If upright walking is so energetically favorable, why do apes still “knuckle-walk”?

I wanted to really quickly give kudos to Afarensis, who dutifully ripped apart a dumb question that a creationist asked in regards to recent research on bipedalism. If you come from the camp that thinks there isn’t such a thing a stupid question… then I’m sorry to rain on your parade. There is such a thing as a stupid question and the following is a prime example of idiocy in its purest form. Here’s question,

“If upright walking is so energetically favorable, why do apes still “knuckle-walk”?”

Questions like this have been part of the creationist canon for some time. They use it, albeit ignorantly, because they think it is a valid attack point and weakens evolution. Unfortunately for them, as Afarensis points out, there’s a lot of flaws in thinking that way.

I want to take the time to answer this question and also add/clarify that the recent research I reviewed, on bipedalism energetics, simply shows that bipedalism is more energetically favorable for us. And that’s because our bodies are adapted to this form of locomotion. I’ll provide a lot of comparative anatomy to argue this point.  For example, the vertebrae in our backs are organized in a way to distribute the weight down to our pelvis which has a very different structure compared to other great apes. Our legs are longer and the bones are more robust than our arms because they bear more weight than the arms. The knee joint and the foot also exhibit differences that beneficial to bipedal walking.

Bipedalism is not a favorable form of locomotion for chimpanzees because their bodies are adapted primarily for terrestrial quadrupedal knuckle walking. Compared to humans, their arms are longer than their legs, their backs aren’t as specialized in weight distribution, and their hands, rather than their feet, exhibit robusticity because they bear lots of weight and force.

Now it is not all about the differences in bones and the skeletons. The illustration to your right, Comparison of Chimpanzee to Human Biomechanicsfrom a American Museum of Natural History webpage, compares some the soft tissue involved in the biomechanic differences between chimps and humans.  In the top left of the illustration, you see drawings of the three semicircular canals located in the inner ear, the primary organs for maintaining balance. In humans, two of the three canals are specialized to  stabilize the head. Also, in humans, there are fewer muscle connections between the head and the shoulders when compared to the chimpanzee. That’s cause quadruped chimps have to fight gravity in order to hold their heads up while walking on fours. Our head just sits on our necks.

In contrast to the head and neck, humans have more connections between the gluteus maximus muscle in the butt and the hip than chimpanzees do, which stabilizes the femur into the pelvis and helps keeps the trunk and leg moving together. Both the Achilles tendon of the heel and the tendon of the arch of the foot are much smaller in chimpanzees than they are in humans; in a running person they act like springs, absorbing and releasing energy.

So to ask, “why do apes still knuckle walk?” is straight up stupid. They don’t walk upright because it hurts, it is draining and inefficient.

You maybe thinking, “Hey, I’ve been to the zoo! I saw the YouTube video clip of the chimp and dog you shared with us. I’ve seen chimps run around on twos!” Chimps sometimes walk in short bipedal bursts. I’m not saying they don’t. But as the paper calculated, when they do walk bipedally, they experience more tension on their bones and joints than we do. That added tension and force costs more energy for chimps to walk bipedally because they aren’t adpated for it.

I imagine a similar but opposite conclusion can be made if the energetics of human knuckle-walking quadrupedalism is calculated and compared to that of a chimp. Try walking on all fours and not look like a idiot at the same time. You’ll soon experience tension on your bones and joints. After maybe about a dozen yards or so, fatigue will overcome your ability to keep up this form of locomotion. Why? Because our bodies are not adapted for and haven’t been selected for quadrupedal locomotion.

Any one, creationist or not, who thinks that bipedalism is a better form of locomotion should revise their train of thought. Apes still knuckle-walk because that’s part of the ecological niche they occupy. We humans walk on our two legs because that’s part of the ecological niche we occupy. Natural selection, or some other evolutionary force, continues to select for each of us to move about that way. Their bodies are damn efficient at knuckle-walking. Our bodies are damn efficient at bipedal walking. Simple as that.

41 thoughts on “If upright walking is so energetically favorable, why do apes still “knuckle-walk”?

  1. So when the population of the ancestors that modern apes and humans shared split, the ones that would become human beings had an evolutionary force that preferred using less energy and drove bipedilism, or was there some other force that that caused us to walk on two feet like needing to use our hands?

  2. So, which came first… The longer legs or the upright walk? The weight distributing vertebrae or the pelvic bone that could take the weight?

