Not impressed by the Extended Evolutionary Synthesis

This article in the Guardian, “Do we need a new theory of evolution?” has it’s moments, but I hated the title and didn’t care at all for the opening. It’s true, scientists don’t know everything, but we know more than the author thinks.

Strange as it sounds, scientists still do not know the answers to some of the most basic questions about how life on Earth evolved. Take eyes, for instance. Where do they come from, exactly? The usual explanation of how we got these stupendously complex organs rests upon the theory of natural selection.

You may recall the gist from school biology lessons. If a creature with poor eyesight happens to produce offspring with slightly better eyesight, thanks to random mutations, then that tiny bit more vision gives them more chance of survival. The longer they survive, the more chance they have to reproduce and pass on the genes that equipped them with slightly better eyesight. Some of their offspring might, in turn, have better eyesight than their parents, making it likelier that they, too, will reproduce. And so on. Generation by generation, over unfathomably long periods of time, tiny advantages add up. Eventually, after a few hundred million years, you have creatures who can see as well as humans, or cats, or owls.

This is the basic story of evolution, as recounted in countless textbooks and pop-science bestsellers. The problem, according to a growing number of scientists, is that it is absurdly crude and misleading.

For one thing, it starts midway through the story, taking for granted the existence of light-sensitive cells, lenses and irises, without explaining where they came from in the first place. Nor does it adequately explain how such delicate and easily disrupted components meshed together to form a single organ. And it isn’t just eyes that the traditional theory struggles with. “The first eye, the first wing, the first placenta. How they emerge. Explaining these is the foundational motivation of evolutionary biology,” says Armin Moczek, a biologist at the University of Indiana. “And yet, we still do not have a good answer. This classic idea of gradual change, one happy accident at a time, has so far fallen flat.”

But we don’t take the existence of light sensitive cells for granted at all! It’s biochemistry. There are organic molecules that can absorb the energy of a photon and undergo a conformational change; there are single-celled organisms that can recognize the impact of light and change their behavior or biochemistry. We don’t need to explain any stepwise change in the properties of abiological materials, because that’s just physics or organic chemistry. Is evolutionary biology incomplete if it doesn’t argue that physics evolved? Are we allowed to understand that chemistry existed long before life?

The article spends a lot of time on the Extended Evolutionary Synthesis, giving it more credibility than it deserves, and plays up the drama of evolutionary theory changing, as if that wasn’t a normal scientific response to new evidence and ideas. Stuff like this doesn’t help.

Then came a devastating series of new findings that called into question the theory’s foundations. These discoveries, which began in the late 60s, came from molecular biologists. While the modern synthesists looked at life as if through a telescope, studying the development of huge populations over immense chunks of time, the molecular biologists looked through a microscope, focusing on individual molecules. And when they looked, they found that natural selection was not the all-powerful force that many had assumed it to be.

They found that the molecules in our cells – and thus the sequences of the genes behind them – were mutating at a very high rate. This was unexpected, but not necessarily a threat to mainstream evolutionary theory. According to the modern synthesis, even if mutations turned out to be common, natural selection would, over time, still be the primary cause of change, preserving the useful mutations and junking the useless ones. But that isn’t what was happening. The genes were changing – that is, evolving – but natural selection wasn’t playing a part. Some genetic changes were being preserved for no reason apart from pure chance. Natural selection seemed to be asleep at the wheel.

Evolutionary biologists were stunned.

“Devastating.” “Stunned.” Nah. There’s an ongoing argument about the relative importance of various processes, but no one was emotionally wrecked by the discovery that evolution is complicated. There are conservative scientists who refuse to budge or even acknowledge the existence of stuff like neutral theory, but they’re not particularly interesting. On the other side, there are wacky extremists with their hair on fire screaming that the existence of developmental plasticity means that we have to throw away everything. Most scientists see new phenomena and say, “Cool. Now how does this fit with that?”

The article links to a Nature article, “Does evolutionary theory need a rethink?”, and it takes an odd angle. It only mentions the EES side, but the Nature article had two sides, one answering the question with “YES, URGENTLY,” the other saying “NO, ALL IS WELL.” So the EES side sets everything up as deeply in opposition to the Standard Evolutionary Theory (SET) side.

