The Evolution of Evolution: Gradualism, or Punctuated Equilibrium?

In some ways I’m glad I’m not an evolutionary biologist, even though the subject matter is undoubtedly fascinating and fundamental. Here in the US, especially, it’s practically impossible to have a level-headed discussion about the nature of evolutionary theory. Biologists are constantly defending themselves against absurd attacks from creationists and intelligent-design advocates. It can wear you down and breed defensiveness, which is not really conducive to carrying on a vigorous discussion about the state of that field.

But such discussions do exist, and are important. Here’s an interesting point/counter-point in Nature, in which respectable scientists argue over the current state of evolutionary theory: is it basically in good shape, simply requiring a natural amount of tweaking and updating over time, or is revolutionary re-thinking called for?

Illustration cichlids from different lakes, by R. Craig Albertson.
Illustration cichlids from different lakes, by R. Craig Albertson.

I’m a complete novice here, so my opinion should count for almost nothing. But from reading the two arguments, I tend to side with the gradualists on this one. As far as I can tell, the revolutionaries make their case by setting up a stripped-down straw-man version of evolution that nobody really believes (nor ever has, going back to Darwin), then proclaiming victory when they show that it’s inadequate, even though nobody disagrees with them. They want, in particular, to emphasize the roles of drift and development and environmental feedback — all of which seem worth emphasizing, but I’ve never heard anyone deny them. (Maybe I’m reading the wrong people.) And they very readily stoop to ad hominem psychoanalysis of their opponents, saying things like this:

Too often, vital discussions descend into acrimony, with accusations of muddle or misrepresentation. Perhaps haunted by the spectre of intelligent design, evolutionary biologists wish to show a united front to those hostile to science. Some might fear that they will receive less funding and recognition if outsiders — such as physiologists or developmental biologists — flood into their field.

Some might fear that, I guess. But I’d rather hear a substantive argument than be told from the start that I shouldn’t listen to those other folks because they’re just afraid of losing their funding. And the substantive arguments do exist. There’s no question that the theory of evolution is something that is constantly upgraded and improved as we better understand the enormous complexity of biological processes.

The gradualists (in terms of theory change, not necessarily in terms of how natural selection operates), by contrast, seem to make good points (again, to my non-expert judgment). Here’s what they say in response to their opponents:

They contend that four phenomena are important evolutionary processes: phenotypic plasticity, niche construction, inclusive inheritance and developmental bias. We could not agree more. We study them ourselves.

But we do not think that these processes deserve such special attention as to merit a new name such as ‘extended evolutionary synthesis’…

The evolutionary phenomena championed by Laland and colleagues are already well integrated into evolutionary biology, where they have long provided useful insights. Indeed, all of these concepts date back to Darwin himself, as exemplified by his analysis of the feedback that occurred as earthworms became adapted to their life in soil…

We invite Laland and colleagues to join us in a more expansive extension, rather than imagining divisions that do not exist.

Those don’t really read like the words of hidebound reactionaries who are unwilling to countenance any kind of change. It seems like a mistake for the revolutionaries to place so much emphasis on how revolutionary they are being, rather than concentrating on the subtle work of figuring out the relative importance of all these different factors to evolution in the real world — the importance of which nobody seems to deny, but the quantification of which is obviously a challenging empirical problem.

Fortunately physicists are never like this! It can be tough to live in a world of pure reason and unadulterated rationality, but someone’s got to do it.

30 Comments

30 thoughts on “The Evolution of Evolution: Gradualism, or Punctuated Equilibrium?”

  1. I heart Gould’s Structure. One thing he points out we need to explain in the fossil record is the predominance of stasis over very long periods. Another is that one of the least well understood aspects of the record is the mechanisms of extinction, yes, individually, but as a whole, too.

  2. Fortunately physicists are never like this! It can be tough to live in a world of pure reason and unadulterated rationality, but someone’s got to do it.

    Things are more settled today but 50 – 60 years ago, physicists used to argue over topics such as bootstrap dynamics vs field theory, which discussions could become quite animated.

