Life Sciences / Science of Learning

01
May

The Biggest Misconceptions About Evolution, And What We Can Do About Them (Part 1)

Despite the fact that 2015 is the tenth anniversary of the pivotal Kitzmiller v. Dover Area School District decision prohibiting the practice, creation science and intelligent design are still taught in far too many classrooms: perhaps more than one in eight, according to a 2011 survey. Outright denialism and overt teaching of non-science, however, is only part of the problem at the heart of America’s issue with evolution. Another part, which involves misconceptions about evolution, is far subtler. Such misconceptions have a variety of sources, but their effect, building up slowly over time, is to impair student understanding of evolution. As a result, the students are vulnerable to confusion and doubt about evolution in particular, or even science in general, after they leave school.

So what are some of the biggest misconceptions about evolution, how do you spot them, and what can you do about them? We’ll cover the first two in this installment, and three more in the next one.

 

In 2007, NOVA captured the emotional conflict over teaching evolution in public schools. Watch "Intelligent Design on Trial" steaming online here.

 

    Misconception #1: Natural selection and evolution are the same thing.

    Correction: Evolution, or descent with modification, describes any change in the distribution of heritable traits within a population over time. A mouthful, I know, but “change over time” is too simplistic—weather changes over time, but you wouldn’t say that weather evolves. Confusing and conflating scientific and common usage of terms, such as “evolve” or “adapt,” exacerbates many of the misconceptions I’ll discuss. An important lesson to impart to all students—and scientists, and science communicators, and, well, everyone—is the importance of context in understanding language. So evolution is heritable change in a population over time, but what is natural selection? Natural selection is one mechanism—a very important mechanism, but still just one—of evolution. Others include genetic drift, gene flow, and mutation.

    What this misconception looks and sounds like: In the classroom, look for students interchanging the two concepts and terms as if they are synonymous. For example, “Evolution explains how the characteristics of populations change over time and occurs when the environment favors certain variations over others.”

    genes2

    Natural selection, genetic drift, gene flow, and mutation are all mechanisms of evolution.

    What to do about it: When covering evolution, be sure to emphasize that natural selection is one of several mechanisms of evolution. It could very well be the case (as in the Next Generation Science Standards) that your curriculum does not explicitly call for exploration of the other mechanisms, but that doesn’t mean you need to give students the impression that it’s natural selection or nothing. You can explain that there are other ways that evolution occurs, but in class, you’ll be focusing on one. If you get an answer along the lines of my hypothetical example, push back a little. Tell the student, “What you’re describing is natural selection—remember! Evolution occurs in other ways, too.”

    I expect, however, that you at least touch on the other mechanisms in your existing suite of evolution lessons. For example, if you go over the diversification of the finches in the Galápagos (and who doesn’t?), you cover not just natural selection but also genetic drift—even if you don’t identify it by name. Recent research has highlighted the role of gene flow in human evolution (your students will love talking about Neanderthal–Homo sapiens interbreeding!), and mutation, itself a mechanism of evolution, is a part of almost any evolution case study. The next misconception is a direct consequence of the last one.

    Misconception #2: All traits are adaptive.

    Correction: A lot of traits are adaptive—but definitely not all. If you want an example of a trait that isn’t adaptive, look no further than your own belly button. A belly button is a scar left from the umbilical cord connection that sustained development. The umbilical cord? Definitely an adaptation. Its scar? Not so much.

    The belly button is an example of a non-adaptive byproduct, but there are other kids of non-adaptive traits, too. For example, tetrapods, such as humans, typically have five digits—why five? There is probably no good reason—it just happened that way. Fingers and toes are of course adaptive, but the specific number of them? Not so much.

    3603295576_29dc50c84f_o copy

    The number of digits on a human hand can be used as an example of a non-adaptive trait.

    What this misconception looks and sounds like: Look for students to ask what everything is for—it’s so easy when learning about such incredible adaptations as the proboscis of Darwin’s hawk moth to the color-changing ability of the octopus to think that everything is for something, so they’ll ask that question again and again. Also look for the inverse—the dread “X evolved for Y,” as in “feathers evolved for flight.”

