Evolution: Six myths

MYTH 1: Evolution is just a theory, not a fact.

When I say I have a theory, it means that I have a guess, a conjecture. But when a scientist says she has a theory, it means that she has a working explanation for a large set of facts. When we confuse these two senses of ‘theory’, we can misunderstand the scientific standing of the ‘theory’ of evolution.

In science, a theory is one of the most sturdy and well-tested ideas, rather than one of the least. Strictly speaking, a scientific theory can never become a ‘fact’ no matter how well-supported it is, because a theory is an overarching explanation rather than a mere observation. Thus, the idea that matter is made of atoms is still the ‘atomic theory’, and the idea that microorganisms cause disease is still the ‘germ theory’.

Because theories make predictions about what will happen in the future, they can be tested and refined over time. Around the 1930s, Darwin’s original theory was replaced by the modern synthetic theory. This “neo-Darwinian” theory incorporated Gregor Mendel’s account of how offspring inherit traits. Mendelian genetics has helped produce the scientific definition of the actual observed process of evolution — as ‘change in a population’s inherited traits’. A common source of confusion is mixing up the physical process, ‘evolution’, with ‘the theory of evolution’ (with explains the process). The process — which can be seen every time children aren’t exact clones of their parents! — can be called a ‘fact’ in the strict sense, whereas the theory of evolution is only a ‘fact’ in the looser sense of being ‘something we know is true’.

So what does the theory actually tell us?

In biology, evolution is the change in a population’s inheritable traits from generation to generation. It boils down to 4 core ideas:

  1. Heredity. Parents pass on their traits to offspring.
  2. Variation. Offspring differ slightly from their parents, and from each other.
  3. Fitness. Some of these differences are more helpful for reproducing than others.
  4. Selection. Offspring with more helpful traits will in turn have more offspring, making the traits more common in the population.

Over time, this simple process of small incremental changes can have dramatic results. As traits become more common or rare in the population over millions of years, a species gradually changes, either randomly or by the environment’s selection of certain helpful traits, into a new species — or branches off into several. This process is called speciation.

MYTH 2: Evolution teaches that we should live by ‘survival of the fittest’.

‘Survival of the fit’ is a better characterization of Darwin’s theory of selection than ‘survival of the fittest’, a phrase coined by the social theorist Herbert Spencer. Selection simply states that whatever organisms ‘fit’ their environments will survive. When resources are limited, competition to survive certainly plays a role — but cooperation does too.

The idea of ‘survival of the fittest’ has been used to justify Social ‘Darwinism’, which amounts to a philosophy of ‘every man for himself’. However, a number of biological misunderstandings underlie the notion that pure selfishness helps the group or the individual. First, even if this were true in nature, that would not automatically make it a good thing — germs cause disease in nature, yet that doesn’t mean we should try to make ourselves sick. Do we want to emulate nature’s brutality, or mitigate it?

Second, the ‘fittest’ species are often the best cooperators — symbiotes, colonies of insects and bacteria, schools of fish, flocks of birds, herds and packs of mammals, and of course societies of humans. Moreover, most ‘weaknesses’ are not genetic, nor so severe that they make the individual unable to contribute to society.

‘Fitness’ also changes depending on the environment. There is no context-free measure of fitness, and what is ‘weak’ today may be ‘strong’ tomorrow. Mammals were ‘weak’ when dinosaurs dominated the planet, but strong afterwards. Which brings us to the next myth…

MYTH 3: Evolution is progress.

When we speak of something’s ‘evolving’, we usually mean that it is improving. But in biology, this is not the case. Most evolution is neutral — organisms simply change randomly, by mutation and other processes, without even changing in fitness. And although evolution can never be harmful in the short term, since a harmful trait by definition won’t be selected, the problem is that evolution only cares about the short term. Although in the long run small evolutionary improvements can add up to massive advantages, it’s also possible for short-sighted, immediate benefits to evolve which doom a species in the long run. This is especially common if the environment changes.

The illusion of progress is created because all the evolutionary ‘dead ends’ tend to end up, well, dead — dead as the dodo. But the idea that evolution has any long-term ‘goals’ in mind derives from us not noticing two things. First, we don’t notice how meandering evolution is — an animal might become slightly larger one century, slightly smaller the next. And the reason neither process amounts to ‘evolving backward’ is because neither process is ‘evolving forward’ either — all hereditary change is evolution, regardless of ‘direction’.