    I think you have to make assumptions somewhere.

    al sends

  3. I fail to get the point of your arguments, but after all I am dumb, because I am an Creationist and have been for better then 45 years. Lets see you believe in evolution, because you do not believe in God or is it that you do not want to believe in God and therefore are an evilutionist? Truth is if God showed up on the seen and hit you over the head with it, you would still not believe. Your very prejudiced and I admit I am very prejudiced, why not just teach nothing at all about either position. The last alternative would be to kill all of us Christians so you can have the whole world to yourselves, apparently the evilutionist is the species that will best adapt or is it?

      1. I’m so tired of hearing this old myth: “you can believe in god and in evolution.” Not really. These two beliefs cannot both be true. God is a supernatural IDEA; that is, part of a supernatural dimension in the human mind. The supernatural exists in defiance of reality; its mythical beings overturn physical law in supposed miracles. It is a closed system. The supernatural is the product of magical thinking.

        Evolution is part of science, an investigative system which seeks to describe and understand natural laws, ie “reality.” It is open ended: evolution does not have a designer or a goal. Life unfolds as part of a prime principle of reality: CHANGE.

        The human brain can “hold” mutually exclusive beliefs because ideas are not things, and there’s a lot of junk floating around in our minds. The human brain and culture are the result of hoarding. Think of an extremely packed basement where nothing is ever thrown out. That’s why human beings are so confused!

  4. Skipping the usual condescending approach of evolutionists AND creationists alike (very present in this blog post also) I will simply ask if this theory presented as fact is the explanation:

    Any one, creationist or not, who thinks that bipedalism is a better form of locomotion should revise their train of thought. Apes still knuckle-walk because that’s part of the ecological niche they occupy. We humans walk on our two legs because that’s part of the ecological niche we occupy. Natural selection, or some other evolutionary force, continues to select for each of us to move about that way. Their bodies are damn efficient at knuckle-walking. Our bodies are damn efficient at bipedal walking. Simple as that.

    …then why did the early ape-man really see it fit to walk on two legs. Isn’t the basis of evolution that we do things from generation to generation out of necessity? Why would it be necessary to “hurt” ourselves for generations until we developed the upright position and all the necessary muscles for it not to hurt?

  5. Kambiz, thanks for the reply…

    I guess my next thought would be that the mechanical advantage of bipedal motion would only develop once the muscular, muscle development caught up with the ape/man who discovered he could see better or whatever from this vantage point.

    Those sill using a modified quadruped would be the strongest, most fit of the group. So, given the assumption that there is a “evolutionary force” that propels the advantage forward I do not see how this would lead to increased mating for the biped. It would be like he was the awkward teenager of the group and the pimply kids never got the girls.

    al sends

  6. Al, at this point, the very first hominins we have in our fossil record show that upright walking came about before we see really long legs like those we see in modern humans.

    How do we know this? Well, hominin footprints on a paleosurface tuff at Laetoli have been dated to be around 3.56 ±0.2 million years ago, which puts these footprints right about the time when Australopithecines were roaming about.

    When one analyzes the fossil anatomy, the Australopithecus hip and hind limbs very clearly show this hominin was bipedal, but these fossils also indicate very inefficient locomotive movement when compared to humans. They simply weren’t as bipedal as us!

    Throughout evolution, bipedalism, for some reason or another, has been selected for. We begin to see longer legs and more restructuring as we move down into the Homo lineage. It is safe to say that hominins that were more efficient in walking upright were surviving to reproductive maturity better, and passing along the alleles or traits for more efficient bipedalism to their offspring. That’s why you begin to see longer legs, and a restructuring of the back, etc.


  7. Aaron, excellent question. You are on a correct train of thought to think that some evolutionary force selected for hominins that used less energy and drove bipedalism.

    I’ll be straight up honest with you and tell you that I don’t know exactly why. Currently, there are actually at least twelve distinct hypotheses as to why bipedalism evolved in hominids.

    I won’t be summarizing them all, but I will summarize one of them that I was taught. Right about the time we see bipedalism evolve in human ancestors, we also see a change in the ecology these apes used to live in. Prior to the change, apes, like chimpanzees lived (and still live) in forests. The ecological change, I talk about, diminished forests in one region of Africa. Savannas emerged instead of forest land, and for the group of apes that were isolated from their forest dwelling brethren, it became more efficient and beneficial for many reasons to walk upright in the savanna than to knuckle walk.