  3. Peter and colnago80, I think Sean Carroll was being humorous with the last comment…
    As to the topic, which is interesting and frustrating at times (revolutions have been proclaimed before, and people like Jerry Coyne have dissected them thoroughly on their websites). I feel an urge to psychoanalyze the revolution hyperbole, the side doing the psychoanalyzing in the nature article, but I can see now, thanks to you Sean, that perhaps it is not the wisest path to take in this discussion.

  4. I think the old Jacque Monod view that speciation can all be explained by random mutation is a vast over simplification, Whether going beyond that view constitutes a new synthesis could be argued either way.

    Gradualism can account for a lot but it has a problem with some of the key discontinuities.

    How did we get simple autocatalytic molecules to viable organisms?

    How did we get from single celled to multi-cellular organisms?

    I think this article by Carl Zimmer shows how complicated speciation can be:

    http://www.nytimes.com/2013/07/04/science/how-simple-can-life-get-its-complicated.html?_r=1&

    It seems like assimilation, hybridization, and co-evolution of a group of organisms in an ecosystem have roles.

  5. Here in Europe, the intelligent design loons are marginalized and almost non-existent. In the US a politician would be afraid to talk about evolution and science for fear of being labeled an atheist, here politicans are afraid to talk about intelligent design for fear of being labeled backwards and medieval. Of course I prefer it this way 🙂

    The Nature paper is not interesting, there is nothing new in it. Evolutionary theory is right and confirmed in countless observations and experiments (like bacteria developping resistance to antibiotics etc). The critic of evolution misunderstands some elementary facts and invents unnecessary words like EES. He probably doesn’t know why a catterpillar differs from a butterfly even if they have exactly the same set of genes 🙂 Epigenetics is nothing new, it is a form of lamarckism that complements the traditional darwinian hereditability. And there is no need to invent new words for it.

    From a mathematical viewpoint, evolutionary theory is modeled best by the evolutionary game theory.
    http://www.nature.com/scitable/knowledge/library/game-theory-evolutionary-stable-strategies-and-the-25953132

  6. Raskolnikov

    I don’t we should equate EES and ID or infer that EES is a critique of natural selection and evolution.

    This is discussion among scientists in Nature. It is more a discussion about how much we can explain with simple genetic inheritance and random mutation or whether we need additional factors. Those additional factors would not disprove natural selection but supplement the genetic inheritance and random mutation model. Whether consideration of these additional factors is revolutionary or not I would leave to others.

  7. James Cross, sorry my mistake, I (wrongly) assumed that it is another attack on the evolutionary theory (and most attacks come from these ID bigots).
    Anyway, in this discussion I take the side of Gregory Wray and hold the view that evolution needs no extension because all the observed phenomena can be accomodated within the existing theory. And the discussion in Nature slightly annoys me. This Kevil Laland should present a concrete example from evolution which he thinks the mainstream theory cannot accomodate and explain why it cannot accomodate it. But I have rather the impression that he is spreading a lot of verbal and vacuous mumbo jumbo without much substance.

  8. In the humble opinion of this evolutionary biologist, it’s like saying we need an Extended Theory of Gravity to explain roller coasters.

    I wonder what Sean Carroll (the real one) thinks, given his lab’s work on one of these “add-on” areas.

  9. Raskolnikov

    Easy mistake to make with so much of the public discussion on this topic in the science vs. ID vein.

    Actually evolution by natural selection became pretty widely accepted in science and among the educated before anyone understood the exact mechanism of it. Eventually the understanding of genes and DNA provided a good explanation for large parts of it. When you add in epigenetics, ecology and social science, we are probably getting to a fairly complete understanding of the mechanisms.

    I certainly think the transition from autocatalytic molecules to viable organisms is probably going to require some additional (but non-supernatural) mechanisms. I am hardly an expert in any of this but my general thought is that in the right environment we might get the self-assembly of primitive viruses. The first viable organisms arose from merging, clumping, and swapping of viral material. This does not negate the fact that most viruses with which we are familiar with today require organisms for multiplication. Here is another great Carl Zimmer article about viruses being the remnants of RNA world.

    http://www.nytimes.com/2014/09/25/science/a-tiny-emissary-from-the-ancient-past.html?_r=1

    By the way, viruses are not necessarily small:

    http://www.nature.com/news/giant-viruses-open-pandora-s-box-1.13410

  10. I’m not smart enough to understand the argument.

    def: evolution = A creature (or molecule) makes a copy of itself. Stuff happens. Surviving creatures (or molecules) go on to make “copies” of themselves. Repeat.

    def: stuff happens = all events, limited only by your imagination and your gift for determining the number of permutations and combinations possible in a given setting.
    def: copy of itself = something close enough, including changes introduced by the copy process.

