The Most Common Misconception About Evolution

Evolutionary Tree of Life

This evolutionary tree of life has a problem. Yes, it beautifully illustrates that we are related to all life on earth, from bacteria to plants and birds. Still. there’s something wrong with it. The problem is that it is constructed from a human viewpoint. You can see that humans occupy a special position at the top branch of the tree, to the bottom right, close to our fellow vertebrates. The more distant a species is related to use, the more it is placed to the left. Such an ordering wrongly implies an (upward) direction in evolution. This was even more explicit in Häckel’s drawing of the tree of life in 1874 (below) where humans are literally placed at the crown of the tree. The idea that evolution has a direction is one of the oldest fallacies in evolutionary thinking, one that has persisted for over 150 years of evolutionary researched. I experienced this first hand during a philosphy course on evolution I followed this semester.

Haeckel's Tree of Life

During this course on evolution and philosophy, the teacher had posed the question whether there is any direction and progress in evolution. I naively expected that most of us would snicker and say ‘No, of course not!’. Naturally, I was wrong (you probably felt this one coming). Several students advocated that there was progress in evolution, pointing to humans as the greatest example of an ‘upward direction’ in evolution. Some of them even stated that ‘humans are more evolved’ than other species! Our supposed dominance over the earth and other animals was given as the principle argument for this standpoint. This kind of reasoning is so flawed, that I was cringing in my seat.

How on earth can evolution be a quantity that you ascribe to species in varying degrees? How are we ‘more evolved’ than cyanobacteria in the ocean, a panda in a bamboo forest or an earthworm in the earth? Cyanobacteria surely photosynthesize a lot better than we do! Likewise, we can better leave digesting bamboo to pandas and I doubt many people would fancy burrowing through soil like earthworms do. Each of those species has evolved to be adapted to their specific environments.

All species that are alive today have the same evolutionary timespan behind them. If LUCA lived 3.8 billion years ago, all species on this planet have been evolving for 3.8 billion years. Sure, some species resemble ancestral species more than others. Maybe they have not changed much in morphology for millions of years. But this does not mean they are more ‘primitive’ or that we are more ‘advanced’ than they are! Jonathan Eisen published an excellent blogpost on this issue here.

I will not deny that humans are unprecedented tool users who can manipulate environments like no species has done before. No cow, crustacean or squid has ever set foot on the moon. This does not mean that we should try to find biological reasons to confirm this notion of  ’specialness’! People have tried, and failed time after time. Our genome is not the biggest, we are not the only tool-users and language is not unique to us.

This notion of an upward direction in evolution has deep roots which seem difficult to eradicate. This is not surprising, because the word evolution itself is part of these roots! The Online Etymology Dictionary has the following entry for ‘to evolve’:

to evolve – to unfold, open out, expand,” from L. evolvere “unroll,” from ex- “out” + volvere “to roll”

So ‘evolving’ finds its origin in ‘rolling out’ of something that was previously enclosed, the unlocking of a potential from within. The term evolution better fits a Lamarckian world view (Lamark hypothesized that an intrinsic drive to perfection caused species to evolve). Herbert Spencer, a Lamarckist, was one of the first people to refer to Darwin’s theory as a theory of ‘evolution’. Because of the great differences between Darwin’s theory and the Lamarckian background of the word ‘evolution’, Darwin was extremely hesitant to use the word evolution to describe his theories. He much preferred ‘descent with modification’. In fact, he only introduced ‘evolution’ in the very last paragraph of the sixth edition of ‘the Origin of Species‘. Even though Darwin tried his best to avoid this confusion, the misunderstanding persists up to this day.

I am by no means an expert in evolution. Evolution is a beautiful and complex, with many intricacies and subtleties. What I do know is that sponges are not ‘primitive’ and that humans are definitely not ‘more evolved’, we are simply different.

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13 comments to The Most Common Misconception About Evolution

  • Darwin himself is not totally innocent in this regard, in the conclusion of The Origin he writes:

    And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.

    Amazingly, there are contemporary evolutionary biologists like Dale Russell and Simon Conway Morris that make similar arguments.

    • @Neil: Thanks for that quote, I never saw it before! It is good to realize that this argument was, for a long time, the most prevalent and accepted opinion.

      @Doug: There’s nothing wrong with playing devil’s advocate: it keeps one sharp ;).
      It is clear that evolutionary rates may differ. After all, homologous proteins may be under different selection pressures in different species. This has oft been misinterpreted as ‘more or less evolved’. Two years ago, it was found that chimpanzees had more fast-evolving protein sequences than humans did. Media quickly picked this up as ‘Chimps are more evolved than humans, OMG!’ (apart from the headline, this piece from Discovery covered the research fairly well). If one would follow this kind of reasoning, bacteria and viruses would be the most evolved species on earth, since their sequences change the fastest in the living world!
      Your last example is a great one! The whale clearly underwent more morphological changes than the shark underwent, since it adapted to extremely different environments in its evolutionary history. But I’m hesitant to say that the whale ‘evolved more’, precisely because it implies that whales are more advanced somehow. For the shark too, is a highly derived form from the common ancestor of sharks and whales..

      I’d like to call the ‘something’, ‘complexity’. I can fully agree with the statement that mammals are more complex than bacteria. Being multicellular (to name one thing) requires division of tasks, detailed regulation of gene expression (when and where) etc. The regulatory networks are more complex than in bacteria, who primarily change gene expression when environmental conditions change.

      I hope this somewhat addresses the valid points that you raised!