    What we do know is that bipedalism evolved before the expansion in human brain size. The fossil record shows the anatomy, like the longer limbs, changed way before the big brains. The different hypotheses are not necessarily mutually exclusive and a number of selective forces may have acted together to lead to human bipedalism.


  8. Al wrote:

    ‘given the assumption that there is a “evolutionary force” that propels the advantage forward.’

    It’s not really that any “force” drives evolution. This confusion of evolution with progress comes about because the theory originated during the industrial revolution and still carries baggage from that time. The term “survival of the fittest” was first use to justify economic ideas. At the time everything was seen as progress, especially the inate superiority of the european “race”. I’d hope we were past that sort of thinking today.

    Back to the problem at hand. There would not be just one individual who could suddenly walk completely upright and so got all the girls (or boys). The whole suite of genes required would acumulate gradually in the population as a whole. Bipedalism may originally have been used only occassionally. So no awkward teenager or pimply kid.

  9. Terry, the phrase ‘evolutionary force’ was not mine but the original poster’s. That being said I see your point and your theory does deal both with the awkward teenager and the problem of inherent racism within evolution. But, it requires and even greater assumption on the part of the holder.

    What you would propose is that genes collect within a subgroup of a species until they reach some sort of critical mass. That the gene for a longer spine, for example, would just mind its own business until the stronger pelvis gene showed up to support it.

    What you end up with is not gradualism, as you suppose, but a sort of punctuated, burst evolution. And I do not see how that is an improvement in the theory at all. Would there not have to be some sort of outside influence that then pushes the species along to deal with that influence? That then requires another assumption.

    But let me ask you… If the mutation is not immediatley beneficial why does it stick around?

    al sends

  10. The question:

    “If the mutation is not immediatley beneficial why does it stick around?”

    I don’t think a mutation necessarily has to be beneficial to stick around. There’s a hell of a lot of variety in any species, including genes that appear to serve no useful purpose. Many of them remain in a population as recessive genes with no outward expression anyway. It’s just that if a change in ecology gives the particular gene, or suite of genes, an advantage it can then sweep through the population. This has relevance to your other point:

    “What you would propose is that genes collect within a subgroup of a species until they reach some sort of critical mass.”

    It is obvious any recessive gene can only be established through inbreeding. Therefore I am proposing almost exactly what you suggest. Once a new suite of genes is established in an inbred population the mutation is free to expand through the wider population, in which many individuals already have some of these genes in recessive form. And I suggest it is this that has given rise to the phenomenon of punctuated equilibrium.

    But this still doesn’t solve the problem of what selection pressure drove human upright walking.

  11. How does it matter in the end. The reality is what we do today. Walk upright and apes dont. The debate between evolutionists and creationists is a waste of time. Majority of the world is not Christian. So which group of creationists are we talking about? In a million years time, we may have changed some more. We wont be there to see it. So lets enjoy the discussion. By the way, I am a student of history and always am fascinated by discussios on the subject by palaeontologists and the rest.

  12. I am surprised that energy consumption is supposedly only one quarter, and if this is so, why so few animals have evolved bipedal locomotion. Mostly birds come to mind, and these mostly don’t use their legs to walk long distances. I always assumed that birds had evolved like this to free the fore-limbs for flying, similarly to humans who need their arms for manipulating things.

    Furthermore, living in a jungle surrounded by tasty fruit as early humans must have done, I don’t see energy conservation having been a top priority. In contrast, we find animals such as centipedes in deserts where energy-rich food must be scarce indeed.

  13. In regards to driving force, if giraffes evolved to have long necks, elephants long trunks. Why wouldn’t our ancestors not evolve due to the needs of the species to survive in there current environment.

    What about dwarfism in Elephants stuck in isolated islands in the west pacific? Scarcity of food may have contributed in that case.

    What would have been the deciding factor to have pushed our ancestors to change? Predators, food?

  14. Hello,
    I am a physical anthropologist. I think that the some of the comments here about “creationists” are cruel and unnecessary. The question referred to, “Why do apes still knuckle-walk,” is precisely the kind of question that led to much of the recent research on bipedalism to which you’re referring. The open hostility toward creationists reveals a certain intellectual insecurity. Aside from that, your approach toward science is uncritical and your evaluation of current research on bipedalism is too credulous. The evolutionary origin of bipedalism is extremely difficult to study with any precision, and the recent research to which you’re referring is far from convincing. The fossil evidence abundantly demonstrates evidence for a physical transition from non-humans to humans. Relatively little is currently known–and will probably ever be known–about the precise reasons for the transition to bipedalism, however. Therefore if you want to debate with creationists, why not concentrate on the strongest evidence? And why increase people’s hostility toward and misunderstanding of evolution, through an attitude of intellectual arrogance?