Second, although we enjoy thinking of ourselves as the ‘goal’ of evolution, we don’t think about the hundreds of millions of other species that were perfectly happy evolving into organisms radically different from us. Bacteria make up the majority of life’s diversity; if intelligent bipeds were the aim of all evolution, we would expect them to have evolved thousands of times, not just once.

MYTH 4: We evolved from monkeys.

You may have heard the question asked: ‘If humans descended from monkeys, why are there still monkeys?’ Next time you hear this, feel free to reply: ‘If Australians descended from Europeans, why are there still Europeans?’

Biologists have never claimed that humans evolved from monkeys. Biologists do believe that humans and monkeys are related — but as cousins, not parent and child.

But then, biologists also claim that all life is distantly related. This theory, common descent, is the real shocker: You’re not only related to monkeys, but to bananas as well! This is based on the fact that all life shares astonishing molecular and anatomical simliarities, and these commonalities seem to ‘cluster’ around otherwise-similar species, like lions and tigers. Just as DNA tests make it possible to determine how closely related two human beings are, so too, by the same principle, do they allow us to test how closely related two different species are.

In the case of humans, the molecular evidence suggests, not that we descended from monkeys, but that we shared a common ancestor with them tens of millions of years ago. This ancestor was neither a modern monkey nor a human, but a now-extinct primate. Humans and monkeys have both evolved a great deal since that time. We’ve just evolved in very different ways.

It should also be noted that we are much closer to the other apes than to true ‘monkeys’ (which have longer tails). Humans are classified in the great ape family, the hominids. This makes our closest living cousins the chimpanzee, gorilla, orangutan, and gibbon — but we didn’t evolve from them, any more than they evolved from us.

MYTH 5: Evolution is random.

It’s sometimes suggested that evolution is too ‘blind’ and ‘random’ to result in complicated structures. But natural selection is only ‘random’ in the sense that physical processes like gravity are ‘random’. Although the genetic differences between organisms derive in part from random mutations, natural selection nonrandomly ‘filters’ those differences based on how well they help the organism survive and reproduce in its environment. The overall process of evolution, therefore, isn’t simply random: Species change in particular ways for particular reasons, such as because of a new predator in the region, or for that matter because of the absence of a predator.

A related myth is the notion that evolutionary theory claims ‘life arose by chance’. This is not an aspect of the theory of evolution, which only describes how life changes after it has already originated. Instead, this is relevant to the study of abiogenesis, the origin of life.

MYTH 6: We still haven’t found a ‘missing link’.

It’s not always clear what this fabled ‘missing link’ is supposed to be, as thousands of fossils of early humans and hominids have been discovered. The problem is that every time a new fossil is found that fills a ‘gap’ in the evolutionary record, it just creates two new gaps — one right before the fossil species, and one right after.

Transitional fossils linking major groups of organisms are also abundant in the record. One of the most famous dates back to Darwin’s day: Archaeopteryx, a proto-bird with feathers, teeth, and clawed fingers. More recent examples include Tiktaalik, a fish with primitive limbs (including wrists) and a neck, predating the amphibians.

More to the point, the central lesson evolution has to teach us is that every organism is a ‘link’ — all life is connected, and every organism that has offspring is equally ‘transitional’, because life is constantly changing. The change is gradual, certainly, and seems minute on a human time scale — but one of the profoundest lessons science has to offer is that drops of water, given time, can hollow a stone.

For more information, see Talk.Origins.


6 thoughts on “Evolution: Six myths

  1. I don’t like the idea, which I’ve heard many times, that it’s a “myth” that humans evolved from monkeys. I feel like this sort of complaint is about scoring some technical point — by defining “monkey” to mean “modern monkey” — rather than really informing the audience.

    Consider the most recent common ancestor of all monkeys. At some time, that ancestor species split in two (speciated), giving rise to two species – which then underwent further splitting, giving rise to two groups (or clades) of related organisms. Both sides of the original split contain monkeys. But as it happens, one side also contains us.

    So we are evolved from something that gave rise to two different clades containing monkeys. Since it was able to do this, it must have been very much like a monkey itself.

