Somewhere between the New Synthesis and the Extended Evolutionary Synthesis, the theory of Punctuated Equilibria appeared… but to understand it requires an Improbability Drive.
I am pre-publishing this sequence of essays here and in social media to elicit comments and other feedback. They will form the framework for my next book, Darwin, Dada, Dalí, Duke, & Devadevàya.
It is perfectly true, as the philosophers say, that life must be understood backwards. But they forget the other proposition: that it must be lived forwards.”
— Søren Kierkegaard
On the Origin of Species
In 1859, Darwin published his historic, science-altering On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Laymen, and even many scientists, often assume that Darwin gave us the concept of evolution, but in reality he simply gave us a theory of evolution. For at least a century before Darwin published, European scientists had been discussing family relationships among various groups of plants and animals. One of the most prominent was Darwin’s grandfather Erasmus, who speculated that all animals descended from mollusks; to support his belief, he changed the motto on the family arms to E Conchis Omnia, ‘Everything from Shellfish.’ What Notsir Charles1)Bishop Wilberforce was not only an intellectual opponent and objector to Darwin’s work, but emerged as a personal nemesis as well. Wilberforce insured that one of the most significant scientists in all of history was never knighted. I found an online petition to have him knighted posthumously, but it has not collected many signatures Wilberforce is famous for his debates with Thomas Huxley, a.k.a ‘Darwin’s Bulldog,’. Some years after the debates, Wilberforce died from a head injury upon falling from a horse. Tradition has it that Huxley quipped, “Wilberforce’s brains have at last come into contact with reality, and the result was fatal.” Darwin and Wilberforce are both buried at Westminster Cathedral in London. But while Wilberforce rests in a fabulously ornate tomb, Darwin lies under a simple marble slab. Darwin, however, is buried next to Newton. gave us, was a mechanism to explain it.
To many of his contemporaries, it appeared that Darwin had solved the entire problem of evolution. As biology has grown, however, we have gained insights to show that, while Darwin certainly cracked the door for a non-theological mechanism explaining the rich diversity of life, subsequent advances have shown that many puzzles remain to be solved. Some of our advances even offer important corrections to the theory of evolution. Darwin would have probably welcomed these; he was a shy man, and much more interest in strong solutions than recognition.2)Darwin’s priority of logic over vanity and personal advancement is demonstrated by his reaction to Fleeming Jenkin’s vigorous criticism of Darwin’s work. Darwin welcomed Jenkin’s criticisms, as they were based in logic & science rather than theology. In fact, he considered the comments some of the most useful feedback he received and admitted to Wallace, “Fleming Jenkyn’s [sic] arguments have convinced me.”
The New Synthesis & the Extended Evolutionary Synthesis
There are at least three important insights that have expanded and modified Darwin’s foundational theory. The first, the New Synthesis, was largely a vindication of his work. That movement began in 1900 with the discovery of Gregor Mendel’s earlier but overlooked work on inheritance. Mendel’s research resolved the obstacle of Darwin’s own concept of ‘blending inheritance’, which threatened his larger theory. Continuing until the beginning of WWII, a number of major biologists contributed to the New Synthesis, building on Darwin’s theory and Mendel’s discovery.
Soon after the War, Watson & Crick generated the second pivotal addition when they discovered the structure of DNA. That essential work deepened the advances of Darwin and Mendel. But ironically, over the past few decades broader understanding of the way genetic material works led to the discovery of non-nuclear effects, including some epigenetic mechanisms that would have been considered apostasy just a few years ago, as they seem to flirt with Lamarckism. These advances, however, led to the Extended Evolutionary Synthesis, which has grown in influence over the last few years.
But right in the middle of all this post-War progress, Gould & Eldridge crashed the party with their 1972 work on punctuated equlibria. The two men pointed out that there is very little evidence for Darwninan gradualism, and in fact, it appears that species are quite stable for millions of years (i.e., ‘stasis’). Then in sudden geologic discontinuities, new species appear, seemingly de novo. Scientists had been aware of this geological evidence for some centuries before Darwin, perhaps even a millennium before, but it had been ignored by Darwinians in favor of a more parsimonious theory of constant gradualism. (Scientists, like all of us, often ignore the obvious in deference and preference to authority and tradition.)
