry bones lacking the strength of their organic matrix often fracture in a straight line, like broken Greek columns, while a hinge fracture is one that changes in direction at one edge. When people see such a fracture that deflects in direction, they often attribute the fracture to fresh bone instead of dry bone.” Many people who have tried cracking a bone to get at the marrow, or for the d*g will have noted that fractures often change direction in the denser bone near the surface. “But in reality, a fracture that passes through a cortical bone layer may deflect in a direction more perpendicular to the bone surface even if the bone is dry, beneath sediment, or mineralized. […] If they [the authors] examined a large collection of faunal fossils from the same context, they would find similar patterns, not from falling out of a tree but from simple post-depositional breakage.” After deposition most sediments suffer varying degrees of compaction. Mudrocks (relatively impermeable to fluid movement, providing the low-oxygen environment conducive to fossilisation) can compact by 70% volumetrically ; sandstones are typically deposited with 20-30% porosity, but most suffer grain-grain dissolution and have a lower porosity as they get buried. Porosity is vital to having a hydrocarbon reservoir, and we study the matter in great detail. It’s the only reason I have for routinely being exposed to radiation sources – measuring formation porosity. That compaction and loss of porosity is why most fossils are fragmented in situ.

      Annnnd … I’ve got to go and do stuff.

      1. I finally read the original paper. It is interesting, but I think Hawks raises several good points. They did not survey fracture patterns on other animals bones found at Hadar (and there are a lot). They do not cite any of the extensive reviews of fracture patterns in living primates that have been published. They do not do a broad comparison with x-rays of similar injuries in living people (they exist). So, while their conclusions are certainly plausible and do seem to fit the condition of Lucy’s bones, they have not sufficiently ruled out other factors, especially fossil fracture caused by sediment loading during fossilization.

  4. An interesting article, but I note that from this simple speculation based on disputed evidence it is now becoming a narrative, complete with exact heights, nests, bee stings and sticks.

  5. They may have some good points, like with the head of the humerus, but what I don’t like is seeing the authors imply that every fracture in Lucy could be a pre-death fracture. John Hawks also makes this point, with some interesting details to add.

    1. What I don’t understand is how 75% of Lucy’s bones would be broken by a fall from a tree. Even from 20m or so. Do people really ‘shatter’ like that? I get that you’d break arms and legs, and damage internal organs, but would you break three-quarters of your bones…?

      I’ve never actually seen the broken corpse of someone who’s just fallen from that height so I don’t know. But that percentage of fractures sounds like what you’d get from jumping off a skyscraper. A kind of ‘wheeee-splacrunch’ effect if you’ll excuse the vivid imagery.

  6. “Lucy has become famous because, with 40% of the skeleton recovered, all in one place, she gave a remarkably complete picture of what one of our ancestors may have looked like…”

    Why would such a large percentage of the skeleton have been lost? Scavengers?

  7. My first thought was “Oh no! What will become of Desi and the chicks?”

    Even if we take the claim of a fall from a tree at face value, I’m not sure it tells us much about the lifestyle of A. afarensis. People die in falls from trees even today, but it would be a mistake to conclude that humans are still partially arboreal.

    1. Since the odds of being fossilized are very very low, as are the odds of finding a particular fossil, it is most likely that a given fossil is probably of a common variety of a species. I think that can also be said that they probably died of something that was not unusual for them.

      1. Fair enough, but if climbing trees for food counts as “partially arboreal”, why wouldn’t that apply equally to Neolithic hunter-gatherers?

        1. Neolithic people could obtain arboreal food resources utilizing technology, which Lucy and her kind did not produce (A. afarensis has no archaeological record, they were nontechnological most likely). Neolithic people were not physically adapted for arboreal life, unlike Lucy who had long arms and curved phlanges. People today can climb trees and do. They also fall out of trees occasionally, but no people today or in recent prehistory would correctly be described as arboreal or partially arboreal.

          1. “no people today or in recent prehistory would correctly be described as arboreal or partially arboreal”

            Yet every juvenile homo sapiens tries to disprove this point.

        2. The “partly arboreal” description of A. afarensis is based, in part on the degree of curvature of the finger bones, which is seen in arboreal primates like gibbons and (to a lesser degree) chimpanzees, but not in non-arboreal humans.