    1. I’m not super interested in pedantry as an end in itself. But — pedantry as a means to making the world a better place? Oh man. I’m all over that.

      Here are three reasons the ‘we evolved from monkeys’ meme is, above and beyond being an easy-to-pick-on creationist error, useful for its positive educational content:

      1. It teaches the difference between monophyletic and polyphyletic biological groupings. Noting that biologists aspire to make their classifications monophyletic in turn makes sense of the important discoveries “humans are animals” (which does a lot to rhetorically undermine anthropocentrism) and “birds are dinosaurs” (which is memorable, interesting, and can really change how one thinks about extinction and about life’s recent history).

      Thinking monophyletically encourages us to see past biological essentialism and recognize the continuity between different forms of life — e.g., it can help make it easier to swallow the pill that we’re all just jazzed up bacteria colonies.

      2. It teaches the difference between anagenesis and cladogenesis, which is essential for understanding Universal Common Descent and for starting to think evolutionarily about natural phenomena. Recognizing cladogenesis, and the fact that other species are ‘just as evolved’ as us, also goes a long way toward rhetorically undermining the ‘Great Chain of Being’ model and orthogenesis.

      3. As humans, we should have some grasp on what our species is, and on our closest living cousins. The two biggest things to know are that (a) chimpanzees are our nearest relative, and (b) we are apes.

      Talking about what a monkey is is very useful for teaching what an ape is, which allows us to teach people ‘humans are apes’ without those just being teachers’ passwords. That is, we can convey our taxonomic status as a part of discussion that actually communicates content about our behavior and morphology, and about the general way large-scale biological groupings work.

      When you’re trying to completely reshape people’s biological intuitions, it’s important to grab at low-hanging fruit like these when you think you can leverage them into deeper revelations. It’s rare to find mistakes as concrete, specific, and nontechnical as this.

  2. You’ve not really spelled out why you consider “we evolved from monkeys” to be an error. * For the reasons I gave, it seems to me that the ancestor I talked about can reasonably be called a monkey. Not a modern monkey, but why must “monkey” mean “modern monkey”?

    As far as I know, “monkey” can be considered paraphyletic, not polyphyletic. There are apparently 147 members ** of the simian clade, all of which are called monkeys except a clade of 14. But paraphyletic groups include the most recent common ancestor as well: i.e. it’s reasonable to call that ancestor a monkey. We really are evolved from monkeys.

    I don’t think I’m alone in this view, e.g. I googled “monkey paraphyletic” and the top hit is apparently by a professor who’s willing to agree “it may very well be that the ancestor of all monkeys and apes … would have been considered a monkey, and therefore YES we are descended from a monkey”

    * Sure, the question “why are there still monkeys?” is idiotic, but put that aside.
    ** Numbers from Lecointre & Le Guyader (2006): The Tree of Life

    1. The problem you’re running into is that ‘monkey’ is mostly a non-technical term, so it’s fuzzy and ambiguous. One way to get at the issue would be to disambiguate ‘monkey’ to ‘morphological monkey’ (an organism that generally looks like a monkey) and’genetic monkey’ (an organism that is either a New World monkey or an Old World monkey). Taking a key part of morphological monkeyhood to be ‘it has a tail’, (genetic) apes, including humans, are descended from m-monkeys, but are not m-monkeys themselves. And we are neither descended from a g-monkey nor are we g-monkeys.

      (To call apes ‘monkeys’ is I think simply a mistake, resulting either from an ignorance of why ‘monkey’ and ‘ape’ are distinct words in the first place, or from a confused attempt to fuse the morphological and genetic senses of ‘monkey’ into a single word, as though morphology were itself under a constraint to be monophyletic.)

      The reason I focus on g-monkeys is that (a) that’s how biologists just about always use the term, (b) biologists almost always use names like this to pick out genetic groups, so knowing about that in the case of monkeys can help increase one’s scientific literacy on a range of biology topics, (c) if we focus on vague and informal senses of ‘what things look like’ and on colloquial conceptions of animals, we risk forgetting that morphologico-behavioral groupings like {pangolin, echidna, aardvark, numbat, vermilinguan} aren’t closely related at all and are just cases of convergence, (d) ‘we’re not descended from monkeys’ reassures antsy creationists and softens them up for later blows like ‘we are animals’, and (e) keeping the discussion focused on genetics will yield more novel and general insights like the one I mentioned above.

