For the people who don't understand (such as Dawn) and those who will nod along to her questions: There is one simple misunderstanding. Evolution isn't a conscious force moving us towards being perfect beings. Evolution works when unadaptive traits start to weed out those among the species that have them. Why do we still have skin cancer (or any diseases, for that matter)? Well, there are multiple reasons, but there are two important ones. First, viruses and cancers are all forms of life themselves, and they evolve to survive like we have. It's like asking why are there still tigers and lions and other animals that can kill us. Evolution doesn't favor humans, it favors any life that can survive. Secondly, evolution doesn't eliminate every 'negative' trait, only those that are maladaptive to procreation. Hence why are bodies shutdown in old age. There is no process that will weed out the common symptoms of old age because by that point most in the species will have already reproduced, thus ensuring the continuation of those particular genetic symptoms. We lost our fur because it led to disease that killed our young. Skin cancer, however, generally doesn't affect people until later in life, so we never evolved an adaptation that would eliminate it (or, rather, someone might have been born with such a mutation, but because it wasn't any more beneficial for procreation, it didn't overwhelm the status quo of our genetics). These are simplifications and a lot more detail could be given, but this should at least answer Dawn's (and the like-minded) questions.

Well, since the comments are going down this road...Evolution just makes more sense than creationism. Scientific evidence > 2000 year old book.

Dawn, why are we not evolving to protect against skin cancer, etc.? I don't think you understand how long these changes take.
Look for instance at the example about losing our hair. People did not in a few generations decide--it's hot. We'll have less hair when we are born now. Somehow our bodies will know and make the children this way. Instead, over thousands of years, people will less hair lived longer because it was less likely they would get diseases from fleas and ticks. Those people had more children because they lived longer. Eventually, the hair characteristic was bred out.
We are evolving--some kids are being born without useless little toes,and Tibetans have developed slightly more dilate blood vessels to combat the cold over 3,000 years and that's pretty fast for this stuff. It takes so long to get to a significant difference you will not see it.

Dawn, evolution is not process of hundreds years, but a process of hundreds of thousands of years.

Dawn's comments are very revealing. Maybe we are closer to a species divergence than we realize. The last time this happened was 200,000 years ago with the emergence of homo sapiens. It cannot be a coincidence that this was also a time of huge climate change. May I suggest homo scientiens and homo superstitiens?

I think Dawn's comment is very revealing. Perhaps we are closer to a species divergence than we realize. The last time this happened was 200,000 years ago, again accompanied by a major climate change. I don't think we can ignore the coincidence. Can I suggest homo scientifiens and homo superstitiens?

You guys are fighting for nothing i believe God made us! I think that the theory of evolutions is fasinating!BUT Get this God made us i am with John Gilbert

Oh brother! What an unscientific load of rubbish.

The last part of #2 is false. I routinely suppress hiccups by thought alone. It has become almost automatic; by the time I notice I have hiccups, I have usually suppressed them already.

I think this article is a joke for real! it is a stretched to believe any of this. My question when I see the picture along with the article is, what is the next step? Why are we not evolving? of course you would say that our enviroment is inhibiting us, but really if we were evolving to our bodies would be crippled, from a bridge shaped spine as the article suggested to a S and then it would continue on to a C, is that not correct?? and what happens to our skin after we have lost our hairy exterior??? I guess you would say elemental damage like sunburn or cancer. Why would our body not evolve with another protective layer? Just a thought

I am fond of the theory that we have descended from aquatic apes who lived near and utilized streams, lakes, and seas. Why do we stand on two legs? To see a greater distance in a savanna means such primates could also be seen by predators from greater distances. Moving about in water on two legs to keep their heads above water sounds possible to me.

Articles on the "Aquatic Ape Hypothesis" can be found by searching...

To Coert,

To what Darwinian stereotype that evolution promotes racism are you speaking of. This idea is an aspect of social darwinism and had nothing to do with Darwin or human evolution.

Most scientist in this field would agree that the differences between different races are so minute that they are almost irrelevant to any real discussion beyond identifying migration patterns.

p.s. If this picture represents a timescale then only the last figure would be a member of our species. The others would not even be subject to the term race.

I really enjoyed reading this article. Lovely, humourously told science, is a pleasure to read.
Interesting point about the 1930s nutritional research that a reader mentioned in relation to wisdom teeth. That was the one I hadn't heard before in the article, which leads me down the garden path of further enquiry to confirm or deny... Maybe I should've been a scientist. Maybe I still can be. Maybe we all are. Big brains are wonderful.

Hrmm I have to say that I'm a little skeptical of #8. I thought that there are archaelogical finds of recent ancestor skulls full of healthy, straight teeth, without occlusion. I perceive today's epidemic of malocclusion as having modern malnutrition as the cause, not evolution. Shrug.

I believe #8 is flawed. If you read Nutrition and Physical Degeneration by Weston A Price, you see that isolated peoples living on traditional diets in the 1930s had fully formed dental arches, no cavities and plenty of room for their wisdom teeth. Their modernized neighbors had malformed dental arches, misaligned teeth and cavities galore. It is our modern diet that makes the extraction of wisdom teeth so often necessary, not evolution.

"survival of the sickest"
Is a book that goes into how many of our diseases have there roots in positive adaptations.

I didn't realize I was such a mess until I read this article! But seriously, even with all of our flaws and cornucopia of physical problems, we are as a species the greatest problem solvers in history. We will eventually figure out how to solve what ails us, regardless of the discomfort. And sure, the world seems like it's in a bit of a mess, and perhaps it is, but there are those pockets of brilliance and goodness that really aren't as isolated as we sometimes think and that should give us cause to hope. As a species, we're going places. And that's always something to anticipate. Nice article.

Commenting on the illistration is completely irrelevant. This article has absolutely nothing to do with race, it has to do with human evolution as a whole. The illistration is obviously meant to depict HUMANS, not the white race. To say that it's racist because the most evoled figure in the illistration appears to be cacausian is ridiculous. It's an example. Does Honda advertise new cars in every single color they produce? No. Because they advertise the MODEL of the car, not the color.
If you want to draw up the new evolutionary illistration that depicts every single race evoling through time be my guest. But it sure will take you a while.

Awesome Article.

It is simply astonishing that in the politically-correct USA, this extremely racist picture is still allowed to be shown. It is interesting that African-Americans fight for their rights and equal treatment on every front, yet meekly submit to the Darwinian stereotype that they are less evolved and therefor inferior to the so-called white race.

Mind boggling, to say the least.

Interesting print, which leads me to assume the Smithsonian agrees with Darwin , that non white people never evolved as far as white people.

An interesting article written in a light-hearted way. I'm in no position to challenge every last detail, & nor would I want to: I firmly believe the central point is true. ( Dare I use that word?)
Wheels: tongue in cheek, presumably. And some amusing responses. But some contributors use terms seeming to imply evolution is purposeful, with an end in mind,which of course it most definitely is not.
I object to the (unfunny) comment about why women talk a lot. This is sexist/misogynist. Is it that we talk a lot, or that we talk a lot about things men don't find interesting? We might not always find men's habits, interests or topics fascinating either........but let's have a bit of respect, & not throw out gratuitous , negative generalisations. (yes, I'm English, we spell it like that.)

To Unger (and others) :

RE_ large jaws and room for wisdom teeth:

anyone ever see Andre the Giant?? human-growth-hormone makes the jaw huge . . Those ergaster proto-humans had more growth hormone and the larger jaws and muscles that result from TgH. We can duplicate that . . . except some find scientific manipulation undesirable . . RH

To Ibraham above:

(H.ergaster or H.heidelbergensis? Out of Africa before us, stronger, faster, just as much brain capacity)

If the evolutionary dead ends above had "just as much brain capacity" as we weakling Cro-Magnon . . why did they get stuck for a million years with broken stone tools . . instead of cast bronze or hammered iron oxide . . Their success was long-lasting but very limited . . RH

It's just my personal opinion but i think the fossil record tells an incredible story of the evolution of consciousness. Every time there was a mass extinction, bigger brains were evolved twice as fast. If you have spiritual beliefs, but are not constained by books written thousands of years ago by guys who didn't even know what those lights in the sky were, you might see what I see.
posted by DAL 2/27/11, 7 p.m.