    1. I have read from time to time that bone fractures that spiral are most likely to have occurred in life. I have no idea why. Some of the major fractures in Lucy have that form.

    2. Also, the fractured fragments of bone were still adhered to the fossilized bone in matrix (the sediment binding the fossil). This is good evidence that the fracture occurred while the bone was still encased in tissue which was not disturbed as the bone fossilized (flesh gradually rotted away). Lucy’s bones show little evidence of her having been scavenged, which is one of the reasons her skeleton was so complete.

    3. The bones were found in a more-or-less articulated position. If scavanging had been a peri-mortem taphonomic event, then the bones would have been more scattered and most would simply not have been found.

  8. What peaceful scenarios! Falling out of bed? Falling while picking fruit?

    How about climbing a tree to get away from a rapist or marauding tribe, and then being pushed by whoever got to the tree first?

    Or maybe she really was picking fruit but so was her jealous sister, Sheila, who pushed her off the branch.

  9. In my own field work, I actually have quite a lot of experience with primates killed falling out of trees. While working in the forests of western Tanzania, I encountered at least 3 examples of Red Colobus monkeys that had died falling from trees. In 2 examples, the bodies were completely skeletonized yet articulated and face-down spread-eagle on the ground. They had clearly fallen from a great height, which is a danger as these monkeys typically make great leaps between trees. I collected the skeletons, which remarkably did not show ANY fractures. The monkeys had fallen from a great height but landed face down in soft, muddy earth, enough to fatally injure them, but not break bones. The topical forest environment skeletonized them rapidly, leaving the perfectly articulated skeletons on the ground. Had they been buried, they would have fossilized perfectly. The monkeys were about 1/2 body weight proposed for Lucy, but still, they fell from more than 40 feet up. I do have photos (although they are in storage past 15 years or so).

    1. That is pretty cool. But being small, it would be harder to break their bones in a fall, I guess. But they could still die of soft tissue injuries & internal bleeding.

      1. Yes, I am amazed I have some data that may have actually been useful in this study! The monkeys were almost certainly killed by severe internal injury in the fall. Still, an adult red Colobus can weigh upwards of 50 pounds or more. No broken bones, tho.

      1. I don’t think so. I spent a lot of time in the forest and saw quite a few monkeys miss branches and take nasty falls. I have a book that documents the condition of bones collected in the region. Many chimpanzees and other primates had healed fractures. watching nature shows on television, you don’t realize that falls are a real danger and occur fairly frequently.

    1. To quote a song sung at the botom of a 285ft cave shaft,
      “It’s so deep
      It’s so effing deep
      Just ask Toby
      The ex-sheep”
      “Toby” was found in installments over about 15 vertical feet. Quite why my partner decided his name was Toby, I don’t know. But since I was de-tackling, I had to put up with the smell for a lot longer than he did.

    1. Didn’t they reference the original, bony Lucy in the film? Isn’t that where Scarlett Johansen’s character got the name? I remember the plot having some fantastically ambitious/pretentious ideas, and I vaguely remember some connection there.

      Enjoyably mental film though, particularly towards the end.

    1. Lucy’s cranial fractures were probably from Charlie Brown who had enough of her football pulling shenanigans, and kicked her in the head.

    2. My heart plummeted when I first read the heading. “OH NO00, not Stephen’s Lucy, the eagle!!” Then I had time to wonder how come, since Lucy can fly…. is it Friday yet?! 😛

  10. That’ll teach Lucy for being an intermediary and not having curvy enough fingers! Damn evolution, can’t brachiate yet can’t hold a pen to write a letter to the in laws.

  11. More cold cases on WEIT but this one a least has evidence we can rely on even if speculation is the best we can do. Her death, is a gift and her ‘fall’ if that’s what it was has a reality based in truth than say, that other ‘fall’.

  12. Bilateral fractures of the humeral heads had me nodding in agreement, but what an embarrassment of riches is that pelvis! I’m used to seeing high energy injuries to the pelvis from car crashes, and lower energy ones to crumbly osteoporotic bone in the old. You would need a steamroller to produce that many pelvic fracturs. That’s either post-mortem injury, or, more likely, artifact.

  13. I don’t buy it. If Lucy was killed by a fall from a tree, something, or someone, would have eaten the body.

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