      So it’s both technically correct and pragmatically useful. Whether it’s an uncharitable reconstruction of what creationists mean doesn’t much worry me, given how much debt creationists are in on the logical rudeness ledgers. If they feel I’m misunderstanding their point, I’ll happily talk about the very morphology issue you just raised; all of this is really just an excuse to start educational conversations, and concessions and nuance can be a great way to keep those civil. But you can’t be infinitely nuanced and precise at the outset, or you won’t get your foot in the door and nothing will be learned.

      I understand the point you’re trying to make with “We really are evolved from monkeys.”, but understand that this is strictly false, and that noting the reason for its falsehood is interesting and pedagogically useful, even if there are also lots of interesting bonus details to be noted by pointing out the (nonstandard or colloquial) sense in which it is true.

      1. You have to ask yourself which you are more interested in doing, when debating creationists: silencing them via bamboozlement or educating them. When a creationist says, “Ha ha, you think we’re descended from monkeys!” they are likely thinking of a tailed non-hominoid simian that lived in trees. Well, we are descended from tailed non-hominoid simians that, in all likelihood, lived in trees! That is the notion that creationists are mocking, and that is what needs to be made more easily digestible. If you reply that we are not descended from monkeys, it will only sound as if you are trying to deny the picture in their head, which is actually a perfectly accurate picture. If you rub that picture out of their minds, you are only decreasing their understanding of what scientists believe, not increasing it. If you are more precise, and you say, “Yes, we are descended from a tailed simian that in all likelihood lived in trees, but I refuse to call it a monkey because I define monkeys in this way…” then all you are doing is distracting from the actual science with irrelevant minutiae about how you personally choose to define words.

        To define a “genetic monkey” as “an organism that is either a New World monkey or an Old World monkey” seems perverse, and I can’t think of any reason for doing that other than for cheap point-scoring over creationists. It conceals the interesting fact that Old World monkeys and New World monkeys share ancestry, which, if anything, plays into the creationists’ hands.

        It’s interesting that you raise the subject of birds being dinosaurs, and encouraging that you find the statement interesting. Well, the statement, “Apes are monkeys,” is true in precisely the same sense that the statement, “Birds are dinosaurs,” is true. Neither statement is strictly true when the words are used as in everyday English, but both reflect truths about shared ancestry that go deeper than definitions. Both statements reflect our modern understanding not only that the old categories of “monkeys” and “dinosaurs” are not monophyletic but paraphyletic but also the more interesting fact that they can be neatly turned into monophyletic taxa simply by extending them via the addition of groups which were not previously known to descend from their respective common ancestors: the apes and the birds, respectively.

        It may be true that scientists use the term “simian” rather than “monkey” to refer to members of the extended monkey clade, but that’s just a matter of conventional nomenclature, not a statement of any underlying truth. The fact that the hominoids are conventionally excluded from the “monkeys” just means that to be more precise, we can define monkeys as the “non-hominoid simians”, which nicely illuminates the shared ancestry of the monkeys at the same time as it warns of the category’s paraphyletic nature. Your definition of the form “something that is either this or that” illuminates nothing.

        The monkeys are in no way analogous to the grouping {pangolin, echidna, aardvark, numbat, vermilinguan}, and they are not defined in terms of vague and informal senses of “what things look like”. The interesting thing about monkeys, and the thing that creationists need help in understanding, is their shared ancestry. They are all simians, and their most recent common ancestor was a simian. Those are the important facts in this context.

        To the creationist, the question of what label you attach to their imagined tree-dwelling non-hominoid simian is of no interest or importance. The interesting question is whether or not we’re descended from it.

        1. You have to ask yourself which you are more interested in doing, when debating creationists: silencing them via bamboozlement or educating them.

          There are many contexts where students should be actively engaged in debate, to test their ability to wrestle with ideas; and there are many other contexts where students should (ideally) be silently listening/reading. In this context, I think the most useful approach is to attempt to educate the creationist as opposed to arguing with them. Arguing with a creationist means accepting how they’ve framed the discussion, and attempting to show that they’re wrong. Educating means using the creationist’s misunderstanding as an occasion for laying out the facts, including facts that are interesting or important but neither accept nor reject the original claim.