    To say “this” or “that” is the driving force (explanatory forcing function) for evolution is too limiting. Evolution is driven by: this, and that, and environmental affects, and geologic events, and so on….

  11. As you screw down into the depths you will find Atoms that combine into molecules and molecules that combine in spiral strings of molecules and cells that combine into groups and groups that combine into Biological life in some way all things being equal. But what if a disruptive event occurs at any one of those events…will the end result change or perhaps not survive? A neutrino, a gamma ray, an EM Field, a chemical imbalance, an anomaly at the lowest of levels could modify the result…in some way. And then, once a successful Biological life reproduces this process then is it not dependent on the environment to be that condition which did not negatively affect the success of survival.
    Lets speak to the amount or degree of effect any of those adjustment conditions could have made to each unit of life each time it is created and then survived. Certainly the ability to succeed is a result of a robust structure that is capable of succeeding with minor changes to the end unit of life, such as a change in the color of a scale, a larger or more dense bone structure, and to be clear, the size and capability of the brain.
    Any discussion about evolution must begin with, at least, an attempt to expose the means and conditions for change and the ability to survive those changes.
    So tell me, is something or someone directing those changes or is the origin of each living unit as a result of that direction, or is the system or process called the physical, robust and able to deal with and correct anomalous variations to a detail. I happen to believe that the entire physical universe is alive and each anomaly, each variation, is natural in an evolving process of interaction that begins at the most fundamental level. But is the most fundamental level a mathematical formulation of prediction? I don’t believe that to be true, I believe that the most fundamental level of interaction rests in a hierarchal position four levels below a Particle in a region of our understanding of the physical that exists in support of change, consistent comparable change, called time, that interacts to form structures in the harmonic, and that has limits both global and local, and to be clear has a certain uncertainty in our perception of the details.
    With this thought that the Universe exists, is alive and evolving out of a singular condition and into another and our faith in what we have found to be true conditions rests in more than just predictability, but also in our belief in our ability to understand that process and that process is far greater in scope than ever believed to be before.
    The Evolution of Evolution begins when we realize that we are somewhere in the middle of our understanding and having faith in what we perceive to be and learn to grow with understanding.

  12. The evil genius strikes again, distracting you from the true nature of quantum mechanics.

    Seriously though, one thing I noticed about other species is that most of them all look the same and are almost like identical twins. Looking at humans, we all have vast difference and subtle differences that are not normally present in other species. If you had a picture of Jay Leno’s chin next to another human, would this be an example of a problem of our understanding of evolutionary theory?

    I think one thing that separates humans from the animal world is that we get around a lot more and travel more around the world. Then people from some small African tribes all tend to look alike, men and women. They remain more isolated, and have a smaller gene pool than people in other parts of the world.

    With the constant influx of new genes being spread, it seems like it allows a species to have more variety. Like butterfly’s and most bugs and insects are attracted to light, like the Sun and Moon. Then they have more variety and can undergo more drastic changes than other species.

    With fish in two different lakes, they are all going to look mostly the same. It would take a flood in order for these two species to interbreed.

  13. Gradualism or Punctuated Equilibrium. Or is that question a false dichotomy.

    Biology/evolution are phenomena in the realm of complexity. There are many strategies that have emerged. Why can’t there be environments/ecosystems where gradual roughly constant rate evolution is the response, and other environments/ecosystems where punctuated equilibrium is the natural response?

    Complex systems create and explore a wide variety of systems. A diverse set of responses and strategies is not surprising.

  14. I think some people misunderstand Sean’s title, which refers not to evolution but to the theory of evolution. 🙂

    Yes, there was a debate of sorts between gradualism and punctuated equilibrium within evolutionary theory, which the title plays on.

    Stephen Jay Gould was a) one of the main authors of the punctuated-equilibrium point of view and b) by far the most popular popular author on the subject, so some readers might have a slightly biased view of the debate if they have read mostly or only Gould.