Evolution as defined by Darwin is a patently flawed concept. Many of the instances quoted above are not evolution, (natural selection) but genetic engineering, e.g. corn from grass, tetrrier from wolf etc. The weaker H. sapiens rules the earth. Why not the eminently better equipped H.ergaster or H.heidelbergensis? Out of Africa before us, stronger, faster, just as much brain capacity. We represent the 'Survival of the weakest.' Publishing soon. Have a nice day.

Great article,I would like to say to the religious nuts that evolution is in action every day all around us.Just look at corn for one, not long ago it used to be a grass.Dogs as well I have a tiny little Terrior that was not created that way she came from wolfs. And that is evolution in just a short time.Not to mention the thousands of different creatures we have forced change upon,and created for our own uses.I think its time for us as humans to step above fairy tales and magic,and for us to give up the god theory, and start to focus on reality.
Thanks Smithsonian for your great wealth of knowledge.

Debate is often a wonderful thing, and I'm not nearly as up on human physiology and paleontology as I probably should be, so I don't have much to contribute here. But about that scientific name for us...standard nomenclature is that the genus name, _Homo_, is always upper-cased, while any other designations (species, subspecies, race, etc.), such as _sapiens_, are lower-cased. So Rob, it should've been, "[...]the evolution of _Homo sapiens_ has left behind[...]"

And frankly, I like the arguments for _Homo sapiens sapiens_, us Cro-Magnon types, and _Homo sapiens neanderthalensis_, or Those Other Guys. I've both met and heard about folks with the same general builds as Those Other Guys, arm length and leg length ratios, partial brow ridges, etc. I think we were close enough to assimilate the poor guys, or they "hid out" in us when their Ice Age melted down.

Two cents from a biologist/copy editor! :-)

The 'God's test' thing is a mistake. It's not accurate at all. Our bodies are imperfect because all of creation fell from its original perfection when sin entered the world. Every living thing's genome has been corrupted increasingly more ever since. It is rather difficult to defend a creation science view when Bible believers can't be bothered to educate themselves well enough to give a proper defense. But that is no excuse for painting every one of us as ignorant,uneducated and narrow minded. There are many who are just as intelligent and educated as the old earthers and willing to rebute the old earth arguments

And people should not make attacks about being close minded when it's the old-earthers who are truly the close minded ones. We offer plenty of evidence from the same fossil and geologic records that shows the Bible's view is correct, yet old earthers are still too blind and afraid to admit that we are the correct ones and that science supports the Bible. It's not us who will eventually fade, it's the attacks on God's truth. God's truth is all that will remain in the end, and all will eventually confess that truth at the end of time.

All this sounds great and makes logical sense except for the science of mathematics.

The earth is only 4 billion years old for starters. Life has existed for only for a fraction of this time. There have been several total extinctions in the earth's history as well. The fossil record proves this as a geological fact.

They have also determined the time available for every possible DNA and genetic mutation makes evolution simply mathematically an impossibility. Space dust invented DNA by accident does not really add up either? Explain that one away. That is rather hard to do considering we don't even know exactly what DNA is or how it does it.

Evolution is a very tidy logical human theory but it is just that, one possible logical PC theory. What we actually know as humans on this planet, is only a fraction of a micron of quark in this complex universe.

The little green men theory is just as valid. No, I don't believe the earth is flat and I am college educated person.

Imagine that, I am someone who questions the scientific majority like Christopher Colombus. The majority of sciectist stated the world was in fact, flat cica 1492.

I can't help but think that we should probably give science a little more breathing room before we decide something is vestigial. While it's obviously hard to tell without more thorough research, based on the comments it seems like most of the things mentioned in the article are actually not vestigial or actually do work, or aren't the fault of leftover bits of evolution.

Okay, great article and all but a few things jump out at me.

Hiccups are diaphragmatic spasm or phrenic nerve irritation.

In regards the trachea, we have evolved constrictor muscles, palatal muscles, and the piriform recess, along with valleculae and highly sensitive vagal nerve ends in the laryngopharynx to stimulate strong co-ordinated cough and swallow reflexes.

The wisdom teeth are put under pressure by the age-wise expansion of the maxillary sinuses, and bone re-distribution, though it does occur later in life, does not happen to a greater degree in the maxilla.

Now if you wanna talk about poor evolution, that very maxillary sinus is badly designed, with its ostium (opening)quite high up, leading to difficult drainage and inevitable medical intervention, for infection.

And PLEASE don't be complaining about hernias, inguinal hernias occur because they follow a migrational tract from the testes. With these migrations, we would have no chance of survival, e.g no neuro development, thyroid etc.
Also, the intestines aren't compressed to the abdominal wall, they hang semi-suspended from the peritoneum and omenta.

And finally,
Mitochondrial myopathies and Leigh's disease etc. are incredibly rare, to argue that it's a mistake is to argue against fundimentals such as genetics.

Cheers.

Alex, you are mistaking 'random' for 'meaningless.' Random means that something came about through chance. If you had a 26 sided die and kept rolling it, you would get a string of letters, mostly gibberish. But once in a while you will get meaningful words, sentences, and even whole books, just by chance. If the phrase 'To be or not to be' came up after trillions of rolls of trillions of dice, it would be a meaningful string of characters. But it would still have been produced randomly.

Regarding causality, you might find this interesting:

http://philosopherspeashooter.blogspot.com/2010/07/causality-buffet.html

Jon.

@alex james
1. Nope, to kick start life only requires the assembly of a single self-replicating molecule. To get life in a cell require that over millions maybe billions of years these self-replicating molecules evolve to organise into the simplest viable cell, possibly going through several stages that are more and more "cell-like". This cell is much smaller and simpler than modern cells.

2. Checksums aren't that complicated compared to even bacterial DNA. That bacteria developed then is not surprising given evolution, indeed given that a mutation which provided this would increase the probability of viable offspring it would be surprising if it didn't happen. I replied to the article in the link you gave, totally disproving it as evidence against evolution.

3. You are basing your analysis on the simplest MODERN cell, which evolution says would be orders of magnitude more complex than the first ones.

4. Ingredients in the MODERN cell are only made by the cell, not ingredients of the first cells.

5. Nothing has to "line up" molecules combine and recombine all the time.

6. Atoms don't need to be "first arranged" into anything, plenty of complex carbon chemistry happens spontaneously.

7. Only if you assume that the first proto-cells had distinct parts of the cell which required different chemistry. There is no reason to believe this.

8. No, parts of the protocell must be protected by something, probably a naturally formed lipid layer.

How could anyone disagree whit what he is saying? He works for the SMITHSONIAN. I think he far more intelligent than anyone that comments on his article...

One cannot be reasoned out of a position that they did not reason themselves into.

Hence, god-botherers, who have a faulty standard-of-evidence mechanism, are impenetrable by reason, evidence and logic when it comes to their celestial emperor and/or their magic book.

Evolution will continue despite religious objections. Let's hope it will eventually reduce the need for delusion and religion to a vestigial remainder.

Raymond, re the useless pinky and ring fingers: they actually contribute most of the grip strength to your hand. You'd be pretty unhappy without them.

Smithsonian should track down David Teller and conduct an interview on his knowledge and opinion on various subjects. I'd pay good money to see that.

An alternate view, and the real answer. Scroll down to near the bottom to see it. It's not evolving that's the cause of these things, but rather the degeneration of the human organism from its original perfection.

http://www.answersingenesis.org/articles/2010/12/11/news-to-note-12112010

I’m afraid I have to disagree with parasite load hypothesis of why humans adapted “naked” skin. Uniquely, humans have cooling-sweat glands almost all over their skin. This is one unusual adaptation—most mammals don’t even sweat to cool—they pant through their nose to cool the brain. Medium-sized to large mammals may have eccrine sweat glands to cool some of their body, but normally in a spot or too, not millions & millions of glands all over.

As noted in the article, a human hallmark is, of course, a VERY fat head (huge brain). How to keep such a large brain cool (nervous tissue produces a great deal of heat when it burns lots of sugar just to run its daily functions), particularly in a tropical mammal that’s most active when the sun is out? Evaporative cooling carries away lots of heat, so is very effective, but not when there’s fur. Imagine putting on a fur coat & then sweating through it? I’m afraid evaporation would be greatly hampered to say the least. I think it’s even easy to predict when humans became mostly “naked”—when they evolved a very large brain. This occurred in the origin of our genus Homo about 2.4 million years ago. At this time, there were lots of evolutionarily paeodomorphic trends happening in our lineage, such as the adult retention of a “baby-shaped” head (large, round cranium with a small face & jaw, which has little to no room for third molar teeth), as well as shorter, finer body hair.

