PHOTOGRAPH BY MICHAEL POLIZA, NATIONAL GEOGRAPHIC CREATIVE
Published May 27, 2014
We humans may be weaklings by nature.
Humans appear to have evolved puny muscles even faster than they grew big brains, according to a new metabolic study that pitted people against chimps and monkeys in contests of strength.
The upshot, says biologist Roland Roberts, is that "weak muscles may be the price we pay for the metabolic demands of our amazing cognitive powers."
Scientists have long noted that the major difference between modern humans and other apes, like chimps, is our possession of an oversize, energy-hungry brain. (Related: "Human Origins Project.") It was the development of that brain that drove the evolution of our early human ancestors away from an apelike ancestor, starting roughly six million years ago.
But the question of just why and how we evolved such big brains, which consume 20 percent of our energy, has long bedeviled science.
"A major difference in muscular strength between humans and nonhuman primates provide one possible explanation," suggests the new study, led by Katarzyna Bozek of Germany's Max Planck Institute for Evolutionary Biology.
The study, published Tuesday in the journal PLoS Biology, looked at how rapidly the metabolic needs of various organs, ranging from our brains to our kidneys, have evolved. Some scientists have suggested that the rapidly evolving metabolism of the human gut, for example, drove the brain's evolution.
Instead, the new study suggests that muscles and brains have essentially traded off their energy use.
The researchers found that in the last six million years, people have evolved weaker muscles much more rapidly—eight times faster—than the rest of our body changed.
Our early ancestors likely possessed apelike strength, at least for the skeletal muscles analyzed in the new study. Today our brawn is much reduced, while other body tissues, like kidneys, have remained relatively unchanged over millions of years.
Over the same time period, the brain evolved four times faster than the rest of the body.
Roberts, a scientist with the Public Library of Science who wasn't involved in the study, called it a "tantalizing preliminary enquiry" in a commentary accompanying the new paper.
He notes that "human muscle has changed more in the last six million years than mouse muscle has since we parted company from mice back in the early Cretaceous." That was about 130 million years ago.
To confirm their findings, which were based on analysis of 10,000 metabolic molecules, the researchers pitted people, chimps, and macaques—another kind of monkey—against each other in a contest of strength. (Related video: "Genius Chimp Outsmarts Tube.")
All participants had to lift weights by pulling a handle.
"Amazingly, untrained chimps and macaques outperformed university-level basketball players and professional mountain climbers," Roberts says. People were indeed only about half as strong as the other species.
Looking for an explanation, the team also subjected the macaques to two months of a "couch potato" lifestyle: little exercise, high stress, crummy food.
At the end of the two months, a strength contest with the couch potato macaques found that the animals' strength hadn't declined much. In fact, the scientists deduced from those macaques that humanity's "soft" lifestyle accounts for 3 percent of the strength difference between people and monkeys.
That appears to confirm the idea that weak muscles, along with a weakness for the couch—so conducive to brain-intensive exercises like watching movies and reading—could be our evolutionary inheritance.
Follow Dan Vergano on Twitter.
What about tool-use? While there are many animals that create and use tools, humans create the most and depend on them more. The more tools that bring food within easier grasp to fuel our learning, enlarging brains, the weaker we became due to not having to work quite so hard in acquiring the food. I think the big question is: When did we acquire this huge desire to learn? Many animals have curiosity, but human curiosity knows no bounds. We don't want to know simply what something is, we want to know what makes it tick...and we will go to all ends in the course of discovery. What gene started this drive in the first place?
Possibly part of the basis for the "dumb jock" "puny nerd" stereotypes as well? Perhaps some people and population groups have traded off brawn more than others.
Does the "weaker body stronger brain trade off" idea work across other species as well, that is species that have also evolved relatively large brains?
Are dolphins, orca, giant octopi, raccoons, elephants for example (if they are smarter now compared to before) considerably weaker than their prehistoric ancestors? For simplicity sake, how about lab rats?
Assuming that food is relatively plentiful, wouldn't a strong physical body be better suited for supporting and protecting a calorie hungry brain? Wouldn't the combination be a win win combination?
Are not all creatures still evolving and adapting? If so are there creature that have become more intelligent? If so, has anyone observed a marked decrease in physical ability of these creatures?
