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Wednesday, January 28, 2015

Human Body Hair is Useless, Right? WRONG!

Posted by jlwile on July 30, 2012

Many evolutionists think that body hair in humans is useless. The data say otherwise. (Click for credit)

One of the many reasons scientists are rejecting the hypothesis of evolution (see here and here, for example) is that many of its predictions have been falsified (see here, here, here, and here for even more examples). The more we learn about the world around us, the more clear it is that the predictions of the evolutionary hypothesis just don’t work. This is probably most apparent when it comes to “vestigial organs,” biological structures that are supposed to serve no real purpose; they are simply leftover vestiges of the evolutionary process. As Darwin himself said, they are like the silent letters of a word. They don’t serve a purpose in the word, but they do tell us about the word’s origin.

I have written about vestigial structures many times before (here, here, here, here, here, here, and here) because they are so popular among evolutionists. However, as the data clearly show, the evolutionists are simply wrong about them, and the more research that is done, the more clear it becomes. The latest example is human body hair. This has always been a favorite among evolutionists. Here are two evolutionary descriptions of human body hair. The first comes from a book specifically designed to help the struggling evolutionist in his attempt to convince people that his hypothesis has scientific merit.1

Humans, like all other organisms, are living museums, full of useless parts that are remnants of and lessons about our evolutionary histories (Chapter 6). Humans have more than 100 non-molecular vestigial structures. For example, our body hair has no known function.

The second comes from a textbook2

Body hair is another functionless human trait. It seems to be an evolutionary relic of the fur that kept our distant ancestors warm (and that still warms our closest evolutionary relatives, the great apes).

As is the case with most evolutionary ideas, serious scientific research has shown that such statements are simply wrong.

Many people are surprised to learn that they are actually a walking ecosystem. Your body is home to roughly ten times as many bacterial cells as human cells. There are also fungal cells, but they have not been nearly as well characterized as the bacterial cells. While this might sound gross, it is actually a good thing. These bacteria are so “thankful” for the food and housing you are providing for them that they “pay you back” by doing all sorts of important tasks for you. Some make chemicals that you cannot make for yourself, some help you to digest your food, and some help you fight off infection. Without them, you would not be nearly as healthy as you are today.

As time has gone on, this community of microorganisms (collectively called the human microbiome) has become an object of intense scrutiny. In 2011, a review paper was published in Nature Reviews Microbiology about the human skin microbiome, surveying what was known at the time. One thing it noted was that the different parts of the skin provide different habitats for different microorganisms. For example, the microorganism population that resides in a hair follicle is different from the population that resides in a sebaceous gland.3 As a web review of the article says:

The folds, follicles and tiny oil-producing glands on the skin’s surface create a multitude of diverse habitats, each with its own community of microbes.

In other words, for a person to have a complete microbiome, he or she must have all the habitats that the skin microorganisms need, including hair follicles.

Why is it important to have a complete microbiome? A paper was recently published in the journal Science that gives a partial answer. The authors studied mice that had been raised in germ-free conditions. They looked at how these mice (which had no microbiome) and normal mice (which had a complete microbiome) reacted to a specific skin infection. When the infecting agent (Leishmania major) was introduced to both groups of mice, they all produced a specific kind of cell (called a T-cell) to fight the infection. However, the activity of the T-cells in the germ-free mice was not nearly as effective as that of the T-cells in the normal mice.

To make sure that it was the actual skin microbiome that caused the difference in the response between the two groups, the authors did two things. First, they gave the normal mice oral antibiotics to kill all the microorganisms in their intestines. Since the intestinal microbiome is known to aid the immune response, it was possible that the intestinal microbiome was the reason the normal mice produced more effective T-cells. However, they found that the normal mice still produced effective T-cells against the infection, even without intestinal microorganisms.

Second, they added a single species of bacterium that is found on human skin (Staphylococcus epidermidis) to the “germ-free” mice. When they did that, the germ-free mice started producing effective T-cells. Here is what the authors conclude:4

Altogether, our work proposes that resident [microorganiams] are necessary for optimal skin immune fitness…Understanding the role of the skin microbiota in maintaining tissue function is not only of primary importance for human health, but will also lead to the development of more rational tissue specific adjuvants and vaccine approaches.

