The Neutral Theory of Evolution

@jongarvey you should also read this paper from 1979 with great relish, thinking about questions of teleology and such,

Read that linked paper, on Panglossian and the Spandrels. That is a modern classic, from Gould. Then review the public debate on natural selection and evolution. Try no to be too appalled by how much they missed the boat, on all sides. Neo-Darwinism has been dead for a long long time.

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@swamidass How do you navigate the fuzzy use of labels when discussing different evolutionary biology models? You are clearly using neo-Darwinism to refer to the early 20th century understanding which did not include neutral theory. Others like Mayr prefer to have neo-Darwinism refer to the current collective understanding of evolutionary biology, whatever that might be (presuming it descends from Darwin’s theory in some fashion, I imagine). Moran seems to go the other way, using neo-Darwinism for the outmoded view that was challenged not by neutral theory but earlier by the modern synthesis, while using Modern Synthesis for a more expansive understanding that (at least partially) accommodates more recent developments including neutral theory. (

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Very good question.

I lean towards with Larry Moran, because I think he has the history and the science most correct.

That is how Moran uses it, and I think that is correct. If you go back and look at the literature in the 1950’s and 1960’s they all defined themselves in opposition to neo-Darwinism, not as an extension of it.

That is a confusing anachronism. I strongly resist this. Such use fo the terminology contributes to a great deal of misunderstanding. I have yet to meet a knowledgeable scientist that considers themselves a neo-Darwnists. This would be like finding a Newtonian physicist.

I’m resistant to the term modern synthesis (which technically predates neo-Darwinism I think). This is one point on which I deviate from Moran. I’ve gone through several options on the right term to use, especially when engaging the public.

Ultimately, I’ve settled on “evolutionary science.” This is the most overarching and neutral term that causes the least confusion. It does not force readers to make a choice in the “modern synthesis vs. EES” internecine war, and it doesn’t invoke the controversy of Darwin’s name, and it doesn’t direct people falsely to positive selection driven change. For all those virtues, when engaging the public, “evolutionary science” is the best term I’ve found.

When asked to clarify, I lean heavily on “common descent” and more specifically on “the common descent of man.” The mechanisms of change are really beside the point for the public. Science is silent on God’s action, and certainly could have inspired mutations. The evidence for common descent, however, is overwhelming and with the most theological consequences in the “common descent of man.” That is where action is. The rest is all really beside the point.


How do you navigate them?

Similar to you, I prefer “evolutionary biology” when possible. Perhaps “science” would be even more appropriate; maybe I still cling to some bias towards my preferred sciences.

I try to avoid all variations on Darwinism when possible, because as you note that invokes all sorts of associations with the person of Charles Darwin. Relatedly, given how often he is referenced, I think some folks think the sum total of science around evolution was done by Darwin and nothing else has been added in 160 years.

I’ll sometimes contrast the modern synthesis and the extended synthesis in the context of conversations around quotes from extended synthesis advocates. And then only in an attempt to explain how those scientists seem to be saying or writing things that sound critical of evolution, but are really critiquing one specific model while simultaneously advocating for another model that is still very much evolutionary biology with common descent.


Your welcome @patrick. I felt the same way when I first learned of all this. It was pretty stunning how much of this is missed by “experts” debating this in public. They are just talking past the current understanding of evolution, not ever really engaging.

Same here. That is one thing that keeps me hook. Ironically, BioLogos was never really that engaged with the scientific side. On the other hand, interlocutors from ID (e.g. @pnelson and @Agauger and @vjtorley) have been informative, even when I have disagreed with them. There has been more than one time I’ve received an email from @pnelson with something in the literature I would never have found without him. I first got to know @Agauger and @vjtorley in a exchange about the evolution of placentals and pseudogenes for egg yolks. That was an immensely informative exchange, where I learned a lot. Evolutionary science is just really interesting, and ironically I’ve learned a lot by engaging its critics.

Except, they are actually advocating for the same model, with just a different name. :smile:

Evolutionary biology is just fine by me.

@jongarvey there is more to this than you’ve seen so far. Larry Moran echos a good point from Koonin:

Koonin also makes an interesting point about species with historically small population sizes. These species accumulate a lot of junk in their genomes because natural selection is powerless to remove it. This junk DNA provides a pool of potential exaptations that usually lead to an increase in complexity (constructive neutral evolution). Thus, paradoxically, a weakening of natural selection often leads to more complexity.

So that junk DNA has a purpose, so is it junk? :smile: Purpose is in the eye of the beholder. There is no such thing as junk, but that is not what we might think it means.


I chose those two species because they’re so closely related but, as soon as you get to observe them, completely distinguishable. Ask any falconer! I could have added a member of the third falcon group, the kestrels, whose form and lifestyle are equally unique.