Humans have many “cool” adaptations in their skin & hypodermis. I don’t think the parasite load hypothesis holds “water.” African herd animals or chimps aren’t “social enough”? Grooming in social primates is important in forming social bonds. Why give that up? -TJ Meehan (I’m submitting for a third time—your site erased what I wrote when I went over the character limit.)

@David. God's punishment to the serpent for tempting Eve was that the snake be condemned to slither on its belly. Before that time it had a nice set of white-wall alloys.

I'm just amazed by how many religious posters here explain everything with "It's a test of faith: god made us this way". I mean you can't argue with someone who is so close-minded that they dismiss everything as a god-driven conpiracy, despite the total lack of evidence!

For evolution to occur, changes in the DNA must be directed to produce a desired result. This cannot happen randomly. Why has the alleged random evolution resulted in new stuff but no in removing the so called "ancient baggage"?

impossible for cell to self-assemble without intelligent external help due to many reasons including the following:
1. To kick start life requires the non-random assembly of trillion molecules into simplest cell. no such thing as random in the Universe, everything behaves according to set of laws that may make it look like random to a not so smart human.
2. smallest part of cell is DNA,intelligent code and not random code. DNA has mathematical checksum. 1940's, Barbara McClintock discovered that damaged DNA in corn maize would reconstruct by making copies of other parts of DNA strand, then pasting them into damaged area. How could a tiny cell possibly know how to do.... that??? A French HIV researcher has found part of the answer. (Hint: The instructions in DNA are not only linguistic, they're mathematical.)http://www.cosmicfingerprints.com/blog/mathematics-of-dna/
3. Impossible mathematically, even if you took the simplest cell, then decomposed it so that all the ingredients will be available and then waited for it to reassemble.
4. ingredients that make up a cell are only produced by a cell, i.e. chicken and egg problem.
5. atoms must be available in an environment in which, if these atoms were to align themselves in positions to kick-start cell processes, the assembled cell must survive and reproduce
6. atoms must first be arranged into the required molecules
7. molecules must then be arranged into the various parts of the cell
8. parts of the cell must all be protected by the cell wall

I would like to add- Appendices once used to digest hay, and giving birth that has become so much more complicated since we stood up right I love eugene's post "In France, we have an unsolved question:
"why women speak so much ?"
Somebody think that it is to frighten the wolves in front of the caverns"

Quirks of human fate. Thanks for bringing to light some of the biggest mysteries of human beings. It is hilarious to learn where hiccups or goose bumps come from. However there still remain one unanswered questions in my mind. Why do we have hair just on the head and not on other parts of our body? Isn´t it weird?

In France, we have an unsolved question:
"why women speak so much ?"
Somebody think that it is to frighten the wolves in front of the caverns.

Uhm...
the arrector pili muscles still serve as a VERY useful thing. We may not have much hair, but we have little, and air serves as an insulator.

I nominate the brain-eye connection as a serious flaw in human development.

Within the first few months of life, the brain learns to focus and interpret the image captured by the eye. But there it freezes.

As the eyes age through life and their shape and lens adjust, the brain sits frozen, unable to adjust and interpret the new image as it did in infancy.

If the brain had the flexibility to compensate for the changing eye, there would be no need for reading glasses caused by aging.

It's also disappointing that every baby is born an ignoramus. How much wiser homo sapiens would be if babies were born with the collected wisdom of their ancestors.

Seems to me if we were a product of evolution that aimed at promoting survival, as the best minds say we are, then gestation would be a time the brain acquired a core dump of useful knowledge.

Alas, no. Einstein, you, and me all came as blank slates.

Some might interpret that as an argument for 90% intelligent design, ie. we are the experimental product of ETs who came here to colonize, and their design for homo sapiens had flaws.

I don't recall. Do you?

Can everyone just drop it with the wheel comment. I think that enough of you have explained that evolved wheels are illogical and we should leave David Teller and what I'm sure he intended to be a harmless comment alone.

Beyond that I thought the article was interesting even if at points may have been slightly incorrect.

One other thing, it isn't fair to blame obesity on our preprogrammed craving for fatty foods. As the article pointed out, humans have developed a fairly large brain, which people should use to make better decisions about what they eat. Inherent or not we do have the ability to override natural impulses to a fairly large extent.

Mr.Dunn:

Please do us a favor and expand this into a book. Thanks in advance.

Re: backaches, Esther Gokhale's research (egwellness.com) provides a counterpoint to the idea that back pain is universal and inevitable.

Who edited this???
"Roll your ankles, each of which once connected a front leg to a paw.

Uh, yes. But in an extremely roundabout way...

David - regarding why we didn't evolve wheels - it's acqually a question worth considering. An octopus has a sort of wheel-like shape (radial symmetry, also employed by echinoderms like sea stars and urchins). For the octopus, each sucker has a sort of tiny brain that allows it to act independently of the other suckers*. Therefore, a wheel-like organism is sort of possible. However, who's gonna fix the flat tires? There is literally a hole in your concept. Sorry to burst your tube.

*(When the octopus is caught and cut up for sushi, so long, suckers!)

The evolution of terrestrial life doesn't seem to have produced anything that would provide a topological path to wheels, but I don't think it's as inconceivable as some in this thread have suggested.

Given an environment where wheels would be a significant advantage and an evolutionary path which produced an axle-like or wheel-like structure (presumably for some other original purpose), it could happen.

Presumably the wheels would be secreted, non-living material, like the shells of molluscs (obviating the concerns about their disjunction from the rest of the body).

I'm pretty sure Piers Anthony wrote a story that included wheeled aliens. At least there's an illustration of the concept in "Barlowe's Guide to Extraterrestrials" (classic SF art book by Wayne Barlowe).

Over time I have realized, or it's been pointed out to me, that one must be careful as to what one deems as vestigial. Often functions of a particular 'vestigial' organ just aren't currently understood. For example, the appendix, which may well try to knock us off on occasion, mine tried when I was 5, actually is now thought to function as a repository for the immune system in the gut to help fight off infectious problems in situ.

Male nipples, at least in some of us, are quite sensitive and serve as erogenous zones, which of course may contribute to furthering the species in terms of multiplication. -And certainly may contribute to our general well being.

"Survival of the Sickest" gives insight into some of evolutions's foibles, specifically genetic-related diseases. I recommend it.

I have never grown wisdom teeth. Does that make me a superior species?

Fascinating. Left me wanting to know more. I still wonder why men have nipples unless we were not meant to be two separate sexes at first.

Great fun, these ten explanations!

Humor. Apparently a sense of humor has not yet spread throughout the genome. Ok so some of the points can be argued, so what? Look them up and believe what you want. The article was entertaining even with a bit poetic (comedic) license Thrown in. Wheels? Why evolve 'em when you can build 'em?

Regarding #8 - I'm nearly 50 and have all four of my wisdom teeth. So are you saying I'm a pea brain?

He apparently took away your ability to reason independently, too, John Gilbert.

Vasoconstriction of the skin (goosebumps) increases resistance to heat loss through the skin. It is a useful way to avoid losing heat from the body to colder surroundings.

Genious!! Just genious, in one article I found the answers to at least 6 questions I always asked myself as a kid and never had an answer too. Its actually scary!
Thanks for the wonderful article!

I disagree VERY strongly with the assessment from number 3. Any upright weight-bearing column buckles under weight, and forms shapes called fundamental modes. The S shape of our back in all likely-hood developed due to this natural strain. Any pole or column or beam that is upright has this same thing. To say that this means the back was not meant designed to hold the weight of our guts just shows that the progenitors of this idea have no idea how to stand correctly and find the position of maximum mechanical advantage.

A course of lessons in the Alexander Technique will convince anyone with a practical bent that back problems are not only preventable but not even natural.

See http://en.wikipedia.org/wiki/Buckling for more about buckling.

While my own take on this given above is still simplistic, I think it is very unscientific to draw a conclusion about a complicated weight-bearing mechanism such as the spine+torso and say that back injury is bound to happen.

I loved this too! How about a series covering the other changes? please :)

To what are we evolving may I ask? :)
And... what do you think of the idea that, evolution is not a slow process at all, but an individual, almost spontaneous one, which is performed whilst the organism is still alive, when it meets certain requirements (for humans... well, i'll let you think about what those are).