Note that, according to these researchers, understanding how the microorganisms (microbiota) maintain tissue function is of primary importance to human health. So in order to be healthy, you need to have a good microbiome. However, to have a good microbiome, you must have all the habitats that the microorganisms need in order to maintain strong populations. This includes hair follicles. Rather than being useless, then, hair is critically important to maintaining skin health, as its follicles provide a necessary environment for certain members of the skin microbiome.

Now the importance of this research goes beyond demonstrating that yet another evolutionary prediction has been falsified. It even goes beyond the author’s suggestion of producing better products to promote skin health and fight off infection. To me, it provides possible insight into the pre-Fall role of certain microorganisms. Creationists have proposed that microorganisms (and even viruses) were initially created as a link between macroorganisms and the environment. They were designed to allow the macroorganisms access to the chemical richness of their surroundings. It makes sense that in a post-Fall world, the skin microbiome, which was likely associated with drawing beneficial chemicals from the environment, would change to becoming a support system against infection.

As we learn more about the specific interactions that take place between an organism’s microbiome and its own cells, we might be able to better understand how the microbiome was (and probably still is) able to perform its pre-Fall role.


1. Sehoya Cotner and Randy Moore, Arguing for Evolution: An Encyclopedia for Understanding Science, Greenwood 2011, p. 193.
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2. Gerald Audesirk, Teresa Audesirk and Bruce E. Byers, Biology: Life on Earth with Physiology (8th Edition), Benjamin Cummings 2007, p. 292.
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3. Elizabeth A. Grice and Julia A. Segre, “The skin microbiome”, Nature Reviews Microbiology 9:244-253, 2011.
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4. Shruti Naik et. al, “Compartmentalized Control of Skin Immunity by Resident Commensals”, Science DOI: 10.1126/science.1225152, 2012.
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64 Responses to “Human Body Hair is Useless, Right? WRONG!”
  1. jlwile says:

    Mia, you seem to think that because something moves slowly, it doesn’t need balance. That is just incorrect. Have you ever been on a jetski? Once it is moving quickly, balance is easy to maintain. The tricky part is keeping the jetski upright when it is moving slowly. The vast majority of jetski turnovers occur when the jetski is moving very slowly, because slow movement is when balance on a jetski is most important. In the same way, a sloth might need MORE balance because it moves so slowly. After all, a fast-moving animal can make quick adjustments to recover if its balance is thrown off. A slow-moving animal cannot. Thus, the high degree of variation could also be due to the fact that balance is so important and thus must be fine-tuned to each individual.

    I understand that the authors of the paper are claiming these things, but Coyne is giving credence to their view, which simply isn’t justified based on what we know about science.

  2. Jacob says:

    Sloths don’t always move slowly. They’ll move quickly in times of a predatory attack. The reason for why they don’t move as fast is because it’ll burn up their calories, a substance that their diet of leaves doesn’t provide a lot of.

  3. jlwile says:

    Excellent point, Jacob. Thanks for bringing it up.

  4. Mia says:

    Jay, your jet ski analogy is ridiculous. Jacob, sloths are easy prey when they go to ground for pooping, which might be a reason they only do it once a week. They do not scamper up a tree to get away. Their natural defenses are living high in trees, moving slowly, and algae that grows on their hair that serves as camouflage when they sleep. All adaptations to avoid predators, not escape them. They are slow. Period.

  5. jlwile says:

    Mia, could you please explain how my jetski analogy is “ridiculous?” It is a real-life demonstration of the fact that when things move slowly, they often require more balance than when they move quickly. In addition, your statement that sloths are “slow. Period.” is simply false. Here’s a first-hand account from a sloth biologist:

    One female took a dislike to me. I’m one of the only sloth biologists who’s been bitten,” he said. “They can use their big claws and slash out. But what she did was run at me, upside down along a vine, as fast as a cat would run along the floor. She grabbed me and pulled my hand to her mouth and then bit. It all happened very quickly. (emphasis mine)

    Also, according to this website, “Sloths eat, sleep, mate, and give birth all while hanging upside down!” That would take a LOT of balance!

  6. Jason says:

    Anyone that rides a bike etc will be able to relate to Dr Wile’s analogy. Once in motion, the bike is easy to balance requiring little effort from the cyclist. On slowing down however, the situation changes.

    What I find particularly interesting is that sloths have to climb down, from their “safe” places, to defecate. Seems this “inconvenience” is kind of “counter” to the creatures evolutionary fitness.