In our view, this ‘gene-centric’ focus fails to capture the full gamut of processes that direct evolution. Missing pieces include how physical development influences the generation of variation (developmental bias); how the environment directly shapes organisms’ traits (plasticity); how organisms modify environments (niche construction); and how organisms transmit more than genes across generations (extra-genetic inheritance). For SET, these phenomena are just outcomes of evolution. For the EES, they are also causes.

Valuable insight into the causes of adaptation and the appearance of new traits comes from the field of evolutionary developmental biology (‘evo-devo’). Some of its experimental findings are proving tricky to assimilate into SET. Particularly thorny is the observation that much variation is not random because developmental processes generate certain forms more readily than others. For example, among one group of centipedes, each of the more than 1,000 species has an odd number of leg-bearing segments, because of the mechanisms of segment development.

Maybe I’m an oddball, but nothing there is in conflict. I learned about plasticity, niche construction, and epigenetics and just took them on as part of the process of evolution, working alongside familiar older ideas about changes in allele frequency. How can anyone think evo-devo is some radical competitor to evolutionary theory? It’s got “evolution” in the name! I’ve been following evo-devo for forty years now, and certainly in the early days some were over-enthusiastic, calling it revolutionary, but really, it’s simply part of evolution. I don’t need to chant slogans or demand wild changes in the textbooks, they’ve all been steadily bringing more and more content about these crazy ideas about mechanisms other than selection into the fold. Nusslein-Volhard and Wieschaus are in freshman college biology texts now!

But the EES fanatics are not satisfied.

The case for EES rests on a simple claim: in the past few decades, we have learned many remarkable things about the natural world – and these things should be given space in biology’s core theory. One of the most fascinating recent areas of research is known as plasticity, which has shown that some organisms have the potential to adapt more rapidly and more radically than was once thought. Descriptions of plasticity are startling, bringing to mind the kinds of wild transformations you might expect to find in comic books and science fiction movies.

Yes, plasticity exists, it’s really neat-o, I’ve read lots of papers on it, and I’m a big fan of Mary Jane West-Eberhard’s work. So? What does it mean, “given space in biology’s core theory”? I don’t understand. I open up an evolutionary biology textbook, and it takes hundreds of pages to explain how evolution works, and it includes plasticity, and punctuated equilibrium, and nearly neutral theory, and lots of ideas that explain a complex process. What is this “core theory”? They talk as if there is some tidy concise kernel that everything is derived from, and they want to wedge in some detail. That’s not how it works. That’s not how anything works. Maybe they should step back and explain accurately what this “core theory” is.

The Guardian article sort of redeems itself at the end by pointing out the obvious: what is this single “core theory” they want to modify? There isn’t one!

The computational biologist Eugene Koonin thinks people should get used to theories not fitting together. Unification is a mirage. “In my view there is no – can be no – single theory of evolution,” he told me. “There cannot be a single theory of everything. Even physicists do not have a theory of everything.”

This is true. Physicists agree that the theory of quantum mechanics applies to very tiny particles, and Einstein’s theory of general relativity applies to larger ones. Yet the two theories appear incompatible. Late in life, Einstein hoped to find a way to unify them. He died unsuccessful. In the next few decades, other physicists took up the same task, but progress stalled, and many came to believe it might be impossible. If you ask a physicist today about whether we need a unifying theory, they would probably look at you with puzzlement. What’s the point, they might ask. The field works, the work continues.

I’m not thrilled with bringing physics into the story. Most people don’t understand evolutionary theory, so trying to compare it to another complex field that most people don’t understand (including myself) is not helpful at all. I agree with Koonin on the evolution part, though: there are a lot of messy moving parts to evolution, why even try to claim that it’s all unified in one simple, clear principle? Embrace diversity and complexity. You’ll never get anywhere trying to claim ownership of the “core theory”.

That might be the real issue here. In 1859, one man, Darwin, could say “This is my theory,” (with a little nod to Wallace). In the mid-20th century, a massive mob of scientists could come up with something called the Neo-Darwinian Synthesis, but no one person could lay claim to it. It was too big and sprawling and crossed multiple sub-disciplines. Now a handful of people want credit for some half-assed idea they call the EES…sorry, people, it’s just some more tasty ingredients for the stew, it’s not replacing anything.


  1. drsteve says

    My doctorate is an applied physics, but my undergraduate majors included biochemistry and in terms of my history of lab research, I was a molecular biologist in a far more modest variation of the model of Francis Crick, or Seymour Benzer.