Nice article--don't forget the appenxix/caecum, how our inner ear bones were derived from reptilian jaw bones, and how we're all made up of a significant amount of seawater :)

Just to throw an oddball idea out, wheels could exist biologically if an organism used some kind of spherical object, like a tough fruit pod, and developed a symbiotic relationship to it so that it could wheel around as a primary mode of transportation. Of course, the spheres would have to be replaced periodically due to wear, and the "axle" part of the organism would have to be extraordinarily tough.

Phillip Pullman had that crazy sci-fi idea in the His Dark Materials series.

But on Earth? Yeah, it's pretty much impossible for wheels to develop as a form of locomotion.

About the wisdom teeth: you don't explain why they grow later in life.

A more plausible explanation is that our recent ancestors had poor hygiene and many of their teeth rotted early. Wisdom teeth come in later to the rescue.

Wisdom teeth are not useless; they're backups in case you're too lazy to brush.

The explanation for #8 is incorrect. Most traditional "foraging" peoples have plenty of room for their wisdom teeth... with brains every bit as big as yours or mine!

That we don't have room is a function of our diets, and the fact that most of us do not stress our jaws (which causes them to grown) or wear our teeth down to the extent that natural selection expects us to.

The basic premise, that a mismatch between our diets and our biology explain impacted third molars (and orthodontic problems such as front tooth overjet and crowding) is correct, but the mechanism invoked in the article to explain it is not.

Hiccups are actually spasms in your diaphragm...

actually animals didnt grow wheeles because they wouldnt be able to walk they would just be able to roll and their balance would be terrible if the wheeles were on both sides. and of course because if animals had wheeles if they fell down there would be no way up unless their arms were like 6 feet ling

i think that the author did a very good job.

@Jason: You're saying God has hiccups?

Interesting, ammusing, and educational- just what i expect in a Smithsonian article. Though you left out one aspect which while not exactly a 'daily' consequence is still life-affecting. The tilting of our pelvis which enables us to stand erect makes for a serious hazard in childbirth. Fitting our (comparatively) oversized heads through the birth canal is fraught with danger, and giving birth was the number one killer of women until the 20th century. Which doesn't necessarily affect you today, but your Mom gave it a whole lot of thought when you were born.

Jason, If God made us in his image why aren't we all Kalahari Bushmen?

I found this article pleasantly enjoyable, and educating. Thank you for this article. It was a good way to start my morning. There are ways however, to accomodate the load more effectively with our backs.Good sound structure, lessened stressors that trigger our psoas and curve our spinal column for fight flight that may just be a looming electric bill. Our mind's eye works well. Our discriminator, which is old wiring, only works toward organismic survival first, but yet responds to the bill like a potential life/death threat. But, absence of any tension would of course be death. Kudos on the article, and thanks again.

NO! Your theories are wrong. God made us in His image. We are not monkeys that evolved into intelligent human beings to survive in the wilderness. We were given superior intelligence so we could reign over all other beings and we don't have to live in the wilderness because we're smart enough to build strong shelter.

We COOK our food, walk UPRIGHT, are INTELLIGENT, and have HICCUPS because God made us that way.

@David Teller
"Hello Why do you think animals didn't evolve computers instead of brains? Thanks"

Erm. We did evolve computers. They're called brains. If you mean "Why didn't we evolve computers exactly like the one on your desk in front of you?", then why should we? We evolved one that was useful for the tasks at hand - finding food & mates, avoiding predators etc.

Ah, evolution, the system of "good enough". You know, I gotta say, if the proponents of Creationism just put five minutes of good thought into their arguments, they'd have to realize they need a new argument. I mean, really, the human eye is perfect? Who puts wiring in front of a camera lens?! Good grief, squid eyes make more sense than human eyes! But that said, I highly appreciate how complex and incredible evolution really is.

I do have to chime in with some other commenters here about the hiccups thing. I know anecdotal evidence isn't much, but I've found that during a hiccuping episode, if I try to time and expect the next hiccup...it never turns up. I'd say 95% of the time this gets rid of my hiccups within 60 seconds.

It is hilarious how many commenters here have been suckered into taking seriously David's obvious joker question. Did you see his 2nd question - he's laughing his head off.

BS on not being able to think hiccups away. Try it. I do it every time, and I learned from my dad.

That's just a harmless mistake. Everyone knows the ankles connected the *hind* legs to paws.

The front legs had wheels.

Great article but I have to disagree with one point. The only way I can get rid of hiccups is to 'think them away'. I breathe steadily and repeat in my head 'I will not hiccup again' and they go. I've always done this - though I admit I've never met anybody else who could. One problem is I need total quiet and total concentration, which means I can't do it when drunk!

I know someone (many people?) will think I'm just talking rubbish, but I've never been able to get rid of them any other way. Although I am willing to concede that breathing steadily helps, it doesn't work on it's own, and wouldn't require quiet and concentration.

I can't believe you all spent that much time replying to an obviously ironic statement from David.

If he seriously meant it, then that deserves even less of a response.

Hello all; here's a wikipedia page related to the wheel question.

http://en.wikipedia.org/wiki/Rotation_in_living_systems

@Hal Lescinsky,

How would neoteny explain our overall hairlessness?

We grow Lanugo in utero, and lose it (usually) prior to birth. In order for neoteny to be the explanation wouldn't that require us to be born prior to (or simply without) the growth of a body covering fur and then never develop it?

This is good stuff, but it mostly covers the physical consequences of our evolution. The mental stuff is WAY more interesting, because our emotions are also vestigial in a lot of ways. The direct consequence is that a lot of people are seriously unhappy because their caveman brains are causing them to interpret and respond to the modern world as they would have to the ancestral one.

The best book on this concept is Healing The Unhappy Caveman by Chris Wilson. (http://www.amazon.com/Healing-Unhappy-Caveman-Designed-Happiness/dp/0978698509).

You can also go to http://www.enlightenedcaveman.com to read the author's blog, which includes a video of one of his talks. It's is about the Artifacts of the Caveman Mind - http://enlightenedcaveman.com/2009/04/23/the_caveman_speaks_artifacts_o/

It's great stuff. Check it out.

JW

I LOVE this stuff! Fascinating! I'm going to learn about 10-100 in more detail.

I want to know about male nipples! And was the "female" the first persuasion? I wonder since male humans have nipples, and all mammal fetus', very early, are "female".

> Why do you think animals didn't evolve wheels instead of legs?

Because the landscape didn't evolve roads?

David,

Evolution causes features in organisms to change based on what is there to begin with. The beginning of legs were there in previous animals so that is what was formed. Wheels were invented by man. Why would animals evolve into something designed and created by man? Nature doesn't know about ideas like wheels that do not come from nature but were invented by man. How could it?

-Betzi

@David Teller. I believe it has something to do with the earth not being full of roads for move of evolutionary history.

So much for "intelligent design." If we were designed, then the designers were idiots.

The evolution of legs had been predetermined by the appendages of fish, long before crawling ashore. Fish (lobe-finned fish, to be exact) fins served for raw material when early terrestrial animals sought to find their way around the land.

To David Teller:

Probably because legs have a much wider array of uses than wheels. You only use wheels for a continuous and speedy ride, while they are unfit for standing, grabbing, digging, swimming, scratching or you name it. You can walk by your feet all around the globe but you can't climb your car on top of a mountain peak.

This is obviously just a guess, I am no expert in this field. There is also a consideration about mechanics physics and aerodynamics and how these laws are applied in biology.

But it's a really funny question though if you try to picture a 4x4 cheetah or a polar bear on a unicycle.

Thoroughly enjoyed this! Reminds me of the first time I read The Naked Ape by Desmond Morris, I know it's rather anthrocentric but there's something truly fascinating about Human evolution!
Thanks for writing it.

It's difficult to climb a tree with wheels.

wheels! hahaha i love it.

Because wheels are a human invention. They also involve a separate piece (the wheel as opposed to the axle) how would a creature have a separate piece?

@ David Teller

If the ancient world contained roads, there may well have been an animal which evolved wheels instead of legs. However, the world only contained roads very recently, and if you ever go on a 4X4 trip, you will soon realise that four paws are a far better method of travelling than four wheels.

David,

1) For wheels to be at all useful you need relatively flat surfaces - something not all that common in nature.

2) When we build a car, we make all the parts and then stick them together. But our bodies are not built, they are grown. Can you think of a simple way to construct a working, efficient and powered wheel using muscles tendons and bones - where intermediate forms between the leg and the wheel still provide an evolutionary advantage? It's not an easy task.