  • Doug

    Of course I agree with you on the most basic level. But to play devil’s advocate a bit: One reason why this concept is so hard is because while cyanobacteria and humans have indeed been evolving for the same amount of time, the rate of change in measurable phenotypes is much greater for humans. Does this mean that we are more evolved because we are evolving faster? There is the concept that some protein sequences change faster than others over time. So even different parts of an organism can be said to be evolving faster than others. So I think that there is room to put a finer point on the argument. Humans may not be more evolved but we are definitely more “something” than bacteria. What do we call that, “differentiated”? “phenotypically changed”?

  • Doug

    Just to show that I can be a complete smart Alec, how would one describe the relative evolvedness or phenotypic change of a whale? A creature that has gone from a water dwelling species, evolved phenotypes to enable land dwelling and then evolved back to water. Is a whale more phenotypically changed than a shark?

  • Have you read “Wonderful Life” by Stephan Jay Gould? He addresses this problem wonderfully (There should be a book review of it appearing on my blog on Tuesday!).

    In terms of the ‘relative phenotypic changes’ arguement, it all depends on what you see as a more interested phenotypic change. Humans obviously look a lot more different from the blobs that they came from, but bacteria have adapted so many more varieties in genetic sequence, even though they look somewhat the same. And as you point out in your comment, bacteria are capible of much quicker genetic change; antibiotic resistance spreads through bacterial populations much quicker than bacteria/viral resistance spreads through human populations.

  • Funny that you mention Stephen Jay Gould! I received ‘The Richness of Life’ as a gift during the holidays, which is a collection of Gould’s essays. I was smiling from ear to ear when I read his essay “The Evolution of Life on Earth” that was published in Scientific American. I found an online version here. More eloquently than I ever could, he already argued against a progressive view of natural history 15 years back :).

  • Szwagier

    Hi, I’ve just found this post while browsing through the site. You say that “language is not unique to us”, and provide a link to the story on Campbell’s Monkeys and their calls. I’ll have to stop you right there. Language, as understood in its technical sense (which is what we should be using if we are going to claim that other species have it), is indeed (so far) unique to us. Animal communication systems, amazing and complex as they are (bee dances, monkey calls, birdsong) are not language.

    As Geoff Pullum, a very distinguished linguist, put it on Language Log:

    At present Language Log has nothing to say, except to utter a long series of about 25 successive alert calls warning you that anything concretely tied to present dangers apparent in the immediate spatiotemporal environment cannot bear a very strong relation to natural use of a human language. The things we say are not just long sequences of “Watch out!”, “Fore!”, “Timber!”, “Stop thief!”, “Hey!”, “Ouch!”, and so on.

    This is not to say that only humans can have language, but we can say quite authoritatively that all the research done to date in the field of animal communication has provided no evidence that animals have anything like it.

    • Thanks for your comment Szwagier!
      Your point is well taken, and (as the non-expert of linguistics that I am) I have to agree with you that human language is unprecedented in the natural world. My (bold) statement that ‘language is not unique to us’ could’ve maybe better been written as ‘complex communication systems are not unique to us’.

      The point that this doesn’t place us at the crown of evolution still stands of course, especially because language as we find it in humans doesn’t seem to be a logical or necessary outcome of evolution. But a wonderful ‘coincidence’, of course!

  • [...] is extinct. From the pattern in the leaves, we deduce that it all came from that tree. Click here to see a more detailed, really cool version. __________________ Lighthouses are more useful than [...]

  • Larry Kyrala

    I realize that the misconception of ordering is quite common so I’m not trivializing that aspect, however I’d like to draw attention to other biases inherent in the problem. Eisenberg’s diagram attempts to sort phyla groups by relative speciation time… it’s unclear where he draws the line for subsorting… but if we take his species and try the same, we might notice that there are only a few that speciate after Man anyway. Eisenberg didn’t notice that and simply put Man on top. Ok, but there’s some evidence here that we’re not dealing with only a personal belief bias — we’re also dealing with a data bias. Why don’t we have other mammals that have speciated after Man? Well, part of this may oversight in the species sampled, but another problem is a bias from time. Speciation is more easily detected when the genetic differences are great… but most models require evolutionary time to get such differences — relatively speaking there simply isn’t a whole lot of evolutionary time since the speciation of Man… so we’ve got a more complex picture than we wanted: personal belief bias, data sample bias, and an evolutionary time bias. That’s an awful lot of biases to overcome, especially when the tree will always (correctly) illustrate the last two biases because they are “baked” into the underlying data.

    • Hi Larry, thanks for your comment!
      So what you’re saying is that as an example, two populations of field mice are technically already separate species, but since our techniques are not sensitive enough to detect this now, we are unable to classify them as such at present. If this is what you meant (and sorry if I misunderstood you – I can be quite slow), I completely agree with you and I thank you for raising a point I hadn’t thought about.

      This indeed goes back to the point that there’s no firm line between subsorting and speciation, only a grey area, so any tree we draw will always be a crude approximation of a biological reality. The distinct branches of trees only ‘work’ up to a certain point, just like newtons laws pf gravity only work for certain scales.

      Again, thanks for making me realize this!

  • Larry Kyrala

    Yep, and no need to apologize — I’ve been immersed suddenly in phylogenies for a senior infovis thesis I’m working on this semester, so I’m ordinarily from the computer, information visualization side of things, not a biologist :). But yes, the question of what speciation is and when it occurs is pretty open from what I’ve heard. My observation is that when the evolutionary time gets large enough, there is a lot more diversity that everyone pretty much agrees represents different species. But when evolutionary time is small.. well, the focus seems to blur from speciation to population-level allele frequencies and sub-populations. It looks like there is a lot of interest in combining species taxa with population phylogeny to get a more complete story of how population shifts lead to speciation — it’s cutting edge research. Mailund has a great post on this topic: — I found your blog because of several of your posts about such trees. Thanks!

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