    From that point of view, I’d say your unfified field theory analogy is absolutely on point.

    (Actually the last, and one of the few, actual biology classes I ever took was a graduate course in molecular evolution, so you can imagine the how your ENCODE post already had my hairs standing up on the back of my neck almost as soon as I woke up this morning.)

  2. says

    If you ask a physicist today about whether we need a unifying theory, they would probably look at you with puzzlement.

    No, they probably wouldn’t. They might ask, “‘Need’ for what purpose? The conceptual case for why we should fit together these two incompatible ideas is as good as it ever has been. If you want to understand the Big Bang, yes, you’ll need quantum gravity. If you’re studying high-temperature superconductors or how a DNA molecule responds to stretching or why ice is slippery, you won’t.”

  3. Robbo says

    I am glad some other physicists chimed in!

    Blake’s answer is what a physicist would say.

  4. says

    Well, you don’t need a unified theory — you can use the theory that works with your current problem — but you’re also missing something. Physicists are definitely troubled by the failure to unify the quantum forces with gravity. It does leave them without a theory for extreme conditions and it implies that there is something fundamental about the universe they don’t understand.

    In the case of evolutionary theory, it seems to me that sure, there are various phenomena that drive evolutionary change, including random drift, sexual selection, natural selection, the occasional horizontal gene transfer, epigenetic inheritance, the exigencies of what you have to work with already, and of the developmental process, stochastic mutation, ecological interactions, speciation and hybridization . . . . All that and more. But a goal should be to deepen understanding of how these processes interact. You can look at them one by one or two by two in a reductionist mode, but ultimately you want to understand how everything works together holistically. A grand unified theory may be a distant goal, but it’s a good one to have, it seems to me.

  5. John Harshman says

    Back to the eye again: where do they get the idea that the eye evolution story begins with “lenses and irises”? It’s as if they’ve never read any of the literature on eye evolution, starting with Darwin’s (in the Origin<.i>) series of living analogs to intermediate steps from light-sensitive cell to camera eye. And once again, no idea of any modern work on the subject, notably Nilsson D., Pelger S. A pessimistic estimate of the time required for an eye to evolve. Proceedings of the Royal Society of London, Series B 1994; 256:53-58. The article builds a strawman version of standard evolutionary biology built on vague “just-so stories”.

  6. says

    It’s Kevin Lalande. And Denis Noble. And Gerd Muller. And the usual crop of niche evolutionary theories that they think should replace the whole.

  7. says

    Versions of the camera eye evolved three times that I know of. I wonder if the sequences were similar or if there were different ways to get there.

  8. chrislawson says

    I found that article too annoying to finish. It’s yet another example of differences of opinion in science being talked up into a battlefield for clicks (as PZ points out, the 2014 Nature piece was a point-counterpoint article but the reporter here describes only the point side of the argument and doesn’t even acknowledge the counterpoint side even though they were published side-by-side, plus it’s yet another example of a journalist thinking something is a novel idea just because it’s the first they’ve heard of it: case in point, the description of epigenetics as a radical new concept in 2014!)

    And it lies. Here’s the article: ‘If another force, apart from natural selection, could also explain the differences we see between living things, Darwin wrote in On the Origin of Species, his whole theory of life would “utterly break down”.’

    Here is the actual quote from Darwin: ‘If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.’

    The reporter uses this misquote in order to drum up a “nearly theological dispute” between “Darwinists” and Thomas Hunt Morgan’s discovery of mutation — it would probably surprise our reporter to learn that Morgan saw himself as “anti-Darwinist” in his early career, right up until he discovered mutation…which changed his mind. The reporter writes as if the discovery of mutation was a problem for Darwinian theory when in fact it answered one of its biggest problems, to wit, where did all the variation come from?

    Then there’s this: “The modern synthesis was such a seismic event that even its flatly wrong ideas took up to half a century to correct. The mutationists were so thoroughly buried that even after decades of proof that mutation was, in fact, a key part of evolution, their ideas were still regarded with suspicion.” Which is completely wrong. Mutation was one of the key planks of the modern synthesis. In fact, the modern synthesis was created after Morgan’s work on mutations, and directly incorporated it.

    The reporter also seems to be singularly unaware that Dobzhansky was both an evolutionary scientist and a Christian. In other words, there’s an awful lot of superficial historical reading and poor comprehension going on in this article.