... of those five at the picture is the first a scientifical relative, the second a chromo relative, the mid a magnon relative, the fourth a some relative and the the last a fiction relativing. To be read on my website biopsychica ...

"Roll your ankles, each of which once connected a front leg to a paw"

Surely you mean "once connected a back leg to a paw"?

@Jason:

Have a look here:
http://www.decimation.com/markw/2007/07/09/what-evolution-left-behind-on-humans/

Interesting article. Another good example for an evolutionary constraint on the human body is the difficult, dangerous and painful childbirth women have to go through. This is caused by the anatomy of our pelvis which is adapted for walking upright and the relatively large heads/brains of our babies.

@ David: I can see at least two reasons:
For one, wheels are pretty much useless in any environment other that a smooth road, which doesn't occur very often in nature.
Secondly, a rolling bearing, which is required in order for a wheel to work, isn't a particularly easy thing to evolve.. it occurs on a microscopic scale (and used to be a major creationist argument) but is exceptional.

Hi I think animals didn`t evolve wheels because there wasn`t any roads.

i think evolve wheels will not be possible,animals too are living things as we do.more so,when you imagine how the process will look like is funny,meaning they will need a machine or battery and needs changes from time to time.

Also, wonderful article!

David, think of how the wheel works on an axle. How could a biological wheel be attached to an animal and allow a complete 360 rotation?

This is a great article. But I think the point about back pain is not correct. There are many indigenous groups where people perform farm labor into old age, or sit weaving for very long shifts, and have no pain. We can blame the trend toward slouching which started in the 1920's, when looking relaxed was cool and good posture seemed stiff and old-fashioned. Now, our postural muscles are weak and our fascia has tightened to support our bad habits, so it's difficult to simply decide to improve our posture. This comes from my perspective as a Certified practitioner of Rolfing(R) Structural Integration, and also from the excellent book, "8 Steps to a Pain-Free Back" which has thousands of photos illustrating the above points. Esther Gokhale is the author, and she has a website with some good information as well.

@David Teller

Find me a place in nature where you can roam freely with your car without crashing or getting stuck. Using tumble-weed as an example (I know, it's a plant) you will see how often they get stuck even in a relatively obstacle free environment.

@ David Teller: Early land-walking species apparently evolved legs from the fins of fish. A fin is the most efficient way for a fish to stabilize and guide itself through the water, and it's easy to see how a fin can evolve into a leg rather than a wheel.

In general, the evolution of a leg is much easier than the evolution of a wheel. The wheels in our technology, from wheelbarrows to trucks, involve a system that somehow rotates continuously around an axis. In an animal, such rotation would cause blood vessels to become twisted around - unless there were no blood vessels, in which case the animal would need a complex system to keep the wheels supplied with oxygen. Only the cornea of the eye does not get its oxygen from blood.

Animals are simply not well-equipped to rotate their body parts. A human eye can rotate through less than half of a circle, and even an owl cannot rotate its head one full turn from a forward-facing position. Wheels spin too much to work in an animal, even though they're more efficient in our machines.

Evolution fueled by improbable mutations operating in context of sexual,group,individual selection with end product favorable mutations translate into increased progeny.This completely explains the function of the appendix/tonsils????

Man alive, what a brilliant fantasy!! In a period of '1 billion year' everything can happen and nobody can verify it. Give me a biology book and I write a similar article...

It requires more faith to believe in evolutionism than being a creationist!

Yes, but can you name a single living creature that has evolved anything even remotely similar to wheels?

@David Teller

Have you considered that, wheels aren't exactly suited for all terrains? Do you think some animals can climb trees better with wheels?

Ankles connected the FRONT leg to a paw? My, things really have changed.

Humans evolved without much body hair. The tick theory is an old one, that has largely been supplanted by the theory that it improved human physical endurance. The lack of hair allows the human body to radiate heat much more effectively, and that means muscles can continue to work without over heating. That's how the bushmen of the Kalihari hunt. They cannot keep up with the prey on a sprint, but if they track it for hours, it will finally not be able to run away, and they shoot it with an arrow from a dozen feet away. Man was able to evolve that way because man had the ability to adapt and wear clothing in colder times and places.

"Roll your ankles, each of which once connected a front leg to a paw."

I'm guessing you meant either

"Roll your WRISTS, each of which once connected a front leg to a paw."

... or ...

"Roll your ankles, each of which once connected a HIND leg to a paw."

@David Teller: (a) animals don't have wheels because they evolved in an environment without roads; (b) even if there were roads for the next few million years, evolution can only "work" with what already exists, and it's hard to see a pathway from legs to wheels in which every step is an improvement on the step before.

1. Those conditions occur when the mitochondria fail. The mitochondria never fight with your cells in any medical condition. They have no fighting abilities. They just die, or suck at functioning.

2. Babies may use hiccups for keep amniotic fluid out of the lungs, it can displace slowly moving food. They generally don't serve a negative function. The reason old features stay around is generally that they serve a function.

3. http://www.spineuniverse.com/anatomy/natural-curves-your-spine

If you don't have curves in your spine you're screwed. It's a really unpleasant condition. They do serve a purpose. We have backpains because we put a sensitive piece of equipment under regular immense strain.

4. Yeah, and it would be easy to modify a sheath to stop that happening. Hopefully evolution will, in time. The fact that it's an evolutionary flaw is why just fixing the condition isn't good enough to prevent reoccurance.

5. Is there medical evidence that cats choke less? I've seen cats choking lots. I'm not sure if the position of the air pipes matters that much.

6. We colonized the arctics, other primates haven't. We have clothes, and are better at dealing with cold than most. This isn't a problem, it's a feature.

7. I've never seen any scientific evidence that goosebumps actually don't help. It should be easy enough to test. Is there actual scientific evidence?

8. Or, our diet changed and so we have greater teeth mass because we eat less abrasive foods, as of recent times. Or, it's due to minor genetic differences- there are lots of adaptions that can minimize this problem, like smaller teeth, or larger jaws.

9. More that we evolved too slow to keep up with society. We've only had processed foods for a century or two.

As to why animals didn't develop wheels:
Some small, microscopic ones actually did, including molecular engines: http://en.wikipedia.org/wiki/Flagellum
But wheels are very bad on uneven land and even worse where vegetation is not scarce. Not to mention the trouble of growing an organ which can rotate full 360 degrees and still having nerves and blood vessels. So, wheels - good on microscopic scale (where they developed), but an engineering nightmare on large scale, where they did not develop.

We, humans, make wheels out of dead matter, and use it on specially constructed roads.

how do you bring blood to a wheel? if you put an artery in the axel, it will be twisted and twisted until it breaks. it could be done, but not as an evolution of parts that in themselves bring advantages...

Hello
Why do you think animals didn't evolve downward-pointing fans instead of legs? Y'know... like hovercraft. Why come there are no hovercraft animals? Thanks

I now understand why our wisdom teeth are actually called "wisdom" teeth.

Because wheels were invented by man, and are not naturally occurring in nature. Also, if animals (assuming quadrupedal) had wheels for legs, they wouldn't be able to move. Imagine a four-wheeled dog. You'd be able to push it around where ever you wanted it to go, which would disadvantageous for the dog, because you could then push it off a cliff, or into oncoming traffic. Even if they were bipedal, over the course of its life would cause untold amounts of stress on the back. Imagine being in a push up stance for 60-70 years, with no way of stopping your leg-wheels from moving.

In most animals, the trachea (the passage for air) and the esophagus (the passage for food) are oriented such that the esophagus is below the trachea.

If by "below" you mean "ventral to", isn't it the other way around?

The reason we have to have our wisdom teeth removed is because we dont eat enough fat soluble vitamins and fat and collagen and minerals.

In people who do they dont need to have their wisdom teeth out.

White flour and sugar are the scourge of the modern man cf Dr Weston A Price and his book Nutrition and Physical Degeneration

Some species did have individuals who, through mutations, had wheels instead of legs. They all died in violent crashes because brakes had not yet evolved.

Probably wheels are of little use in tropical forest without good roads..

i enjoyed reading this very much so :)
very funny stuff. as i read it i had goosebumps coz i was cold so i looked at my arm and giggled while frowning at it. then i choked xD

this was just so nice to notice the little things about the body i didnt know :D

@David

There's plenty of reasons, depending on the "layer" of explanation. They didn't because if they had, you wouldn't be asking the question.