Great story but how about some actual evidence. The use of words like; may, possible and likely should give it away but it looks as though most readers are turning these speculative words into statements of fact. Some monkeys are stronger than some humans (not sure why a study was needed to conclude that) And yes that is a fact and that is where the science finishes and the creative writing begins.
Actual observational science shows that our genome is devolving (that is, we are losing information not gaining it, which judging by the comments, not everyone understands is required for evolution to occur) not evolving. I'm not sure many people grasp this fact.
@Janus Bina Babies are born so dependent on their mothers because if they left it any longer to develop they simply would not fit out of the birth canal. The discovery of fire ties in well with the development of our bigger brains... we cooked food, which made it easier to consume more calories.
Evolution happens because we are not just carbon copies of our parents. When DNA is split there are imperfections in the reproduction which creates variations in our own design (hence you are not identical to your mother/father/siblings). These random imperfections/differences sometimes manifest in a trait which is more suited to the current environment than those which we inherited. Therefore we lose body hair, grow bigger brains, get weaker. Neanderthals probably died out due to disease which we survived due to a better immune system (a result of random mutations that are more appropriate to the current situation).
40 years ago when I was younger and exceedingly fit I read a study on grip strength in chimps. Seems a 90 pound chimp could grip over 1000 pounds. And I had been so proud of the 225 pounds I could compress a scale.
Their true hands and foot hands are necessary to their survival, living by defying gravity in trees.
My survival depended on going distances on the ground efficiently and remembering where and when to go and find passive food.
DNA is proof of evolution in and of itself. To deny evolution is to deny that DNA is the basis of all characteristics that allows life at all.
The devil did not put DNA into living organisms to match what god made for the sole purpose of fooling us. That would be similar to god putting all the photons in space at the right distance and velocity so as to appear that stars are more than 6000 light years distant.
There is a point where knowledge overcomes ignorance and the complications arising trying to force falsehoods becomes more complex than the truth.
Truth is simple, and what appears to be complex truth is merely a great many simple facts working together.
Each rock in the Great Pyramid is simple but when each simple rock is put in it's correct place we have a monument of grandeur.
DNA and evolution are composed of simple straightforward blocks all arranged into staggeringly beautiful life.
Could endurance play a part in our smaller muscles? Smaller muscles would have lower lactic acid build ups and allow us to have higher endurance. This endurance was a huge factor in our evolution. Or as monkeys dont seem to have massive muscles are they just simply more compact? I dont understand this from a biological medical stand point. Would anyone be willing to clear this up?
Since the objective was comparing strenght why were basketball players and mountain climbers chosen? Wouldn't power lifters and gymnast been a better comparison?
MONKEYS ARE related to humans because god made them from similar dna etc
and the neantherthals where just a diffrent type also they didnt die off the bred as
their massive brains helped themto understand that they would die out . they might be smarter than we tought
How does it happen that apes decided to give up having feet that work as hands, give up most of their strength, start to need clothes and shelter, and have off-spring that need care for more than a decade?
What processes could have been involved that required exchanging such useful features for the possibility that a bigger brain might be trained (over decades) to be more useful?
And if a large brain is so important, why did the Neanderthals die out? Were they not as smart as us?
Time to build theories based on evidence?
Thank you for your article. While we do not know where scientific research will take us, it is always a hopeful sign that we are using our brains to discover the past truths and plan for the future through this scientific research. We do not need to be held back by ancient fears that the "gods" would get us if we didn't sacrifice something, including other human beings. Mostly it seems that major religions were formed to maintain power and control over people, and marginalize women especially, so that no one progresses to the point that they realize they really don't need religion for anything. It would definitely put a lot of people out of work and out of power. The "scriptures" may contain valuable information regarding the past, but they should not be used to control the human future. There may be a time that we outgrow this planet; we need people to be free to examine our past and find ways to cope with issues in the future. My humble perspective of at least two current major religions is that they appear to prevent this freedom. For the sake of argument, even if we were "created" as we are now, and did not "evolve" from lower life forms, our "creator" would surely want us to progress and not regress, otherwise "it" would not have "given" us such an inquiring mind. The discussions regarding "creation" and "evolution" will probably continue even after/if/when we have proof of one or the other, just for the sake of argument.
@Jane Davenport Exactly. Everyone knows man is weak because God took the rib from Adam's right side instead of his left to make Eve.
@Jon Col Our genome never "devolves" we always have the alleles in our gene pool, however other alleles are selected over others (ie. Natural Selection.) That being said, mutations occur as well. Some aspects of evolution are beneficial and others aren't, but it is impossible for our genome to devolve.