  7. Mia says:

    Jay, the analogy fails just because it is a non-animate vs. primate comparison. But, even ignoring the category error, jet skis are heavy, float in water, are basically flat bottomed without a keel, and have uni-directional thrust. Bikes balance on a two thin strips of rubber. Are those remotely like a primate that can hang on to a tree with hands and feet? No.

    So one sloth had a burst of house cat like speed over a couple of feet. And something like this is rare. How about finding some video of a sloth moving quickly? (btw, using your variation argument, it could be that this just happened to be the fastest sloth in the world.)

    But the main point here is you misunderstand balance. Balance means keeping track of the 3D orientation of the head. When you are hanging on to ropes or tree branches, it makes no difference how your head is oriented in space to whether you fall or not. It is simply a matter of grip. As long as the sloth is hanging on to something, it doesn’t take any balance to do anything.

    Jason, the adaptation is to poop and pee once a week, rather than much more frequently, like hourly or daily. The selective pressure would be to extend the period between bathroom stops.

  8. jlwile says:

    Mia, the analogy does not fail. First, it is not a category error. The person on the jetski is doing the balancing. Thus, I am comparing a living organism to another living organism. One is moving slowly on the water; the other is moving slowly on a tree. Both need good balance to get the job done, and many times, slow movement requires more balance.

    The point about the fast sloth is that you claimed sloths are slow, period. This example shows that such a statement is simply false. Sloths can move quickly, if they want to. You are right that this could be the fastest sloth in the world. However, since it moved as quickly as a cat, even slower sloths can still move pretty quickly if they need to. After all, I am pretty fast, but not nearly as fast as a cat. Thanks for pointing out how variable species can be, which is probably all that this study really demonstrates.

    I think you need to learn a bit more about balance, because you seem to be confused. I will try to clear things up for you. Balance is not just about knowing the orientation of the head. It is a result of the eyes, the vestibular system, the cerebellum, and proprioception working together. Since all the systems work together, variety in one system will cause variety in another. So, for example, variety in the vestibular system might be the result of variety in sloths’ muscular systems.

    Balance tells the body how to operate the muscles to preserve the position that it wants. If a sloth is hanging upside down in a tree, it needs good balance so that it knows which muscles to contract and relax to move its body in the way that it needs to be moved, especially if it is mating upside down! You might want to learn more about balance by going here.

  9. Mia says:

    When a sloth gets on a jet ski, let me know, I’d like to see that. Species inter vary. So? The question the study addressed is the fact that sloth inner ears vary more than the controls included. Why is that? Do you have a better explanation than that there is less selective pressure on sloth balance than the control species?

    No, balance in this case is a simple way of saying the vestibular system, because the study examined the inner ear. The paper didn’t address the visual or proprioception systems. Sloths have bad eyesight anyway.

    “Since all the systems work together, variety in one system will cause variety in another. So, for example, variety in the vestibular system might be the result of variety in sloths’ muscular systems.”

    You don’t know what you’re talking about, do you? How would you test that hypothesis?

    Again, balance on your link means all three systems. The paper just considered vestibular. “Balance is the ability to maintain an upright position.” But even there it fails, because this quote only applies to something that walks on the ground. The sloth can be upright, downright, sideright or just right and it doesn’t affect his ability to stay in the tree.

  10. Jacob says:

    Just to give an example of a primate climbing a tree, I’ll give a human climbing a tree.

    If you climb a tree, moving slowly requires a lot of focus on your hands and legs. Moving quickly also requires a lot of focus as well, but moving slowly normally requires more focus and balance because of the time it takes from moving yourself from point A to point B.

    I would assume that it would be even harder hanging upside-down, because now you have vision that doesn’t see right-side up.

  11. jlwile says:

    Mia, I didn’t imply that sloths ride jetskis. I was just using the jetski to make a perfectly valid analogy that demonstrates quite clearly that many times, slow movement requires more balance.

