Neutral changes can hardly be non-Darwinian if Darwin included them in his original thesis.[quote=“Swamidass, post:41, topic:36348”]
Notice that they do not identify as Darwinians or emphasize positive selection in their response. Instead they acknowledge all the non-Darwininan mechanisms raised by the EES as already part of “evolutionary theory.”
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The problem is that the mechanisms they list are either Darwinian or irrelevant to the evolution of species (e.g. epigenetics). Without natural selection you don’t have neutral drift. Neutral mutations are as Darwinian as beneficial and detrimental mutations.
This is false. Selection does not cause drift. Period.
Moreover, neutral drift is about 3 orders of magnitude more important than selection in understanding DNA.
That is not whant defines “Darwinian” in the 1940s 50s and 60s. That is the what most people mean when they use the word.
Even Darwin thought neutral changes (organismically) were a minor contributor. However, in DNA we find they are the dominant mechanism. Darwin did not anticipate this. That is why the early neutralists (Kimura) are commonly said to have falsified strict Darwinian theory (positive selection dominated change).
One of the more entertaining quotes by Kimura compares adaptationalists (those who focus on Darwinian dominate change) to flood geologists…
To emphasize the founder principle but deny the importance of random genetic drift due to finite population number is, in my opinion, rather similar to assuming a great flood to explain the formation of deep valleys but rejecting a gradual but long lasting process of erosion by water as insufficient to produce such a result.
And that is in a peer-reviewed scientific paper. Ha.
You can’t define neutral without relating it to beneficial and detrimental.[quote=“Swamidass, post:43, topic:36348”]
That is not whant defines “Darwinian” in the 1940s 50s and 60s.
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Then it isn’t defined correctly.[quote=“Swamidass, post:43, topic:36348”]
Even Darwin thought neutral changes (organismically) were a minor contributor. However, in DNA we find they are the dominant mechanism.
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Where did Darwin state that neutral changes could not be the dominant mechanism at the molecular level?
Darwin did not expect neutral changes to be the dominant mechanism on any level.
Vestigial organs, by the way, are not an example of neutral change a all.
Take the hip bones of a whale. The loss of limbs was driven by positive selection. The failure to remove the hip bones were either due to the limits of positive selection (because this is a weakly negative trait, i.e. a weakly detrimental trait) or because it has some important residual function (i.e. muscle attachments) that prevents its removal entirely (purifying or negative selection).
Either way, vestigial organs are not an example of neutral change in Darwin’s thought. At most this is a recognition that in boundary conditions a neutrality might stagnate some features from the distant past. This is not neutral theory at all.
Then please quote Darwin saying that neutral changes could not be the dominant mechanism at the molecular level.[quote=“Swamidass, post:47, topic:36348”]
Vestigial organs, by the way, are not an example of neutral change a all.
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They are changes to an organ that do not affect fitness. Those are neutral changes.
Of course I can’t do that because he never considered the possibility. Instead he argued that everything was dominated by positive selection. Which is exactly the point.
How about you show me a quote where he claims neutral changes are more import common and important than positive selection. You will find none. Darwin was a brilliant scientist, but he was an adaptationist, not a neutralist. He was right about many things. He was ahead of his time. He was wrong about this, at least regarding genetics.
Why should we be surprised? We did not even know about DNA at the time. The man was a brilliant scientist. He was not a prophet.
This is false. Neutral does not require a relationship between beneficial and detrimental. It just means no selection.
If he never commented on things at the molecular level, then how could he have argued that everything was dominated by positive selection? [quote=“Swamidass, post:49, topic:36348”]
How about you show me a quote where he claims neutral changes are more import common and important than positive selection. You will find none.
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It would seem to me that Darwinian evolution is open to both possibilities.[quote=“Swamidass, post:49, topic:36348”]
This is false. Neutral does not require a relationship between beneficial and detrimental. It just means no selection.
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"There is one point connected with individual differences, which seems to me extremely perplexing: I refer to those genera which have sometimes been called ‘protean’ or ‘polymorphic,’ in which the species present an inordinate amount of variation; and hardly two naturalists can agree which forms to rank as species and which as varieties. We may instance Rubus, Rosa, and Hieracium amongst plants, several genera of insects, and several genera of Brachiopod shells. In most polymorphic genera some of the species have fixed and definite characters. Genera which are polymorphic in one country seem to be, with some few exceptions, polymorphic in other countries, and likewise, judging from Brachiopod shells, at former periods of time. These facts seem to be very perplexing, for they seem to show that this kind of variability is independent of the conditions of life. I am inclined to suspect that we see in these polymorphic genera variations in points of structure which are of no service or disservice to the species, and which consequently have not been seized on and rendered definite by natural selection, as hereafter will be explained. "–Charles Darwin, “Origin of Species”
If that isn’t Neutral Theory, then I don’t know what is.