They didn't because legs have so much more use, legs can climb, sneak, crawl, run over uneven terrain, and even adapt into arms. Wheels need a very specific terrain of a flat even road, something that with only a few exceptions, never became common.

Legs are bones with a pair of muscles for each joint, every other detail is negotiable. Wheels are a near-perfect circle, with any flat spot making the wheel useless. Along with that, a wheel needs lubricated bareings, an axle to balance the load, and without shock absorbers you're in for a bumpy ride.

An imperfect set of legs can still limp, while an imperfect wheel cannot move.

As a species changes over the millions of years, the legs can shrink or grow to accommodate a changing individual, tiny changes to each part of the leg across millions of generations, but wheels can't adapt as easily. If the wheels grow just a little, the support structure has to be able to take the new strain.

And that's just ignoring all the biological problems with an organic wheel. How would blood vessels get to the wheel without being twisted apart when the wheel turns?

@David Teller

I think Richard Dawkins talked about wheels in one of his books. There is one documented single celled organism that rolls on wheels, but a free-spinning axis is only possible in simple molecular structures. In larger animals, things like blood vessels and such would get tangled. It's a physiological problem. Furthermore, wheels require flat terrain to be useful, which doesn't occur much in nature (imagine an ant trying to navigate a jungle on tiny wheels). I think it was in The Ancestor's Tale that Dawkins discussed wheels in evolution.

Because wheels are only useful on roads and unnaturally smooth surfaces...

THERE IS MORE EVIDENCE, IN THAT THE ANTERIOR LONGITUDINAL LIGAMENT IS VERY BROAD AND STRONG AND THE POSTERIOR LONGITUDINAL LIGAMENT IS QUITE THIN AND WEAK. THIS IS AN ADVANTAGE ONLY TO A FOUR LEGGED ANIMAL AND A BIG DISADVANTAGE TO HUMANS.

Probably because wheels have to be able to rotate indefinitely around a fixed axle, and would thus have to be made of dead matter, since you cannot wire up blood vessels and nerves to a rotating thing - the best you could do would be to have an array of muscles around the top edge of the wheel that contract in sequence to drag it around, and you'd still need to solve the problem of how to replace the material of the wheel as it wore away. Not an insuperable engineering challenge, but a much harder one than a leg, and natural selection must necessarily choose the path of least resistance.
This point becomes more apparent when we remember that land animals evolved from aquatic animals, who had already developed fins, which are far more easily modified into legs than into wheels.
Also, wheels are only of use on reasonably firm, smooth, dry ground, whereas legs can go more-or-less anywhere, so legged animals would be able to gather food from areas wheeled animals couldn't, and thus have a great competitive advantage.

I think Richard Dawkins mentions more-or-less the same points in The Ancestor's Tale.

David Teller:

Let me take a stab or two at the wheel question.

No organism I know of has wheels. Nerves and blood vessels would have to be connected through a rotating hub -- a notoriously difficult problem even for mechanical engineers, who avoid such connections wherever possible. Also, there's the problem of providing a rotational force.

Humans, in particular, evolved from brachiators, that is, organisms that climb trees, a task for which wheels are singularly unsuited. Indeed, wheels only work on fairly smooth terrain; even tracks have severe limitations.

Given the fact that wheels are not a good fit with the natural environment, there's no strong pressure to overcome the difficulties of evolving wheeled mechanisms.

In response to the above comment, animals have legs because most terrain is not smooth. Wheels work wonderfully over smooth ground, such as floors or highways, but are not suited to mountains or desserts. Legs can be used any where, over terrain that is smooth or broken, level or steep. They also work better with arms for climbing.

David,

Wheels are generally difficult to evolve in nature, period. Think about bones. They need a system of veins to keep them alive. How could you do this with a wheel considering it spins? Any system will be a lot more complex and prone to failure/infection than a foot. Not to mention in most terrains (forest, mud, shallow water, etc) a wheel is sub-optimal.

Mr. Teller, wheels would have required intelligence.

You're welcome.

David, it's because the previous bodily systems had already been established. The method of circulation had already been evolved, so when it came time to evolve legs for locomotion, wheels were out of the question since wheels and the circulation of blood would not work together.

I am a bit disappointed in this article from smithsonian.com. There are incorrect facts and half-truths. Animals that walk on all four frequently get inquinal hernias. It is not an effect of us walking upright, but a side effect of having external testicles- which evolution arranged for us to make sperm production more efficient. It wasn't an accident. Any animal with an inguinal ring (external testicles) can get an inguinal hernia.
Every animal I've ever intubated has the esophageal opening above its trachea. In the neck, the esophagus is slightly dorsal and to the left of the trachea. In the chest, it is above the trachea. It is never below the trachea. As for male nipples- that isn't evolution's fault! It is nature saying, 'we'll make fewer mistakes if the two sexes are as similar as possible'. The arteries and veins that provide the ovaries twist around each other in a complex plexus intended to cool the blood feeding the external testicles to keep them below body temp. It is embryonic, not evolutionary.
I know this was just a fun, silly article, but I expected more attention to facts from smithsonian!

I remember reading(Piers Anthony -- Geoddyssey series) that early people began standing upright to see further. But, they started staying upright because it was cooler in the hot African sun. Less body exposed to direct sunlight. Maybe hair stayed on the head to protect that part of the body from the heat.

I can't imagine anyone interested in this article who would not be fascinated by the above mention books. Each chapter is in a newer era of history. Starts with cave-dwellers and ends in a high-tech society.

@ David Teller
A wheel must be attached to but segregated from an axle in order to turn. How could blood and stuff get into the wheel? Even something hoof-like would still need a way to get the cells from the rest of the body. Blood vessels would break after a couple of turns. Imagine riding a bike with a tire pump connected.

Hi David, Ever tried to pull a wheel over uneven ground? What about up a rocky mountain? The foot evolved in all creatures to deal with their terrain. Perhaps in a few million years some urban creature will have wheels to deal with all the pavement.

Oh, but we did. You see, evolution led to the human thought capacity. Human intelligence led to the invention of the wheel. Therefore, evolution is directly responsible for the invention of the wheel.

P.S. Having permanent wheels instead of legs would not be good for survival. So even if there were animals born with organic wheels instead of legs; they would not have survived.

David,
Because any axel-based bone structure would quickly lead to infections and worn out cartilage, causing the subset to die off. This inherent danger, along with the low probability of the axel and wheel structure developing simultaneously, is why we don't have wheels.

In "Dragons of Eden", Carl Sagan proposes that most of the archetypes of dreams & nightmares are evolutionary leftovers. Our ancestors used to live in trees. Hence we dream of flying through the air & we startle awake at night out of fear of falling to our deaths.

We see this "return to our roots" fantasy perpetuated in films such Tarzan & Avatar.

Supposedly %25 of humans have nightmares of snakes & reptiles. This is due to the fact these creatures used to be our ancestors' mortal enemies. And only the mammals programmed to fear snakes would eventually survive. Practically every other film has terrifying snakes including Indiana Jones & Harry Potter.

Sagan proposes that sleep may also be an evolutionary response to reptiles. That the surviving humans would sleep during the day while the reptiles walked the earth. While the humans with no trait for sleep failed to survive because they would be on the ground and eaten up by predators. Our ancestors were better off sleeping in their trees.

Even cooler still, Sagan proposes that sleep serves the purpose to trick our reptilian brain into submission, as we dream the R complex becomes sated of its primal desires. Not knowing that what it's experiencing isn't real. This is why we get cranky and impulsive when we haven't slept. Our neocortex (which is primarily responsible for reason) forfeits control to the R-complex which only cares to satisfy our basest desires.

I <3 Sagan

You should have covered about why men have nipples too.

i am so glad to see recognition and attention to our having evolved, and the results in daily experience. Clever and pleasantly written, too. Yet you missed one, a crucial and important one: We Need Each Other. Our brains, endocrine systems, limbic systems, emotions, and expectations evolved to expect membership in a social support network stable from cradle (well, sling) to grave. We belong in a shared-food shared-work group of 90-to-150, and things go wrong when we live in isolated nuclear so-called 'families' within cultures of much larger size including strangers. An amusing introduction to this Dunbar's Number is at http://www.cracked.com/article_14990_what-monkeysphere.html Some further sense of this, including implications for childrearing, at http://www.continuum-concept.org/book.html We evolved to function and thrive in tribes, not get frustrated in empires. More at http://on.fb.me/hksytq which is http://www.facebook.com/note.php?note_id=67834695824

David -- Evolution is very path dependent, it only can select between available variations on existing forms. Once you got to having control given by nerve fibers & nourishment by blood veins & capillaries, it got pretty hard to stumble on something like a wheels & axles.