  9. Louis says

    It seems, yet again, that:

    a) “ZOMG OVERTURNING DARWIN!eleventy111!!!” is a truly superb go to for clickbait

    b) Presenting complex science as a series of simplistic controversies that, instead of enraging scientists, largely make people in the field look up and go “Huh? Yeah that’s not that big a deal, we just need more data.” is also good for the clicks.

    {Le sigh}


  10. billringo says

    As a spectator in the bleachers I appreciate the critiques of the article and to a lesser extent of the cited authors. Nice to go over a bridge without having to worry about trolls for a change.

  11. Louis says


    Quoting PZ: “…just … organic chemistry”.

    Just? Just!? JUSSSTTTT!?!!!?

    You know how to hurt a boy.


  12. PaulBC says

    As an interested non-biologist, I would say that the diversity of life on earth should in principle be explainable by reproduction, variability, selection, as well as constraints imposed by physics and chemistry. (Maybe I missed something here.) You can come up with all kinds of names for your frameworks, but it’s still basically the same explanation if it adheres to the above list. Does EES add something fundamentally new?

    As PZ points out, the constraints of physics and chemistry can’t be neglected. The development of photoreceptors is not a stretch because many materials are already photosensitive. The development of a lens is not a stretch either. Any droplet of water can form a lens. And for that matter, a pinhole will also focus an image very well. The answer to “the first” instance of a functioning organ is usually that we find things like it already. First eye? Sure. First wing? Anything with sufficient surface area to weight can at least glide. “First placenta” doesn’t even belong on the list, since many ways already existed for nourishing a growing embryo before the emergence of placental mammals.

    On the one hand, there is the nonsense of ID that neglects how much is readily observed in self-organizing systems and does not require “design” even if we had a good definition of “design” that didn’t already involve copying nature using trial and error. On the other hand, there is a popular misconception of evolution as a directional force towards “advanced” forms of life that would indeed lack any reasonable explanation in naturalistic terms. Unless EES really needs something brand new to explain the diversity of life on earth, it is still just evolutionary theory.

  13. bcw bcw says

    Just ran into this piece of crap and came over to see if you’d commented on it. The worst effect of this kind of bull is that it leaves the uniformed with the idea that evolution is some rickety structure built on opinion. Of such things is vaccine denial built.

  14. PaulBC says

    The argument from personal incredulity isn’t just for religious people. Journalists also like to cast doubt on anything they don’t understand. I’m reminded on the claim in the NYT 1920 (cursory search shows it’s not a myth) that rockets couldn’t work in space because “there’s nothing to push against.” (And I’m sure there are others who place great weight on personal incredulity.)

    It is certainly quite surprising, at least at first, to think that all the forms of living things could emerge from natural processes without any intent or goal. It’s also true that in over a century and a half since Darwin, there are many details that remain to be understood. So you can start with that and try to understand what is known, or you can stick with your initial surprise and keep looking for an indication that all those “ivory tower eggheads” don’t know what they’re talking about. While this tendency is consistent with a religious and teleological worldview, it’s not the only possible cause of it.

  15. PaulBC says

    Sorry for not collecting my thoughts in one comment, but I feel compelled to reply to:

    Strange as it sounds, scientists still do not know the answers to some of the most basic questions

    Halfway through the first sentence–were it not for my impeccable self-control–I would have to stop reading and start yelling at my computer screen (which is not nearly as satisfying as yelling back at a TV).

    Uh, what? That doesn’t sound strange at all. The business of science is to look for answers, not to “know” them. Unless you really think science is over (time to mothball those silly journals and partay) then it should come as no surprise that there are still a lot of things left to figure out. What kind of idiot writes things like this? Why should I keep reading past a laughably flawed premise?

  16. nomdeplume says

    It was a really bad article based on really bad science. The whole thing reeks of “Intelligent Design”/Creationism. Yet another attack on science, and from within.

  17. Rich Woods says

    First thought: Betteridge’s Law of Headlines. I wonder if the editor wasn’t as confident of the author taking a neutral position as the author seems to be.

    When I read the Graun article first thing this morning it jarred, but I don’t know enough about biology to be confident that my reaction was justified, so thank you, everyone, for clearing that up.