The resistance to punctuated equilibria is understandable, but for political rather than scientific reasons. If species appear suddenly, that would seem to support creationism. But this threat is disarmed by the shared anatomical and genetic characteristics between the new species and the parent species, as well as by the conserved developmental pathways evident in embryology. If ‘God’ were truly creating new species, then we would certainly expect punctuated appearances; but we would not expect the new species to unfailingly conserve most of the characteristics of the ancestral species. From time to time—or really, for a omniscient deity, for each and every new species—we would expect something inexplicable, perhaps even something with a completely different genetic coding mechanism.
The Extended Evolutionary Synthesis has made notable strides in articulating punctuated equilibria with the New Synthesis. It is worth considering, however, that just as the geologic record presents an apparent biological discontinuity, punctuated equilibria also presents conceptual discontinuities: abrupt shifts in the patterns of biology offer us wide, surprising, and intriguing new angles of attack for explaining the diversity of life.
Statistics & Innovation
The most powerful tool that emerged from the New Synthesis has become fundamental for all sciences: statistics. Statistics has three starting metrics: centrality/normality; distribution/variability; and from those two, likelihood/probability.
Consider those three, however, in respect to the discontinuities of punctuated equilibria. What are we to do with a sudden, truly novel evolutionary event? It is not immediately clear how gradualistic approaches might explain the sudden appearance that is abnormal/eccentric, something which completely violates our distributions and variabilities. And which is also improbable: the obvious conclusion from punctuated equilibria, particularly when considering the millions of years of stasis, is that meaningful evolution is an extraordinarily rare event in the history of a species. Translating ‘extraordinarily rare’ into statistical terms means ‘highly improbable.’ In fact, punctuated equilibria suggest a result that is so improbable, that we cannot calculate the probability, at least not in any predictive way.3)Retrospective analyses are certainly possible, but calculating these will require additional considerations that we will cover in later posts. This last point is pivotal, because a discipline without strong predictive power is not a science.
The whole point of evolution, and of the big puzzles we attempt to solve in biology, is that evolution is innovative. Innovation is what sets biology apart from the hardest sciences: life creates things that have never existed before. Granted, the physicist and the chemist produce new compounds, but their efforts are dwarfed by the scantily-explored catalog of natural compounds and chemical processes in life. Other sciences are eclipsed by the innovation of organic evolution.
And in an important insight, chemists and physicists are generally designing compounds that they have envisioned and postulated, i.e., things that are predictable. In Wonderful Life, Stephen Jay Gould makes the point well: if we started evolution all over again, we would not end up with the same world we have now. We cannot know what we have before we have it.4)It might appear that human imagination defies that. It does not, and that will be a key insight in future discussions. And as we noted, the innovation of biology is largely unpredictable.
We should not define biology by our easiest problems, but by our largest aspirations. The largest of those, without doubt, is the origin of life: the first cell, the Last Universal Common Ancestor, or LUCA.
LUCA is a critical topic for research, and offers an insight here. The New Synthesis, and even today the Extended Evolutionary Synthesis, are still built around the tools of gradualism.
As such, they focus on evolution through the shuffling and selection of alleles, which is short for allelomorph, the ‘other forms’ (of a gene). Alleles are the different DNA strings which code for a specific genetic feature or task; blonde, brunette, and redhead are all expressions of different alleles. But punctuated equilibria and LUCA raise a critical question: where does the first allele, or any set of alleles, come from in the first place? Remember, the problem that Darwin’s book sought to solve was the origin of species. But before we can begin to address the larger problem of new species, or even the first species, we must first explore the origins of new alleles.
The extensive research on alleles has been essential to biological understanding.
But it can’t help us to understand the fullest expression of innovation, which again, is the transition from no allele to any allele. Where did the first gene in a class of possibilities come from? How do we generate the first appearance that establishes a class of alleles? Our current approaches certainly can’t help with extreme expression of this problem, the transition from inert matter to life. Statistics can’t help us calculate the probability for something that does not yet exist and is therefore completely unknown.
As we noted, the true, large-scale innovation of punctuated equilibria is extraordinarily rare. Thorough innovation is not the process of allelic shuffling, it is not simply eccentric or abnormal; it is extraordinarily improbable. To explore truly large-scale evolution, and to resolve problems posed by punctuated equilibria, we will need an improbability drive,5)Fans of The Hitchhiker’s Guide to the Galaxy will recognize the term ‘infinite improbability drive.’ I’m not suggesting that such a piece of machinery could even exist, and I am certainly not proposing that it could help explain biology. But how could I pass up a once-in-a-lifetime opportunity to use the term? some mechanism that will allow us to generate and select wildly improbable results. In fact, as we go we will see that the needed level of improbabilities appears to be so large that even biological numbers may not large enough to solve the problem.