Animals didn't evolve wheels mostly because wheels aren't a very good solution to getting around rocky, muddy, fallen tree filled terrain. They're awesome when you have flat paths, but terrible for 99% of the habitable world.

@david Wheels are not suitable for any organism...You will need to give them disc brakes then...

Hi David

Animals don't evolve wheels because they involve two seperate parts - an axle and the wheel itself - to locomote. One is useless without the other and so neither can be selected for without foresight or some kind of 'intelligent design' which doesn't exist.

If you want to see an ad hoc evolutionary solution to a plumbing problem in our species then check out the male reproductive tract. From the testes the vas deferens goes up and over and round the back of the bladder then through the prostate and finally joins up with the urethra. It's all very convoluted and it might be thought that evolution could have come up with a simpler system. But evolution doesn't start of with a design in mind. Like all other systems in all other life forms the male human reproductive tract is a pastiche of adaptations cobbled together over evolutionary time scales. At each stage the system has still be able to work or we wouldn't be here to talk about it but the final arrangement can look like a hodge podge and not like soemthing one would have designed from scratch. Which to me is just further evidence of the truth of evolution and a slap in the face for creationsists - no grand design thought out before hand, just slow natural change over time. In this case from the simple to the complex. It can of course go the other way in evolution - from teh complex to the simple.

"Nor of the muscles some of use to wiggle our ears." You missed an "us" there, but a good and informative article.

An excellent article. Once you've rested your back please commence writing 11-100.

Probably because they're not very useful in a natural environment. Is that a serious question?

David: probably because there's nothing in the animal's body that is circular and can support our weight. We have to make do with the four legs. As for why legs and not wheels in the first place, well, wheels are rather useless in water, which is where we evolved from, whereas fins (which legs come from) make swimming easy.

Rob: fascinating article. Thanks! I'm totally tweeting this.

Hi David Teller,

You raise a good question--it is generally understood to be biologically impossible for a single organism to develop wheels, as that would require parts which were entirely free of each other. A wheel and axle need to be entirely disconnected for the mechanism to function, and a single organism can't grow parts that aren't connected to each other, since they need to have some way to share blood flow, nerve endings, and the likes.

(Thus, the only way a wheel could occur naturally would be some kind of symbiotic relationship between distinct organisms, as seen in The Amber Spyglass).

That was a fantastic article, please go on and talk about the blind spot in our eyes and so on.

More! More! I could read about numbers 10-100 for the rest of the night--as could everyone I'm sharing this with. Great work!

I only wish you had mentioned the appendix or toes or head and pubic hair, as well! Or how about these functionally useless pinky and ring fingers of mine? If I lost them, I wouldn't miss them terribly; they aren't even connected by proper knuckles with which to punch. Waste of skin and blood.

@ David Teller

because bits would get stuck in the spokes. you wouldn't be able to spin a biological 'wheel', veins and muscles and nerves and bones and stuff would get all tangled up. legs are way easier to evolve and work. evolutions lazy, it always goes for the short-term easiest option. kinda like me.

@David Teller

Something to with blood vessels, the way muscles work and the whole impossibility of it all if you think about it for more than 2 minutes.

"Why do you think animals didn't evolve wheels instead of legs?"

I think it's because with legs you can climb and do other things which you can't with wheels.

"and so try as you might, you cannot think hiccups away."

I disagree with this -- every time I've had the hiccups in the last few years, I've thought, "don't let this next hiccup happen," and if I concentrate, my hiccups stop. It's easy to say that it's just coincidence and that my hiccups were going to stop anyway, but this has happened many times without fail.

Interesting read. Please tell me why I can stop hiccuping by thinking about it if, as you say, this is an evolutionary impossibility.
Thanks

David Teller:

If you want an honest answer, it's because wheels are only advantageous on roads, and I'm pretty sure animals had no roads for the first few million years.

"So take a moment to pause and sit on your coccyx, the bone that was once a tail."

You don't sit on your coccyx you sit on your ischial tuberosities. Just wanted to clear that up for you.

98% of this article is refuted, succinctly, by modern anthropology. I'm surprised this was published.

So I suppose one could say we are not very intelligently designed at all...

@David Teller,

How could wheels evolve? A wheel needs either to be detached from the axle, or the axle and wheel need be detached from the larger body with bearings or something of the like facilitating rotation. Wheels require parts that are completely disconnected from each other, which in animals would require something like our fingernails growing and then falling off to then form a separate, ordered component of our body.

I can't see how this would occur, but I won't call it impossible.

A great book for follow ups and more details is "Your Inner Fish" by Neil Shubin.

To David Teller, evolution isn't perfect or finished. There are good designs that nature has not built because it has no actual designer, just revisions. Axles, propellors and the like require two completely separate physical bodies working in perfect cooperation–bodies which are useless on their own. That is a gap evolution has not managed to cross very well. Perhaps it's in the future for some species of animal that currently grows a shell to eventually grow a set of wheels.

On the other hand, legs are better on most terrain than wheels, which is why we need to build roads for cars but can walk just about anywhere.

@david theyre called cars

Hello Why do you think animals didn't evolve computers instead of brains? Thanks

@David Teller

what roads would these wheels roll on? animals didn't "evolve wheels" for the same reason they didn't evolve guitars sticking out of their heads: natural selection didn't favor it.

David Teller: There are a lot of reasons. One is that a wheel requires being separate from its axle, which is impossible, as an animal can't have two completely unconnected parts. Another is that it would cause too much friction and therefore wear and tear. Here are some more reasons: http://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems (Also, Mr. Dunn, great article!)

"Roll your ankles, each of which once connected a front leg to a paw."

Did you mean to say that our ankles each used to connect a *rear* leg to a paw? Or are you suggesting that some vertebrate ancestor of ours had front legs that migrated to become our rear legs? If you are indicating the latter then that seems to conflict with everything I've ever studied about vertebrate evolutionary anatomy.

Excellent. But you weaken the brilliant case that you've made by two minuscule errors in the concluding paragraph.

"... the muscles some of ->[us]<- use to wiggle our ears" ....

"... ankles, each of which once connected a front [?] leg to a paw" ....

David, wheels are only efficient where there are roads. Even in a road, a simple obstacle such as a trunk could stop you.
Try to run in a forest with wheels. Try to climb a tree to escape a predator. Try to climb a mountain, or to swim.
Legs are much more versatile than wheels.

Let's not forget the #1 most likely to get you spontaneously killed, vestigial organ: the appendix. Seems its modern-day purpose consists of weeding out those who can't get to a hospital in time.

#8 is incorrect. our jaws are too small because we don't get enough vitamins a/d in our diets to fully develop them. people who eat traditional diets have perfect teeth with no crowding. their wisdom teeth come in just fine.

but don't take my word for it:

http://gutenberg.net.au/ebooks02/0200251h.html

Liked the story for the most part, but in what way did ankles once connect a front leg to a paw?

Rob, a quick correction - you *can* think hiccups away. Just tell whoever you are near that you will inform them prior to your next hiccup. You will not hiccup again. Try it.

@Hello

How do you think the muscular system could work if that were the case?

Gotta walk before you can roll?

@David

For the same reason humans haven't evolved rocket boots.

Although that would be AWESOME!!!

David, a couple of reasons spring to mind:

1. Unless on very hard surfaces walking is more energy efficient than wheels - there is a reason why there are recommendations concerning the depth of carpets in office buildings - it would be very difficult for wheelchair bound employees to move around.

2. Terrain - wheels are dreadful for rough terrain. Without four wheel drive, highly treaded tires, or wheels that are not even wheels (think a tri-spoked wheel without a rim), getting over any step that's more than the radius of the wheel is a no go.

3. Nutrient supply. While a few limited examples of propulsion from circular motion occur in nature (see flagellum in certain cells) these are limited to tiny creatures that have low energy needs. Our need to supply muscles with oxygen and other nutrients to cells would require some very complex system to pass the oxygen through the bearing.

4. Shoes would fit very badly.

"Roll your ankles, each of which once connected a _front_ leg to a paw."