  15. OK, I will admit i have not read many of the comments for the sake of length and also to keep myself from most likely doing multiple face-palms. But I will state just some general ideas that I think most people do not really look at, especially those people that post on articles like this. For starters, does evolution rule out a god? No. Even if all of these scientific theories that creationists argue against are completely true there still may be an omnipotent being beyond what we can see. Our stories may not be all be true but there still may be a God out there. Secondly, religions have played a huge roll in human civilization. But at this point in time, I personally think that we need to stop worrying about the hard evidence and stories, and focus on the moral issues. Being respectful, kind, and helpful, etc. etc. etc. I personally believe that human civilization has moved beyond the primitive state where they need to feel threatened into doing good things. I do not have anything against any religions. In fact, I agree with a lot of moral teachings of many religions. I simply am asking EVERYONE to look beyond the religion and to look science and take a look at what is really important.

    P.S. I know this comment got a little long, which is exactly the kind of thing that I dislike, Sorry!

  16. I tend to subscribe to the aquatic ape theory for the evolution of bipedalism. Basically, it says we didn’t go into the savannas when the environment changed, but migrated to the shallow waters instead. In the water we were practically forced to walk upright or drown. Monkeys and apes go into the water sometimes, and we can see thm walking upright when they do.

    In addition to bipedalism, we have other deviations from the apes that can be indicative of an aquatic ancestry, such as fat babies, our prominent nose, our ability to hold our breath (which is essential for speech, btw), and other adaptations (hairless bodies, except you Robbin Williams, wtf?).

    Plus, it’s just cooler to think we chilled out in the water with the fish. The savanna has lions and pack predators that would tear us up, the water has fish (brain food anyone?).

    1. You can believe in all the straw men you want, but you’re wrong. We haven’t found an aquatic ape nor does it look promising that we’ll find one too.

  17. Kambiz,
    What is the point of your last comment? Are you somehow opposed to moral thought?

    Robert S.- Thank you for your intelligent comment. You are the one who should be writing web articles for this site.

    1. No, I’m not opposed to thought, Mrs. Cook. In fact I’m all for rational, science based, intelligent discussion — not Bible thumping ignorance.

      Also, welcome to my site.


  18. The question of “If upright walking is so energetically favorable, why do apes still knuckle-walk?” is not a stupid question, but really rather deep. The assumption underlying the current theories for our bipedalism is that gradually some bent-hip-bent-knee (BHBK) bipedal gait or some quadruped gait transitioned to our efficient upright inverted pendulum (IP) gait. That is, some long term selection pressure acted on natural variations to produce our IP gait. This transition to IP gait seems to have happened only once, so the question above can be restated as such; if the selection for IP gait is so strong, why has it occurred only once?
    To me, this casts real doubt on the validity of all the current theories for the rise of bipedalism in human ancestors. What could those particular variations mentioned above possible do that made the difference between BHBK and our IP gait? No differences seems to really be an absolute necessity as supported by trained Japanese macaque monkeys that can walk upright with an IP gait (tachibana2003, Hirasaki2004). Because mammal brains are very plastic in the motor cortex and reflexes, bipedal walking can even be done by dogs and rats. Furthermore, it is that plasticity that lets those macaques become very skilled at IP gait, but that skill does not then translate into normal usage of the gait. When not on the training task, they revert to a BHBK gait or a quadruped gait. Why would they do that? They are well rewarded when on the training task but not at other times for the IP gait.
    While our IP gait seems very natural because we are so expert at it, it actually is a learned gait. Toddlers do not start with an IP gait, nor do they start with a BHBK gait. It takes newly walking toddlers several months of rather intense practice to become competent IP walkers. It seems to clearly be a learning time.
    So back to the modified original question, if an IP gait is possible via learning in monkeys and presumably other apes, why has our IP gait emerged only once? May be another interpretation of the question is; why is it that humans can easily do a BHBK gait, but we learn to do an IP gait naturally, and apes can learn to do an IP gait but do a BHBK gait naturally? The answer to this question, I think, really lies at the heart of why we are IP bipedal.