    What to do about it: The best way to make students see the fallacy of the hyperadaptive view of life is to point out clear examples of non-adaptive traits, so talk about belly buttons and male nipples! Provide examples to help students understand that adaptive functions can change (whale hip bones) and even be lost (human tail bones). Also, introduce an adaptation litmus test: To be an adaptation for a particular function, the trait must be heritable, have the function it was selected for, and increase fitness. Return to the litmus test again and again as you discuss everything from peacock tail feathers to dinosaur forearm feathers.

    Help students understand the fallacy of “feathers evolved for flight” by exploring how feathers evolved over millions of years.

    So evolution occurs via several mechanisms and not all traits are adaptive. This may somehow feel like a de-emphasis of natural selection, and in a way it is—but it is not a de-emphasis of evolution. Cracking down on these misconceptions, and the ones I’ll discuss in the next part of this post, will give your students a more sophisticated understanding of evolution, and by extension, a more sophisticated understanding of the world around them.

    Read part two of our evolution misconceptions series.

  • TS

    I’m not sure I agree with the notion that the number of human fingers and toes is not adaptive. Dexterity is a one of our human traits, and higher levels of dexterity are possible with five instead of four fingers. More specifically, an odd number of digits seems to confer an extra level of dexterity than an even number.

    • Stephanie

      Certainly, dexterity is important — but we’d be even more dexterous with six, or seven, wouldn’t we? A panda has even modified a wrist bone to get a kind of sixth digit that confers a clear advantage. So why the specific number five? Why not more? It’s that specific number, five, that is thought to be a byproduct of something else, rather than a specific adaptation.

      • Steve Juszczak

        I suggest reading the Panda’s thumb , by the late Stephen J Gould

      • Geoffry Kalisen

        I would imagine our number of digits is the result of our common ancestry with small mammals who also have 5 digits. The right selection powers could use them, but I don’t see extra digits evolving. I think the number of digits is most likely correlated for dexterity, but also or muscle and strength distribution. Too many fingers would get in the way and also make them have to be weaker.

    • James Downard

      Early tetrapods had way more than 5 fingers (alanine repeats in the Hox13 determine how many), and apparently the pentadactyl model proved a nicely reduced but functional mode for land animals overall. Our synapsid lineage of mammals have tended to be very conservative when it comes to not altering that mode, compared to the diapsid dinosaurs dropping digits in many lineages, including their bird descendents. So my guess would be that our having just five fingers is more a derived general trait than a directly adaptive layout.

    • Dave Bryant

      Technically, four fingers and one opposable thumb….or digit, or finger if you must.

  • Derp

    My solution- read more Steven J. Gould!!

    • Stephanie

      Always a good idea.

    • Dan Watts

      Except for the mismeasure of man [http://discovermagazine.com/2012/jan-feb/59]

  • mtn_man

    5 fingers and 5 toes have been traced way back to a sub group of jawed vertebrates about 340 million years ago. 360 million years ago there were tetrapods with limbs having 6, 7, 8 digits. (http://www.scientificamerican.com/article/why-do-most-species-have/). This pretty much shows that tetrapods with 5 digits were more successful than 6+ – which could be considered an adaptive trait. Definitely an example of natural selection.

    • Stephanie

      , five has been traced back a long way, so on one level, the answer “why five?” is “Because a common ancestor had five.” But why did that ancestor have five? Because it was more adaptive, or because of chance? We really don’t know. Ed Young had a good article about the most recent research into digit development on his blog, and it ends with: “So, why five? No one really knows.” Check it out: http://phenomena.nationalgeographic.com/2014/08/01/how-did-you-get-five-fingers/

      • John Mathews

        ” … we really don’t know” Truer words have never been spoken.

        • Stephanie

          Yes, but we will one day find out. Science doesn’t shy away from the unknown, rather, the unknown fuels science.

  • I suppose I should say right off that I’m a creationist. It seems if I don’t wear this yellow star of notification and an evolutionist finds out, it’s cause for great consternation and accusations of being sneaky, etc. It’s too bad, because I could otherwise overlook the popular misconception that ID and creation science are simply “Outright denialism and overt teaching of non-science,” and compliment Ms. Keep on the rest of the article. Actually, I can consider myself an evolutionist, since evolution is defined or described as “descent with modification” specified as “any change in the distribution of heritable traits within a population over time.”