          To define a “genetic monkey” as “an organism that is either a New World monkey or an Old World monkey” seems perverse, and I can’t think of any reason for doing that other than for cheap point-scoring over creationists.

          This is how biologists already use the word “monkey”; it’s how Wikipedia defines the word “monkey”; etc. We can talk about the genetic features that set monkeys apart, or about the morphological features; and in either case it’s a paraphyletic grouping. You say I’m deceiving creationists with how I “personally choose to define words,” inventing ad-hoc definitions just to spite creationists, etc.; but the definitions I’m appealing to are just the standard ones biologists use.

          I agree with you that words aren’t so important in their own right, but I disagree with you that it’s rhetorically ineffective to get people interested in more precision and seeing-past-appearances in how they classify living things; and I disagree with you that the most common scientific meaning of the word “monkey” is whimsical or arbitrary or malicious. Rather, it tells us something interesting and generalizable about scientific nomenclature that “monkeys” and “apes” were historically distinguished by whether they possessed a tail, and that biologists then refined this definition when it turned out to almost correspond to a cladistic division, but with a few wrinkles.

          (The wrinkles being that Old World monkeys are genetically closer to apes than to New World monkeys, and that two morphological “apes” (i.e., tailless simians) are genetically Old World monkeys, and for that reason are considered monkeys and not apes by modern biologists: the Barbary macaque and the Celebes crested macaque.)

          Neither statement is strictly true when the words are used as in everyday English, but both reflect truths about shared ancestry that go deeper than definitions.

          I’d say that there really isn’t such a thing as “strict truth” (or strict falsehood) when it comes to colloquial usage like this. Ordinary English usage underspecifies the intension and extension of words like “monkey” and “dinosaur.” You can say that pigeons clearly aren’t what most people have in mind when they say “dinosaur,” but you can equally say that humans aren’t what most people have in mind when they say “monkey” (or “ape”); so both terms look polyphyletic.

          Except relying on vague prototypes is not really all that useful in a domain that requires as much Extreme Nitpicking as evolutionary biology. Many people would say that pterosaurs, therapsids, and plesiosaurs are “dinosaurs” too (while denying that crocodiles are “dinosaurs”!). The bastardized genetic sense in which birds are “dinosaurs” would then also be a sense in which humans and other mammals are “dinosaurs”. Rather than attempting to build up an ad-hoc concept of “dinosaur,” “monkey,” etc. that splits the difference between formal and informal usage, I’d rather just defer to the formal usage of biologists. If that’s confusing, then we can use taxonomic names and just steer clear of words like “reptile” and “monkey”; but that obviously has its own disadvantages.

          the old categories of “monkeys” and “dinosaurs” are not monophyletic but paraphyletic but also the more interesting fact that they can be neatly turned into monophyletic taxa simply by extending them via the addition of groups which were not previously known to descend from their respective common ancestors: the apes and the birds, respectively

          Couldn’t you make the same point by just using the word “simian” in place of “monkey”? Or, better yet, using the word “ape” in place of “monkey” and explaining why humans are apes (which has the advantage of being informative, close-to-the-issue, and technically correct), rather than trying to explain why apes are monkeys.

          As you note, we already have a perfectly good word for the idea you’re trying to use “monkey” to refer to, and that word is “simian.” The phrase “higher primate” is also an equally good word to use here. I don’t see the advantage of trying to redefine “monkey” to capture a category we already have a name for, while thereby losing any term for referring to the (admittedly less important) paraphyletic grouping ‘Old World monkeys plus New World monkeys’.

          I agree that the thing you’re describing is in no way an incoherent way of extending the folk concept. But there are dozens of other non-incoherent ways of extending the folk concept, too. Deferring to biological usage (or just dropping the word altogether) seems more useful than trying to argue for one specific nonstandard extension, whether we’re talking to creationists or non-creationists.

          I think you’re underestimating the harm of using words in scientifically nonstandard and creative ways. The fact that words are arbitrary labels and it’s silly to argue about them gives us extra reason to be studiously consistent in how we use them, because studious consistency is the best way of minimizing argument and misinterpretation. I also think you underestimate the value of saying ‘monkey is defined as X’ in an argument, having the creationist Google the word ‘monkey’, and having the first hit (Wikipedia’s ‘monkey’ article) repeat exactly the same definition back to them that you just used.

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