Alleles, Neolleles, & Meaningful Genes
Fortunately, in future posts we will also see that punctuated equilibria provides an insight that might allow us to begin understanding very large improbabilities, and that might open up paths for better understanding evolution. Those insights will also become the foundation for subsequent discussions. A new allele—a neo-allele, or neollele—poses new problems, but it also opens up new opportunities.
To that, in recent years research has uncovered the importance of de novo genes in evolution, genes that have never existed before, or perhaps which did not previously exist in the considered species. But these entities still do not escape the improbabilities: a de novo gene can certainly provide a genetic sequence on which to work, but that is not the same as a meaningful gene, something that is useful to the receiving organism. And while any new gene, even one that codes for gibberish, will produce evolution within the tightest definition—i.e., a change in gene frequencies—that is not the same as meaningful evolution.
In fact, de novo genes illustrate the situation we are trying to understand. It would not be hard to imagine any number of mechanisms that might assemble a novel sequence of DNA or other genetic material. Any de novo gene process, whether duplication, fission/fusion, transposition, transfer, or some as-yet-undiscovered mechanisms, can produce a novel string of genetic ‘letters’, which will certainly code for some protein.
But that misses the point: the chances that the new protein will ‘make sense’, that it will be useful and meaningful within the needs of the organism, are still incredibly remote. We are still stuck with the problem of large improbabilities, the situation of typewriting monkeys. And even when a gene appears which was meaningful in another organism, the chances that it will be meaningful in a new, unrelated host, is also unlikely.
However, if by chance a de novo gene is transferred from another organism, and it works; or, if it represents the resurrection of a retired ancestral code, and is also immediately meaningful within the host; that still has not solved our problem: How was that original de novo gene, whether exotic or ancestral, created?
We will combine insights from punctuated equilibria and the neollele to expand our perspective on a number of current problems:
- microevolution & macroevolution;
- genetic isolation and allopatric speciation;
- evolutionary pressure;
- fitness, and the fuzzier concept of ‘the fittest’;
- Wright’s fitness landscape;
- the critical importance of ‘the weak’ in evolution, which we will find is not the same as ‘the unfit’.
Together these suggest new pathways for the course of evolution, which we will address over the next several essays.
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Footnotes [ + ]
|1.||↑||Bishop Wilberforce was not only an intellectual opponent and objector to Darwin’s work, but emerged as a personal nemesis as well. Wilberforce insured that one of the most significant scientists in all of history was never knighted. I found an online petition to have him knighted posthumously, but it has not collected many signatures Wilberforce is famous for his debates with Thomas Huxley, a.k.a ‘Darwin’s Bulldog,’. Some years after the debates, Wilberforce died from a head injury upon falling from a horse. Tradition has it that Huxley quipped, “Wilberforce’s brains have at last come into contact with reality, and the result was fatal.” Darwin and Wilberforce are both buried at Westminster Cathedral in London. But while Wilberforce rests in a fabulously ornate tomb, Darwin lies under a simple marble slab. Darwin, however, is buried next to Newton.|
|2.||↑||Darwin’s priority of logic over vanity and personal advancement is demonstrated by his reaction to Fleeming Jenkin’s vigorous criticism of Darwin’s work. Darwin welcomed Jenkin’s criticisms, as they were based in logic & science rather than theology. In fact, he considered the comments some of the most useful feedback he received and admitted to Wallace, “Fleming Jenkyn’s [sic] arguments have convinced me.”|
|3.||↑||Retrospective analyses are certainly possible, but calculating these will require additional considerations that we will cover in later posts.|
|4.||↑||It might appear that human imagination defies that. It does not, and that will be a key insight in future discussions.|
|5.||↑||Fans of The Hitchhiker’s Guide to the Galaxy will recognize the term ‘infinite improbability drive.’ I’m not suggesting that such a piece of machinery could even exist, and I am certainly not proposing that it could help explain biology. But how could I pass up a once-in-a-lifetime opportunity to use the term?|