    And of course it’s well said that natural selection is not evolution. I wonder, though, if there isn’t a better expression than to say that it and genetic drift, gene flow, and mutation (etc.) are “mechanisms of” evolution. The expression has a certain ID implication, “mechanism” being primarily associated with machines, i.e. intelligently designed things. Apart from that, it seems to imply that it is one kind of evolution, a complete cause, as is implied also by the suggested correction, “Evolution occurs in other ways, too.” Evolution never occurs by natural selection alone. Nor are all natural processes involved in evolution equal. Essentially, it comes down to mutation and natural selection as the major, common natural processes. (Horizontal gene transfer and incorporation of symbiotes are thought by many to have been the major events early on, and gene duplication is suggested as having a key role along the way by the observation of repetition of certain genetic/chromosomal features.)

    The other point is a good one, too, especially “the dread “X evolved for Y,” as in “feathers evolved for flight.”the dread “X evolved for Y,” as in “feathers evolved for flight.”” Sadly, versions of this are repeated even by lead researchers in paleontology and other evolution-related fields. The NATURE report on the recently-discovered “bizarre” Yi qi included the phrase “the evolutionary experimentation that took place close to the origin of birds.” This wording gives the impression that something was actively seeking (by experimentation!) to grant flight to dinosaurs. In an interview, one of the authors even said (http://news.yahoo.com/weird-winged-dino-sets-science-world-aflutter-185348254.html) “Close to the origin of birds (from dinosaurs)… many lineages tried in a different way to get into the air, but finally only one group succeeded.”

    Allow me to say as an outsider, it begins to look as if misconceptions are part of belief in evolution in the first place. I can hardly wait to see what others have been selected.

    • Stephanie

      You make an excellent point about the poor language choices used by scientists. I do not think it’s because “misconceptions re part of belief in evolution,” however. Rather, it’s because being vigilant about their language choices is not often a priority for researchers–but it should be, for precisely the reason you have hit upon: How can we expect students to get it right if the scientists don’t? NCSE is hoping to develop a webinar for scientists along the lines of: How to talk about evolution. Perhaps I’ll contact the authors of the Xi paper once it’s ready!

  • “…non-adaptive traits, so talk about belly buttons and male nipples! Provide examples to help students understand that adaptive functions can change (whale hip bones) and even be lost (human tail bones). ”

    Keep in mind that “non-adaptive” doesn’t mean that the trait is harmful or a problem. A lot of things are not especially beneficial or harmful. However, what is adaptive or increases fitness may not be obvious. Male nipples may not be helpful themselves, but it may be advantageous on the genetic level to have the coding remain the same for both sexes on this point. You’d also have to go back quite a way to find a posited human ancestor with a tail, and a tail may not be an adaptive trait for someone who is habitually upright. If humans had evolved from therapod dinosaurs, it would be a different matter.

  • RevolutionNumberNine

    I was hoping you were going to point out the common misconception I repeatedly hear that natural selection removes attributes that produce no survival advantage. This is untrue. An attribute will be removed only if it produces a survival disadvantage. In other words, natural selection is no efficiency manager. It allows neutral attributes to persist.

    In grade school, I once had a teacher who claimed that human hair would not exist in the future since it produced no advantage. This is idiotic on a number of levels but most because of the misunderstanding of the mechanism.

  • jeffro1969

    “Intelligent Design” is every bit as clever as science, for the simple reason that it is purely an exercise in semantics. Instead of “natural selection” and “evolution” it replaces those words with “God’s design” and “God’s plan”. But everything else is exactly the same.

    It comes down to a preference of one over the other. The facts and evidence are exactly the same, only the conclusion differs.

    • Bonnie Lowry

      I made similar assumptions, but was corrected when I learned more about the overall claims of intelligent design. I strongly recommend The Language of God, by Francis Collins for a detailed but highly readable treatment of the differences between the two. They are *not* the same.

    • Nope, Intelligent Design does not replace “natural selection” or “evolution” with “God’s design” or “God’s plan”. I have been reading their literature for almost 20 years and never came across such replacements.

    • m k

      Not even close to the same thing. “Design” and “plan” imply conscious decisions made by a sentient being (God or whatever). So, Intelligent Design states that God conceived of, planned out, and executed an intended end result. In evolutionary science, there is no forethought. No intelligence planned out which traits would be selected, no intelligence picked out certain mutations and made them happen.