  19. To Mark Riggle,: the newborn brain always has an acclimation period to the body it must controll.
    To Mrs. Robert Cook,: looking at green beans, and old bones, and the motion of stars leads to very interesting concepts, binding themselves into a mass that is science. Gods are an arcane dying concept, and it’s dwindling adherants feel science is the one taking off the white beard and red coat to reveal their fathers.
    To iSwim,: I think the nakedness is to increase sweats efficiency, babies aren’t born fat, lastly, what about crocodiles?
    To morals,: you don’t exist. A grandmother will run into a burning pre-school to save first her grandaughter, THEN her daughter, then maybe fellow creatures that could help her genes continue. The lesbian stripper was diddled by her dad. It’s like Nat King Cole sang in Nature Boy….

  20. @ Patrick,
    While it is very possible that you are correct, quit being such a baby. “Gods are an arcane dying concept”? Not any more likely than the theory of evolution, etc.
    Remember Patrick, people considered to be the most intelligent of society not long ago were those who thought the world was flat, due to their “logic”. I’m not saying you have to be religious, or NOT to believe in evolution, etc (I do (to some extent)) but I think it’s arrogant and ignorant to keep such a closed mind to anything that we havn’t proven 100% COMPLETELY correct. After all, “they could see with their own eyes” that the world was flat.
    I’m trying to be as little biast as possible. I am in fact christian, but maybe not so much someone who goes word-for-word out of the bible. As stated earlier, I’ve devised my own beliefs (which havn’t yet been proved wrong by any theories) in which evolution is a very likely.

    Just reminding everyone that humans actually “don’t know shit” ;) Keep an open mind kids.


    1. Lukas, what are you trying to say?

      Are you seriously using Galileo’s theory of a round world that rotates around the Sun to state that we should also keep an open mind to the idea of an Intelligent Designer?


  21. Kambiz,
    I am glad you are the moderator for this site. You don’t let people get away with ludicrous ideas/ statements and you are not afraid to keep it real. (i.e. tell creationists that they’re simply wrong. and stupid too.) Love it.

  22. @Kambiz

    I love the word intelligent designer :P :)

    But no, I’m just saying just because evolution is something we’re looking into now doesn’t rule out the fact that there could very well be something about our creation that we know nothing about, SUCH AS an intelligent designer. It could be anything. I don’t know anymore than you do, and vice versa.

    The comparison I was making to the round/flat world is that the socially accepted view of the world, by the top dogs of the time, was that the world was flat. There were those (mainly Galileo) who believed otherwise, and were considered absolutely absurd (and in his case prosecuted) in the eye of the public. The fact that he was found correct by the end may or may not be relevant to this situation.


    Just to clarify, I’m not a “stupid” creationist. I’m not creationist at all. I personally think that that’s taking it too far. HOWEVER, I don’t see why it’s wrong or stupid in any way to be creationist. Let them be, you won’t tell them they’re wrong and get away with it unless you’ve died and come back to tell the tale with memory. Unlikely. Grow up a little, both sides take this fight way too seriously.

    Wrong or right, let people believe what they want to believe without harshing on them. My point is who knows. As much as one side may think they’re right, the other side side believes the same thing just as strongly. Back off guys. It’s not hurting anyone. Leave them alone. They’re good people! :P

  23. I’m not familar with this argument at all, but the points being made imo are completely arbitrary. The better question is why didn’t chimps evolve to be bipedal?

  24. Everyone seems to be ignoring the part mutations play in evolution. “Mistakes” can prove to be beneficial as well as harmful, and without mutations, change would be nonexistent.

  25. Good points Lucas and dexadog my two cents in response to google search is that environment plays a factor in evolution as well. If chimps began spending alot of time walking around they would eventually evolve similar bipedal mechanisms as we did. The crux of evolution is that life is easier for those with the random mutations mentioned by Lucas that happen to be beneficial aka an ape walking around millions of years ago with a bigger big toe than the rest.

  26. knuckle heads! ‘I’ve got a good idea, lets lets stand up whenever a really fast moving predator attacks, and run on two legs, this ‘ll be a good way also, to lose strength in our very powerful shoulders and arms. and in about 5-10 thousand years our species will reap the benefit’! just an imaginary thought from a prehistoric ape wandering across the savannah in Africa some time ago,

    IF there’s any for of evolution going on better to look at how apes regulate their body temperature and ask why humans, supposedly from the same Savannah, don’t but rather use a system more akin to aquatic animals by employing subcutaneous fat

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