It is not neutral theory. It is Darwin guessing that there is more to it than he knows. He is right, and he is pointed in the right direction. This still is not neutral theory.
I would also add that this contradicts your own definition of Darwinian evolution.
Which I suppose is my point all along. “Darwinian” is not a helpful way to describe evolutionary theory.
The common definition of “Darwinian” does not even match the nuance of Darwin’s view.
Non-Darwinian mechanisms are very important too, often much more important than positive selection. They are much more important to DNA than Darwin ever imagined.
Darwinian is often equivocate with Darwinism (i.e. atheism) by those stoking unnecessary conflict.
For all these reasons we should not describe current evolutionary theory as Darwinian. I would rather explicitly reference Darwin when his thoughts are relevant, as they often are.
“I am inclined to suspect that we see in these polymorphic genera variations in points of structure which are of no service or disservice to the species . . .”'–Charles Darwin, “Origin of Species”
As part of his theory, Darwin is saying that variations can include those which have no service to the species. That is the neutral theory. We could also add . . .
“Mere chance, as we may call it, might cause one variety to differ in some character from its parents, and the offspring of this variety again to differ from its parent in the very same character and in a greater degree; . . .”–Charles Darwin, “Origin of Species”[quote=“Swamidass, post:52, topic:36348”]
I would also add that this contradicts your own definition of Darwinian evolution.
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How does it contradict my definition? Random mutations include neutral mutations.
My main point is that it isn’t helpful to misrepresent the theory that Darwin put forward.
However, you claim that it isn’t helpful to use “Darwinian”, and yet you continue to use “non-Darwinian mechanisms” as if that has meaning. Why not just say what the mechanisms are without using the “Darwinian” moniker?
There are some important concepts to grasp on such topics. First, there is a difference between the cells in your functional tissues (i.e. somatic cells) and the cells used for reproduction (i.e. germ line cells). Changes that occur in somatic cells are not passed on, so they are irrelevant to the process of evolution.
What you are referencing is called phenotypic plasticity. This refers to the ability of the body to change in response to environmental cues. A good example in humans is tanning. If you expose yourself to UV light and damage DNA your body responds by making more melanin. However, if you get a really dark tan and then have a baby, that baby will not have darker skin simply because you tanned. What your offspring will inherit is the ability to produce melanin in response to UV DNA damage.
Ultimately, the variability that this article is referring to is a product of DNA sequence just as your ability to tan is due to the DNA sequences found in your genome. You inherit a toolkit of responses to environmental cues.
We should all know how to equate “Non-Darwinian Mechanisms” to “Phenotypic Plasticity” !
They are non-Darwinian only in that the mechanism in question is triggered by the environment … but the propensity to be able to be “triggered” is quite definitely supported by the organism’s genotype!
Thanks for sending us here. In general, the science news here is good to identify interesting articles, but I would avoid them almost entirely in terms of understanding them. There is no substitute for reading the actual papers. In this case you can find the paper here…
This is good work, but it hardly shows that genetics are not as important as we thought. Rather it shows a specific phenotype where the whole organism system has to be understood to understand phenotype. This has been well known for a very long time, in principle. Now in practice, we are getting more examples of exactly how genotype works in a system and is influenced by environment to produce a phenotype. That is important, but hardly a surprise.
The use of epigenetic here is a great demonstration that epigenetics can be refer anything that isn’t an obvious effect of a single gene. Epigenetic is a nearly contentless words right now. It seems everything is epigenetics, even genetics.
“Non-Darwinian” is a silly phrase used by people who are attempting to indicate that Darwin was somehow wrong, or that Evolution somehow doesn’t apply to the way an organism responds to its environment!
I hope you both use the phrase as an educational moment.
Because the next thing you’ll hear from a YEC is that “non-Darwinian mechanisms have been proved to shape animal development”… as though they are saying something earth-shaking!
Question!:
How exactly is something non- Darwinian if it helps the creature prosper and thrive?