    I have already given you a better explanation for the results of the study. Let me remind you of what it was:

    The fact that sloth inner ear features are more variable than the inner-ear features of other animals could just as well indicate that the sloth sense of balance is more individualized than the sense of balance of other animals. After all, a squirrel…uses its sense of balance to run quickly in the trees and do amazing feats of acrobatics. That kind of balance could easily be less variable simply because it isn’t affected strongly by an animal’s individual traits. So sloth inner ears could easily be more variable simply because they need to “fine tune” their balance to their individual characteristics more than do other animals. Until we know the details of the sloth’s sense of balance, it seems rather silly to suggest that it is under less selective pressure than the sense of balance for other animals.

    Also, you still seem to be confused about balance. Once again, I will try to help clear things up for you. Yes, the study focused on the vestibular system, but the vestibular system does not act alone. It acts in concert with three other systems. Thus, any changes that are observed in that one system could be the result of changes in the systems with which it interacts. Thus, you can’t make accurate conclusions by just looking at the vestibular system. You ask how I would test this “hypothesis,” but it is not a hypothesis. It is a known fact. For example, we know that the skeletal system works in concert with the muscular system. If you study athletes, you will find that their bones are significantly different from the bones of non-athletes, because their muscular systems are different from those of non-athletes. Anyone with a basic knowledge of physiology understands that variations in one system will affect the characteristics of the other systems with which it interacts.

    You are quite incorrect when you say that a “sloth can be upright, downright, sideright or just right and it doesn’t affect his ability to stay in the tree.” If a sloth is upright in the tree, he will have to use one set of muscles to stay in the tree. If he is downright, another. If he is sideright, he needs another set of muscles. Each set of muscles must be controlled by the cerebellum, which relies on the vestibular system to get the information it needs to know in order to control the relevant muscles. Thus, the vestibular system is vitally important in each possible orientation of the sloth. As a result, it is not surprising that slot vestibular systems are highly variable. They are more variable than the controls because for the sloths, balance has to be much more individualized.

  12. Mia says:

    Yes, and your explanation is special pleading. I was trying to be nice but you keep on insisting. For example, are athletes’ tendons and ligaments significantly different from non athletes? They are not, and yet they are more closely related to muscle operation than bones.

    Another point is that athletes have different bones and muscles than non athletes for the same reason: the high stress placed on both systems and the ability of those systems to physiologically change as a result. This example is also off point because non humans do not have the great variability that humans do in activities such as working out. The variability in human muscles and bones is a result of human activity. Sloths do not cause the variability in the sloth population of inner ear components.

  13. Mia says:

    Oh, to explain special pleading. You chose muscles and bones because it strengthened your position (or you thought it did). You avoided muscles and ligaments because it didn’t. Neither choice can be shown to any more reasonable comparison than the other.

  14. jlwile says:

    Mia, you tried the “special pleading” angle before, and it doesn’t work. My explanation simply takes what we know from science and applies it to sloths in a way that explains the data better than Coyne and the authors of the study.

    I think you need to learn a bit more about tendons, because the tendons of athletes are, indeed, different from those of nonathletes. In general, the tendons of athletes are thicker and stronger than the tendons in non athletes. As this sports medicine site says about one particular tendon, “In the non athletic population, the Achilles tendon becomes weak and thin from disuse …” The same is true of ligaments. For example, this study of rabbits showed, “…that changes in stress and motion significantly altered the tissue properties as well as mass in the case of ligaments and digital extensor tendons.”

    You say that “non humans do not have the great variability that humans do in activities such as working out. The variability in human muscles and bones is a result of human activity. Sloths do not cause the variability in the sloth population of inner ear components.” However, that simply isn’t true. Sure, sloths don’t “work out,” but they definitely have different levels of activity depending on the situation. As this article points out, sloths in captivity sleep a lot more than sloths in the wild. The article speculates, “Wild sloths might be wakeful because they need to find food or avoid predators, Rattenborg suggests. Or there might be INDIVIDUAL DIFFERENCES: the 16-hour figure comes from a study published in 1983, which looked at an unspecified mixture of adult animals and juveniles. Young animals tend to sleep more.” If the article’s first explanation is correct, then slots that are in safer environments will sleep more than sloths in environments with more predators or less food. As a result, there will be substantial variation. Of course, his second explanation is more likely – that there is a lot of individual variation in sloths.

    I agree that comparing muscles and bones is just as reasonable as comparing muscles and tendons or muscles and ligaments. In each case, the use of one affects the other. Once again, my explanation simply takes what we know from science and applies it to this study to come up with a more reasonable conclusion than Coyne and the study’s authors.

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