What you have tried to explain here is natural selection. This is not evolution. It involves the use of existing information and is not a mechanism for creating new information. It usually involves the loss of existing information. That is not to say that the loss of that information is not beneficial in certain circumstances.
Gregor Mendel showed that our characteristics are passed on from our parents. He did this by actual observational science. Charles Darwin (a contemporary of Mendel) on the other hand saw some finches that looked similar but with some different characteristics and without any scientific investigation came up with the Theory of evolution.
You can believe what Mendel showed through experimentation of what Darwin thought up ( quite creatively I must admit) but not both.
@Philip Olson You were doing so well until you threw fiction into your answer. Please stick to science and leave superstitions out of it...
@Warren Bailey because power lifters and gymnasts are specially trained and they present a non-average human strength. While basketball players for example possess relatively the same brawn and exercise relatively the same as our ancestors. We have to compare comparable data.
@Eliasz G. The claim that we use only a limited percentage is a myth.
@Eliasz G. We do use 100% of our brains....
@robbie butler God is a creation myth, so your comment is absurd.
@robbie butler If you don't believe organisms evolve, you probably are not going do contribute much to biological science conversations.
@Janus Bina Well, the big advantage that humans had over Neanderthals, based on what we know now at least, is that humans had a much higher levels of hand-eye coordination. To put it another way, humans hunted using bows and hurled devices and could kill from a distance, Neanderthals could not. This was a game changing advantage. That, and the ability to fashion sharp weapons are huge advantages.
Our ancestors didn't decide to give anything up. Evolution is an unguided process and is not something that organisms decide.
Your questions has some built in assumptions that are not true.
1) grasping feet are better than energy efficient feet under all circumstances
2) we lost strength, hair and developed longer maturation times in advance of and in anticipation of gaining intelligence
Let's address those assumptions...
There is a trade off between the benefits of being able to grasp with your feet and being able to walk efficiently with your feet.
It is a combination of lifestyle and environment that determines which configuration gives greater fitness under which conditions.
The fossil evidence shows that human like feet evolved before other human like features but this wasn't in anticipation that one day higher intelligence would result.
Human like feet have a natural spring that makes upright walking more efficient. This would have been a benefit to animals walking long distances, The upright stance also lets you see further.
Our ancestors could benefit from being better upright walkers independently of their ability to think. The benefits would be energy efficiency in locomotion and the ability to see further in open grassland.
The same reasoning applies to the reduction in hair. We not the fastest animals but we have great endurance. Our lack of fur and are ability to sweat a lot lets us run fast animals to exhaustion. This ability is beneficial in its own right and does not depend on an aptitude for high intellectual achievement.
I have some observations on your questions:
1) Your questions are trivially easy to answer - you could have answered them yourself.
2) Your questions seem to be rhetorical. It's as if you don't really want to understand how those features could evolve. It's like your intention was to show how evolution could not work.
3) Your inability to answer your own questions is because you don't WANT to answer them.
@Janus Bina read "the origin of species", these "deep" questions you think you are asking have all been answered over a hundred years ago...
to give you a simple answer, when chimps move away from the jungles to areas without many trees, hand-feet are no longer useful, so over thousands and thousands of years, the ones with shorter finger-toes out competed and out-bred any that still had long fingerlike toes...its so much more complex than that, but something tells me you are going to opt for an ignorant creationists viewpoint, no matter how detailed a response you receive...because religious malarkey doesn't require learning or understanding...and that's why it is so popular with the uneducated...
@Janus Bina see "natural selection". There is plenty of evidence that supports evolution -- all you have to do is look.
@Hilda Roberts no it's not...no more than gravity is a matter of belief...it's proven scientific fact...
@Hilda Roberts But evolution is a matter of fact.
@Brittain Elswick @Jon Col I think he is referring to the fact we have two less chromosomes than our primate ancestors due to the fusing of two that occurred in humans. I would however argue the point that any change, whether an addition or subtraction, would qualify as evolution. Correct me if I'm wrong but wouldn't devolution mean the genome is reverting to a former state?
@Jon Col So how did the first polar bear become white? That was a DNA mutation giving advantage to one member of a species over another. That is evolution, however made up you wish it to be.
Or perhaps specific science facts do not fit your worldview which seems to contain magic as a fundamental aspect?