Anatomically, there are diferences such as the specialised nostrils of the peregrine enabling it to stoop at 200mph while breathing (and emulated by jet fighters). You can just see the lack of those in your hobby photo (though it’s the Australian rather than the British model).

Comparably, the wing geometry of the two is different, and it’s no surprise that the more swift-like wings of the hobby are employed in a flying style that is very similar to swifts and swallows - which are its prey.

The behaviour, as a package, is entirely distinct: most characteristically the peregrines will appear as a pair once in a few weeks - ranging a mile or so from home, at which distance their unique vision can spot prey - soaring high and, if they attack, coordinating their stoops from a great height to make a killing blow. If the tiercel misses, the falcon has a go, because they’re too fast to turn quickly. The hobbies, on the other hand, one encounters singly, typically finding them flying at head height in front of your car the way and following the corners the way swallows do - they take out dragonflies and swallows in level flight. Hobbies fly for fun - peregrines save their energy for the hunt.

The flight of the Hobby is unique. When hunting it will
fly along at a fair height, gliding and winnowing alternately.
If it sees a prospective quarry it hurls itself after it, following
the turns and twists of its prey with rare skill and great

Nothing like a peregrine at all.

Nesting (including brooding, feather and feeding development), calls, flight, diet, flocking are all different, but the overall impression is that you are seeing two different specialists - to the extent that after awhile, a mere glimpse is enough to distinguish them. I’m reminded of Arthur Jones who, doing his PhD work on Cichlid fish, was able to spot a species he’d not seen before in an aquarium out of the corner of his eye, from the way it behaved.

These are just the gross differences - ornithologists will note very many differences in character and behaviour that make up their unique roles in the world.

Now, one way of viewing this would be to say that, finding itself lumbered with unique nostrils, wing-shape, habits etc by neutral evolution, the peregrine soon found out it would starve trying to chase swallows, and elbowed itself the vacant niche of fastest bird in the world. Net result - superb adaptation of the entire lifestyle to a mainly accidental body plan. And such lucky accidents all within 10m years! Owing to a series of manufacturing errors, the Ford factory ends up with an F1 instead of a people-carrier and decides, consequently, to race, the company being equipped with “minds that can adapt their behavior to their form.”

Likewise for the hobby which, suffocating if it tried to stoop at high speed, was lucky enough to find itself with more manoeuvrable wings and body (remarkably similar to the most aerial birds in the world, the swifts, which touch ground only to breed); and with a convenient supply of swallows and swifts now within grasp. It took to nesting in trees rather than on cliffs (because it found itself with a compulsion to co-opt old nests instead of preferring laying on bare ledges).

All this, according to neutral theory, occurs because of the overload of adaptive selection in small populations, and a lot of weeding out of rubbish by purifying selection… fortunately the random changes keep the birds’ mental agility intact so they have the wit to turn the outrageous blows of cruel fortune into what - to all appearances - resembles supreme design for a special role.

And that’s how the elephant got his trunk.


I believe you!

I’m not saying its only neutral theory. Of course there is selection at play here. Though many of the distinctions you point our are behavioral too, and it is unclear how much of this is independent of the changes in form. Some of the behavioral differences might be them making the best use of the body plan they have.

I never said that natural selection wasn’t part of it. I’m sure it was.

I also never said that design wasn’t part of it. I would also agree, that this…

All these things can be true at the same time. However, the more granular the details, the more likely it is to be neutral. Even most OEC and YEC would agree the two share a common ancestor. That does not deny natural selection or design. It is just that most of the differences are likely to be neutral.

Well, one needs to cash out that first sentence philosophically and theologically: is a process of truly neutral change (in evolutionary terms every bit as undirected as any other mutations, only also undirected by selection) also capable of being designed? We still have the problem of arrival of the fittest that plagued Neodarwinism.

It’s the old problem of ontological randomness being seen as a cause. What does “neutral” mean if the total result is a peregrine falcon? That the changes were random? But that’s a naturalist metaphysic that lacks any coherence anyway: it means we don’t know what caused them. That the changes were not directed to the organism’s benefit, and not made so by selection? But here’s the peregrine, the bird flown only by princes because it is so special, and here’s the hobby keeping up with swifts. Don’t tell me most of the F1 car is due to mildly deleterious accidents when it’s just won the world championships.

In the two falcons, I’ve chosen examples in which virtually all the identifiable differences contribute to their specialist roles and excite the admiration of naturalists and engineers. In that context, to attribute the majority of features to neutral change… and to limit natural selection or design to some unspecified role, raises more questions that it answers.