    • Rick Lutes

      How is replacing the word ‘evolution’, a descriptor of a testable, measureable, natural process; with ‘G-d’s Plan’, an active untestable, immeasurable, unprovable action by an unseen supernatural deity “exactly the same?”
      Your argument makes as much sense as the question “Is it warmer in the summer or in the country?”
      All the words are there.
      The rules of grammar have been met, but it is a nonsense sentence.

      • jeffro1969

        No, what I said is more akin to, “Is it hotter in July, or in the 7th month of the year”.

  • Pingback: The Biggest Misconceptions About Evolution, And What We Can Do About Them (Part 1) – Engaging Science — Engaging Science | PBS | Mark Solock Blog()

  • Chad Hall

    I look at this way. Evolution is creation. The specimen is being created through evolution.

  • Gary Reed

    I promote in my classes that the mechanisms for evolution are gene flow, genetic drift, mutations, endogenous retroviruses, and to some extent epigenetics and transposons. Our microbiome is also in play but hard to determine how much of a factor (but it does add an estimated million genes over our appx. 22,000 to each of us). But it is natural selection, whether driven by climate, disease, diet, or culture whether those mechanisms are “successful” or not.

  • Chad Hall

    Science and spirituality or something greater than us can work together or actually be one in the same.

  • samurai_with_sword

    Seems like just common sense to me. I don’t know if specific examples given are 100% true, but in general, not everything happens for a reason, sometimes things just happen for no reason and you have to deal with them 🙂 It may happen that there is a very successful species on an island, but they are all short in height. They survived and are adapted very well to their environment, but the short height may not necessarily be because of adaptation and natural selection, it might just be because the gene pool simply lacked the gene for tall height. For example, one island has 3 humans, 1 short female, 1 short male, 1 tall male. Males are trapped in a cave with tiger. Tiger decides to eat the taller male because that will give him the most amount of meat. In this case, even if the taller male is more desirable, stronger, more clever and more adapt than the shorter male, as long as he cannot over power or oversmart the tiger, the tiger is going to kill the taller male. Giving the shorter male a chance to escape, while the taller male is being eaten. Then on, that island has short humans.
    Some people may argue that short height was useful in survival in this case and hence short male survived because of natural selection. But take yet another example, same 3 humans, earthquake happened, and land slid beneath the taller male and he fell in to the abyss. Shorter male survived just because land beneath him did not slide. Then on, the island has short humans.

  • Rick Lutes

    You missed the #1 Myth I have had to deal with as a teacher. They myth that Evolution works towards a goal and is an active process. This is commonly seen in the statement that Evolution is making humans more/less . The Chain of Being is a dead concept that keeps creeping in to the Public’s conception of Evolution.

    I try to tell my students Evolution is not a cook making a cake. Evolution is merely the oven where the baking takes place. It is a Process and not a Goal.

    • samurai_with_sword

      “Evolution is not a goal” is a strong statement. More like “It may not be a goal, just a process”. Who knows, may be someone designed the planets and earth to get a certain outcome. In science you always have to he a skeptic. A true skeptic in both or all directions. If something is not true, it does not mean it is wrong. It may be wrong, or it may be partially right. Saying that something is wrong just because it is not 100% right may again lead to some misconceptions. I am not saying that there is a god who designed everything. When I used to make a sling shot or a fan as a kid, sometimes I would make mistakes and the extra notches made by mistake sometimes used to ruin the outcome, but surprisingly enough, at times they also used to make the outcome more useful. So evolution may or may not be a goal. But even if it is a goal, it is not “error” free.

    • Stephanie

      Yes…stay tuned for part 2 (:

  • Pingback: The Biggest Misconceptions About Evolution, And What We Can Do About Them (Part 2) - Engaging Science — Engaging Science | PBS()

  • Bill Clawson

    Nobody really looks at the losers of natural selection much. They also inherited traits, just like the winners, but their traits didn’t provide them with a better fit for their environment, and thus, they lost. For every winner, there might be millions or billions of losers on whom we don’t focus (Except for paleontologists).

    • Stephanie

      Perhaps more important to note is that having adaptive traits ups your chances for reproductive success, but it isn’t a guarantee. And similarly, plenty of individuals without the “best” traits go on to reproduce just fine. So “winners” and “losers” shouldn’t be defined in terms of their traits, but whether of not they got the chance to pass on their genes.

  • Lisa

    So then autism…. is it just a part of evolution or just much more readily diagnosed?

  • Man_of_Sin

    Some people actually still believe that evolution happens in a lifetime.

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