Or perhaps mentioning discounted religious beliefs brings in superstition by association?
Your reply has me puzzled as I espoused no belief in magic or any religion or superstition in my comment. This lack of belief in nonsense may be the very problem you are finding fault with. Secular humanism is not a belief in magic, it is merely acknowledging facts as observed in studying nature.
Humans are part of nature, not separate from the natural world.
@Seth Forbis @Janus Bina haha "religious malarkey doesn't require learning or understanding?" Seems like you're the one who's coming from an ignorant viewpoint. Please ask any reverend or priest how many years of schooling he went through. They have master's degrees and sometimes a PhD. Not to mention most of history's greatest philosophers were religious.
And to rebuttal your "origin of species" comment, Darwin never claimed the book to be based on science at all. It was merely his own logical understanding. He doesn't use any fossil evidence in his argument because he knew it would directly contradict his claims. Here's the quote,
"Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain [fossils]; and this, perhaps, is the most obvious and serious objection which can be urged against my theory." - Charles Darwin
The original poster merely wanted to point out that there is no logical connection between apes and humans based upon macroevolution. Nature definitely wouldn't choose a human to be king, it goes against all that is natural.
@J. Reynolds @Janus Bina My questions are quite specific and I have yet to find evidence to deal with any of them. Reciting the magic incantation "Natural Selection" does not seem to me an adequate response.
@Seth Forbis @Hilda Roberts Proven? Well, let's not be hasty with drinking the Kool-Aid. Can we really compare Gravity, which is measurable and meets the high standard of the scientific method that test results are repeatable, with the Theory of Evolution, which despite MANY attempts has not been repeatable and on the processes of which even a small sampling of scientists would not have a clear consensus? Please count how many speculative terms--like "appears to", "likely" and "suggests"--are in this one article alone. You will find about the same proportion in much of the literature. Sorry, but this doesn't meet MY standard for "proven scientific fact"! I'm not sure why it meets ANYONE's standards other than they want to believe it. So as Hilda said, pick your belief!
Punctuated equilibrium, if you had an education in what you are debating, which is requisite, the answer would naturally be known. Did any of those seminary "PhD's" discover anything new? At best they are highly biased archaeologists, which have only limited use within their cultural clade.
@Janus Bina Why don't you do some research to answer your questions, which don't actually have much relevance to the article...
@Janus Bina Intelligence is more important that strength and dexterity to a point where natural selection may just start to not select for the traits you mentioned. Go to the zoo. Notice you're on the more favorable side of the glass.........
@Janus Bina Natural selection *is* the process in question.
The environmental conditions that selected the traits you are curious about are open to speculation.
@Chris L You are confused.
There is lots of evidence for evolution, all of which is repeatable, but probably not by you as you seem to be confused about what scientific research is, never mind its processes.
@Chris L why do you think anybody is being hasty in "drinking the Kool-Aid" given the massive amount of evidence supporting evolutionary theory?
A small sample of repeatable experiments that can be performed demonstrating the validity of evolutionary theory:
*Richard Lenski's E. Coli long term evolution experiment.
*Evolutionary computation. If evolution didn't work, we wouldn't be solving difficult numerical optimization and engineering design problems with methods inspired by Darwinian evolution.
*Evolutionary theory predicts conserved genes across related species, and these genes do indeed exist -- see: molecular genetics.
@J. Reynolds @Janus Bina Except natural selection wouldn't choose humans to advance... natural selection is merely how much of a mutated species survives, it doesn't account for why. The original poster posed the question of "why?" in order to point out that in reality, you have no idea why nature would naturally select homo sapiens over the neanderthals. It makes no sense.
If our advanced brains were the reason, why haven't other animals become more intelligent?
@Grant Choi Other animals are becoming more intelligent, it just takes time, more time than you or I will live.
Welcome to Nagoro, Japan. Human population: 37. Doll population: 350. When villagers die or move away, a woman makes a life-size doll and places it in a spot that was meaningful to that person.
As an ancient drought took hold, a water temple saw more offerings from desperate Maya, archaeologists report.
From sugarcane farmers in Mozambique to fishermen in the Philippines, here's a collection of some of the best images from our Future of Food series.
The Future of Food
How do we feed nine billion people by 2050, and how do we do so sustainably?
We've made our magazine's best stories about the future of food available in a free iPad app.