I’ll happily grant that the hobby’s red trousers (absent from its Australian cousin) might be of no adaptive significance: with over 700 genes known to contribute even to human height, a few spandrels are almost bound to occur if you’re talking about the hobby genome. No doubt hobbies have learned to love red trousers as somehow crucial to their chosen ecological niche.

Now that might give a lead. We put the falcons to one side, and home in on the molecules, and lo and behold, most of the change appears neutral. But equally, if you forget me as a thinking human being and home in on my cell fluids, it will look to be mostly Brownian motion going on at the granular level. But zoom out again, and Brownian motion has not explained the man at all. And that takes me back to my original point at the top of the thread: when one’s evolutionary theory is driven by uncorrected accidents, the existence of “forms most beautiful” likely has a better explanation waiting to be discovered.

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I reviewed Koonin 2009 back in 2011, so am reasonaly familiar with his overview. Koonin also says that over evolutionary history there is no tendency to increased complexity:

There is no consistent tendency of evolution towards increased genomic complexity, and when complexity increases, this appears to be a non-adaptive consequence of evolution under weak purifying selection rather than an adaptation.

But complexity isn’t the issue - making complicated things is easy. Making complicated things that work beautifully is not. It seems not to have got any easier since we began to see that most phenotypic traits are related to most genes, and that that is complicated by epigenetics and sophisticated mechanisms like alternative splicing (large differences between similar species like chimps and humans, or perhaps hobbies and peregrines).

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That I agree with. There is no good account of beauty in evolution. I fall back on CS Lews and Is Theology Poetry? Have you read this yet?

Though variations on a theme very beautiful. As a musician you should know…

I wonder why that is?

Nope, but I will. Thanks for the link.

That, of course, is one of those “functions” that all theories of evolution leave out. I was tempted in the previous comment to say that the hobby’s red trousers help ornithologists both in identification and appreciation, but it would go beyond my point. Yet what else is the entomologist’s appreciation of a trayful of near-identical mosquiotes, but a finely-honed sense of the beauty of minor variation?

But to answer the Lutheran, I think he sets up a false dichotomy between art and engineering. One of the things I like about music is that it’s a technical and mathematical as well as an aesthetic challenge, perspiration as well as inspiration. Not to mention the emotional, spiritual, communicative and so on.

So to play a spoken piece in 5/4 time is as much a process of calculation and physical training as (one hopes) an aesthetic experience for the hearer. And of course the George Lowden’s design for the guitar is art and technique too.

The beauty of a peregrine is, to a large extent, that it is such a superbly efficient killing machine. I certainly agree that impressing research funders is not on God’s agenda, but that was not what motivated Ettore Bugatti, R J Mitchell or Leo Fender, either.

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Shouldn’t we be calling solar power theory and applications “Teslaism?” : )


Last paragraph is a classic. It is fundamental to my point of view on these things.

Ha, yes, well, there is that. Still, it can be helpful in providing context for the quotes from extended synthesis folks to explain that they at least think they are advocating for a different model – or that the same model has evolved enough to warrant a new name. (And so the species problem comes to evolutionary biology at yet another level.) At the same time, it can also be helpful to bring up the point you are making; after all, the whole reason there is an ongoing conversation from which to pull such quotes is that some folks don’t see different models.

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(The above is quote of @swamidass quoting Larry Moran, but I haven’t mastered the forum formatting sufficiently to make that clear. Thus this text, so we all know the actual source of the statements.)

This reminds me of something similar that Stuart Kauffman talks about with regard to autocatalytic sets. An autocatalytic set is a set of molecules (or more generically, entities) that collectively catalyzes the production of its members. These sets tend to be larger rather than smaller, which might seem surprising at first because you might expect it to be easier to make a few molecules than a lot. But basically, as you add molecules (or entities) to a set, the number of things you need to make grows linearly, but the number of interactions that can produce those things grows exponentially. Thus we would expect such autocatalytic sets to be relatively complex.

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7 posts were split to a new topic: Is Quantom Randomness Ontological?

Yes indeed Joshua - another excellent piece by Lewis. One wishes more scientists - even Christian scientists would read it. It would be interesting to have heard the conversation at the Socratic club afterwards - no doubt there were Wellsians amongst their number, since logical positivism was much in vogue. But it seems Lewis’s thought outlived that of Ayers.

For myself, I’m reminded of a stanza from the poem extemporized by Mr Toad, which I didn’t quote in my “Indegenous Theologian” piece on the Hump, out of modesty…

The clever men at Oxford
Know all there is to be knowed
But they none of them know one half as much
As intelligent Mr Toad.

I learned that at age 10, of course, for my role. Maybe that’s the subconscious reason I didn’t apply for Oxford…

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