  15. For folks who are interested there is a fascinating article in the February 1999 issue of Scientific American on the Chichlids in the lakes of the Rift Valley in east Africa.
    Through convergent evolution a lot of the Chichlids in one isolated lake look astoundingly similar to Chichlids occupying similar niches in other isolated lakes yet are remotely related genetically but are closely related to vastly dissimilar looking Chichlids in their home lake that occupy other niches.

  16. Robert Sapolsky of Stanford University addresses the conflict between gradualism and punctuated equilibrium in his Human Behavioral Biology lectures (at the end of Molecular Genetics II). He resolves it in an interesting way by showing how multiple stacks of punctuated equilibrium over long periods of time can look exactly like gradualism, so you can have both happening simultaneously. “Traits come in packages, so if you have a bundle in a punctuated way, they look gradual.” I don’t know where the current discussion on this stuff stands but that lecture is the last time I heard anything about it.

  17. I have always said that the intelligent design crowd have got biologists spooked good.

    It is a pity, frank puzzlement in science often comes before a breakthrough. There should be room for scientists to scratch their heads and say “There’s something missing in this picture” without someone jumping in and saying “Aha!”.

  18. What Phillip Helbig said.

    Sean clearly stated in the OP,

    “The gradualists (in terms of theory change, not necessarily in terms of how natural selection operates), . . . “

    . . . and many other cues. While he is intentionally playing off of the Gradualist / PE argument from the past, in this article he (Sean) is using “Gradualist” as a label for the view that the TOE will change gradually, incrementally over time in the future. In direct contrast he uses “Punctuated Equilibrium” as a label for the view that the TOE will experience major, revolutionary changes over time in the future. Neither the OP nor the article it references are about the old Gradualist / PE argument ala Gould et al.

    James Cross,

    In addition to the Gradualist / PE misunderstanding, the following from the OP directly addressed your stated views.

    “As far as I can tell, the revolutionaries make their case by setting up a stripped-down straw-man version of evolution that nobody really believes (nor ever has, going back to Darwin), then proclaiming victory when they show that it’s inadequate, even though nobody disagrees with them. They want, in particular, to emphasize the roles of drift and development and environmental feedback — all of which seem worth emphasizing, but I’ve never heard anyone deny them.

    Read “nobody” and “anyone” as colloquial for “no significant number of experts.”

  19. There was a comment on evolutionary stasis over long periods of time in the fossil record. What is very important to understand is that it actually takes a huge amount of evolution for a species to maintain its appearance in the face of mutation.

    If it were possible to compare DNA samples from individuals of a seemingly single single species that were separated by 100 million years, the genomes would be vastly different from each other. If it were possible to bring the organisms together, it is very unlikely that they could produce viable offspring, and would have to be considered as different species . In effect, time separates species just as well as mountain ranges do.

  20. I don’t think there is much support for intelligent design among scientists.
    I know there are a few like the Nobel laureate in chemistry Richard Smalley and RAN physicist Vladimir Fortov

  21. Given that this post will attract a few ID-Creationist weirdos I sense that physicist Sean Carroll is about to know what it’s like to be biologist Sean Carroll.

    As to the subject matter, I tried to read Gould’s book on the subject but found myself infuriated by his flip-flop statements on the repercussions of PE: first he would state that PE was just tinkering at the edges of evolutionary theory, then he would claim that it was a revolutionary new paradigm that would influence not just biology but things like politics and the social sciences; then, a few pages later, he would be again claiming that PE was a minor adjustment.

    The upshot of this was my complete loss of confidence in the author’s credibility on this subject at least. I would like to make another attempt at reading this in case I was exaggerating or imagining Gould’s contradictory statements.

  22. Which book? His thick tome?

    Of course, it could be just a tinkering within evolutionary theory and nevertheless have great influence on other fields. Frankly, my views are whatever its status in evolutionary theory, its relevance for other fields is minimal at best. But where does Gould claim this? Do you have any quotes? Page numbers in the hardback edition?

  23. I had to stop reading the article at some point because I felt it is too vacuous for my taste and I am wasting my time.
    Michael Rose a renowned evolutionary biologist regularly complains that the field is lacking rigor (i.e. no math please) and mostly it is not science what people are doing. I guess I start to understand what he means …

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