I suspect this should say "HIND" leg. I highly doubt that there was a spontaneous jump between the position of the ankle in modern humans, and earlier quadrupeds. The body pattern has existed for millions of years, so it seems unlikely that bones that make up a back leg would co-mingle or cross-fertilize with those that make up the front.

@David Teller

Wheels cannot exist in nature. There is no way you could have an evolutionary predecessor to a wheel. How would a wheeled animal be able to have a blood supply connected to its wheel?

"Roll your ankles, each of which once connected a front leg to a paw." Front leg? Wouldn't that be a rear leg? With our hands in the front?

David, evolving to have wheels instead of legs is not possible because a wheel requires an axis upon which to spin. This would imply that the wheel would have to be a separate part of the body entirely, meaning that it could not grow as part of the body. Let us consider for a moment the possibility of wheels instead of legs. In what environment would this be beneficial? Certainly not in forest or rocky environments. In snowy climates it wouldn't be of much use either. Also consider the fact that wheels require maintenance. Broken axle, lubricant between wheel and axle, etc. I hope this helps improve your understanding.
You're welcome.

I think the reason we didn't evolve wheels instead of legs is because it would have been WAY too much of an evolutionary jump. You can't really go from paws to a simple machine crafted from the human consciousness. Plus the disadvantages of having wheels far outnumber the advantages. Also, the minor mutations in between the paw to wheel conversation probably would die off before ever getting to the wheel, if you could even imagine what a foot would look like 50/50 foot/wheel. I doubt someone with that mutation would get around for very long. also, you'd have to change the physics of the foot completely which would take much much much much longer on the evolutionary time scale. As in millions and millions of years

I'll bite the troll bait: I don't see what use would wheels have in a world without roads.

To David Teller;

I think the short answer is because of the steps required to get to locomotion.

What intermediate steps would get an animal to wheels? It's not to say that it's not possible, as rotary apparatuses do exist in nature, such as the rotary flagellum on bacteria.

However, such apparatus do not translate well to large scale locomotion.

On the other hand, legs as we know them started out from things like flagellum; appendages that were useful for locomotion and evolved into fins that provided more thrust and maneuverability. Then eventually more muscles and support structures (cartilage, bones, etc) to provide added strength, and these became the tools of locomotion in shallow water and eventually land.

Wheels would not only be more difficult to evolve on a non-bacterial scale due to the problems of physical function on a larger scale (how would the "axle" form? What would provided the necessary power for actual locomotion? etc), but because there is a less clear line of how wheels would have been effective for locomotion in water where all life as we know it first evolved.

Evolution is a product of traits useful for the survival and reproduction of a thing in its current environment, and later traits are necessarily built upon what came earlier. This is why there is such a clear physiological lineage in our family tree... and why all successive living things in a particular branch of the tree continue to share the same fundamental forms with finer and finer grained changes built around those building blocks. This is why for instance all protostomes have blue blood (squid, octopus, mollusks, etc) and all deuterostomes have red blood (including ourselves)... and why you don't find a single case of one it being the other way around.

In this sense we cannot have wheels for locomotion through evolution because our ancestors further back on the "family tree" didn't evolve anything that would or could become wheels.

Ankles once connected back legs to paws, not front legs.

David,
Most likely because the smooth surfaces that are conducive to wheels are a recent man-made development. It would be impossible to climb, jump, or maneuver in most wild terrain with wheels. About the only ecosystem where wheels would be an advantage would be a salt flat or something similar.

"I have not even mentioned male nipples. I have said nothing of the blind spot in our eyes. Nor of the muscles some of use to wiggle our ears..."

Well, don't just leave us hanging there! What's the answer?!

I can wiggle my ears. My mother was able to wiggle not only her ears but also her nostrils. Also, when I get the hiccups, I can stop them at will about 95% of the time. I would get the hiccups, my ex girlfriend would ask if I had the hiccups, I would say no, and they would stop.

David Teller: Animals didn't evolve wheels because they evolved legs. Natural (that is to say, muscular) atomistic wheels would be vastly inefficient, more susceptible to injury and infection and would greatly raise the mortality rate of a species. Animals evolve legs instead of wheels because of efficiency. Also, we as humans created wheels as a tool. A natural wheel made out of flesh and bone would not be nearly as efficient as a wheel that we made today.

There is no way to innervate or vascularize a wheel-like structure in an organism (think about it), which is the widely accepted reason why animals have legs instead of wheels.

@David Teller:

> Why do you think animals didn't evolve wheels instead of legs?

Some did. Unfortunately, the mullet haircut didn't evolve until much later, so they couldn't get as many mates while cruising and their line quickly ended.

@David Teller

Hey fellow David. There are a number of reasons why animals did not evolve wheels. First and foremost, animals began in the water. Wheels would not be very useful in the water. As we moved to land, our fins turned to arms and legs-- a much smaller adjustment, and therefore highly more probable.

This touches upon the second reason-- evolution is not a directed process. Animals do not get to choose what they evolve. Mutations randomly happen during the shuffle of DNA between mother and father at conception, with successful mutations being kept (by those animals reproducing more) and unsuccessful ones being discarded (through less procreation). To read into your comment a support of intelligent design/creation, the appropriate response would be "why didn't god give us wheels?"

Finally, it should be noted that wheels are biologically impossible. For a wheel to function, there must be no connection between axle and wheel, so that the wheel can rotate freely. In other words, the wheel would have to be a separate organism entirely.

@David, because the natural world doesn't include any roads, and legs + feet/paws/hooves/etc are better in almost every off-road condition.

"I have not even mentioned male nipples." - I don't know if you're aware, but they're actually functional in some cases: http://en.wikipedia.org/wiki/Male_lactation

David Teller: Excuse me for butting in here, but wheels and a drive train to drive them are extremely complicated. There are actually micro-organisms that have something akin to an outboard motor (flagellae - http://en.wikipedia.org/wiki/Flagellum) that actually turns on an axle - that would scale extremely badly and therefore be impractical and inefficient in big animals. Another problem is that there are no roads. You need roads for wheels. You also can't climb mountains with wheels. etc. etc. - there are a lot of advantages of legs over wheels.

God simply designed us this way to test our faith. Please read the bible and see it is 100% inerrant and no one has ever disproven it. Christianity is the only way to be saved, science has never given us anything worthwhile except suffering and pollution. Jesus gives us love and eternal happiness.

Interesting article! But I must disagree about people not being able to "think hiccups away" since I am always able to do just that. Maybe you should have said MOST people instead.

This link mentions a few more of our human vestiges

http://en.wikipedia.org/wiki/Human_vestigiality

this is great and helps me to add to my examples of "well then...after millions of years of human evolution, why aren't we all perfect with wings and super powers and things?!" I really like the information about hiccups.

David - Animals did evolve wheels but they couldn't evolve brakes until they had wheels to brake and given the timeframes involved in evolution, they all rolled off steep drops to their deaths.

Wonderful article, loved it. Though I have to ask re:

"Roll your ankles, each of which once connected a front leg to a paw."

Surely you mean hind leg? Or am I missing something here?

> Why do you think animals didn't evolve wheels instead of legs?

Ever tried to ride a bicycle over a mountain?

The comment on Hiccups is not complete and the function is certainly not vestigal as implied. Human babies have regualar episodes of hiccups from approximately three months before birth to approximately three months after birth. This is thought to be a mechanism to strenthen the diaphragm before regular breathing is part of everyday life. So that all-important first breath is preceded by a significant amount of preparatory exercise.

Jason, for further reading, take a look at "Your Inner Fish", by Neil Shubin.

While it certainly true that lots of human traits are best explained as evolutionary vestiges, a couple points in the list made me cringe as a scientist. Hairlessness is probably a side effect of neotony (there are plenty of social furry animals)and to suggest that we learned to cook in order to compensate for our flimsy jaws (which were flimsy because somehow the bone material was comandeered to grow a bigger skull)can only be understood (charitably) as teleological thinking. I would hope the Smithsonian could keep pieces like this precise and scientifically accurate, because otherwise I probably would have used this piece in a class.

Hello
Why do you think animals didn't evolve wheels instead of legs?
Thanks

I find this so fasinating. If there is a site or article somewhere with a longer litany of evolutionary foibles I would love to read it out of strong curiosity mind you not hypochondria. any suggestions?

I loved this! In two short pages you've illuminated many of the quirks of the human body. I never really knew why our wisdom teeth usually need to be pulled, or where hiccups come from. Thanks :)