    I did look up the journalist and it seems he was originally a researcher in immunology, so you’d like to think that he had enough background to know better. But maybe he was just writing for the reaction, or maybe he’s one of those people who holds an extremist opinion, who happens to have a platform and this one got through.

  18. hemidactylus says

    I have a hard time getting enthused over ESS and this thread. Niche construction is actually kinda cool, but the rest seems to derail over sexed up “epigenetics” which is often an excuse to rub one out over Lamarck’s grave even though his views weren’t very different from his contemporaries and Darwin sucked very badly at inheritance too.

    I myself once thought Ed Steele’s views on immunology at least interesting at arm’s length in Lamarck’s Signature. But he’s gone way off into what the fuck land in some weird COVID cosmobiology brainfart.

  19. KG says

    Well, be fair, there hadn’t been a “new theory of evolution needed!”/”Darwin was wrong!!”/”Evolutionary heretics burned at stake!!!!” article in the popular press for at least six months.

    I was irritated by the article, read the linked Nature article, and came away from that with the impression that there was little substantive disagreement, mostly just differences in emphasis and presentation.

  20. Hoosier Bluegill says

    The only part of this that I’m qualified to comment on, is that there is no “University of Indiana”. Dr Moczek, who I know personally, teaches at an institution named “Indiana University”.

  21. hemidactylus says

    Some of the ideas pursued by EES are interesting to me. Genetic assimilation or Baldwin effect have long fascinated me. I think of such as the Piagetian mode, that changes in behavior could lead subsequent evolution. Arguably the cultural construct of dairying in humans is an example to the extent that keeping cattle and other milk source livestock has resulted in lactase persistence. But this occurred in humans and we have the linguistic capacity to share ideas and shift behavioral norms.

    I had wondered to what extent we can go back and apply this to tetrapod evolution. Lobe finned fish already had a cooptable capacity to support themselves outside of water, but did a behavioral shift to pursue landborne prey convert the lobe fins into an exaptation???

  22. says

    Good account, and many good comments here. Somehow the focus is always on giving evolutionary theory a new name, such as the ESS, as if this changes everything.

  23. DanDare says

    @PZ when you talk in your posts about how genes don’t necessarilly lead to certain traits, it depends on environment and development, I think it can read as dismissing heritable traits as the norm.
    Genes by and large lead to expected results on most life forms, and we lay people normalise that “by and large” as “always”. When scientists try to get it back to “by and large” it seems the reaction by many is to think you mean “never”.

  24. Owlmirror says

    I was thinking that you could use the multiple factors that can affect the climate as an analogy…

    Wait, so you mean that changes in solar activity and changes in the Earth’s orbit due to gravitational interactions and vulcanism and plate tectonics and types of plant growth and (so on and so forth) can all affect the climate? Wha?

    There’s no unified theory of climate either . . . but that doesn’t change the fact that humans dumping gigatonnes of carbon dioxide into the atmosphere is an important recent factor in current climate change.

  25. Owlmirror says

    This is perhaps a minor point, but it seems that the “photograph” of a spadefoot toad on the page was a hack photoshop job (that was misidentified as a spadefoot on the image page itself):

    Why did no one tell me that the “Do we need a new theory of evolution?” article in the @guardian contained this gem? Anaxyrus sp toad with a photoshopped chameleon tongue grabbing a photoshopped dragonfly, placed on top of a toadstool & incorrectly labeled as a spadefoot toad.

    I don’t think Buddy Mays is a particularly diligent person (there’s a comment on the page that says “unbelievable capture”, to which Mays responds with thanks rather than honestly acknowledging that it’s a photoshop)(maybe the commenter was making an ironic joke?). I also noticed on the bottom right the line: “Hurter’s spadefoot toads are rare and endangered.” Well, I checked Wikipedia (to see if there were pictures (there are, and they don’t match), and WikiP links to the IUCN Red List, which asserts that as of 2014, at least, Hurter’s spadefoot toads are Least Concern.

  26. Owlmirror says

    Oh, and the while you can see it in the web archive, the Guardian webpage no longer has the contentious image.

  27. Ted Lawry says

    Surprise! The Discovery Institute (Klinghoffer) has discovered ( the Guardian article and is “over the moon” as the British say. “The article is full of scandalous admissions:” etc. Klinghoffer was especially happy since the Guardian is “left-leaning!” It seems ID is easily fooled by sloppy, biased, thinking if only it is anti-evolution.

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